chapter 10 : transport

7/28/2019 Chapter 10 : Transport

1/188

TRANSPORT


2/188

EXAMPLES OF MATERIALS TRANSPORTED

INTO THE CELL

-OXYGEN

-NUTRIENTS

-WATER

-HORMONES

OUT OF THE CELL

-CARBON DIOXIDE

-UREA

-HEAT


3/188

TRANSPORT IN UNICELLULAR ORGANISMS

-TRANSPORT MATERIALS OVER SHORT DISTANCE, SUCH AS BETWEEN

ADJACENT CELLS.

- BY SIMPLE DIFFUSION, OSMOSIS, ACTIVE TRANSPORT OR CYCLOSIS

(CIRCULATION OR STREAMING OF CYTOPLASM WITHIN THE CELLS)http://www.youtube.com/watch?v=PFtzs_cUddI&feature=player_detailpage

- ITS CELL MEMBRANE IS IN FULL CONTACT WITH ITS ENVIRONMENT.

SO, THE MATERIALS NEEDED ARE TRANSPORTED DIRECTLY INTO THE

CELL.

-IN Paramecium sp., GASEOUS EXCHANGE OCCURS BY SIMPLE DIFFUSION.

MATERIALS ARE TRANSPORTED WITHIN ITS CYTOPLASM BY CYCLOSIS.


4/188


5/188

TRANSPORT IN MULTICELLULAR ORGANISMS

-CELL DO NOT CONTACT WITH EXTERNAL ENVIRONMENT

- THERE ARE LAYERS OF CELLS BELOW THE EPIDERMAL CELL LAYER

-SIMPLE DIFFUSION CANNOT TRANSPORT SUBSTANCES (OXYGEN,

NUTRIENTS, CO2 AND WASTE PRODUCTS) TOB THE BODU CELLS.

-NEED TRANSPORT SYSTEM TO TRANSPORT OXYGEN AND FOOD TO THE

CELLS AND REMOVE CO2 AND METABOLIC WASTES FROM THEM.


6/188

EPIDERMAL LAYER IN MULTICELLULAR ORGANISMS


7/188

LIVING ORGANISMS AND THEIR TOTAL SURFACE AREA TO VOLUME

RATIOS

-THE TOTAL SURFACE AREA TO VOLUME (TSA/V) RATIO : THE TOTAL

EXTERNAL SURFACE AREA OF A STRUCTURE TO ITS CAPACITY

-TSA/V RATIO OF A CELL : THE TOTAL SURFACE AREA OF ITS PLASMA

MEMBRANE TO THE VOLUME OF THE CELL.

-TSA/V OF A MULTICELLULAR ORGANISM : TOTAL SURFACE AREA OF THE

SKIN TO VOLUME OF ITS BODY

-TSA/V IS USED TO MEASURE :A) SURFACE AREA AVAILABLE FOR GASEOUS EXCHANGE

B) RATE OF MOVEMENT OF SOLUTES TO THE INTERIOR OF AN ORGANISM


8/188

- By using a cube, we found that the TSA/V ratio of a cube is

inversely proportional to its size.

Size 1

tsa/v

-The physical implications are :a) smaller living organisms have larger TSA/V ratios. A large

TSA/V ratio helps in the efficient gaseous or solutes diffusion

b) larger living organisms have very small TSA/V ratios. A smallTSA/V ration limits the rate of gaseous or solutes diffusion.


9/188

- How to overcome the transport problem?

- Organism A : a)unicellular organism

b)has very high TSA/V ratio

c)has cells where nutrient and oxygen molecules

can easily diffuse into the cell and waste products

diffuse out of the cells through its entire cell

surface

A

B

C


10/188

-Organism B : a) multicellular organisms

b) has a very low TSA/V ratio

c) less surface area per unit cell for diffusion of

nutrient and oxygen molecules into its

epidermal cells

d) impossible for simple diffusion to occur

-Organism C : a) same size as organism Bb) has transport tube linking to the interior cells

c) increasing TSA/V ratio of organism

d) tube transport nutrient, oxygen and unwanted

waste molecules in and out of cells


11/188

CIRCULATORY SYSTEM

-Circulatory system transports substances such as nutrients,

water and oxygen to the body cells and removes carbon dioxide

and other nitrogenous wastes from the body cells.

-The circulatory systems of humans and animals consist of 3

components:

a) a medium/fluid required to carry materials around the

circulatory system (blood, haemolymph)

b) vessels tubes for the medium to flow through

c) pump heart that help to propel and circulate the medium

around the body


12/188

HUMAN BLOOD

Blood cells Plasma

Erythrocytes

(red blood cell)

Leucocytes

(white blood cell)

Thrombocytes

(platelets)

Granulocytes

basophil

Neutrophil

eosinophil

Agranulocytes

monocytes

Lymphocytes

Fibrinogen

Serum


13/188

ERYTHROCYTES

- 5 million per mm3 of blood

-Tiny (8m), biconcave, disc shape

-Do not have nucleus, mitochondria or

ribosomes

-Full of haemoglobin

- made in the bone marrow, live for about 120

days

- Destroyed and recycled in the liver


14/188

-Adaptations of erythtocytes:

a) have no nucleus provide more space for haemoglobin

b) transport oxygen haemoglobin combine to oxygen and form

oxyhaemoglobin

c) transport CO2 haemoglobin combine to CO2 as hydrogen-

carbonate

d) biconcave, disc shape increase the TSA/V ratio for optimum

gaseous exchange

e) small and flexible can diffuse through narrow capillary walls


15/188

LEUCOCYTES

Leucocytes in blood

-colorless, do not have haemoglobin

-Larger than erythrocytes, fewer in number

-7000 per mm3 of blood. Raised the number

of leucocytes (leucocytosis), decrease thenumber of leucocytes ( leucopenia)

-Irregular shape, have nucleus

-Important in body defence mechanisms against disease

- divided into 2 basic types : granulocytes and agranulocytes


16/188

Granulocytes

-Have granular cytoplasm and

lobed nucleus.

granules

Bi-lobednucleus

-Amoeboid

movement and

engulf bacteria by phagocytosis

-Produce in bone

marrow

-Divide into 3 types:

a) Neutrophils form 70% of

total leucocytes

- has multi-lobed

nucleus

- engulf bacteria byphagocytosis

b) Eosinophils 2-4% of total

leucocytes

- detoxify chemical,

reduce inflammation

c) Basophils 1% of leucocytes


17/188

GranulocytesAgranulocytes


18/188

AGRANULOCYTES

Have non-granular cytoplasm,

compact nucleus

Divide into 2 typesa) Monocytes

- Largest of the five types of

white blood cell

- Produce in bone marrow

- Consist 5-8% of all leucocytes

- Have bean-shaped nucleus

- Ingest bacteria by phagocytosis

b) Lymphocytes

- Has large, rounded

nucleus and small

amount of non-granular

cytoplasm

- Large nucleus contain

genes for antibody

protein production

- Produced in lymph

glands and lymphatic

nodes

- Produced antibodies


19/188

THROMBOCYTES (PLATELETES)

- Are tiny fragments of megakaryocytes (bone

marrow cell) found in the bone marrow.

- Colourless, irregular shape, no nucleus.

- Measures about 2-3m across.

- Made in the bone marrow and last for about

6-7 days.

- Have amoeboid movement

- Important in blood clotting, repairing damaged tissues and

maintain the integrity of blood vessel wall.


20/188

PLASMA

- Yellowish liquid which the blood cells are suspended.

- Consist about 90% water, 10% dissolved substances.

- Dissolved substances consist of plasma proteins, dissolvedgases, absorbed food molecules, excretory waste products,

hormones and salts.

- Heat produced by respiration is being absorbed by plasma.


21/188

Content Composition

Water 90% of the plasma

As a solvent and transport mediumProteins Albumins for viscocity and osmotic balance

Antibodies e.g. globulin for immunity

Clotting factors such as fibrinogen and

prothrombin

Dissolved gases Consist of CO2 and O2

Absorbed food

molecules

Consist of glucose, amino acids, fatty acids,

vitamins

Excretory waste

products

Consist of CO2, urea, uric acid, creatinine

Hormones Adrenaline,insulin,glucagon, antidiuretic hormone

Salts Consist of dissolved ionic salts; sodium,potassium,

calcium,magnesium

Content of blood plasma


22/188

FUNCTION OF BLOOD AND HAEMOLYMPH IN TRANSPORT

- Functions of blood:

a) transport of materials

b) defence against diseases


23/188

FUNCTIONS OF BLOOD IN TRANSPORT

Materialstransported

Examples Transported in Transportedfrom

Transported to

Gases

Oxygen Haemoglobin

in erythrocytes

Lungs Respiring

cells

CO2 Haemoglobin

in erythrocytes Respiringcells LungsHydrogen

carbonate ions

in plasma

Absorbedfood

Amino

acidsPlasma Intestines

Liver andbody tissuesGlucose

Vitamins


24/188

Mineral salts

Iron

Plasma Intestines

Bone marrow

Calcium Teeth and

bonesIodine Thyroid

glands

Hormones Insulin

Plasma

Pancreas Liver

Antidiuretic

hormonePituitary

gland

Kidney

Excretory

products

Urea, uric

acid,

ammonium

salts

Plasma Liver Kidney

Heat Metabolic

heat

Whole

blood

Liver,

muscles

Whole body


25/188

FUNCTION OF HAEMOLYMPH IN TRANSPORT

- Haemolymph is the circulatory fluid in the body cavities of insects

that have an open circulatory system.

- Known as insect blood.

- Contains water, amino acids, sugars, salts and white blood cells

- Help to transport hormones, nutrients, salts and metabolic wastes

around the body.

- Does not contain haemoglobin

- Does not transport oxygen and CO2 in insects, these gases are

transported by the tracheal system.


26/188

OPEN AND CLOSED CIRCULATORY SYSTEM

a) Open circulatory system- found in insects, crustaceans (prawns) and molluscs (snails).

- blood pump from heart aorta arteries body

cavities.

- Haemolymph reach the body cells directly

- Haemolymph diffuses between body cells and re-enters the

heart through open-ended veins.


27/188

b) Closed circulatory system

- found in all vertebrates (human, fish) and invertebrates

(earthworms).

- blood is pump within a vessel and never comes in direct

contact with the body cells.

- can transport oxygen and other materials faster


28/188

THE STRUCTURE OF HUMAN BLOOD VESSELS

- The heart is connected to a series of tubes called blood vessels.

-The main types of vessels : artery, arterioles, capillary, venule and

vein.


29/188

ARTERIES

-Carry blood away from the heart at high pressure.

-Carry blood that is rich in oxygen (except in the pulmonary artery)

- have 3 layered walls consisting of:

a) endothelium inner layer, single flatten

cellb) smooth muscles and elastic fibres

thick middle layer

c) fibrous connective tissue external layer

-Able to transport blood under high pressuredue to the strength of the thick elastic fibres

-Contract their smooth muscles to decrease

the diameter of the lumen, decreasing the volume of blood flow.


30/188

- Relax their smooth muscles to increase the diameter of the lumen

and increase the volume of blood flow.


31/188

ARTERIOLES

-Smaller thin walled, branches of the arteries that end in capillaries.

- carry blood from arteries to the capillaries.

-Constrict and dilate to regulate blood flow and pressure.


32/188

CAPILLARIES

-Microscopic thin-walled (one-cell thick) blood vessels.

-Carry blood from arterioles to venules.

-Have diameters of about 7-9m

-Form capillary networks in most of the organs and tissues of thebody.


33/188

VENULES

-Small veins which carry blood from capillaries to the veins.

-Have 3 layered wall : inner endothelium, inner layer of muscle and

elastic tissue, outer layer of fibrous connective

tissue.

- Have thinner walls than arterioles.


34/188

VEINS

-Carry a slower-flowing blood at low pressure towards the heart.

-Carry deoxygenated blood (except in pulmonary vein).

-Have 3 layered walls, but these layers are thinner and less

muscular than those in the arterial wall. So, they collapse when

empty.

-Have internal valves (semi-lunar valves) to prevent a backflow

of blood.

- Have skeletal muscle to move the blood more quickly.


35/188

Vessels

Aspect

Artery Capillary Vein

Structure of

wall

3 layers

endothelium,

smooth muscles,fibrous connective

tissue

Single layer-

endothelium

3 layers-

endothelium,

smooth muscle,fibrous

connective tissue

Thickness of

wall

Thick Very thin Thinner than

artery

Direction of

blood flow

Away from the

heart

From arteries to

veins

Towards the heart

Valve Absent Absent Present

Oxygenated

blood

Yes (except

pulmonary artery)

Arteriole carry

oxygenated

blood.

Venule carry

deoxygenated

blood

Carries

deoxygenated

blood (except

pulmonary vein)


36/188

Blood pressure High Decreases from the

arteriole to the

venule

Low


37/188


38/188

STRUCTURE AND FUNCTION OF THE HUMAN

HEART

-Enveloped by a membrane called pericardium.

- Made up of cardiac muscles

-Cardiac muscles are made up of muscle fibres

-Each muscle fibre is made up of

interconnecting muscle cells.

-Muscle cells are joined one to another by

intercalary disc that allow the rapidtransmission of nervous impulses from cell to

cell through the tissue.

-Myogenic, it can relax and contract on its own (do not need nerve

to stimulate).

Contractile cell


39/188

Muscle fibre of a heart


40/188

-Has 4 chambers :

a) 2 upper auricles / atria

b) 2 lower ventricles

-A thick muscular wall, called medium septum completely separate

the right side of the heart from its left side.

-The heart functions as 2 separate pumps side by side:

(a) The right side of the heart pumps deoxygenated blood

(b) The left side of the heart pumps oxygenated blood


41/188

-Contraction of the atria:

(a) when the right atrium contracts, blood passes into the lower right

ventricle.

(b) when the left atrium contracts, blood passes into the lower left

ventricle.

-Contraction of the ventricle:

(a) when the right ventricle contracts, it pumps blood out into the

pulmonary arteries.

(b) when the left ventricle contracts, it pumps blood out into theaorta


42/188

-Thickness of the muscular walls:

(a) Atria have thinner and less muscular walls because they only

pump blood down the ventricles.

(b) Right ventricle has to pump blood to the lungs, and therefore

has a thick wall.

(c) Left ventricles has to pump blood to the body and has thickest

wall.

-Has 4 valves :

(a) Tricuspid valve on the right side of the heart

has 3 flaps

prevents the backflow of blood into

the right atrium when the

right ventricle contracts.(b) Bicuspid valve/ mitral valve

on the left side and has 2 flaps

prevents the backflow of blood into

the left atrium when the left

ventricles contracts.

Tricuspid

valve

Bicuspid

valve

Aorta

Pulmonary

artery


43/188

(c) Semi-lunar valves

found at the base of pulmonary artery and aorta

prevent the backflow of blood into the right and the left

ventricles when they relax.


44/188

Bicuspid valve (3D)Upper part tricuspid valve

Lower part bicuspid valve


45/188

TESTING YOURSELF


46/188

THE CIRCULATION OF BLOOD IN HUMAN

-Humans have closed, double circulatory system:

a) It is closed because the blood is contained within the heart and

the blood vessels, does not come in direct contact with the

respiring body cells.

b) It is double circulatory system because the blood passes

through the heart twice for each complete circuit of the body.

-Consist of 2 sub-circuits:

(a) Pulmonary circulation heart lung heart

(b) Systemic circulation heart rest of the body heart


47/188

Pulmonary

circulation

Systemic

circulation


48/188

PULMONARY CIRCULATION

- Deoxygenated blood from the heart is pumped from the right

ventricle through the pulmonary artery.

-Oxygenated blood from the lungs then return to the left atrium

through pulmonary vein.


49/188

SYSTEMIC CIRCULATION

- Supplies blood to all parts of the body, except the lungs.

-Oxygenated blood is pumped from the left ventricle into the aorta

before it is distributed by:

(a) subclavian arteries to the arms

(b) carotid arteries to the neck and head

-Superior vena cava collects deoxygenated blood from the upper

part of the body and return it to the right atrium.

-Inferior vena cava collects deoxygenated blood from the lower

part of the body and returns it to the right atrium.

-Heart receives blood form a pair of coronary arteries leading from

the aorta.


50/188


51/188

THE PUMPING OF HEART

- Two atria contract simultaneously:a) blood from the right atrium is forced into the right ventricle

b) blood from left atrium is forced into the left ventricle

- Two atria relax simultaneously:

a) left atrium receives blood from the pulmonary veinsb) right atrium receives blood from the superior upper part of

body) and inferior (lower part of body) vena cavae.

- After a slight pause, two ventricles contract (systole)

simultaneously :

a) blood in the right ventricle is forced into the pulmonary artery

and blood in the left ventricle is forced into the aorta.


52/188

b) Blood in the right ventricle and the left ventricle is prevented

from flowing back into the atria by the closure of bicuspid

tricuspid valve.

c) The simultaneous closure of the two valve will produce lubsound.

- When 2 ventricles relax (diastole):

a) the volume of the ventricles increase; drawing in blood from

the atria.

b) blood in the arteries (pulmonary artery and aorta) is prevented

from flowing back to the ventricles by the closure of both the

two semilunar valves, produce dub sound.

- A heartbeat consist of a systole (lub sound) and a diastole

(dub sound).

- Normal heartbeat 72 times/minute


53/188


54/188


55/188

BLOOD PRESSURE AND THE REGULATORY MECHANISM

- Blood pressure is the force that blood exerts on the walls of the

blood vessels, which is measured in millimetres of mercury

(mmHg).

- Caused by the contraction of the heart and by the muscles thatsurround blood vessels.

- Blood pressure in the arteries is highest when the ventricles

contract (systole) and force the blood into the pulmonary artery

and the aorta.

- Blood pressure decreases when the two ventricle relax (diastole).


56/188


57/188

-Normal blood pressure : 120/80 mmHg , 120 over 80

- The first number represent the pressure when the ventricles

contract.

-The second number represents the pressure when the ventricle

relax.

-In human, blood pressure is regulated by:a) nervous system send impulse to speed up or slow down the

heart rate

b) kidney regulate blood pressure by controlling the amount of

fluid in our blood. When blood pressure is too high, kidneysremove water from the blood (less volume of blood), blood

pressure become lower.


58/188

REGULATION OF BLOOD PRESSURE BY THE NERVOUS SYSTEM

-Baroreceptor / stretch receptors groups of nerve fibres within

the walls of the carotid sinus (a swelling of the internal carotid

artery) and the aortic.


59/188

-If blood pressure in the arteries is high:

a) the baroreceptors detect it and send impulses from the sensory

nerves to the cardiovascular centre in the medulla oblongata ofthe brain.

b) Cardiovascular centre of the brain sends impulses (in the vagus

nerve of the parasympathetic nervous system) to the heart to

decrease the heart rate and also the cardiac output (volume of

blood pumped by the heart).


60/188

c) At the same time, the cardiovascular centre sends nervous

impulses to relax the smooth muscles of the arterioles,causing the arterioles to dilate (vasodilation) and reduce the

resistance to blood flow.

d) A reduced heart rate, a lowered cardiac output and a

vasodilation of the arterioles will help to reduce the blood

pressure.


61/188

If bl d d t l


62/188

-If blood pressure drops too low:

i) The baroreceptors detect it and stimulate the cardiovascular

centre to send the nervous impulse (via the sympathetic nervous

system): to increase the heart rate (via the sympathetic nerve)

to stimulate the smooth muscles in the arterioles to contract

(vasoconstriction) to decrease flow of blood.

ii) An increased heart rate and a vasoconstriction of the arterioleswill help to increase blood pressure.


63/188

(Baroreceptor)/medulla

Stimulatesmooth

muscle

in the

arterioles

to contract


64/188


65/188

-Single circulation blood passes through the heart only once in

a complete circulation of the body

-Double circulation blood passes through the heart twice in acomplete circulation of the body

lizards, snakes, and turtles have incomplete septums,

oxygenated blood and deoxygenated blood may

mix to some degree.

In crocodiles a complete septum and a valve prevent this

from happening.

FISH


66/188

FISH

- Has a simple two-chambered heart, consisting of an atrium and

ventricle that are separated by atrio-ventricular valve.

-Atrio-ventricular valve prevents the backward flow of the blood

from the ventricle into the atrium.

-Blood circulation:

a) ventricle of the heart pumps deoxygenated blood to the capillary

network of the gills to be oxygenated.

b) Arteries carry the fully oxygenated blood from the gills to


67/188

b) Arteries carry the fully oxygenated blood from the gills to

various parts of body capillaries.

c) Deoxygenated blood from the body capilaries returns to the

atrium of heart.

Heart

(ventricle)Gills Body

Heart

(atrium)

-Fish have a

a) single circulation blood is pumped through the heart only

once.

b) closed circulation blood is always contained within the

heart and blood vessels.

-Disadvantage of the single circulation single heart has to pump

blood through the gill capillary network and the body capillary

network. Thus, reduce blood pressure and sluggish flow of blood


68/188


69/188

AMPHIBIANS

- Has 3 chambered heart, consist two atria and one ventricle

(partially divided).

-Blood circulation:

Pulmonary artery carries blood

from the ventricle to the

pulmonary capillary network,where gas exchange occurs.

Pulmonary vein returns

oxygenated blood from the lungs

to the left atrium of the heart

Vena cava returns deoxygenated

blood from the systemic capillaries

to the right atrium.

Single ventricle receives both

oxygenated blood and

deoxygenated blood.

Pulmonaryartery Pulmonary

vein

Vena

cavae

Aorta

When the ventricle contract a mixture of oxygenated and


70/188

When the ventricle contract, a mixture of oxygenated and

deoxygenated blood is pumped into both the pulmonary artery

and aorta.

-Amphibians have: incomplete double circulation although blood is pumped through

the heart twice in a circulation,

there is a mixing of oxygenated

and deoxygenated blood in the

ventricle. closed circulation blood is contained within the blood vessel

-Advantage for incomplete double circulation is higher blood

pressure, so the flow of blood is more efficient compared to fish.

BIRDS


71/188

BIRDS

-Have 4-chambered heart that completely separate oxygenated and

deoxygenated blood.

-Septum of the heart is complete, providing 2 separate circulatory

systems:

Pulmonary circulation right atrium and right ventricle

receives deoxygenated blood fromthe body and send it to the lungs

Systemic circulation the left atrium and left ventricle receive

oxygenated blood from the lungs and

sends it to the body tissues.


72/188

-Birds have higher metabolic rate than humans, the pulse rate of

chicken can reach 400 beats/minute.

-Its ventricle have more muscle mass and less chamber space than

human.

BLOOD CLOTTING


73/188

BLOOD CLOTTING

-Importance of blood clotting:

a) prevents excessive blood loss which make blood pressuredangerously low.

b) prevents the entry of microorganisms and foreign particles

into the body

c) forms scabs and helps in the healing of wounds

d) maintains the circulation of blood in a closed system

MECHANISM OF BLOOD CLOTTING


74/188

MECHANISM OF BLOOD CLOTTING

- Blood flowing in blood vessels is prevented from clotting by asubstance called heparin (family of carbohydrate) found in the

blood plasma.

-Blood clotting is initiated by the:

a) clotting factors from damaged cells e.g. fibrinogen, prothrombin, thromboplastin, calcium ions

b) Collagen fibres from damaged blood vessel wall

- Mechanism of blood clotting:

Damaged blood vessel,I th f l i


75/188

Damaged blood vessel,tissue or platelets releasean enzyme,thrombokinase (also

known as thromboplastin,which is a protease)

In the presence of calciumions and vitamin K,thrombokinase convertsthe protein prothrombin to

thrombin

Thrombincatalyses theconversion of thesoluble proteinfibrinogen toinsoluble fibrin

Fibrin, a fibrous

protein, form ameshwork of fibresover the woundtrapping the red bloodcells and seals thewound

The trappedcells dry andharden forminga protectivescab.

IMPAIRED BLOOD CLOTTING MECHANISM


76/188

IMPAIRED BLOOD CLOTTING MECHANISM

a) Deficient in calcium and vitamin K:

o It will take a longer time than normal

o cause bleeding

b) Haemophilia

Blood is unable to clot because the deficiency of blood

proteins

Cause bleeding or death

c) Thrombosis

Thrombosis is the formation of a clot or thrombus inside a

blood vessel, blocking the flow of blood. The blockage stops the tissues from receive blood flow and

oxygen

cause damage to the tissues in that area

A l t f d i t h t tt k


77/188

A clot formed in coronary artery cause heart attack.

A clot formed in the brain cause strok.

Heart attack Strok

LYMPHATIC SYSTEM


78/188

LYMPHATIC SYSTEM

-The space between tissue cells

interstitial space

-Interstitial space is filled with a

colourless liquid interstitial fluid

-The formation of interstitial fluid andlypmh :

a) Blood enters the arterial ends of the

capillary network under high pressure

b) Endothelial cell walls of the capillaries act as filter. Large cellularcomponents (red blood cell) and large protein molecules cannot

pass through. Only water and dissolved substances of

the plasma (oxygen, products of digestion and hormone) can

diffuse out of the cell.

c) Blood plasma diffuse out into the interstitial spaces to form


79/188

c) Blood plasma diffuse out into the interstitial spaces to form

interstitial fluid.

d) The process of producing interstitial fluid from the blood is

called ultrafiltration.

e) The interstitial fluid circulates among the tissue cells and

returns to the blood circulatory system in two ways:

(i) passes into the venous end of the capillaries

ii) drain into the lymph capillaries as lymph


80/188

ii) drain into the lymph capillaries as lymph

f) Lymph and interstitial fluid have the same composition, thedifference is interstitial fluid is found between the cells, while

lymph is found inside the lymph vessel.

Fluid

CharacteristicBlood Plasma Interstitial fluid Lymph


81/188

Characteristic

Appearance Red Light yellow Pale brown

colour

Clear watery

fluid, sometimes

yellowish

Location Within the heart, arteries, veins

and capillaries

Interstitial

space

Within the

lymph vessel

Originate from Bone marrow,

lymph nodes,

thymus gland

Water and

dissolved

substances

absorbed byalimentary

canal

Plasma Interstitial fluid

and fatty acids

absorbed by the

ileum

Function Transport and

defence

Transport

over long

distance

Transport over

short distance

Transport and

defense

Moved by Pumping of the heart, muscle

contraction, breathing action

Hydrostatic and

osmotic forces

Hydrostatic

forces, muscle

contraction,

breathing action


82/188

Direction of

flow

Circulates around the

body and back to the

heart

Out of the arterial

end and returns into

the venous ends of

the capillaries

From the tissues

and towards the

heart

Contents Blood Plasma Interstitial fluid Lymph


83/188

y p

Water

Plasma

proteins(albumin,

globulin,

fibrinogen)

X (proteins

remain inblood

capillaries)

Platelets X X X

Leucocytes X X (lymphocytes)

erythrocytes x x x

Ions

(Na+,K+,Ca2+)

Nutrients

(glucose,

amino acids,

fatty acids,

vitamin)

(more fats

from lacteal)

Waste products


84/188

Waste products

(urea, uric acid)

Gases

Hormones

- The importance of interstitial fluid:

a) tissue fluid fills the interstitial spaces between the tissue cells,

providing them with a stable external environmentb) nutrients and oxygen from the bloodstream in the capillary

network diffuse across the capillary walls into the interstitial fluid

and then into the tissue cells.

c) waste products that accumulate within the active cells diffuse

in the opposite direction across the interstitial fluid from the cells

to the capillaries.

STRUCTURE OF THE LYMPHATIC SYSTEM


85/188

-Lymph is found inside the lymph vessels.

-The composition of lymph is similar to interstitial fluid but with

more fats.

-Main structures of the lymphatic

system:a) Lymphatic capillaries:

- larger in diameter than the

blood capillaries

- located next to blood

capillaries in tissue spaces

- very permeable to tissue

fluid

- found as lacteals in the villi

of the small intestine

b) Lymphatic vessel


86/188

b) y p at c esse

- formed from lymph capillaries

- similar as veins (have 3 layered walls), but have thinner

walls and more valves

- carry lymph away from the tissues

c) Lymph node

- small round or oval structures

- contains a network of fibres and irregular channels acting

like a filter- filter lymph when it

flows through the

nodes

- eliminates bacteria

and cellular debris byphagocytosis

d) Spleen


87/188

) p

- an organ located on the left side of the abdomen near the

stomach

- produce lymphocytes, filters the

blood, store blood cells, destroy oldblood cells.

e) Lymph ducts (larger lymph vessel)

- lymph vessels drain their contents

back into the bloodstream- Thoracic duct (left lymphatic duct)

and right lymphatic duct.

-Movement of lymph within the lymphatic system;


88/188

Movement of lymph within the lymphatic system;

a) interstitial fluid drains into the lymph capillaries to form lymph

b) lymph capillaries join together to form larger lymphatic vessel

c) the walls of the lymphatic vessels contain

valve-like pores that allow the entry of cell

debris and bacteria

d) the contraction and relaxation of the

skeletal muscle contract and relax the

lymphatic vessel, pushing lymph to the

lymph nodes

e) Semilunar valves within the lymphatic

vessels keep the flow of lymph in one

direction

f) Lymph nodes remove the suspended solid and bacteria from


89/188

) y p p

the lymph by phagocytosis

g) The lymphatic vessels return the lymph to the heart via two ducts:

i) Right lymphatic ducts- drain lymph from the right arm, right side of head and the

thorax and opens into

the right subclavian vein

near the heart

ii) the thoracic duct (leftlymphatic ducts) drains

lymph from the rest of the

body into the left

subclavian vein near the

heart


90/188

Right subclavian vein

- Lymph is moved along the lymph vessel by:


91/188

a) Hydrostatic pressure of interstitial fluid- push lymph along the

lymphatic capillaries

b) Contraction of skeletal muscle lymph flow along the lymphaticvessel

c) Valves within lymphatic vessel lymph flow away from the tissue

to the heart in one direction

d) Inhalation reduce pressure in thoracic cavity and drawing lymph

towards the thorax.

Lymphatic capillaries Lymphatic vessel Lymphatic nodes


92/188

Lymphatic capillaries Lymphatic vessel Lymphatic nodes

Lymphatic vessel

Right lymphatic duct

Left lymphatic duct

Superior vena

cavaeHeart

Right subclavian

vein

Left subclavian

vein


93/188

-Function of lymphatic system:


94/188

a) transport interstitial fluid back to the bloodstream

b) distributes fluids and nutrients in the body and drains excess

fluids and protein so that tissues do not swell upc) transport fat and fat-soluble vitamin from small intestine into

the blood circulation

d) provides immunological defence against disease by:

(i) produce lymphocytes and antibodies to fight and destroy

microorganisms(ii) filtering out microorganisms and other foreign substances

from the lymph by the lymph nodes and from the blood by

the spleen.


95/188

WHEN INTERSTITIAL FLUID FAILS TO RETURN TO THE


96/188

CIRCULATORY SYSTEM

-Too much interstitial fluid is produced, but little or none isreabsorbed back into the circulatory system.

-Cause the organs and tissues of the body to swell up- oedema

-Oedema can be caused by:a) increase in the capillary blood

pressure, forcing an excess fluid

leakage to the interstitial space

b) blockage of the lymphatic vessel

which slows down the drainage

of excess interstitial fluid.

-Elephantiasiscaused by the blockage of the bodys lymphatic


97/188

system by certain parasitic round worms leading to oedema.

ROLE OF THE CIRCULATORY SYSTEM IN BODY DEFENCE MECHANISM


98/188

Line of defencemechanism

Inborn, nonspecificdefence mechanism

First line ofdefence

- Skin

-mucous

membrane

Second line ofdefence

-White blood cell

Acquired, specificdefence mechanism

Third line of defence- Lymphocytes

- Antibodies

-First and second lines of the defence mechanism:


99/188

a) nonspecific they do not distinguish infectious pathogens

b) inborn they are natural built-in defences

- for example :skin act as barrier to the pathogens

: phagocytesengulf pathogens

c) provide immediate protection against invading pathogens.

-Third line of defence mechanism:

a) specific distinguish specific pathogens. For example,

lymphocytes produce specific type of antibody to fight

pathogens.

b) Acquired and developed

c) takes a longer time to be effective, but remember the pastinfections. So, it can be better prepared for future invasions by the

same type of pathogens.

FIRST LINE DEFENCE


100/188

-Skin

provides a continuous layerprotect a whole body.

Few microorganisms canpenetrate the layers of deadcells at the surface of the skin.A cut in the skin allow themicroorganisms to enter the body.

Blood clots plug the wound and prevent the entryof microorganisms.

-Mucous membrane


101/188

lines all tissues and organs such as respiratory,digestive, urinary and reproductive tracts.

secrete mucus, which is thick, slippery liquid thatprotect the membrane and keep it moist and soft.

protect the interior surfaces of the body that may beexposed to pathogens

-Both the skin and mucous membrane are nonspecificdefence because:

a) use the same barrier against all types ofmicroorganisms

b) not directed against any particular pathogens


102/188

CHEMICALS USE BY SKIN AND MUCOUS MEMBRANE


103/188

CHEMICALS USE BY SKIN AND MUCOUS MEMBRANE

-Perspiration/sweat Excreted from sweat glands contains lysozyme and

acids that destroy harmful bacteria and inhibits thegrowth of fungi.

-Lysozyme

also present in tears, saliva and nasal secretion

-Sebum low pH prevents the growth of certain microorganisms

and fungi

- Mucus trap microorganisms and dirt particles


104/188

trap microorganisms and dirt particles.

-Cilia little hair that carry the mucus,trapped microorganisms and dirttowards the glottis to the throat

- Acid in gastric juice kills microorganisms present infood or water on in swallowedmucus.

SECOND LINE DEFENCE


105/188

-Take action when pathogens can penetrate the skin

or mucous membrane.

-Nonspecific immune response because use samemethod of defence to all type of pathogens.

-The nonspecific immune response include:a) phagocytosiscarried out by white blood cells such

as neutrophils, macrophages andoccasionally eosinophil.

b) natural killer cellsdestroy infected cells and pre-cancerous cells.

c) Inflammationinvolve redness, heat, swelling, pain


106/188

d) Feverhigh temperature kill bacteria bydenaturing their protein and help healing

process

PHAGOCYTOSIS


107/188

-Phagocytosis (phago = eat; cyte = cell) attack,

engulf and destroy pathogens

-Two common types of phagocytes are neutrophils andmacrophages

-Neutrophils: circulate freely through the blood vessels squeeze between cells of the capillary wall to reachthe site of infection, attracted by the chemicals

released by the microorganisms (chemotaxis). first phagocytes to arrive at the injured tissues beforemacrophages.


108/188

-Macrophages


109/188

p g another type of phagocyte developed frommonocytes (white blood cells)

longer-lived and arrived at the inflamed site some3-7 days later after the neutrophils.


110/188

Phagocytes extendits plasmamembrane(pseudopod) aroundthe pathogens

Bacterium engulfedand enclosed in aphagocytic vesicle(phagosome)

Lysosome, amembrane-boundorganelle containing

hydrolytic enzyme,fuse with phagosometo formphagolysosome

Bacterium is

destroyedby enzymes

Afterdigestion,indigestiblematerial is

dischargedfromphagocytes

PROCESS OFPHAGOCYTOSIS


111/188

NATURAL KILLER CELLS


112/188

NATURAL KILLER CELLS

INFLAMMATION


113/188

THIRD LINE OF DEFENCE


114/188

- Immunity : ability of the human body to resist infection

- Immune response : bodys defence reaction when anantigen is recognized and specific antibodies are

produced by lymphocytes to defend againstpathogens

- Antigen : foreign protein molecule (bacteria, virus,fungi) that enter the body and stimulate the

production of antibodies

- Antibody : a protein substance produced by immunesystem to recognize antigen.

: Y shaped protein molecule that also knowni l b li


115/188

as immunoglobulin.: functiondestroy or weaken a pathogen and

neutralise its toxin

- 2 white blood cells that involved:a) lymphocytesproduce antibodiesb) macrophages - phagocytosis

- Antigen recognition and the production of antibodiestakes place when:


116/188

takes place when:

When pathogens enter the humanbody, it stimulate lymphocytes toproduce specific antibodies

Lymphocytes recognize thetype of pathogen by the uniqueantigen on the surface ofpathogen

Lymphocyte produceantibodies to match themolecular shape of antigens

Antibodies attack antigens bybi di t th i ti


117/188

binding to them, using antigenbinding sites

Antibodies start to kill thepathogen in several waysbefore it is digested bymacrophages


118/188

WAYS WHICH ANTIBODIES HELP TO DEFENSE BODY


119/188

a) Agglutinationb) Opsonisationc) Neutralisationd) Precipitation

AGGLUTINATION


120/188

-Antibodies and antigens stick together and the

microorganisms clump together in large numbersmaking the antigens harmless.

-The inactive pathogens are then ingested by

phagocytes.

OPSONISATION


121/188

- An antigen is covered with antibodies which make it

easier for ingestion by phagocytes.

-An antibody-coated pathogen can be made to burst(cell lysis), killing it before being ingested by phagocytes.

Cell produce fromdifferentiation of

monocytes


122/188

NEUTRALISATION


123/188

- Antibodies bind to the toxins (antigens), neutralise the

poison of the toxin.

-When an antibody binds to a toxin, it is called antitoxin

-The neutralised toxin is then ingested by thephagocytes

-Virus and bacteria are similarly neutralised to preventthem from attach and penetrate the body cells.


124/188

PRECIPITATION


125/188

- Antibodies bind to the soluble antigens, cause them

to precipitate.

- Then, they will be ingested by phagocytes.

VARIOUS TYPES OF IMMUNITY


126/188

-

After an initial infection, some lymphocytes are keptin the body as a memory. This helps the body todefend itself against further attacks by the sameantigens.

-As this memory may last for years, the body is said tobe immune to the disease.

-There are 2 types of immunity:

a) active immunityb) passive immunity

Active immunity Passive immunity


127/188

Active immunity Passive immunity

Acquired when

lymphocytes in thebody are activated byantigens to produceantibodies

Occur when a person

becomes temporaryimmune to an antigen byreceive ready-madeantibodies from anotherperson or animal.

Lasts for a long time Lasts only for a short timeas the antibodieseventually die off orremoved from the body asforeign proteins.

ACTIVE


128/188

IMMUNITY

NATURALACTIVE

IMMUNITY

-Lymphocytes

are activated

by antigens

to produce

antibodies

- Natural

infection

ARTIFICIALACTIVE

IMMUNITY

- Antigens are

injected into the

body to artificially

stimulate the

lymphocyte toproduce antibodies

- Vaccination


129/188

- Some vaccines are made from:a) live attenuated (weakened) pathogensmeasles,


130/188

) ( ) p gmumps, rubella, chickenpox

b) killed pathogensinfluenza, Japanese encephalitis(J.E), hepatitis A, typhoid fever

c) toxoidbacterial toxin that has been weakenedand no longer toxictetanus, diphtheria

EFFECTS OF HIV ON THE BODYS DEFENCE MECHANISM


131/188

-HIV : Hfor Human, because it infect humans

I - Immunodeficiency, because virus attack thebodys immune system, weakening it so thatit cannot fight other deadly disease

VVirus belong to the group, retrovirus

- AIDSAcquired, person get HIV from another infectedperson


132/188

person.- Immune, refer to the bodys defence system

- Deficiency , making the immune systemdeficient

- Syndrome, refer to a group of illness

When HIV infects a person


133/188

When HIV infects a person,HIV antibodies is producedto fight pathogens. But, HIVantibodies cannnot fight theinfection

HIV weakens the immune

system , attack thelymphocytes (T -cell)

HIV uses its RNA and DNA of T-

cells to replicate, thusdestroying the T-cells

Destruction of T-cells by HIVweakens the immunesystem making the


134/188

system, making theinfected personimmunodeficient

A weak immune systemcannot effectively defendthe body against otherpathogens


135/188


136/188

- When the immune system is weakened:a) the body becomes vulnerable to a variety of


137/188

a) the body becomes vulnerable to a variety ofinfections and cancers.

b) other infections take advantage of the weakenedimmune system. These called as opportunisticinfections.

c) the body becomes so weak, and the person dies.


138/188

TRANSPORT OF SUBSTANCES IN PLANTS


139/188

-Transport system is necessary because:a) CO2 is absorbed and transported to

photosynthesising cellsb) O2 is released from photosynthesising cells into

the atmosphere.c) water and minerals from the roots have to be

transported to the leavesd) photosynthetic products (sugar, amino acids)

have to be transported away from the leaves

for storage and to other tissues.

- Transport functions are carried out by xylem andphloem.

VASCULAR TISSUE IN STEM, ROOT AND LEAF


140/188

-Consist of phloem and xylem.

- Roles of vascular tissue:a) xylemtransport water

support the plantsb) Phloemtransport nutrient

- Vascular bundle strand of conducting tissue

(xylem and phloem) Stemphloem is located

outward facing theepidermis, xylem is toward the centre.

Leafphloem facing at the lower part, xylemat the upper part.


141/188

- A mature vascular bundle consist of xylem, phloemand cambium. Cambium separate the xylem andphloem.

STRUCTURE OF VASCULAR TISSUE


142/188

- The main tissues in a stem of a dicot :a) epidermisb) cortex, that contain collenchyma, chlorenchyma

and endodermisc) vascular bundle, that contain phloem and xylem

d) the pith


143/188

- The pith is the tissue located inside the vascular bundlering.


144/188

g

-

Parenchyma- cells with thin primary walls that retaintheir protoplasm- Collenchyma - cells with thick primary walls that

retain their protoplasm- Sclerenchyma- cells with lignified secondary walls

that have lost their protoplasm atmaturity, i.e. are 'dead'

- Chlorenchyma - Containing Chloroplast

VASCULAR TISSSUE IN THE LEAF OF A DICOT


145/188

- Vascular bundle consist of:a) xylemfaces the upper epidermisb) cambiumthat divides to produce xylem and

phloem cellsc) phloemfaces the lower epidermis

VASCULAR TISSUE IN THE ROOT OF A DICOT


146/188

- Vascular tissue is packed in the centre.

- Other structures observed in the root:a) root hairextension of the epidermal cells

- increase absorption of water by the

surface

b) epidermisabsorption of water and minerals

c) cortexconsist of endodermis and parenchyma cellthat store starch.

d) pericyclelayer of parenchyma cells inside theendodermis where lateral root originate


147/188


148/188

RELATING THE STRUCTURE OF XYLEM TO TRANSPORT


149/188

-

Functions of xylem:a) transport water and dissolvedminerals from the root toother parts of cell (one way).

b) provide mechanical support

- Xylem consist:a) vesselb) tracheid

c) fibre (rigid secondary cell wallfor support and protection)

d) parenchyma (store food)

- Vessels Dead cells that form hollow tube, which connect

the root to the leaf


150/188

the root to the leaf. Deposited by lignin to strengthen it and support

the stem

The structure of xylem vessel is adapted totransport water because :

o it has continuous lumen without any walls andprotoplasm within it to allow the flow of waterand minerals salts

o the walls are lignified to provide strength andprevent the water from collapsing


151/188

- Tracheids Dead cells when matured


152/188

Long, slender cells with tapered, overlapping end

Have thick, hard, lignified secondary cell wall Smaller lumen than xylem vessel No sieve plates at the end walls

- The movement of water in tracheids:a) water moves sideway through the pits in adjacent

tracheid cells before going upward


153/188

tracheid cells before going upwardb) movement of water upwards is slower than in

vessel

RELATING THE STRUCTURE OF PHLOEM TO TRANSPORT


154/188

-Transport food such as sugars and amino acids fromthe leaves for storage in stem and root

- Transport food from storage in roots to other parts of

plants.

- 2-way flow

- Components of phloem :a) sieve tube


155/188

b) companion cells

c) parenchymad) fibres

a) Sieve tube


156/188

- made up of a single row

of elongated and thin-wallliving cells called sieve tubecells.

- A mature sieve tube has onlythin layer of cytoplasm, nonucleus or central vacuole,lost most of its organelles

- Sieve plates separate sievetube cells at both ends.

- Sieve plates allow cytoplasmicconnections between vertically-stacked cells that willtransport food by diffusion and active transport.

b) Companion cell

lie next to each sieve tube cell


157/188

- lie next to each sieve tube cell- has a nucleus, endoplasmic

reticulum, ribosomes andmitochondria

- provide metabolic support for thesieve tube cells in the transport of

manufactured food


158/188

TRANSLOCATION


159/188

- Movement of sugars and other organic materials fromone place to another within the plant body

- The importance:a) distribute food to other parts of the plants such as

seed, root, tuber.b) without translocation, plants would not be able to

metabolise food for energy, growth andmaintenance

TRANSPIRATION


160/188

-The loss of water by evaporation from the parts of

plants through the stomata of the leaves.

-Transpiration occur:a) mainly through the open stomata90% of water

b) waxy cuticlevery little water escape through thecuticle of the leaves

c) lenticels of woody stem


161/188

PROCESS OF TRANSPIRATION


162/188

-There are intercellular air spaces among the spongymesophyll cell.

- Spongy mesophyll cell hasmoist surface

- Water evaporates fromthese cells into theintercellular spaces and

diffuse through the stomatato the drier air outside theleaf.

- As these border of mesophyll cells lose water, their cellsap becomes more concentrated and therefore drawswater by osmosis from the cells deeper inside the leaf.


163/188

water by osmosis from the cells deeper inside the leaf.

- These cells in turn draw water from the xylem of theplant veins by osmosis.

-Water forms an unbroken water chain (by cohesion and

adhesion force of water molecule) from the outersurface of leaves to the roots.

-As the water evaporates from the plant leaves, theyattract other water molecules which are still in the plantsto the top.


164/188

Transpiration in plants

THE IMPORTANCE OF TRANSPIRATION


165/188

- The roles of transpiration:

a) cooling the plants As water evaporates from the leaves, it remove

heat from the plant in the form of latent heat of

vaporisation, thereby cooling the plant

b) Provide support by turgor pressure because water diffuse from higher concentration

to lower concentration, all the cells in the plantsbecome turgid.

c) Transport water and mineral salts

Transpiration create a transpiration pull, liftingt d di l d i l lt th l t


166/188

water and dissolved mineral salts up the plant

from the root to the leaf.

- Negative effect of transpiration:a) if the rate of transpiration exceeds the intake of

water by the roots, plants growth would be affectedb) any excess loss of water causes the plant to wilt and

die

THE PATHWAY OF WATER FROM SOIL TO THE LEAVES

Soilwater


167/188

water

Root haircell

Cortex

Xylem

vessel ofthe root

Xylemvessel ofthe stem

Vein lo leaf

MesophyllcellStomata


168/188

Absorption and movement of water in plant

MOVEMENT OF WATER FROM SOIL TO ROOT


169/188

- The cell sap of root hairs is more concentrated than

soil water.

-The high solute concentration of the cell sap is due tothe active transport of the solute molecules into the

cell.

-Water moves from the soil water into the cell sap of roothair by osmosis.

-When water enter the vacuole of the root hair cell:a) the cell sap becomes dilute and its concentration

and osmotic pressure are reduced

b) the turgor pressure of the cell increase and reduceits suction pressure

c) the cell sap become hypotonic the cell sap of


170/188

c) the cell sap become hypotonic the cell sap ofadjacent cell

- Water from hypotonic root hair cell sap move toadjacent hypertonic cells.

-Therefore, water move out from the root hair cell into theadjacent cells, cortex and then into the xylem.

PATHWAY OF WATER UP THE STEM


171/188

-The movement of water in the xylem up the stem iseffected by:a) root pressureb) transpiration pullc) cohesion- adhesion theory of water

a) Root pressure

- the pulling of water into the xylem from the


172/188

p g ysurrounding cells produces a hydrostatic pressure

inside the xylem, forcing water upwards.- this positive pressure is called root pressure.

b) Transpiration pull- when water evaporates from mesophyll cells, their

cell sap becomes more concentrated


173/188

cell sap becomes more concentrated.

- these mesophyll cells in turn draw water byosmosis from the cells foundin deeper inside the leaf.

- these inner cells which areadjacent to the veins drawwater from them by osmosis.

- the column of water iscontinuous from the root upto the leaves

- as the mesophyll cells suck water from the xylemvessel, the whole column of water is pulled up fromroot to leaf (due to cohesive and adhesive of water


174/188

root to leaf (due to cohesive and adhesive of water

molecule)

- The pulling force is called transpiration pull


175/188

EXTERNAL CONDITIONS AFFECTING TRANSPIRATION


176/188

- The amount of water lost from the plant in transpiration

depend on:a) light intensityb) temperaturec) relative humidity

d) air movement


177/188

b) Temperature- High temperature increase the kinetic energy of

water molecules which increases the rate of


178/188

diffusion through the stomata

- the rate of transpiration is directly proportionalto temperature

c) Relative humidity

- intercellular air spaces in the leaf are saturated with


179/188

intercellular air spaces in the leaf are saturated with

water vapour.

- water vapour diffuse from the intercellular space tothe air outside.

- this saturated water vapour diffuse out of the leaf ata :

i) higher rate if the air outside is dry (higherrelative humidity)

ii) lower rate if the air outside is damp (lower ratehumidity)


180/188

Graph humidity

d) Air movement

- In still air water vapour that diffuse out through the


181/188

- In still air, water vapour that diffuse out through the

stomata forms a layer of still moist air around theleaf

- Moist air decrease the rate of water vapour diffusionand drop the rate of transpiration.

- Moving air carry away this layer of moist air formedaround a leaf and increase the rate of transpiration.

- The rate of transpiration is directly proportional tothe velocity of the air current.


182/188

THE OPENING AND THE CLOSING OF THE STOMA


183/188

-

The uneven thickening of the outer and inner wall ofthe guard cells provide a mechanism for the openingand the closing of the stoma.

- The inner concave wall of each

guard cell is very thick, butthe outer convex wall is thinner

- For high light intensity, the rate

of photosynthesis increase andthe guard cells absorb waterand become turgid.

- Water in each guard cell push the thin outer wallthat enlarge the stomata opening.


184/188

-Under poor light, the turgor pressure of the guard cellsdrop, it become flaccid and the stoma becomesmaller or closes.

HOW STOMA OPENS IN DAYLIGHT

Photosynthesis take place in the guard cell


185/188

- Photosynthesis take place in the guard cell

Sugaraccumulates in

guard cell

Osmoticpressurein guard

cell

increase

Waterenter theguard cellby osmosis

Guardcell

becometurgid

Stoma opens

- Photosynthesis take place in the leaf cells

Concentration of pHStarch in the

cell is


186/188

CO2 in the leaf cell

drops

goes

up

cell is

convertedinto sugar

Stoma open

HOW STOMA CLOSES AT NIGHT


187/188

- Photosynthesis in guard cells stop

Concentration ofsugar in guardcell decrease

Osmoticpressure in

guard celldecrease

Waterleaves

guard cellby osmosis

Guardcell

flaccid

Stoma close


188/188

chapter 10 : transport

Documents