year 1 biology chapter 2 revision

8/9/2019 Year 1 Biology Chapter 2 Revision

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2.1.10 Outline one Therapeutic use of Stem Cells

Stem cells are cells that have yet to be specialised and have the ability to repeatedly

divide and differentiate into various cell types.

Adult stem cells can divide an unlimited amount of times, producing a new stem cell and a

new body tissue each time. (i.e. blood stem cells present in our bone marrow produce a

full range of different types of blood cell) . in fact stem cells can grow into any of the 300

different types of cells found in the human body.

Stem cell research seeks to use the human embryonic stem cells, obtained for embryos

only a few days old. These cells are more flexible in that they may be coaxed to grow into

any type of mature cell. ES cells may be extracted from human embryos that have been

discarded during fertility treatment. Therapeutic cloning is the creation of human

embryos for the sole purpose of producing ES cells rather than cloning to produce a new

human being.

The hope is that the ES cells that have been grown within a laboratory, will be able to help

cure patients to treat diseases like Alzheimers, Parkinsons or Type 1 diabetes. It is also

hoped the genetically engineered stem cells could eventually be able to treat the genetic

fault underlying sickle cell disease.

Those patients with cystic fibrosis might be treated but removing their own stem cells and

genetically modifying them with the cystic fibrosis gene. The cells then would be planted

back in the patient in a way that may lead to the formation of healthy cells lining the

airways. This would eliminate the problem of tissue rejection that occurs in transplant

surgery.


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2.2 Prokaryotic Ce

s

Unit

2 2 2 Annot

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di

of

p o

ot

ith th

fun

tionsof

h st u

tu

n

d

2 2 4

t

t

th

t p o

oti

ll di

id

b

bin

fission

Binary fission is the process where DNA replicates which is followe by theseparation of

DNA and thecell.

Cell Wall- provides protection from

physical damage maintainsshape

and reventse

cess water u take.Flagellum/ flagella- allow

thecell to move.

Fimbria- also called pili.

Used to stick to another cell

and inanimate objects

Cell membrane controls theentry of raw

materials into thecell. Acts as a boundary layer

to contain thecytoplasm interlocking surface

that bindscells together

Plasmids-e

tra chromosomal

DNA. Can replicate

independently from

chromosomal DNA

Ribosome site of

rotein s nthesis.

DNA (genetic material)- nucleic acid that

contains genetic instructions used in the

development and functioning of living

organisms.

Capsule-

Binary fission begins with DNA replication. DNA replication starts

from an origin of replication, which opens up into a replication

bubble. The replication bubbleseparates the DNA doublestrand,

each strand acts as template for synthesis of a daughter strand

bysemi conservative replication, until theentire prokaryotic DNA

is duplicated.

After this replication process, cell growth occurs.

Each circular DNA strand then attaches to thecell membrane.

Thecell elongates, causing the two chromosomes to separate.

Cell division in bacteria iscontrolled by the FtsZ, a collection of

about a dozen proteins that collect around thesite of division.

There, they direct assembly of the division septum. Thecell wall

and plasma membranestarts growing transversely from near the

middle of the dividing cell. Thisseparates the parent cell into two

nearlye

ual daughter cells, each having a nuclear body.

Thecell membrane then invaginates (grows inwards) and splits

thecell into two daughter cells, separated by a newly grown cell

plate.


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2.3 Eukaryotic Cells

Unit

2.3.1 Draw and label a diagram of the ultrastructures of a liver cell

2.3.3 Identify structures in a eukaryotic cell. (know there functions)

Organelle Function Plant/Animals Prokaryotic/Eukaryotic

Nucleus The control centreDNA is dispersed in the cellEncloses DNA

Y/Y N/Y

Chloroplast Site of photosynthesis and storage ofstarch.

Y/N N/Y

Mitochondria Removes unwanted structural debris.Energy-supplying organelle.Produces ATP and the site of aerobicrespiration

N/Y N/Y

Ribosomes Site of protein synthesis. Y/Y Y/Y

Cilia & Flagella For a single cell it allows them to swim.For cells anchored in a tissue movesliquid over the surface of the cell.

Y/Y Y/Y

Golgiapparatus

It stores and later transports the proteins Y/Y N/Y

Endoplasmicreticulum

Series of membranous channels fortransport inside the cell.Channels through which the newly madeprotein is moved within the cell.

Y/Y N/Y

Cytosol Its a structure element of the cell.Protects the cell from germs and dirt.

Y/Y Y/Y

Cell wall Provides protection from physical

damage.Semi-rigid, protective structure depositedby the cell outside the cell membrane.Maintains the shapePrevents excess water uptake

Y/N Y/Y

Cell membrane The structure that controls the entry ofraw materials into the cell.Acts as a boundary layer to contain thecytoplasm.Interlocking surface that binds cellstogether.

Y/Y Y/Y

Vacuole removes unwanted debris, isolates Y/Y N/Y


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harmful material and maintains moleculesLysosomes Lysosomes contain enzymes that help to

break up food so it is easier to digest.N/Y N/Y

Centrioles Centrioles are a very important part

of centrosomes, which are involved

in organizing microtubules in the

cytoplasm. The position of the

centriole determines the position of

the nucleus and plays a crucial role

in the spatial arrangement of the

cell.

N/Y N/Y

2.3.4 Compare prokaryotic and eukaryotic cells

Prokaryotic

(e.g. bacteria)

Feature Eukaryotic

(e.g. animals, plants, fungi)

Cells are extremely small, SIZE Cells are larger, typically 50-150m


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typically 5-10m

Nucleus absent; circular

strand of DNA helix in the

cytoplasm.

GENETIC

MATERIAL

Nucleus has a distinct nuclear

membrane (with pores), and

chromosomes of linear DNA helix.

Cell wall present ( not of

cellulose)

CELL WALL Cell wall present in plants and fungi

Few organelles; membranous

organelles absent or very

simple

ORGANELLES Many organelles bounded by

double membrane (e.g.

mitochondria, nucleus) or single

membrane (e.g. Golgi apparatus,lysosomes, vacuole, RE)

Proteins synthesised in small

ribosomes

PROTEIN

SYNTHESIS

Proteins synthesised in large

ribosomes

Some cell have simple

flagella, 20nm in diameter

MOTILE

ORGANELLES

Some cells have cilia or flagella with

internal structures, 200 nm in

diameter.

Prokaryotic cells vs. Eukaryotic cells

y Contain nakedDNA vs.DNA associated with proteiny DNA in cytoplasm vs. DNA enclosed in a nuclear envelopey No membrane-enclosed organelles vs. membrane-enclosed organelles (e.g.,

mitochondria, chloroplasts)y 70S vs. 80S ribosomes

2.3.4 State the difference between plant and animal cells

Difference between plant and animal cells

Plant Cells Animal Cells

Cell membrane Cell MembraneCytosol CytosolEndoplasmic reticulum Endoplasmic ReticulumRibosomes RibosomesGolgi Apparatus Golgi Apparatus

Cilia and Flagella Cilia and FlagellaLarger vacuole Smaller vacuole

Chloroplast mitochondria

Cell wall

Chlorophyll

Only plant cells have:

y Cell wallsy Chloroplastsy Large central vacuoles and tonoplasty Plasmodesmatay Starch granules for storage of carbohydrates

Only animal cells have:

y Centriolesy Cholesterol in the plasma membraney Glycogen for storage of carbohydrate


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2.4 embranes

Unit

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p ! op$

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s ofphospholipids h$

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1 2fin 2 :

Hydrophilic 3 Having an affinity for water; readily absorbing or dissolving in water.

Hydrophobic 3 Repelling, tending not to combine with, or incapable of dissolving in water.

Hydr4 5

6

ili7

m4

le7

8le

9 @

re@

ttr@

7

tedt4

waterA Hydr4 5

6

4

B

i7

m4

le7

8le

9

are notattractedto

waterC butare attractedto each otherA The phosphate headis hydrophilic andthetwo

hydrocarbon tails are hydrophobic. In waterC phospholipidsform doublelayers with the

hydrophilic heads in contactwith wateron both sides andthe hydrophobictails awayfrom

the centre. The attraction between the heads andthe surrounding watermakes membranes

very stable.

2D

4D

3 List thE

funF

tions ofGE

G b HI

nE

s p H otE

ins

Type Description Examples

In PQ

gR

aS

pR

o PQ

T

nU

oR

P

R

anU V Q V

bR

anQ

pR

o PQ

T

nU

Span the membrane and have a

hydrophiliccytosolic domain, which

interacts with internal molecules, a

hydrophobic membrane-spanning

domain that anchors it within thecell

membrane, and a hydrophilic

extracellular domain that interacts with

IonW

hannQ

S

U

X pR

o P on

puV

pU

X G pR

o PQ

T

n-W

oupS

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dR Q W Q

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Hydrophilic End

Hydrophobic End


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external molecules. The hydrophobic

domain consists of one, multiple, or a

combination of -helices and sheet

protein motifs.

Lipid anchored

proteins

Covalently-bound to single or multiple

lipid molecules; hydrophobically insert

into the cell membrane and anchor the

protein. The protein itself is not in

contact with the membrane.

Y proteins

Peripheralproteins

Attached to integral membrane proteins,or associated with peripheral regions of

the lipid bilayer. These proteins tend to

have only temporary interactions with

biological membranes, and, once

reacted the molecule, dissociates to

carry on its work in the cytoplasm.

Some enzymes, somehormones

PEECH:

Pumps for active transport.

Enzymes

Electron carriers

Channels for passive transportHormone binding sites.

- Hormone binding sites: Exposed on the outside of the membrane which allows it to bind to

one specific hormone. A signal is transmitted to inside of cell.

- Enzymes: Located in membranes and catalyze reactions inside or outside of cell depending

on its position (inner/outer active site).

- Electron carriers: Arranged in chains in the membrane which allows electrons to pass from

one carrier to another.

- Channels for passive transport:Passages through the centre of membrane proteins that

allows a specific substance to pass through

- Pumps for active transport: Release energy from ATPand use it to move specific substances

across the membrane.

2.4.5 Explain passive transport across membranes in terms of simple diffusion and

facilitated diffusion

Diffusion:

A few substances can diffuse directly through the lipid bilayer part of the membrane. The only

substances that can do this are lipid-soluble molecules such as steroids, or very small

molecules, such as H2O, O2 and CO2. For these molecules the membrane is no barrier at all.

Since lipid diffusion is (obviously) a passive diffusion process, no energy is involved and

substances can only move down their concentration gradient. Lipid diffusion cannot be

controlled by the cell, in the sense of being switched on or off.


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Facilitated Diffusion:

Passive transport is the transport of substances across a membrane by a trans-membrane

protein molecule. The transport proteins tend to be specific for one molecule (a bit like

enzymes), so substances can only cross a membrane if it contains the appropriate protein. As

the name suggests, this is a passive diffusion process, so no energy is involved and substances

can only move down their concentration gradient. There are two kinds of transport protein:

Channel Proteins form a water-filled pore or channel in the membrane. This allows charged

substances (usually ions) to diffuse across membranes. Most channels can be gated (opened

or closed), allowing the cell to control the entry and exit of ions.

Carrier Proteins have a binding site for a specific solute and constantly flip between two states

so that the site is alternately open to opposite sides of the membrane. The substance will bindon the side where it at a high concentration and be released where it is at a low concentration.

Mention channels for facilitated diffusion. A molecule or ion that crosses the membrane by

moving down a concentration or electrochemical gradient and without expenditure of

metabolic energy is said to be transported passively/diffused. All molecules and ions are in

constant motion and it is the energy of motion - kinetic energy - that drives passive

transport. Transport of uncharged species across a membrane is dictated by differences in

concentration of that species across the membrane - that is, by the prevailing concentration

gradient. For ions and charged molecules, the electrical potential across the membrane also

becomes critically important. Together, gradients in concentration and electric potential

across the cell membrane constitute the electrochemical gradient that governs passive

transport mechanisms.Facilitated diffusion is diffusion that is "facilitated" by proteins that span the membrane and

provide an alternative route or bypass. It is similar to simple diffusion in the sense that it

does not require expenditure of metabolic energy and transport is again down an

electrochemical gradient. Two major groups of integral membrane proteins are involved in

facilitated diffusion:

1. Carrier proteins (also known as permeases or transporters) bind a specific type of solute

and are thereby induced to undergo a series of conformational changes which has the effect

of carrying the solute to the other side of the membrane. The carrier then discharges the

solute and, through another conformational change, reorients in the membrane to its

original state. Typically, a given carrier will transport only a small group of related

molecules.

2. Ion Channels do not really bind the solute, but are like hydrophilic pores through themembrane that open and allow certain types of solutes, usually inorganic ions, to pass

through. In general, channels are quite specific for the type of solute they will transport and

transport through channels is quite a bit faster than by carrier proteins. Additionally, many

channels contain a "gate" which is functions to control the channel's permeability. When the

gate is open, the channel transports, and when the gate is closed, the channel is closed. Such

gates can be controlled either by voltage across the membrane (voltage-gated channels) or

have a binding site for a ligand which, when bound, causes the channels to open (ligand-

gated channels). Ion channels allow currents to be carried across the membrane and are thus

of particular importance in the physiology of excitable cells like neurons and muscle cells.


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2.4.6 Explain the role of protein pumps and ATP in active transport across membranes

Active transport is the pumping of substances across a membrane by a trans-membrane

protein pump molecule. The protein binds a molecule of the substance to be transported on

one side of the membrane, changes shape, and releases it on the other side. The proteins are

highly specific, so there is a different protein pump for each molecule to be transported. The

protein pumps are also ATPase enzymes, since they catalyse the splitting ofATP gADP +

phosphate (Pi), and use the energy released to change shape and pump the molecule.

Pumping is therefore an active process, and is the only transport mechanism that can

transport substances up their concentration gradient.

Active transport is the movement of substances across membranes using energy from ATP.

Active transport can move substances against a concentration gradient. Protein pumps inthe membrane are used for active transport. Each pump only transports particular

substances so cells can control what is absorbed and what is expelled.

2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and

reform during Endocytosis and Exocytosis.

The movement of large materials into or out of a cell is called bulk transport. There are

two main categories:

1. Exocytosis2. Endocytosis

Endocytosis:

Endocytosis is the transport of materials into a cell. Materials are enclosed by a fold of the cell

membrane, which then pinches shut to form a closed vesicle. Strictly speaking the material has

not yet crossed the membrane, so it is usually digested and the small product molecules are

absorbed by the methods above. When the materials and the vesicles are small (such as a

protein molecule) the process is known as pinocytosis (cell drinking), and if the materials are

large (such as a white blood cell ingesting a bacterial cell) the process is known as phagocytosis

(cell eating).


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Exocytosis

Exocytosis is the transport of materials out of a cell. It is the exact reverse of endocytosis.

Materials to be exported must first be enclosed in a membrane vesicle, usually from the RER

and Golgi Body. Hormones and digestive enzymes are secreted by exocytosis from the

secretory cells of the intestine and endocrine glands.

In endocytosis part of the plasma membrane is pulled inwards. A droplet of fluid becomes

enclosed when a vesicle is pinched off. Vesicles can then move through the cytoplasm

carrying its contents.

In exocytosis vesicles fuse with the plasma membrane. The contents of the vesicles are then

expelled. The membrane flattens out again.


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2.5 Cell Division

Unit

2.5.1 Outline the stages in the cell cycle, including Interphase (G1,S, G2), mitosis and cytokinesis

Stage Description Illustration

Interphase Chromosomes condense copy

Chromosomes appear as thread like coils

(chromatin) at the start but each chromosomes

and its copy (sister chromosomes) change intosister chromatides at the end of this phase

Interphase

(G1)

Growth and normal metabolic roles

The duplication of organelles

Interphase

(S)

DNA replication- it produces another copy of

each chromosome

Interphase

(G2)

Growth and Preperation for mitosis- second

growth stage

Prophase

(1st phase)

Mitosis begins (cell begins to divide)

Centrioles appear and begin to move to oppositeend of the cell

Spinclole fibres from between the poles

Nuclear membrane begins to dissolve

Metaphase

(2nd

phase)

Chromatids (or pair chromosomes) attach to the

spindle fibres via the centromeres

Anaphase

(3rd phase)

Chromatids separate and begin to move to

opposite ends of the cell

Spindle fibres shorten causing the duplicated

chromosomes to split

Telophase

(4th

phase)

Nuclear membrane begins to reform creating

two new nuclei

Chromosomes appear a chromatin (threads

rather then rods)

In an plant cell and cell plate will form in themidline. This is where the cell wall will be formed

Cytokinesis The division of the cytoplasm enclosing each of

the new cells which become Interphase


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2.5.2 State that tumours (cancers) are the result of uncontrolled cell division and that these can

occur in an organ or tissue

Tumours can be classified as either:

y Terminal/Malignanty Benign

Procedure Explanation

Surgical Removal Aspiration Biopsy: a needle is inserted into the tumour

and a sample is withdrawn.Needle Biopsy: a special cutting needle is inserted into

the core of the tumour and a core sample is cut out.

Incisional Biopsy: a portion of the tumour is removed.

Excisional Biopsy: the whole tumour is removed

w/surrounding normal tissue.

Radiation Therapy Radiation therapy is the use of a certain type of energy

(ionizing radiation) to kill cancer cells and shrink the

tumours. Radiation therapy injures or destroys cell in

the area being treated by damaging their genetic

material, making it impossible for these cells to grow

and divide.

Limits harm to neighbouring healthy tissue.Chemotherapy Chemo for short, means taking certain drugs to treat

cancer. You may take these drugs before or after cancer

surgery or with radiation treatment. Most of chem. Is

given into your veins through a needle or catheter. This

is called venous chemo.

Quite simply, cancer evolves when cells divide uncontrollably and unregulated. The process is

something like;

1. A single cell in a tissue suffers a mutation in a gene involved in the cell cycle, e.g., an

oncogene or tumor suppressor gene.

2. This results in giving that cell a slight growth advantage over other dividing cells in thetissue.

3. As that cell develops into a clone, some if its descendants suffer another mutation in

another cell-cycle gene.

4. This further deregulates the cell cycle of that cell and its descendants.

5. As the rate of mitosis in that clone increases, the chances of further DNA damage increases.

6. Eventually, so many mutations have occurred that the growth of that clone becomes

completely unregulated.

7. The result being full-blown cancer.

Sometimes, mitosis gets out of control and a cell begins to divide and the new daughter cell

begins to divide as well. Soon, this overflow of cells is called a tumor. Tumors can occur in

any organ. Cancer is a disease caused by tumors.

2.5.3 State that Interphase is an active period in the life of a cell when many metabolic reactions

occur, including protein synthesis, DNA replication and mitochondria and chloroplast.

During interphase the cell grows larger. Genes of chromosomes are subsequently

transcribed to allow for protein synthesis. The DNA is then replicated.


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2.5.4 Describe the events that occur in the four phases of mitosis

Prophase (1st

phase)

Mitosis begins (cell begins to divide)

Centrioles appear and begin to move to opposite end of the cell

Spinclole fibres from between the poles

Nuclear membrane begins to dissolve

Metaphase

(2nd phase)

Chromatids (or pair chromosomes) attach to the spindle fibres via the

centromeres

Anaphase(3

rdphase)

Chromatids separate and begin to move to opposite ends of the cellSpindle fibres shorten causing the duplicated chromosomes to split

Telophase

(4th

phase)

Nuclear membrane begins to reform creating two new nuclei

Chromosomes appear a chromatin (threads rather then rods)

In an plant cell and cell plate will form in the midline. This is where the

cell wall will be formed

Include supercoiling of chromosomes, attachment of spindle microtubules, splitting of

centromeres, movement of sister chromosomes to opposite poles and breakage and

reformation of nuclear membranes.

y During Prophase, the mitotic spindle (made from microtubules) starts growing(going from pole to pole).Chromatin coil up to form distinct chromosomes. (Each

chromosome contains two identical sister chromatids, attached to each other at thecentromere region.) The nuclear envelope starts breaks down.

y During Metaphase, each chromosome attaches to two spindle microtubules (onegoing to each pole) at the centromere region, so that they line up at the (virtual)

equator of the cell. The mitotic spindle is fully developed: some microtubules are

attached to chromosomes and reach to the equator, whilst others go from pole to

pole.

y During Anaphase, the spindle microtubules pull the sister chromatids to oppositepoles (each sister chromatid becomes one new chromosome of the daughter cell).

y During Telophase, each sister chromatid reaches its pole (becoming a chromosome).The nuclear envelope starts to reform. Spindle microtubules deteriorate. Cytokinesis

(division of the cytoplasm) takes place.

2.5.5 Explain how mitosis produces the genetically identical nuclei.

The result of the process of mitosis is two nuclei. During S phase, each chromosome

replicates (forms an exact copy of itself). These copies are called sister chromatids. These

identical sister chromatids are separated during Anaphase, and are moved to each pole.

When they are separated they are referred to as chromosomes. The result is two nuclei,

identical to each other and to the original nucleus.


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Extra Info that might be needed

Unit

2.4 Osmosis:

Osmosis is the diffusion of water across a membrane. It is in fact just normal lipid diffusion,

but since water is so important and so abundant in cells (its concentration is about 5 0M),

the diffusion of water has its own name - osmosis. The contents of cells are essentially

solutions of numerous different solutes, and the more concentrated the solution, the moresolute molecules there are in a given volume, so the fewer water molecules there are.

Water molecules can diffuse freely across a membrane, but always down their

concentration gradient, so water therefore diffuses from a dilute to a concentrated

solution.

year 1 biology chapter 2 revision

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