Module 2 – Foundations in biology

Question 1

C2) How do you do gram stain technique

Answer 1

Used to separate bacteria into two groups: Gram-positive bacteria and Gram-negative bacteria

Crystal violet is first applied to a bacteria specimen on a slide, then iodine, which fixes the dye

The slide is washed with alcohol

Gram-positive bacteria retain the crystal violet stain and will appear blue or purple under a microscope

Gram-negative bacteria have thinner cell walls and therefore lose the stain. They are then staying with safranin dye,which is called a counterstain. These bacteria will then appear red

Gram-positive bacteria are susceptible to the antibiotic penicillin, which inhabits the formation of the cell walls

Gram-negative bacteria have much thinner cell walls is not susceptible to antibiotic pencilling

Question 2

C2) How do you do the acid-fast technique

Answer 2

Are used to differentiate between species of mycobacterium from other bacteria.

A liquid solution is used to carry carbolfuchsin dye into the cells being studied

The cells are washed with a die loot acid solution.

Mycobacteria are not affected by the I said alcohol and retain the stain- bright red

Are the bacteria lose the stain and are exposed to a methylene blue stain, which is blue

Question 3

C2) What are the features of a light microscope

1) expense
2) Radiation used
3) Size
4) Maximum magnification
5) Maximum resolution
6) Type of image produced
7) sample preparation
8) Vacuum needed?

Answer 3

1) not expensive
2) Light
3) Small and portable
4) x 1500
5) 200 nm
6) 2d
7) Sample procedure
8) No-can you live in specimen

Question 4

C2) What are the features of a scanning electron microscope

1) expense
2) Radiation used
3) Size
4) Maximum magnification
5) Maximum resolution
6) Type of image produced
7) Vacuum needed?

Answer 4

1) Expensive to buy and operate
2) Beam of electrons
3) Large
4) X 500,000
5) 2.2 nm
6) 3D
7) Yes-dead

Question 5

C2) What are the features of a transmission electron microscope

1) expense
2) Radiation used
3) Size
4) Maximum magnification
5) Maximum resolution
6) Type of image produced
7) Vacuum needed?

Answer 5

1) Expensive to buy and operate
2) Beam of electrons
3) Large
4) X 1,000,000
5) 0.1 nm
6) 2D
7) Yes-dead

Question 6

C2) What other parts of an animal cell

Answer 6

Cell-surface membrane

Cytosol

Ribosome

Centriole

Rough endoplasmic reticulin

Smooth endoplasmic reticulin am

Cytoskeleton

Secretion vesicles

Mitochondria

Golgi apparatus

Nucleus

Nucleolus

Golgi Vesicles

Microtubule network

Question 7

C2) What are the parts of an plant cell

Answer 7

Cell membrane

Cell wall

Ribosome

Rough endoplasmic reticulin

Smooth endoplasmic reticulin

Mitochondria

Golgi apparatus

Nucleus

Nucleolus

Golgi Vesicles

Chloroplast

Vacuole membrane

Raphide crystal

Druse Crystal

cytoplasm

Large central vacuole

Amyloplast (starch grain)

Question 8

C2) What are the structural components of cytoskeleton of a cell

Answer 8

MICROFILAMENTS – Fibres made from the protein Actin. They are responsible for movement of the cell and cytoplasm during Cytokinesis.

MICROTUBULES – Formed by the globular protein Tubulin. They polymerise to form tubes that determine the shape of the
cell. They also act as tracks for organelles moving around the cell.

INTERMEDIATE FIBRES – Gives strength to
cells and helps maintain integrity.

Question 9

C2) What is the function of the cytoskeleton of a cell

Answer 9

Providing mechanical strength to cells

Aiding transport within cells

Enabling cell movement.

Question 10

C2) What are the structural components of the nucleus of a cell

Answer 10

Double Nuclear Envelope – A double membrane which
compartmentalises the Nucleus and prevents damage. Protects the DNA.

Nuclear Pores – Allows molecules to enter and leave the cell

Nucleolus – Site of ribosome production. Composed of RNA and
proteins.

Chromatin – is the DNA. Contains the Genetic Code which controls the activity of the cell.

Question 11

C2) What is the function of the nucleus of a cell

Answer 11

1) Controls all the activity of the cell.
2) Where the Genetic Code (DNA) of the cell is stored, replicated, and copied into RNA (transcribed).

The Nucleus is attached to the Rough ER so the mRNA can easily get to ribosomes.

Question 12

C2) What are the structural components of the Rough Endoplasmic Reticulum of a cell

Answer 12

System of hollow tubes and
membrane bound sacs which form sheets called cisternae.

attached to the nucleus and covered with ribosomes.

Consists of an interconnected system of
flattened sacs.

Question 13

C2) What is the function of the Rough Endoplasmic Reticulum of a cell

Answer 13

Site of protein synthesis.

Question 14

C2) What are the structural components of the smooth Endoplasmic Reticulum of a cell

Answer 14

similar to RER but lacks ribosomes -is a system of interconnected tubules.

Question 15

C2) What is the function of the smooth Endoplasmic Reticulum of a cell

Answer 15

responsible for carbohydrate & lipid synthesis, and storage.

Question 16

C2) What are the structural components of the ribosome of a cell

Answer 16

A 2 subunit organelle.

Made from RNA and protein.

Not membrane bound.

Very small organelles: about 22nm in diameter.

Found free floating in the cytoplasm or attached to the Rough ER

Question 17

C2) What is the function of the ribosome of a cell

Answer 17

These are where protein is made.

They assemble amino acids into proteins in chains using mRNA.

Question 18

C2) What are the structural components of the mitochondria of a cell

Answer 18

Oval shaped.

Surrounded by two membranes (double membrane).

The inner membrane forms finger-like structure called cristae which increases the surface area.

The solution inside is called a matrix which contains enzymes for respiration.

Mitochondrial DNA – Small amounts of DNA, enable mitochondrion to reproduce and create enzymes.

Question 19

C2) What is the function of the mitochondria of a cell

Answer 19

Site of aerobic respiration.

As a result of respiration, they produce ATP (energy carrier in cells).

Question 20

C2) What are the structural components of the Golgi apparatus of a cell

Answer 20

Stack of flattened, membrane bound sacs (cisternae).

These are continuously formed from the ER at one end and budding off as Golgi vesicles at the other.

Question 21

C2) What is the function of the Golgi apparatus of a cell

Answer 21

Allows internal transport.

Receives proteins from the RER

Modifies and processes molecules (such as new lipids and proteins) and packages them into vesicles.

These may be Secretion vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell).

Makes lysosomes

Lipid synthesis

Question 22

C2) What are the structural components of the lysosome of a cell

Answer 22

They are spherical sacs surrounded by a

single membrane.

Question 23

C2) What is the function of the lysosome of a cell

Answer 23

They contain powerful hydrolytic
digestive enzymes known as lysozymes.

Their role is to break down worn out components of the cell or digest invading cells.

Question 24

C2) What are the structural components of the cilia of a cell

Answer 24

‘Hair like’ extensions that protrude from some animal cell types.

In cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle.

Known as a 9 +2 arrangement.

Arrangement allows movement.

Question 25

C2) What is the function of the cilia of a cell

Answer 25

sensory function (e.g. nose), beat 
creating a current to move fluid/mucous/objects

For locomotion

Question 26

C2) What are the structural components of the flagellum of a cell

Answer 26

Similar to cilia but longer.

They stick out from the cell surface and are surrounded by the plasma membrane.

Like cilia they have a 9 +2 arrangement.

Question 27

C2) What is the function of the flagellum of a cell

Answer 27

(Whip-like) enables a cells mobility.

The microtubules contract to make the flagellum move.

Propel cells forward e.g. sperm cells.

Question 28

C2) What are the structural components of the chloroplast of a cell

Answer 28

Double membrane which encloses the
stroma.

Stroma contains: Starch grains, lipid stores, DNA, RNA, ribosomes.

Series of membrane-bound flattened sacs called thylakoids in the stroma.

Thylakoids stacked together are called grana.

Grana are linked together by lamellae.

The grana contain chlorophyll

Question 29

C2) What is the function of the chloroplast of a cell

Answer 29

Photosynthetic reactions

Question 30

C2) What are the structural components of the Large Permanent Vacuole of a cell

Answer 30

Single membrane bound (membrane is called a tonoplast).

Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc).

Selectively permeable barrier

Question 31

C2) What is the function of the Large Permanent Vacuole of a cell

Answer 31

Stores cell cap

Support herbaceous plants by making cells turgid.

Helps maintain shape and gives support by maintaining turgor pressure.

Sugars and amino acids act as a temporary food store.

Question 32

C2) What does the DNA look like in a prokaryotic cell

Answer 32

The structure of DNA is fundamentally the same as in eukaryotic cells but it is packed differently

Prokaryote generally only have one molecule of DNA, A chromosome, which is supercoiled to make it more compact.

The genes on the chromosomes are often grouped into operons, meaning a number of jeans are switched on or off at the same time

Question 33

C2) What does the ribosomes look like in a prokaryotic cell

Answer 33

Are smaller than those in eukaryotic cells.

The relative size is determined by the rate of which they settle, or form a sediment in solution.

The larger eukaryotic ribosomes are designed 80s in the smaller prokaryotic ribosomes are 80s

Both are necessary for protein synthesis, although the larger 80s ribosomes are involved in the formation of more complex proteins

Question 34

C2) What does the cell wall look like in a prokaryotic cell

Answer 34

Made from peptidoglycan, also known as murein

A complex polymer formed from amino acids and sugars

Question 35

C2) What does the flagella look like in a prokaryotic cell

Answer 35

The flagella of prokaryotes is thinner than the equivalent structure of eukaryotes and does not have the 9+2 arrangement

The energy needed to move the flagellum is supplied by the process of chemiosmosis, not from ATP as in eukaryotic cells

Question 36

C2) What are the features of a Eukaryotic cell

1) Nucleus
2) DNA
3) DNA orientation
4) Extra chromosomal DNA
5) Organelles
6) Cell wall
7) Ribosomes
8) Cytoskeleton
9) Reproduction
10) Cell type
11) Cell-surface membrane

Answer 36

1) Present
2) linear
3) Associated with proteins called histones
4) Only present in the certain organelles such as chloroplasts and mitochondria
5) Both membrane-bound and non-membrane-bound
6) Chitin in fungi, Celulose in plants, not present in animals
7) Larger, 80s
8) Present, more complex
9) asexual or sexual
10) Unicellular and multicellular
11) Present

Question 37

C2) What are the features of a prokaryotic cell

1) Nucleus
2) DNA
3) DNA orientation
4) Extra chromosomal DNA
5) Organelles
6) Cell wall
7) Ribosomes
8) Cytoskeleton
9) Reproduction
10) Cell type
11) Cell-surface membrane

Answer 37

1) Not present
2) Circular
3) Proteins fold and condense DNA
4) Circular DNA called plasmids
5) Non membrane-bound
6) Peptidoglycan
7) Smaller, 70s
8) Present
9) Binary fusion
10) Unicellular
11) Present

Question 38

C4) why are enzymes important

Answer 38

So that chemical reactions can happen very fact

Enzymes are biological catalysts

They are globular proteins that interact with substrate molecules

Question 39

C4) What is the role of enzymes in a reaction?

Answer 39

Involves in the synthesis of large polymer-based components

Digestion is also catalysed by range of enzymes

Question 40

C4) How does an enzyme action work?

Answer 40

For a reaction to happen molecules need to collide in the right orientation. When High temperatures and pressure are applied the speed of the molecules will increase, so will the number of successful collisions and the overall rate of reaction

Different enzymes are produced by living organisms as each enzyme catalyses one biochemical reaction of which there are thousands in every given cell. This is termed the specificity of the enzyme

Energy needs to be supplied for most reactions to start this is called activation energy.

Question 41

C4) What is the meaning of anabolic reactions

Answer 41

The chemical reactions required for growth are anabolic (building up) reactions and they are all catalysed by enzymes

Question 42

C4) what is the meaning catabolic reactions.

Answer 42

Energy is released from large organic molecules like glucose, in metabolic pathways consisting of many catabolic (barking down) reactions. Catabolic reactions are also catalysed by enzymes

Question 43

C4) What is the meaning of Metabolism

Answer 43

Reactions rarely happen in isolation but as part of a multi-step pathways. Metabolism is the sum of all the different reactions and reaction pathways. Can only happen because of the control and order imposed by enzymes .

Question 44

C4) What is Vmax

Answer 44

Enzymes can only increase the rate of a reaction to a certain point

Question 45

C4)How does an enzyme affect the activation energy of a reaction

Answer 45

The amount of energy needed is so large it prevents a reaction in happening. Enzymes help the molecules collide successfully and therefore reduce the activation energy required

Question 46

C4) What is the lock and key hypothesis

Answer 46

In the same way that only the right key will fit into a lock only a specific substrate will fit the active site of an enzyme

When the substrate is bonded to the active site and enzyme substrate complex is formed.
The substrate that reacts and the product are formed in a enzyme product complex

Question 47

C4) what is the active site

Answer 47

An area within the tertiary structure of the enzyme, that has a shape complimentary to the shape of a specific substrate molecule

Question 48

C4) how is the substrate broken down in the active site.

Answer 48

The substrate is held in away by the enzyme that the right atom groups are close enough to react. the R-groups within the active site of the enzyme will also interact with the substrate, forming temporary bonds. This puts strain on the bonds within the substrate helping the reaction to occur

Question 49

C4) What is the induced fit hypothesis of an enzyme

Answer 49

Research suggests that the active site of the enzyme actually changes shape slightly as the substrate enters.

This is a modification on the lock and key hypothesis.

The initial interaction between the enzyme and substrate is relatively weak but these week interactions rapidly changes the enzymes Tertiary structure that strengthen binding, putting strain on the substrate molecule. This can weaken a particular bond in the substrate therefore lowering the activation energy for the reaction

Question 50

C4) What are intracellular enzymes

Answer 50

Enzymes that work within a cell

Question 51

C4) How does an intracellular enzyme help

Answer 51

The synthesis of polymers from monomers. For example polysaccharides from glucose require enzymes

An example of this is hydrogen peroxide

Question 52

C4) what are extracellular enzymes

Answer 52

All of the reactions happening within cells need substrates to make the product. The substrate need to be constantly supplied to cells. Nutrients present in the diet or environment of the organism supply these substrates

Nutrients are supplied in the form of polymers such as proteins and polysaccharides. These large molecules can’t enter cells directly. They need to be broken down

Enzymes are released from cells to break down these large nutrient molecules into smaller molecules in the process of digestions. These are called extracellular enzyme they work outside the cell that made them.

Question 53

C4) How is starch digested

Answer 53

It begins in the mouth and continues in the small intestine

1) Starch polymers are broken down into maltose a disaccharide. The enzyme involved is called amylase produced by the saliva glands and the pancreas. Released in the saliva into the mouth and in pancreatic juice into the small intestines
2) maltose is broken down into glucose which is a monosaturated using the enzyme maltase which is present on the small intestine

Question 54

C4) how is protein digested

Answer 54

Trypsin is a protease enzyme that catalyse proteins into smaller peptides which can then be broken down into amino acids.

Trypsin is produced in the pancreas and released with the pancreatic juice into the small in testing and acts on proteins.

Question 55

C4) how can an enzyme structure be affected

Answer 55

By factors such as temperature and pH. They cause a change in the shape of the active site.

Question 56

C4) how does temperature affect the rate of a reaction of an enzyme

Answer 56

Increasing the temperature, increases the kinetic energy of the particles. As temperature increases the particles move faster and collide more frequently.

Increasing the temperature will result in more frequent successful collisions between substrate and enzyme leading to an increase in the rate of reaction

Question 57

C4) What is the definition of the temperature coefficient of the reaction

In enzyme

Answer 57

Is a measure of how much the rate of a reaction increases with a 10°C rise in temperature

For an enzyme reaction it is usually two meaning that the rate of reaction doubles with a 10°C temperature increase

Question 58

C4) how does enzymes denature from temperature

Answer 58

As enzymes are proteins high temperatures affect the bonds holding the protein together making it vibrate more.

As the temperature increases the vibration increases onto the bonds strain and then break

The breaking of these bonds result in changes in the tertiary structure of the protein

Meaning it has denatured

When an enzyme is denatured the shape of the active site has changed and no longer complimentary to substrate therefore enzyme Will not function as a catalyst

Question 59

C4) what is the optimal temperature of an enzyme

Answer 59

Optimal temperature is the temperature at which enzymes have the highest rate of activity.

In the human body optimum temperature is around 40°C

In thermophilic bacteria (Hot Springs) the optimal temperature is around 70°C

In psychrophilic organisms (cold areas) the optimal temperature is below 5°C

Question 60

C4) how does denaturing above and below the optimal temperature affect the rate of a reaction

Answer 60

Denaturing above the optimal temperature, decreases the rate of reaction rapidly. This is because all of the enzyme molecules have a change in the active site and and it happens at about the same temperature so the loss of activity is rapid

Denaturing below the optimal temperature, decreases The rate of reaction. This is because the enzyme has not denatured they are just less active

Question 61

C4) how do enzymes adapt to extremely cold environment

Answer 61

They tend to be more flexible structures, particularly that the active site making them less stable than enzymes to work at higher temperatures. Smaller temperature changes will denatured them

Question 62

C4) how to enzymes adapt to extremely hot environments

Answer 62

The enzymes in these organisms are more stable than enzymes in other organisms this is due to the increased number of bonds, particularly hydrogen bonds and sulfer bridges in the tertiary structure.

The shapes of these enzymes and the active site are more resistant to change as the temperature rises

Question 63

C4) how does PH affect an enzyme reaction

Answer 63

As enzymes are proteins, the hydrogen bonds and ionic bonds between amino acid r groups hold proteins in the precise 3-D shape because of interactions between polar R groups

The change in pH refers to a change in the hydrogen ion concentration. More hydrogen ions present in the low pH environment. Fewer hydrogen ions present in high pH environments

Hydrogen ions interact with polar r groups therefore increasing hydrogen ions increases the interactions. So more hydrogen ions present the less r groups are able to interact with each other this leads to bonds breaking and shapes changing. Reverse for lower PH

The active site will be at the right shape at a certain hydrogen ion concentration known as the optimal PH

When the pH changes The structure of the enzyme and therefore the active site is altered

Question 64

C4) what is a renaturation of an enzyme

Answer 64

If the pH returns to the optimal then the protein will resume its normal shape and catalyse the reaction again

Question 65

C4) How does an increased Number of substrate molecule affect the rate of a reaction

Answer 65

Leads to a higher collision rate with the active site of the enzyme and formation of a more enzyme substrate complexes therefore an increased rate of reaction

Question 66

c4) how does an increased number of enzyme concentration affect the rate of a reaction

Answer 66

Will increase the number of available active sites in a particular area leading to an increase in enzymes from free complexes at a faster rate therefore increase the rate of a reaction

Question 67

C4) what happens when the rate of reaction increases to V-max

Answer 67

At this point all of the active site occupied by substrate particles and no more enzyme substrate complex is can be formed into products are released from the active site

Question 68

C4) what is an enzyme inhibitor

What are the two types of enzyme inhibitors

Answer 68

Inhibitors are molecules that prevent enzymes from carrying out the normal function of catalystis

Competitive and non-competitive enzyme inhibitors

Question 69

C4) How does competitive inhibitor affect the rate of a reaction

Answer 69

Competitive inhibitors reduce the rate of reaction from a given concentration of substrate but does not change the Vmax of the enzyme it inhibits

If Substrate concentration is increased enough there will be so much more substrate than inhibitors that the original Vmax can still be reached

Question 70

C4) how does it and non-competitive inhibition work

Answer 70

The inhibitor binds to the enzyme at a location other than the active site this is called an allosteric site

The binding of the inhibitor causes the tertiary structure of the enzyme to change meaning the active site changes shape

This results in the active site no longer being complimentary shape to the substrate so unable to bind to the enzyme

The enzyme cannot carry out its function and is inhibited

Question 71

C4) What are examples of irreversible noncompetitive inhibitors

Answer 71

Irreversible inhibitors cannot be removed from the part of the enzyme they are attached to. They are often very toxic but not always.

Protein pump inhibitors are used to treat long-term indigestion. They Irreversibly block and enzyme system responsible for secreting hydrogen ions into the stomach

Question 72

C4) why is end product inhibition important

Answer 72

A control mechanism for the reaction.
Excess products are not made and resources are not wasted.
It is an example of non-competitive reversible inhibition

Question 73

C4) what are cofactors and co-enzymes

Answer 73

Some enzymes need a non-protein helper component in order to carry out the function as biological catalysts

They may transfer atoms or groups from one reaction to another in a multistep pathway or may actually form part of the active site of an enzyme this component is called a cofactor

If the cofactor is an organic molecule it is called a coenzyme

Question 74

C4) how are coenzymes obtained

Answer 74

They are derived from vitamins, a class of organic molecules found in the diet.

For example vitamin B5 which is used to make coenzyme A essential in the breaking down of fatty acids and carbohydrates in respiration

Question 75

C4) what is precursor activation

Answer 75

Many enzymes are produced in an inactive form known as inactive precursor enzymes

Particular enzymes can cause damage within the cell producing them water tissues where they are released, or enzyme this action needs to be controlled and only activated under certain conditions

Question 76

C4) how are precursor enzyme activated

Answer 76

Precursor enzymes often need to undergo change in the tertiary structure particularly to the active site.

This can be achieved by the addition of a cofactor.

Before the cofactors added the precursor protein is called an apoenzyme. When the cofactors and in the enzyme is activated it is called a holoenzyme

Sometimes the change is brought about by the action of another enzyme. Sometimes a change in conditions such as pH or temperature and bring about the change these types are called proenzymes

Question 77

C4) what is the prosthetic group

Answer 77

They are cofactors, required by certain enzymes to carry out the catalytic function.
Whilst some cofactors are loosely or temporarily bonded to the enzyme protein in order to activate them.

Prosthetic group are tightly bound and form a permanent feature of the protein

Question 78

C4) how are inorganic cofactors obtained

Answer 78

Obtained via the diet and minerals including iron, calcium, chloride and zinc ions.

For example the enzyme amylase which breaks down starch is contain a chloride ions, necessary for the formation of a correctly shaped Active site

Question 79

C4) how does competitive inhibition work

Answer 79

A molecule or part of a molecule with a similar shape to the substrate can fit into the active site of an enzyme

This blocks the substrate from entering the active site preventing the enzyme from catalysing the reaction

The ends and cannot carry out its functions and is inhibited

The non-substrate molecule that binds to the active site is a type of inhibitor. Substrate and inhibitor molecule present in a solution will compete with each other to buy into the active site of the enzyme. This will reduce the number of substrate molecules binding to active site in a given time and slow down the rate of a reaction. The degree of inhibition will depend on the relative concentration of substrate, inhibitor and enzyme

Most competitive inhibitor only bind temporarily to the active site, so it is reversible. An exception is aspirin

Question 80

C4) what are examples of competitor inhibitors

Answer 80

Statins are competitive inhibitor is of an enzyme use in the synthesis of cholesterol. Statins are regularly prescribed to help reduce blood cholesterol concentration which can result in heart disease

Aspirin irreversibly inhibits the active site of COX enzymes

Question 81

C4) What are the effects of non-competitive inhibitors on the rate of reaction

Answer 81

Increasing the concentration of enzymes or substrate will not overcome the effects of non-competitive inhibitors.

Increasing the concentration of inhibitors how old will decrease the rate of a reaction further as more active sites become unavailable

Question 82

C4) what is the meaning of end product inhibtion

Answer 82

Term used for enzyme inhibition that occurs when the product of the reaction X as a inhibitor to the enzyme that produces it – Negative feedback

Question 83

C4) what is the temperature coefficient

Answer 83

R1 / R2

Question 84

C4) what is an example for cofactors and prosthetic group

Answer 84

Cl – as a cofactor for amylase

Zn2+ as a prosthetic group for carbonic anhydrase a

Question 85

C5)What are Intrinsic proteins

Answer 85

Are transmembrane protein that are in bedded in both layers of the membrane

Have amino acids with hydrophobic r groups on the external surface which interact with the hydrophobic core of the membrane keeping them in place

Question 86

C5) what are the two intrinsic proteins and how are they held in position

Answer 86

Channel proteins provide a hydrophobic channel that allows passive movement down a concentration gradient. Held in position by interactions between the hydrophobic core of the membrane and hydrophilic or groups on the outside of the protein

Carrier proteins plays a role in both passive, down a concentration gradient and active transport, against a concentration gradient by changing the proteins shape

Question 87

C5) What are the uses of glycoproteins within the cell surface membrane

Answer 87

Intrinsic proteins that are embedded in the cell surface membrane with attach carbohydrate chains

Plays a role in Cell adhesion cells joining together to form a tight junction and as receptors for chemical signals

Helps with cell signalling-when the chemical binds to the receptor the cell responds causing a direct response (neurotransmitters at a synaptic junction) or a cascade of events (hormones)

Question 88

C5) what is the plasma membrane

Answer 88

The cell-surface membrane which separates the cells from its external environment

Question 89

C5) what is the importance of glycolipids on the cell surface membrane

Answer 89

They are lipids with attached carbohydrate chains

These molecules are called antigens and can you be recognised by the cells of the immune system as self and nonself

Question 90

C5) what extrinsic proteins

Answer 90

Are present in one side of the bilayer

Normally have hydrophobic r group on the outer surface and interact with the polar heads of the phospholipid bilayer

Can we present in either layer and some moves between layers

Question 91

C5) What is the importance of cholesterol in the cell surface membrane

Answer 91

Cholesterol is a lipid with a hydrophobic end and a hydrophilic end

Regulate the fluidity of the membrane

Cholesterol molecules positioned between phospholipids in a membrane bilayer

The hydrophilic end interacting with the heads and the hydrophobic end interacting with the tails pulling them together. Therefore adding stability to the membranes without making them rigid

The cholesterol molecule prevents the membrane becoming too solid by stopping the phospholipid molecules grouping too closely and crystallising

Question 92

C5) How can the cell-surface membrane be a site for chemical reactions

Answer 92

Proteins in the membrane forming organelles or present within organelles have to be in particular positions for chemical reactions to take place

Question 93

C5) how does temperature affect the permeability of the cell surface membrane

Answer 93

Phospholipids are constantly moving within the membrane when the temperature increases the phospholipid gain more kinetic energy and will move more

Making the membrane more fluid leading to it losing its structure. Continued temperature increase will entirely break down the cell

The loss of structure increases the permeability of the membrane making it easier for particles to cross

Carrier and channel proteins in the membrane will denature at higher temperatures, which is involved in transport across the membrane

Question 94

C5) Why do solvent affect the permeability of the plasma membrane

Answer 94

Water is essential in the formation of the phospholipid bilayer. The hydrophobic tail of a phospholipid is oriented away from water creating a hydrophobic core and the hydrophilic heads interact with water keeping the bilayer intact

Many organic solvents are less polar or more polar than water which will dissolve membranes and disrupt cells. This is why alcohol is used as an antiseptic wipe as it dissolves the membranes of bacteria in a wound

Pure or very strong alcohol are toxic as they destroy cells. Non-polar alcohol molecules can enter the cell membrane and
the presence of these molecules between the phospholipids disrupt the membrane

When the membrane is disrupted it becomes more fluid and more permeable.

Some cells need intact cell membranes for specific functions for example transmission of a nerve impulse by Neurons, when its membrane is disrupted the nerve impulse no longer transmits as normal for example the changes in peoples behaviour when on alcohol

Question 95

C5) Why are membranes considered to be partially permeable

Answer 95

Diffusion can only happen if the membrane is permeable to the particle for nonpolar molecules such as oxygen defuses through freely down a concentration gradient

The hydrophobic interior of the membrane repels substances with a positive or negative charge so they cannot pass through.

Polar molecules such as water can diffuse through but at a very slow rate. Smaller polar molecules pass through easier the larger ones

Question 96

C5) what is facilitated diffusion

Answer 96

When polar molecules pass through a channel protein to diffuse across the membrane

Movement of molecules is down a chemical gradient and does not require external energy

The rate of facilitated diffusion is dependent on temperature, concentration gradient, membrane surface area and thickness but is also affected by the number of channel proteins present

Question 97

C5) why can a membrane be considered to be selectively permeable

Answer 97

Membranes with protein channels can be selectively permeable as most protein channels are specific to one molecule or ion

Question 98

C5) What is active transport

Answer 98

The movement of molecules into out of the cell from a region of lower concentration to a region of higher concentration requiring the use of ATP and a carrier protein

ATP is needed as particles are moving up a concentration gradient in the opposite direction of diffusion

The process is selective- specific substrates are transported by specific carrier proteins

Question 99

C5) What are the stages of active transport

Answer 99

The molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell

On the inside of the cell ATP binds to the carrier protein and is hydrolysed into ADP and phosphate

Binding of the phosphate molecule to the carrier protein causes the protein to change shape opening up the inside of the cell

The molecule or ion is released to the inside of the cell

The phosphate molecule is released from the carrier protein and condenses with ADP to form ATP

The carrier protein returns to its original shape

Question 100

C5) What is bulk transport

Answer 100

A different form of active transport

Larger molecules such as enzymes and hormones which are too big to move through channel or carrier proteins

ATP energy is required for movement of Vesicle along the cytoskeleton, changing the shape of cells to engulf material and diffusion of cell membranes as vehicles form

Question 101

C5) how does endocytosis occur

Answer 101

Bulk transport of materials into the cell

Two types of endocytosis: phagocytosis for solids and pinocytosis for liquids the process is the same

1) The cell-surface membrane first invaginates (Bends inwards) When it comes into contact with the material to be transported
2) The membrane enfolds the material until eventually the membrane fuses forming a Vesicle
3) The Vesicle pinches off and moves into the cytoplasm forming a endosome which transfer the material for further processes

Question 102

c5) how does exocytosis occur

Answer 102

Secretory versicles produced mainly by the Goldie apparatus moved towards and fuses with the cell-surface membrane the contents of the vehicle is released outside the cell

1) The secretary versicles moves out of the cytoplasm to transfer the material outside of the cell
2) The membrane unfolds the material until eventually the membrane fuses
3) The cell-surface membrane invaginates (Bends inwards) When it comes into contact with the material to be transported out

Question 103

C5) What is the effect of osmosis on plants and animal cells

Answer 103

The diffusion of water into a solution lead to an increase in the volume of the solution

If the solution is in a closed system this results in an increase in pressure called hydrostatic pressure

Question 104

C5) How does osmosis affect animal cells

Answer 104

If an animal cell is placed in a solution with a higher water potential than the cytoplasm, Water will move into the cell increasing the hydrostatic pressure inside. The cell surface membrane cannot stretch much and cannot withstand the increased pressure, the cell wall will burst called cytolysis

If an animal cell is placed in a solution with a lower water potential than The cytoplasm water is lost to the solution. It will cause a reduction in the volume of the cell and the cell surface membrane Will become crenated

Question 105

C5) What are the effects of osmosis on plant cells

Answer 105

Plant cells have a strong Celulose cell wall surrounding the cell surface membrane.

When water enters by osmosis the increased hydrostatic pressure pushes the membrane against the rigid cell wall this pressure is called Turgor. As the Turgor pressure increases it resist the entry of further water and is said to be turgid

When plant cells are placed in a solution with a lower water potential than its own water is lost from the cell by osmosis leading to a reduction in the volume of the cytoplasm which eventually pours the cell-surface membrane away from the cell wall this is called plasmolyse

Question 106

C6) What is the Cell Cycle

Answer 106

The cell cycle is the process that all body cells (in multicellular organisms) use to grow and divide.

It starts with a cell that has already been produced by cell division and ends with this cell dividing to produce 2 genetically identical daughter cells.

Question 107

C6) What are the 2 ways that eukaryotic cells divide

Answer 107

Mitosis: division into two daughter cells that are genetically identical to each other and to the parent cell.

Meiosis: division into four unique daughter cells with half the chromosomes of the
parent cell.

Question 108

C6) Why is the cell cycle important

Answer 108

Produces genetically identical daughter cells (i.e. clones –maintains same number of chromosomes as the parent cell).

Growth of tissue/organism (not of cells)

Replacement of worn out/damaged cells

Repair of body tissues (e.g. bone, muscle etc)

Asexual reproduction/cloning

Question 109

C6) What are the stages of the cell cycle

Answer 109

The cell cycle has two stages:

Interphase: G1, S and G2 phases
mitotic Phase:Mitosis and Cytokinesis

Question 110

C6) What happens in G1

Answer 110

First growth phase of cell, synthesis of proteins, organelles replicate e.g. mitochondria, ribosomes etc. Cell increases in size.

End of G1 checkpoint.

Question 111

C6) What happens in S

Answer 111

Synthesis phase. Replication of each chromosome in the nucleus

Question 112

C6) What happens in G2

Answer 112

Second growth phase, cell continues to grow in size. Duplicated DNA is checked for errors. Energy stores (i.e. ATP molecules) are increased.

End of G2 checkpoint.

Question 113

C6) What happen in G0 phase

Answer 113

phase where the cell leaves the cell cycle either temporarily or permanently.

Why?

Differentiation (& no longer able to divide)

DNA may be damaged

As you age the number of these cells in your body increases

Few types of cells can be stimulated to go back into the cell cycle from G0

Question 114

C6) What is checked for at the G1 checkpoint

Answer 114

Cell size

Nutrients

Growth factors

DNA damage

Question 115

C6) What is checked for at the G2 checkpoint

Answer 115

Cell size

DNA replication

DNA damage

Question 116

C6) What is checked for at the spindle assembly checkpoint

Answer 116

Chromosome attachment to spindle

Question 117

C6) What happens if the DNA is not checked

Answer 117

Mutations

Faulty DNA produced

Error in copying daughter cells

Daughter cells will not receive identical genetic information

Proteins not made or do not function properly

Question 118

C6) What is the structure of a chromosome

Answer 118

Chromosomes are only visible during cell division.

Each chromosome consists of two chromatids joined somewhere along its length at the centromere.

Genetic information (genes/alleles) carried on each chromatid is identical.

During interphase DNA combines with proteins chalked histones to form chromatin

Question 119

C6) What is a Homologous Chromosomes?

Answer 119

A pair of chromosomes – one maternal (from mother) and one paternal (from father)

The chromosomes carry the same genes but may carry different forms of the genes. A alternate form of the same gene is called an allele.

Question 120

C6) What is the definition of sister chromatids

Answer 120

identical, carry the same versions of all their genes because one was produced as an exact copy of the other

Question 121

C6) What does the acronym to remember the stages of mitosis and meiosis

Answer 121

PMAT

P = Prophase 
M = Metaphase 
A = Anaphase
T = Telophase

Question 122

C6) What happens during prophase in the cell cycle

Answer 122

Chromosomes condense and thicken (and therefore become visible)

Consists of sister chromatids (2) joined at the centromere.

Two centrioles migrate to opposite poles of the cell (in animal and some plant cells)

Spindle fibres attach to specific areas on the centromeres and start to move the chromosomes to the centre (equator) of the cell.

Nuclear envelope disappears.

Question 123

C6) What happens during Metaphase in the cell cycle

Answer 123

Brief phase

Individual chromosomes are moved by the spindle fibres to align at the metaphase plate/equator at the centre of the cell.

Chromosomes are attached to the spindle fibres by the centromere.

Question 124

C6) What happens during Anaphase in the cell cycle

Answer 124

Centromeres holding the pairs of chromatids in each chromosome divide.

Chromatids separate

Spindle contracts (fibres shorten)

Each chromatid is pulled by their centromere to opposite poles of the cell.

Question 125

C6) What happens during Telophase in the cell cycle

Answer 125

Chromatids have reached opposite poles of the cell. They uncoil and become long and thin again.

They are now called chromosomes

Spindle fibres disappear

Nuclear envelope reforms and enclose around the chromosomes at each pole.

Question 126

C6) What happens in cytokines in the cell cycle

Answer 126

This is the phase where the cytoplasm divides.

In animal cells a ‘cleavage furrow’ forms. In plant cells a ‘cell plate’ forms.

This results in 2 genetically identical daughter cells being formed.

Question 127

C6) What is meiosis

Answer 127

Meiosis is the process of cell division which produced four daughter cells which are not identical - they are different from each other. They have half the number of
chromosomes as the parent cell, making them haploid.

The process involves 2 nuclear divisions.

Question 128

C6) What is the Importance of meiosis

Answer 128

Takes place in sex organs

Gametes produced here

Important to have genetically different gametes

This promotes genetic variation and allows for Natural Selection to take place

Question 129

C6) What happened during interphase?

Answer 129

Before mitosis can occur, each DNA molecule (chromosome) in the nucleus is replicated during the interphase.

Each chromosome is converted into two identical DNA molecules called chromatids.

The two chromatids are joined together at a region called the centromere.

Condensed chromosomes combined with histone proteins are called chromatids.

Question 130

C6) What are the stances of meiosis

Answer 130

two-stage process:

Meiosis I introduces genetic diversity by randomly dividing a cell’s genes in two. It results in two haploid cells.

Meiosis II is similar to mitosis. It splits each chromosome into its two chromatids and places one in each daughter cell. It results in four haploid gametes.

Question 131

C6) What is the difference between Haploid and Diploid cells

Answer 131

A human somatic (body) cell contains
46 chromosomes. These consist of 23 pairs of homologous chromosomes.

Sex cells, or gametes, have only one copy of each chromosome: they are haploid. A somatic cell, containing two of each, is called diploid.

Question 132

C6) How does genetic variation occur during meiosis?

Answer 132

Sexual reproduction creates genetic
diversity within a population, which is vital to a species’ survival.

Two processes during meiosis determine the unique genetic make-up of the four daughter cells:

During meiosis I, homologous pairs of chromosomes swap parts of their genetic material. This is crossing over.

The chromosomes from each pair are randomly allotted to the daughter cells by independent assortment.

Question 133

C6) What happens in prophase 1 of the meiosis cycle

Answer 133

Chromosomes condense

Nuclear envelope disintegrates

Spindle formation begins.

Homologous chromosomes pair up forming bivalents.

Crossing over of genetic information occurs.

Question 134

C6) What happens in Metaphase 1 of the meiosis cycle

Answer 134

Homologous pairs of chromosomes
assemble along the metaphase plate (instead of individual chromosomes – as in mitosis).

The orientation of each homologous pair is random and independent of any other homologous pair.

This is called independent assortment.

Question 135

C6) What happens in Anaphase 1 of the meiosis cycle

Answer 135

The homologous chromosomes separate.

Each homologous chromosome (consisting of two chromatids) moves to opposite sides of the cell

The result is that 23 chromosomes (each
consisting of two chromatids) move to one pole, and 23 chromosomes (each consisting of two chromatids) move to the other pole.

Question 136

C6) What happens in Telophase 1 of the meiosis cycle

Answer 136

Very similar to telophase in mitosis

Chromosomes assemble at each pole

Nuclear envelope reforms

Chromosomes uncoil

Cell undergoes cytokinesis

Question 137

C6) How does Independent (random) assortment of chromosomes during anaphase 1 work

Answer 137

When homologous pairs line up along the equator of the cell during metaphase 1 and get separated during anaphase 1 of meiosis 1 it is completely random which chromosome from each pair ends up in the daughter cell.

This gives rise to new combinations of alleles.

Question 138

C6) What happens in Prophase 2 of the meiosis cycle

Answer 138

Beginning of second division:

Chromosomes pair up and re-condense

Nuclear envelop breaks down again

Spindle fibres reform

Question 139

C6) What happens in Mataphase 2 of the meiosis cycle

Answer 139

Chromosomes (sister chromatids)
are a lined on the equator by the spindle fibres.

Centrioles move to opposite poles of the cell.

Question 140

C6) What happens in Anaphase 2 of the meiosis cycle

Answer 140

Centromere divides

Sister chromatids are separated

Spindle fibres contract

Chromatids move to the poles of the cells

This is the same as anaphase in mitosis

Question 141

C6) What happens in Telophase 2 of the meiosis cycle

Answer 141

Chromatids uncoil

Spindle fibres break down

Nuclear envelopes reform

The cell undergoes Cytokinesis

4 haploid daughter cells are produced

Question 142

C6) How does crossing over during prophase 1 work

Answer 142

During prophase 1 of meiosis 1 homologous chromosomes pair up as bivalents.

Chiasmata (‘twisting around each other’) form between chromatids of different but homologous chromosomes.

The chromatids still have the same genes but now have a different combination of alleles.

Question 143

C6) What happens in Cytokinesis of the meiosis cycle

Answer 143

Cytoplasm and surface membrane divide, creating four independent haploid daughter cells.

Question 144

C6) What is a Stem cell

Answer 144

Before a cell has differentiated, or specialised, it is called a stem cell

A stem cell is a cell that has not yet become a specialised cell
(undifferentiated).

A stem cell:

Can replicate many times (self renewal)
Has the potential to become specialised (i.e. different types of cell) (potency)

Question 145

C6) what are embryonic stem cells

Answer 145

Embryonic stem cells are stem cells found in embryos are known as embryonic stem cells and can develop into almost every cell type under the right conditions in a lab.

Present a very early stage of embryo development.

Embryonic stem cells are totipotent before 7 days and pluripotent after the blastocyst forms.

Question 146

C6) What are adult stem cells

Answer 146

Adult stem cells are stem cells found in adult tissues (such as bone marrow, brain, muscle, liver stem cells). These cells can only differentiate into the same type of cell as the tissue they came from e.g. liver stem cells can only become liver cells.

Present throughout life from birth.
Found in specific areas e.g. bone marrow and are mulitopotent.
Could be artificially triggered to become pluripotent.
Can be harvested from umbilical cords of newborn babies.

In animals, adult stem cells are used to replace damaged cells.

Question 147

C6) What are the different potencies of stem cells

Answer 147

Totipotent – Totipotent stem cells that are able to differentiate into any type of cell found in body and into extra embryonic cells such as those in the placenta. These cells are found in the embryo at an early stage called the blastocyst. The ‘total’ individual. E.g. zygote

Pluripotent – Can form any cell type (e.g. embryonic stem cells) but not the whole organism.

Multipotent – Can differentiate into a number of closely related cell types within a certain type of tissue (e.g. haematopoeitic adult stem cells in bone marrow give rise to different types of blood cells).

Unipotent – Can not differentiate, but are capable of self renewal (e.g. progenitor cells, muscle stem cells)

Question 148

C6) what are the sources of plant stem cells

Answer 148

They are present in the meristematic tissue (meristems) implants. This tissue is found wherever growth is occurring in plants.

This tissue is also located sandwiched between the phylum and xylem tissues and this is called the Vascular Cambium

Question 149

C6) What are four uses of stem cells

Answer 149

Heart disease- muscle tissue in the heart is damaged as a result of a heart attack, normally irreparably - been tried experimentally with some success already

Parkinson‘s disease- the symptoms are caused by the death of dopamine production cells in the brain; drugs currently only delay the process of the disease

Muscular degeneration- this condition is responsible for causing blindness in the elderly and diabetes; scientists are currently researching the use of stem cells in its treatment and early results are very encouraging

Spinal injuries- scientists have resolved some movement to the hindlimbs of rats with damage to spinal cords using stem cell implants

Question 150

C6) What areas have stem cells already been used in

Answer 150

The treatment of burns- stem cells grown on biodegradable meshes can produce new skin for burning patients, Quicker than the normal process of taking a graft from another part of the body

Drug trials- potential new drugs can be tested on the cultures of stem cells before being tested on animals and humans

Question 151

C6) what are the ethical dilemmas to do with stem cells

Answer 151

The destruction of the embryo when stem cells of collected - not only religious but also moral beliefs as people believe life begins at conception and therefore this would be murder.

Lack of consensus about the rights of the embryo itself and who owns the genetic material being used in the research

Umbilical stem cells came over these ethical dilemmas but these are less useful than embryonic stem cells

Question 152

C6) What is the meaning of a specialised cell

Answer 152

I saw that has differentiated to carry out a specific function

Question 153

C6) how are Erythrocytes specialised for their function

Answer 153

Flattened biconcaved shape to increase the surface area to volume ratio essential to transport oxygen around the body

No nuclei or many organelles this increases the space available for haemoglobin the molecule that carries oxygen

Flexible so they can squeeze through narrow capillaries

Question 154

C6) how are neutrophils specialised for their function

Answer 154

Essential role in the immune system

Multilobed nucleus making it easier for them to squeeze through small gaps to get to the sight of infection

Granular cytoplasm contains many lysozymes that contain enzymes used to attack pathogen

Question 155

C6) how are Sperm cells specialised for their function

Answer 155

Function is to deliver genetic material to the female gamete the ovum

Have a flagellum so they are capable of movement and contain many mitochondria to supply the energy needed to swim

Acrosome on the head of the sperm contains digestive enzymes which are released to digests the protective layer around the ovum and allows the sperm to penetrate leading to fertilisation

Question 156

C6) how are Palisade cells specialised for their function

Answer 156

Present in the Mesophyll containing chloroplasts to absorb large amounts of light for photosynthesis

Rectangular box shapes, closely packed to form a continuous layer

They have a thinwall increasing the rate of diffusion of carbon dioxide

Large vacuole to maintain turgor pressure

Chloroplast can move within the cytoplasm in order to absorb more light

Question 157

C6) how are root hair cells specialised for their function

Answer 157

At the surface of roots need the growing tips

Large extension is called root hairs which increases the surface area of the cells

Maximise the uptake of water and minerals from the soil because of the large permanent vacuole, thin Celulose cell wall

Question 158

C6) how are a pair of guard cells specialised for their function

Answer 158

On the surface of leaves form small opening is called The stomata,Necessary for carbon dioxide to enter plants for photosynthesis

Guard cells lose water and become less swollen as a result of osmotic forces, they change shape and stomata closes to prevent further water loss from the plant

The cell wall of a Guard cell is thicker on one side so the cell does not change shape symmetrically as its volume changes

Question 159

C6) what is the meaning of tissue

Answer 159

Made up of a collection of differentiated cells that have a specialised function

Question 160

C6) What are the Four main categories of tissues in animals

Answer 160

Nervous tissue - adapted to support the transmission of electrical impulses

Epidermal tissue – an adapter to cover body surfaces, internal and external

Muscle tissue - adapted to contract

Connective tissue - adapted either to hold other tissues together or as a transport medium

Question 161

C6) what is the structure of squamous epithelium

Answer 161

Made of squamous epithelium cells

Known as pavement epithelium due to its flat appearance

Very thin due to the flat cells that make it up and because it is only one cell thick

Present when rapid diffusion across its surface is essential

Forms the lining of the lungs and allows rapid diffusion of oxygen

Question 162

C6) What is the structure of ciliated epithelium

Answer 162

Made up of ciliated epithelium cells

Hairlike structures called cilia that moves in a rhythmic manner

Goblet cells are also present releasing mucus to trap any unwonted particles present in the air

Prevents the particle from reaching the alveoli inside the lungs

Question 163

C6) What is the structure of cartilage

Answer 163

Connective tissue found in the outer ear

Contains fibres of the proteins elastin and collagen

Is a firm flexible connective tissue composed of chondrocyte cellEmbedded in an extra cellular matrix

Prevents the bones rubbing against each other causing damage

Question 164

C6) what is the structure of muscle

Answer 164

Needs to be able to shorten in length in order to move bones

Different types of muscle fibres. Skeletal muscle fibres contain myofibrils contains contractile proteins

Question 165

C6) what is the structure of epidermis

Answer 165

Single layer of closely packed cells covering the surface of the plant

Covered by a waxy waterproof cuticle to reduce the water loss

Stomata formed by a pair of Gard cells can open and close are present in the epidermis

Question 166

C6)What is the definition of an organ

Answer 166

A collection of tissues that are adopted to perform a particular function in an organism

Made up of muscle tissues and connective tissue

Question 167

C6)What is the definition of an organ system

Answer 167

Is comprised of a number of organs working together to carry out a major function in the body

Question 168

C3) what are the roles of these cations

1. Calcium ion
2. Sodium ions
3. Potassium ion
4. Hydrogen ion
5. Ammonium ion

Answer 168

1. Nerve impulse transmission
   Muscle contraction
2. Nerve impulse transmission
   Kidney function
3. Nerve impulse transmission
   Stomatal opening
4. Catalysis of reaction
   PH determination
5. Production of nitrate ions by bacteria

Question 169

C3) what are the roles of these anions

1. Nitrate ion
2. Hydrogen carbonate ion
3. Chloride ion
4. Phosphate ions
5. Hydroxide ion

Answer 169

1. Nitrogen supply to plants for amino acid and protein formation
2. maintenance of blood pH
3. balance positive charge of sodium and potassium ions in cells
4. cell membrane formation
   Nucleic acid and ATP formation
   Bone formation

Question 170

C3) what is the bond that holds water molecules together and what is its characteristics

Answer 170

Hydrogen bond

Hydrogen bonds are relatively weak interactions, which break and reform between the constantly moving water molecule

Question 171

C3) How is water a polar molecule

Answer 171

1) The atoms with the greater share of the negative electrons Will be slightly electronegative while the other item would be slightly electropositive
2) oxygen always has a much greater share of the electrons in an O-H Bond
3) oxygen and hydrogen bonded together is called an hydroxyl group
4) water contains two of these hydroxyl groups

Question 172

C3) how does hydrogen bonds hold water molecules (H2O) together

Answer 172

Polar molecules interact with each other as the positive and negative regions of the molecule attract each other and form an hydrogen bond

Question 173

C3) what are the characteristics of water.

Answer 173

high boiling point - takes a lot of energy to increase the tamp of water and change it to gas because of the hydrogen bonding

when frozen into ice it is less dense than other substances in solid form - because the hydrogen bonds are fixed to there positions father apart in a solid

water has cohesive properties - it can move as one mass because the molecules are attracted to each other

water is adhesive - water molecules are attracted to other materials

water has a skin of surface tension - as they are more cohesive to each other

Question 174

C3) how is water important for life

Answer 174

water acts as a solvent - the solutes in an organism can be dissolved in it because it is a polar molecules

water acts as a medium for chemical reactions and also help transport dissolved component into and out of cells

water makes a very efficient transport medium within living things - cohesion between water molecules means that they stick together when transported through the body. Adhesion occurs between water molecules and other polar molecules and surfaces. Effects of adhesion and cohesion results in water exhibiting capillary action this means water can rise up a narrow tube against the force of gravity

Water acts as a coolant - helping to buffer temperature changes during chemical reactions because of the large amount of energy required to overcome hydrogen bonding

Water is stable - it does not change temperature will become aghast easily therefore providing a constant environment

Question 175

C3) why is glucose a polar molecule and soluble in water. Why is this important

Answer 175

Because of the hydrogen bonds between the hydroxyl group and water molecules

Solubility in water is important because it means glucose is dissolved in the cytosol of a cell

Question 176

C3) how is maltose (disaccharides) created

Answer 176

Condensation reaction between two alpha glucoses

Question 177

C3) how is Cane sugar created (Sucrose)

Answer 177

Fructose + glucose = sucrose (disaccharides)

Question 178

C3) what are Fructose and galactose

Answer 178

They are also hexose monosaccharides, six carbon molecule

Fructose is sweeter than glucose

Glucose is sweeter than galactose

Question 179

C3) How is lactose created

Answer 179

Galactose + glucose = lactose (disaccharide)

Question 180

C3) What are pentose monosaccharides

Answer 180

Sugars containing five carbon atoms.

To pentose sugars are important components of biological molecules:

Ribose is a sugar present in RNA nucleotides
Deoxyribose is the sugar present in DNA nucleotides

Question 181

C3) what is the relationship between starch and glucose

Answer 181

Many alpha glucose is joined by glycosidic bonds form 2 slightly different polysaccharides known collectively as starch. Starch made by photosynthesis is stored as starch in chemical energy stores

Question 182

C3) How is amylase formed

Answer 182

One of the polysaccharides in starch

Alpha glucose molecules joined together only buy 1-4 glycosidic bonds.

The angle of the bonding means that the long chain glucose twist to form a helix which is further stabilised by hydrogen bonding within the molecule

Making the polysaccharide more compact and less soluble than glucose molecules are used to make it

Question 183

C3) How is amylopectin formed

Answer 183

The second polysaccharide formed in starch

Made by 1-4 glycosidic bonds between alpha glucose molecules but unlike amylase there are also glycosidic bonds forming by condensation reaction between carbon 1 and carbon 6 on 2 glucose molecules

Allowing amylopectin a branching structure with 1-6 branching points approximately once every 25 glucose subunits

Question 184

C3) How is glycogen adapted for its function

Answer 184

Glycogen form more branches than amylopectin which means it is more compact and less space is needed for it to be stored this is important because animals are mobile

The branching of these poly saccharides make them very compact ideal for storage

Branching also means that there are many free ends where glucose molecules can be added or removed allowing the process of storing and releasing glucose molecules to speed up

Question 185

C3) What are the key properties of amylopectin and glycogen

Answer 185

That they are insoluble, branched and compact

Question 186

C3) How is cellulose formed

Answer 186

2 Beta glucose molecules are unable to join together in the same way as alpha glucoses because the hydroxyl groups of carbon 1 and carbon 4 are too far apart to react in a condensation reaction

Only way beta glucose molecules can join together is if alternate beta molecules are turned upside down

When this occurs it is unable to coil or form branches. A straight chain molecule is formed called cellulose

Question 187

C3) What is the test for reducing sugars

Answer 187

Benedict’s reagent = copper II sulphate

1) placed the sample to be tested in a boiling tube. If it is not in liquid form grind it up and blend it with water
2) add an equal volume of Benedict’s reagent
3) heat the mixture gently in a boiling water bath for five minutes

Reducing sugars will react with the copper ions in the reagent. Resulting in addition of electrons to the blue Cu2+ reducing to brick red Cu+

The results could be Blue showing none, green colour showing low concentrations, yellow amber orange showing medium concentration and red showing high concentration

Question 188

C3) What is the test for non-reducing sugars

Answer 188

Non-reducing sugars do not react with benedict’s solution

Sucrose is the most common non-reducing sugar

If sucrose is first boiled with hydrochloric acid it will give a positive result when warmed with benedict’s solution. Because sucrose has been hydrolysed into glucose and fructose

Question 189

C3) what are lipids and what are their properties

Answer 189

Fats are molecules containing carbon, hydrogen and oxygen. Fats are lipids that are solid at room temperature and oils all lipids that are liquid at room temperature

Lipids are not soluble in water because lipids are nonpolar molecules because the electrons are equally distributed than polar molecules

Question 190

C3) What is Triglycerides made off

Answer 190

One glycerol member of a group of molecules called alcohols

Three fatty acids member of a group of molecules called carboxylic acid’s consisting of a carboxyl group with a hydrocarbon chain

Question 191

C3) what is the difference between saturated and unsaturated fats

Answer 191

Fatty acid chains that have no double Bonds present between the carbon atoms are called saturated because all the carbon atoms form bonds with hydrogen atoms

fatty acid with double Bonds between some of the carbon atoms are called unsaturated

Monounsaturated means one double bond between carbon atoms while polyunsaturated means 2 or more double bonds

Double bonds cause the molecule to Kings and bend and they cannot pack so closely together therefore making them liquid at room temperature I therefore describing oils

Question 192

C3) what type of Triglyceride is healthier

Answer 192

I plants containing unsaturated triglycerides occurring naturally as oils tend to be more healthier in the human diet than saturated triglyceride

Question 193

C3) How do phospholipid behave when interacting with water

Answer 193

A layer on the surface of the water with the phosphate heads in the water and the fatty acid tales sticking out of the water because of this they are called surface active agent

Or form a bilayer where the hydrophobic tails point inwards to the centre protected by the hydrophilic heads with a 2 layered sheet formation

Question 194

C3 what are the characteristics of sterols

Answer 194

Another type of lipids found in cells.

They are not fat oils and have little in common with them structurally

Complex alcohol molecules based on a four carbon ring structure with a hydroxyl group at one end

They have a dual hydrophobic/hydrophilic characteristic. The hydroxyl group is polar and therefore hydrophilic. The rest of the molecule is hydrophobic

Question 195

C3) what is the structure of cholesterol

Answer 195

Is a sterol

Manufactured primarily in the liver and intestines

When it is added to the cell membrane it regulate their fluidity by keeping membrane fluid at lower temperatures and stopping them becoming too fluid at higher temperatures

Question 196

C3) how is the phospholipid formed

Answer 196

The phosphate ions PO3- have extra electrons and so are negatively charged and make them soluble in water

One fatty acid chains in a triglyceride molecule is replaced with a phosphate group

Question 197

C3) Is the role of lipids

Answer 197

Because lipids are nonpolar the rules include:

Membrane formation and the creation of hydrophobic barriers

Electrical insulation necessary for impulse transmission

Waterproofing in birds feathers and paint leaves

Triglycerides have an important role in long-term energy store. Stored under the skin around vital organs which provide:

Thermal insulation to reduce heat loss

Cushioning to protect vital organs such as the heart and kidneys

Buoyancy for aquatic animals

Question 198

C3) What is food synergy

Answer 198

It is believed that nutrition does not work in isolation but as part of the combined efforts of a whole range of Nutrients.

Question 199

C3) What are the different amino acid is found in cells

Answer 199

20 different amino acids are commonly found in cells

Five of these are said to be non-essential as our bodies are able to make them from other amino acids

Nine are essential and can be obtained from what we eat

Six are said to be conditionally essential as they are only needed by infants and growing children

Question 200

C3) what enzyme binds Multiple peptides together

Answer 200

The enzyme peptidyl transferase present in the ribosome catalyse the joining together of many amino acids with peptide bonds to make polypeptides

Question 201

C3) What is the food test for lipids

Answer 201

The emulsion test

The sample is mixed with ethanol which is then mixed with water and shaking

If a white emulsion forms as a layer on top of the solution it is a positive indication of lipids if not then it is a negative result

Question 202

C3) what is the primary and secondary structure of a protein

Answer 202

Primary structure - is a sequence in which the amino acids are joined. It is directed by information carried within DNA. Only bond involved is the peptide bond

Secondary structure- the oxygen, hydrogen and nitrogen atoms of the basic repeating sequence of amino acid interact. Hydrogen bonds may form within the amino acid chain into a alpha helix.
Polypeptide chains can lie parallel to one another joined by hydrogen bonds forming a beta plated sheet

Question 203

C3) what is the Quaternary structure of a protein

Answer 203

The Association of two or more individual proteins called subunits.

The interactions between the subunits are the same as in the tertiary structure except they are between different protein molecules

Protein subunits can be identical or different. Enzymes often consist of two identical subunits whereas insulin has two different subunits.

Question 204

C3) how does hydrophobic and hydrophilic interactions occur within a protein

Answer 204

As proteins are assembled in aqueous environment of the cytoplasm.

the way a protein foods will depend on whether r groups are hydrophobic or hydrophilic. Hydrophilic groups are on the outside of the protein while hydrophobic groups are on the inside of the molecule shielded from the water in the cytoplasm

Question 205

C3) what is the food test for proteins

Answer 205

Peptide bonds form violet coloured complexes with copper ions in alkaline solutions.

Add equal volumes of 10% sodium hydroxide. Then add 1% copper sulphate solution until it is blue.

A mixture of an alkaline and copper sulphate solution is called biret reagent

Question 206

C3) What is the tertiary structures of proteins

Answer 206

Tertiary structure - folding of a protein into its final shape. The coiling or folding of proteins into the secondary structure brings R groups of different amino acids closer together so they are close enough to interact and further folding of the sections will occur

Hydrophobic and hydrophilic interactions - weak interactions between polar and nonpolar r groups

Hydrogen bonds - these are weakest of the bonds formed

Ionic bonds - these are stronger than hydrogen bonds and form between oppositely charged r groups

Disulphide bridges- these are covalent and the strongest of the bonds but only form between R groups that contain sulphur atoms

These produce a variety of complex shape proteins with specialised characteristics and functions

Question 207

C3) what are the characteristics of globular proteins

Answer 207

A compact, water-soluble and usually roughly spherical in shape

They form when proteins fold into the tertiary structure in the way in which the hydrophobic r groups of the amino acids are kept away from the aqueous environment, The hydrophilic r groups are on the outside of the protein meaning protein is water-soluble

Solubility is important for many different functions of globular proteins.

Question 208

C3) what are the characteristics of insulin

Answer 208

Is a globular protein.

Is a hormone involved in regulating blood glucose concentration.

Hormones are transported in the blood system so need to be soluble.

Hormones also have to fit into specific receptors on the cell surface membranes to have The effect therefore need to have specific shape

Question 209

C3) what are the characteristics of conjugated proteins

Answer 209

Conjoined proteins are globular proteins that contain a non-protein component called a prosthetic groups

Proteins without A prosthetic groups are called simple proteins

Different types of prosthetic groups. Lipids or carbohydrates can combine with proteins forming lipoproteins or glycoproteins. Metal ions and molecules made from minerals can form prosthetic groups

Haem groups are prosthetic groups. They contain iron II ions. Catalase and haemoglobin both contain in groups

Question 210

C3) How is haemoglobin a conjugated protein

Answer 210

Haemoglobin is the red, oxygen carrying pigment found in red blood cells.

It is a Quaternary protein made from four polypeptide, 2 alpha and 2 beta subunits

Each subunit contains a prosthetic haem groups. The iron II ions present in the prosthetic groups are each able to combine reversibly with oxygen molecules allowing haemoglobin to transport oxygen around the body.

Question 211

C3) how is catalase a conjugated protein

Answer 211

Catalase is an enzyme which means it increases the rate of reaction and each enzyme is specific to a particular reaction or type of reaction

Catalase is a Quaternary protein containing 4 haem prosthetic groups

The presence of iron II ions in the prosthetic groups allow catalase to interact with hydrogen peroxide and speed up its breakdown

Hydrogen peroxide is a common byproduct of metabolism but is damaging to cells if allowed to accumulate

Question 212

C3) what is a fibrous protein

Answer 212

Formed from long insoluble molecules.

This is due to the presence of High proportion of amino acids with hydrophobic r groups in their primary structure. Containing a limited range of amino acids usually with small r groups

Very repetitive primary structure of amino acids

Very organised structure is reflected in the rose fibrous proteins have. Keratin, elastin and collagen are examples of fibrous proteins

Fibrous protein tend to be strong, long molecules which are not folded into complex three-dimensional shapes like globular proteins

Question 213

C3) What are the characteristics of keratin

Answer 213

A group of fibrous proteins present in hair, skin and nails

Has large proportion of the sofa containing amino acid, cytosine.Resulting in strong disulphide bonds forming strong, inflexible and In soluble materials.

The degree of disulfide bonds determines the flexibility, hair contains fewer bonds making it more flexible than males.

The unpleasant smell produced when the hair is burnt is due to the presence of relatively large quantities of sulfur in these proteins

Question 214

C3) what are the characteristics of elastin

Answer 214

A fibrous protein found in elastic fibres

Elastic fibres are present in the walls of the blood vessels and in the alveoli of the lungs- gives the structures the flexibility to expand when needed but also to return to normal size

Quaternary protein made from many stretchy molecules tropoelastin

Question 215

C3) what are the characteristics of collagen

Answer 215

Fibrous protein

Is a connective tissue found in skin, tendons,Ligaments and the nervous system

A number of different forms but all are made up of three polypeptide wound together in a long and strong rope like structure

Collagen has flexibility

Question 216

C3)What are nucleic acids are made of

Answer 216

Contains the elements carbon, hydrogen, oxygen, nitrogen and phosphorus

Large polymers formed from many nucleotidesLinked together in a chain

Question 217

C3) what is the structure of a nucleotide

Answer 217

A pentose monosaccharide, contains five carbon atoms

A phosphate group, in organic molecule that is acidic and negatively charged

A nitrogenous base-complex organic molecules containing one or two carbon rings in its structure as well as nitrogen

Question 218

C3) What is deoxyribonucleic acid

Answer 218

The sugar in deoxyribonucleic acid is dioxiribose - are you sugar with one fuel oxygen atoms than ribose

Question 219

C3) why is DNA said to be antiparallel

Answer 219

Each strand of the DNA helix has a phosphate groupAt one end and a hydroxyl group at the other end

The two parallel strands are arranged so that they run in opposite directions

Question 220

c3) what is the importance of complimentary base pairing

Answer 220

Helps to maintain a constant distance between the DNA backbone resulting in parallel polynucleotide chains

Allowed DNA to have equal amounts of A and T as well as equal amounts of C and G

Question 221

C3)Why is ribonucleic acid important

Answer 221

The DNA of each eukaryotic chromosomes is a very long molecule, comprising of many hundreds of jeans and is unable to leave the nucleus in order to supply the information directly at the site of protein synthesis

To solve this short sections of the long DNA molecule corresponding to a single gene is transcribed into a similar short messenger RNA molecule

Each individual mRNA is therefore shorter than the whole chromosome of DNA

Polymer comprising of many monomer nucleotides

Question 222

C3) How is an RNA polymer created

Answer 222

RNA nucleotides are different to DNA nucleotides as the pentose sugar is ribose rather than deoxyribose

The RNA nucleotides form polymers in the same way as DNA nucleotides by the formation of phosphodiester bonds in condensation

RNA polymers are small enough to leave the nucleus and travel to the ribosomes where they are processed for protein synthesis

After protein synthesis the RNA molecules are derogated in the cytoplasm. The phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused

Question 223

C3) what are the stages of semiconservative replication

Answer 223

The unwinding and separating of the two strands of The DNA double helix is carried out by the enzyme DNA helicase. It travels along the DNA backbone breaking the hydrogen bonds between complimentary base pairs, unzipping

Free DNA nucleotides will then pair with a complimentary bases which have been exposed as the strands separate, Forming hydrogen bonds

DNA polymerase catalyses the formation of phosphodiester bonds between these nucleotides

Question 224

C3) what is degenerate code

Answer 224

As there are four different bases which means that there are 64 different base triplets or codons possible

this includes one code on the acts as the start codons, Signalling the start of a sequence that codes for a protein - methionine
Stop codons do not code for any amino acids and signal the end of the sequence

Having a single codon to signal the start of a sequence insures that the triplets of bases are read in frame meaning it is read from base 1 rather than base 2 or 3, so there are no overlapping

Only 20 different amino acids are regularly occurring in biological proteins, therefore many amino acids are coded for by more than one codon

Question 225

C3) what is the sense strand

Answer 225

Only one of the two strands of DNA contains the code for the protein to be synthesised

Runs from 5 to 3 end

Question 226

C3) what is the antisense strand

Answer 226

3 to 5 end

Is a complimentary copy of the sentence trend and does not code for a protein

It acts as a template strand during transcription, so that the complimentary RNA strand formed carries the same base sequences as the sense stand

Question 227

C3) what are the enzymes that control transcription

Answer 227

DNA helicase which helps with breaking off hydrogen bonds between the bases

RNA Polymerase which help with forming phosphodiester bonds between the RNA nucleotides

Question 228

C3) what is the importance of ribosomal RNA

Answer 228

Is one of the two subunits that make up ribosomes along with protein, composed of equal amounts

Important in maintaining the structural stability of the protein synthesis sequence and plays a biochemical role in catalysing the reaction

Question 229

C3) what is the importance of the ribosome in translation

Answer 229

The mRNA binds to a specific site on the small subunit of a ribosome

The ribosome holds mRNA in position while it is translated into a sequence of amino acids

Many ribosomes can follow on the mRNA behind the first, so that multiple identical polypeptide can be synthesised Simultaneously

Ribosomes act as the binding site for mRNA and tRNA E and catalyse the assembly of the protein

Question 230

C3)What is the importance of transfer RNA

Answer 230

Necessary for the translation of the mRNA

Composed of a strand of RNA folded in such a way that three bases, called anticodons are at one end of the molecule

Anti codon will bind to a complimentary codon on mRNA a following the natural base pairing rules. The tRNA molecules carry an amino acid corresponding to that codon

Question 231

C3) why do cells require energy

Answer 231

Synthesis-for example of large molecules such as proteins

Transport any further sample pumping molecules or ions across cell membranes

Movement-for example protein fivers in muscle cells and cause muscle contractions

Question 232

C3) what is the structure of ATP

Answer 232

Adenosine triphosphate are able to supply energy

Composed of a nitrogenous base, a pentose sugar and three phosphate groups

The base of the ATP is always Adenine

The sugar in ATP is ribose

Question 234

C3) why is ATP a bad long-term energy store

Answer 234

The instability of the phosphate bond in ATP means that it is a bad long-term energy Store

Fats and carbohydrates are much better for this Energy is released in the breakdown of the molecules in cellular respiration

Question 236

C3) what is phosphorylation

Answer 236

Occurs by reattaching a phosphate group to an ADP molecule

A water is removed in this process it is an example of a condensation reaction

Question 238

C3) why is ATP a good Immediate energy store

Answer 238

The interconversion of ATP and ATP is happening constantly in living cells, meaning cells do not need a large store of ATP

Due to the instability of ATP, cells do not store large amounts of ATP

Question 240

C3) what are the properties of ATP

Answer 240

Small - moves easily into, out of and within cells

Water-soluble - energy requiring process is happening aqueous environments

contains bonds between phosphate with immediate energy - large enough to be used for cellular reactions but not so large that energy is wasted as heat

Releases energy in small quantities - quantities are suitable to most cellular needs, so the energy is not wasted as heat

Easily regenerated - can be recharged with energy

Question 240

C3) what are the 3 tests for carbohydrates

Answer 240

Benedict’s test

Iodine test for starch - yellow to purple/black

reagents strips - use a colour chart to determine the concentration of sugars

Question 240

C3) what are the different chemical elements that make up biological
molecules

Answer 240

C, H and O for carbohydrates
C, H and O for lipids
C, H, O, N and S for proteins
C, H, O, N and P for nucleic acids

Question 240

C3) what are the chemical tests for foods

Answer 240

biuret test for proteins

Benedict’s test for reducing and non-reducing sugars

reagent test strips for reducing sugars

iodine test for starch

emulsion test for lipids

Question 240

what is the formula for Rf

Answer 240

distance moved by the solute /

distance moved by the solvent