9.2.3 plants and animals regulate the concentration of gases, water and waste products of metabolism...
TRANSCRIPT
9.2.3
• Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and interstitial fluid
• TEXTBOOK – Chapter 3; Pg. 70 - 102
Friday 23rd November
• AIM – To be able to explain why the concentration of water in cells should be maintained within a narrow range AND why the removal of wastes (excretion) is essential
• REF – TEXT Pg. 70 – 72, KISS Pg. 24-25
Excretion - DEFINITION• Process by which substances formed during body
reactions (cellular activity) are removed from the body• Excretion may occur via:– the kidneys – urination– the lungs – removal of CO2
– skin – sweating (water & salts)– and large intestine – excretion of bile pigments
• NB - normal passing of undigested substances is NOT excretion because they are not products of metabolism, instead = defaecation
Diffusion
Smell Particles & Air Particles
Solution
Smell Particles diffused evenly into the Air Particles
Diffusion is the passive movement of particles from a high concentration of particles to a lower
concentration until they are spread out evenly
Diffusion
• This is similar to what happens when you dissolve sugar or coffee granules in water ....
Sugar Particles & Water Particles
Sugar particles diffused into water Particles = solution
Solute
Solvent
Solution
Diffusion Notes
• Diffusion does not require energy – it’s passive
• Diffusion depends on the random movement of particles.
Solutions
• A solution is made up of two parts: the solute and the solvent.
• The solute dissolves in the solvent• Before a gas can diffuse across a membrane it
must dissolve into a liquid.
Diffusion & Gas Exchange• Animal cells use oxygen, so oxygen is less concentrated
inside the cell than outside. This causes oxygen to diffuse into the cell
• Carbon dioxide is produced in an animal cell, so it is more concentrated inside than outside – so it diffuses out of the cell
Diffusion for Photosynthesis
• Diffusion of gases also happens in leaves:
• For photosynthesis to happen Carbon Dioxide has to get inside the leaves. It diffuses in through stomata
• Water vapour and oxygen diffuse out of the leaf at the same time
Water + Carbon Dioxide → Oxygen and Glucose (& a little water)
Rate of Diffusion
• The rate of diffusion depends on:• Size of the particles: smaller = faster• Temperature (eg. kinetic energy): hotter = faster• The concentration gradient: the higher it is =
faster the rate.• State of the particles: gas > liquid > solid• Distance - thickness of the exchange surface:
thinner = faster• Surface area available: larger = faster
Facilitated Diffusion
• Transport proteins carry specific molecules across the cell membrane
• Movement is along a concentration gradient (i.e. From higher to lower)
• Each type of transport protein will carry only one type of molecule.
• This is how glucose is moved.
Facilitative Diffusion
Investigating the importance of Surface Area for Cells
• Raw materials enter a cell by diffusion via the cell membrane. The number of molecules which diffuse into a cell depends on its surface area. To function efficiently a cell needs a large surface area relative to its volume
Osmosis Defintion
• Osmosis is a special type of diffusion. • Osmosis is the diffusion of water.
Osmosis is the movement of water molecules from a high concentration
of water to a low concentration of water through a semi-permeable
membrane
Osmosis Experiment
1. Fill the partially permeable membrane with strong sugar solution
2. Tie it to a capillary tube and stand it in a weak sugar solution
3. Use your ideas about osmosis to explain why the liquid rises in the tube
Glass tube Level of sugar solution
Weak sugar solution
Visking Tubing with Strong Sugar solution
Osmosis in Potato Cells
1. Cut three potato chips to exactly the same size. Measure their length and write it down.
2. Label and Set up the following test-tubesa) Distilled waterb) Weak sugar solutionc) Strong sugar solution
3. Place one chip in each test-tube and leave it for 30 minutes
4. Re-measure each chip
Questions: Osmosis in Potato Cells
1. Which chip has increased in size? Write a sentence to explained what has happened in relation to osmosis.
2. Which chip has got shorter? Use your knowledge of osmosis to explain this.
3. Feel the chip that was in test-tube A. Why does it feel firm?
Osmosis and Cells - Notes
• Cells are surrounded by a cell membrane that separates the contents of the cell from the outside environment. The cell membrane has tiny holes in it. This allows small molecules to pass through, but not large ones. The cell membrane is partially-permeable.
• Osmosis occurs when two solutions are separated by a partially permeable membrane
Class Activity: Correctly LabelWeak Solution
Strong Solution
Solute Molecule
Water Molecule
Partially Permeable Membrane
Which way will the water flow???
Types of Solutions
• Isotonic – when both solutions have the same concentration
of dissolved substances• Hypotonic– A solution with a lower concentration of dissolved
substances (ie. More water cf. solutes)• Hypertonic– A solution with a higher concentration of
dissolved substances (ie. More solute cf. water)
Cells in distilled waterWhat type of solution?
Cells in a salt solutionWhat type of solution?
Water in
Cells eventuallyexplode
Water out
Cells shrivel &die
Osmosis
Hypotonic Hypertonic
Plasmolysis in Elodea
Plasmolysis in Elodea: http://www.mrphome.net/mrp/Membrane_Transport.html
Osmosis & pH
• Can you relate CO2 concentration and the need for water balance to maintain pH, and therefore homeostasis?
• REF – Text book Pg. 72, KISS Pg. 25
The importance of the removal of wastes
• Accumulation of wastes may be toxic to cells and so metabolic wastes and so must be excreted as soon as possible. – Nitrogenous Wastes (contain Nitrogen)• Ammonia – increases pH• Uric Acid – birds, reptiles, insects• Urea – mammals, amphibians
– Carbon dioxide• Changes to acidity affect the optimal functioning of
enzymes.
HOMEWORK
• Read Reference Pages:– Text Pg. 70-72– Kiss Pg. 24-25
• Complete worksheet 11 KISS booklet
DATE
• Aim – To be able to explain why diffusion & osmosis are inadequate in removing nitrogenous wastes in some organisms AND Identify the role of the kidney in the excretory system of fish and mammals
• REF – Text Pg. 72-74, 76, KISS Pg.
Problems with Diffusion & Osmosis
• They are PASSIVE transport and are therefore, SLOW
• They rely on a concentration gradient and therefore reach EQUILIBRIUM & so not all wastes would be removed
• Osmosis may cause TOO MUCH water to be lost in urine
• THEREFORE ACTIVE TRANSPORT IS ALSO REQUIRED TO ENSURE ADEQUATE HOMEOSTASIS
The Kidneys & Homeostasis
• The kidneys are part of the body’s excretory system
• The kidneys basically act as filters to “clean” the blood
• They perform three main roles:1. Remove urea from the blood2. Adjustment of ions (salts) in the blood3. Adjustment of water content in the blood
Kidney: Structure
• Kidneys are located on the dorsal wall of the body and have fat stored around them.
1. Removal of Urea
• Urea is produced in the liver.• Proteins can NOT be stored by the body so
excess amino acids are broken down by the liver – this is called deamination
• The waste product is urea, which is passed into the blood to be filtered out by the kidneys. Urea is also lost partly in sweat.
• Urea is poisonous and must be excreted.
2. Adjustment of Ion content
• Ions such as sodium are taken into the body in food, then absorbed into the blood.
• Excess ions (salts) are removed by the kidneys.• Some ions are also lost in sweat (which tastes
salty).• The important thing to remember is that the
balance of ions is maintained by the kidneys = homeostasis
3. Adjustment of water content• The hypothalamus in the brain monitors the water
content of the blood and instructs the pituitary gland to release the hormone ADH (Anti-diuretic hormone) into the blood accordingly:
Too little water in blood:1. Hypothalamus detects &
Pituitary releases ADH2. More ADH enters kidney -
more water is reaborbed3. So less urine which is more
concentrated is produced
Too much water in blood:1. Hypothalamus detects &
Pituitary releases LESS ADH2. Less ADH enters kidney - less
water is reaborbed3. So more urine which is less
concentrated is produced
The Nephron
1. Ultrafiltration at the Bowman’s Capsule – high pressure squeezes water, urea, ions & glucose out of blood (big molecules eg. Proteins stay in the blood).
2. Reabsorption along the nephron – all sugar & sufficient ions are actively reabsorbed. Sufficient water is reabsorbed according to the level of the hormone ADH.
3. Secretion – excess ions and chemicals such as drugs are excreted into nephron
4. Release of wastes as urine - urea, excess ions and water are not reabsorbed and pass from the collecting duct to the ureter to be excreted as urine.
Thursday 29th November
• Aim – To explain how filtration and reabsorption in the nephron regulate body fluid composition AND
• Distinguish between active & passive transport and relate these to process occuring in the kidney
• REF – Text Pg. 74 – 75, 78 – 82, Handouts, Kiss Pg. 26
Active & Passive Transport
• Passive transport limitations– Requires concentration gradient (so max 50%
wastes could be removed this way)– Too slow (toxins would build up = bad)
• Active Transport uses ATP (Energy from respiration)– It moves substances AGAINST a concentration
gradient• Movement of substances between blood & kidney
nephrons involves both passive AND active transport
Passive Transport in Kidney
• Excess water moves by osmosis
• Some urea & ammonia move by diffusion
• See Fig. 3.6 Pg. 81
Active Transport in Kidney
• Salts are moved by ‘sodium pump” by active transport back into bloodstream. The movement of salts, alters the osmotic gradient of blood & so water is drawn into blood passively (Fig. 3.7 Pg. 82 Text)
• ALL Glucose & amino acids are reabsorbed from nephron into bloodstream actively
• Addition nitrogenous wastes & H+ ions are secreted into nephron actively
Tubular Secretion
• Toxic substances are secreted into nephron from the capillaries:
• Active secretion– Uric acid, drugs, hydrogen ions
• Passive secretion– Urea, ammonia
Friday 30th November
• Aim – To be able to outline the role of the hormones aldosterone and ADH in the regulation of water and salt levels in the blood.
• Ref – Pg. 83-84, KISS Pg. 27-28, Handouts
Hormones
• The hormonal system, or endocrine, system helps maintain homeostasis.
• Hormones can affect things like the rate of metabolism, growth and sexual development.
A hormone is a chemical produced by an endocrine gland that travels in the blood
to activate target cells
Hormones
• Can you place the following endorcrine glands?
• Adrenal• Ovaries• Testes• Thyroid• Pituitary• Pancreas
Aldosterone
• Brings about RETENTION of salts in body• Low sodium (salt) levels in blood cause the
adrenal gland to secrete aldosterone• Aldosterone reaches target cells in the kidney
and increases the permeability of nephron to sodium, therefore INCREASES reabsorption of sodium back into capillaries
• Salt levels increase to normal again
Anti-diuretic hormone (ADH)
• Diuretics make you pee more eg. caffeine• Anti-diuretic hormone causes water
reabsorption (conservation) in the body• If blood volume drops, hypothalamus detects
the change & stimulates the pituitary gland to secrete ADH
• ADH acts on the target cells of the kidney to cause greater REABSORPTION of water
3. Adjustment of water content• The hypothalamus in the brain monitors the water
content of the blood and instructs the pituitary gland to release the hormone ADH (Anti-diuretic hormone) into the blood accordingly:
Too little water in blood:1. Hypothalamus detects &
Pituitary releases ADH2. More ADH enters kidney -
more water is reaborbed3. So less urine which is more
concentrated is produced
Too much water in blood:1. Hypothalamus detects &
Pituitary releases LESS ADH2. Less ADH enters kidney - less
water is reaborbed3. So more urine which is less
concentrated is produced