topic 1 (biological membrane)

Question 1

what is metabolism?

Answer 1

all the chemical processes that take place in a living organism

Question 2

what is a reducing sugar?

Answer 2

A sugar that can donate an electron or hydrogen to a chemical to reduce it.
All monosaccharides and some disaccharides are reducing sugar

Question 3

what is the test for reducing sugar?

Answer 3

Add 2cm of sample to test tube
If not in liquid form grind with water
Add equal amount of benedicts reagent
If sample is a reducing sugar the solution should turn from blue to orange/brown

Question 4

what are the monosaccharides joined to form maltose

Answer 4

glucose + glucose

Question 5

what are the monosaccharides joined to form sucrose

Answer 5

glucose + fructose

Question 6

what are the monosaccharides joined to form lactose

Answer 6

glucose + galactose

Question 7

what type of reaction are dissacharides produced from?

Answer 7

condensation reaction between monosaccharides that remove h2o forming a glycosidic bond

Question 8

what type of reaction are dissacharides broken down in?

Answer 8

hydrolysis reaction by adding h2o that breaks the glycosidic bond and leaves 2 monosaccharides

Question 9

test for non reducing sugar?

Answer 9

as only some dissacharides are reducing sugars
Add 2cm of sample (grind and add water to make liquid)
heat with equal amount of benedicts solution (5mins)
if it remains blue and doesnt go orange it means it is not a reducing sugar
Add 2cm HCL to hydrolyse disaccharides
Add sodium hydrogencarbonate to neutralise acid
Add Benedict reagent (only works in alkaline test pH)
Re test heating up (5 min)
It should now turn orange/brown

Question 10

describe the features of polysaccharides

Answer 10

large molecules that are insoluble

suitable for storage

Question 11

test for starch

Answer 11

Add 2cm of sample
Add potassium iodide solution
Will go from yellow to blue/black if starch is present

Question 12

where is a starch found and describe its structure?

Answer 12

its a polysaccharide made from glycosidic bonds between a-glucose.It can be branched/unbranched. When branched it coils tightly making it compact.
It is found in plants.
the branched form has many endings which enzymes can act on to release glucose monomers quickly

Question 13

describe the function and role of starch

Answer 13

insolouble so doesnt affect water potential
Large so cannot diffuse out of cells
can hydrolyse to form a-glucose that can be used in respiration
compact so lots can be stored in small space

Question 14

describe the structure of glycogen and where it is found?

Answer 14

its a polysaccharide made from glycosidic bonds between a-glucose.It has shorter chains but highly branched
It is found in animals in small granules in the liver and muscles

Question 15

describe the role of glycogen

Answer 15

insolouble so does not affect water potential/ water doesnt come into cell via osmosis
large does not diffuse out of cell
compact can be stored in small spaces
more branched than starch so can be broken down be enzyme to produce glucose monomers which is used in respiration
this is useful as animals have a higher metabolic reaction and therefore higher respiratory rate

Question 16

why is little glycogen stored in the body?

Answer 16

Fat is the main energy store

Question 17

describe the strucutre of cellulose and where it is found?

Answer 17

polysaccharide made from glycosidic bonds between b-glucose.
It has straight unbranched chains that are parralel
forms hydrogen bond cross linkages between adjacent chains
this strengthens cellulose

Question 18

what are fibres and microfibrils formed from?

Answer 18

cellulose molecules join to form microbrils which can be arranged in parralel groups called fibres

Question 19

what is the role and function of cellulose?

Answer 19

provides rigidity to the plant cell
prevents the cell from bursting as water enters by osmosis it does this by exerting inward pressure stopping water from entering
this makes plant cell turgid and push against making non woody parts of the plant semi rigid.
This is important in maintaining stems and leaves in a turgid state so they can provide maximum surface area for photosynthesis

Question 20

what are the role of lipids?

Answer 20

source of energy - release double the energy of carbohydrates
waterproof- insolouble in water
insulation - slow conductors of heat and
protection - stored around delicate organs e.g kidneys

Question 21

the structure of tryglecerides and how they are related to their properties?

Answer 21

High ratio of energy storing C-H bonds to C atoms making it an excellence source of energy
Good mass to energy ratio allowing more energy to be stored in a smaller space.
This is useful for animals as they can carry more energy
Large non polar and insolouble so do not affect water potential and osmosis
high ratio of H to O making it a useful water supply when tryglycerides are oxidised

Question 22

test for lipids/emulsion test?

Answer 22

add 2cm of sample
add 2cm3 of ethanol
add 5cm of water
If it goes cloudy white lipid present

Question 23

describe the funcional group of an amino acids?

Answer 23

H
NH2-C -COOH
R

Question 24

how peptides form dipeptides?

Answer 24

condensation reaction
         H                         H
NH2-C-COOH + NH2-C-COOH  
         R                          R
hydrogen and oxygen removed from COOH
Hydrogen removed from NH2
         H              H
NH2-C-CO-NH-C-COOH
         R               R

Question 25

describe primary structure of proteins?

Answer 25

Primary structure is based on the amino acids and their order. A single change in amino acid sequence can create a different polypeptide

Question 26

describe 2nd secondary?

Answer 26

In C=O the C is slightly negative while in NH2 the H is slighlty positive. This causes hydrogen bonds between them This can cause a-helix and b-pleated sheets in the polypeptide

Question 27

describe tierary structure?

Answer 27

disulphide bridges- strong ionnic bonds -between nh2 and cooh that are not used in peptide bonds hydrogen bonding

Question 28

describe quarternary strucutre?

Answer 28

various polypeptides linked with non-protein prostheic group e.g haem groups in hameoglobin

Question 29

test for protein?

Answer 29

Add equal volume of sample and NaOH Add few drops of copper(II) sulfate solution blue to purple indicates protein presence

Question 30

describe induced model fit

Answer 30

The enzyme is flexible and can mould itself around the substrate .As it changes shape it puts a strain on the substrate. This distorts bonds in the substrate lowering activation energy required to break.The reaction happens and the products and the enzyme returns back to its original shape

Question 31

how to measure enzyme catalysed reactions?

Answer 31

the formation of products | the dissapearance of substrate

Question 32

how does temperature affect enzyme activity?

Answer 32

increasing temperature increases kinetic energy.particles move around quicker and faster so their is a higher chance of achieving activation energy.So reactions are more successful. However increasing too much distorts enzyme bonds denaturing it

Question 33

how does pH affect enzyme activity?

Answer 33

Change in pH alters the charges on the amino acids that make up the active site of the enzyme. So the substrate is no longer complimentary and enzyme-substrate complexes are not formed. A significant change in pH can cause the bonds that make the tiertary structure of the active site to change

Question 34

what are competitive inhibitors?

Answer 34

they are molecules that have a similar shape as the substrate. This means they can occupy active sites as they are complementary. At low conc these do not affect reaction rate that much. However at higher conc it will affect reaction rate as the active site is occupied by them and not with the substrate

Question 35

what are non competitive inihibitors?

Answer 35

Non competitive inihibitors do not bind at the active site but rather at a binding site. In doing this they change the shape of the active site so it is no longer complementary to the substrate.An increase in substrate conc will not help as the enzyemes are no longer complementary and cannot produce the enzyme-substrate complex needed to catalyse the reaction

Question 36

what are the components for one DNA nucleotide

Answer 36

Pentose (deoxyribose sugar) base (adenine, guanine cytosine,thymine ) phosphate group

Question 37

what bonds DNA nucleotides to another nucleotide?

Answer 37

Dna bases can form a phosphodiester bond between phosphate group and ribose sugar

Question 38

what are the compnonents of RNA?

Answer 38

pentose (ribose sugar) nucleotide base (Adenine guanine cytosine uracil) Phosphate group

Question 39

which of the nucleotides are complementary?

Answer 39

Adenine and Thymine/Uracil | Guanine and Cytosine

Question 40

What makes DNA stable

Answer 40

the phosphodiester bond protects the more chemically reactive organic bases inside the double helix the hydrogen bonding between nucleotide pairs especially C-G as it produces the most hydrogen bonds (3 more)

Question 41

what is DNA adapted for?

Answer 41

stable molecules that allows it to be passed on without mutations mostly 2 strands that can be opened for DNA replication and protein synthesis Large so can carry a lot of genetic information

Question 42

what is required for semi conservative replication?

Answer 42

DNA helicase DNA polymerase Energy source ATP DNA template

Question 43

Describe the process of semi conservative replication

Answer 43

hydrogen bonds between nucleotide bases is broken by DNA helicase This opens up the 2 stranded DNA A template strand is chosen complimentary nucleotide bases around the nucleus are bonded to the template strand This is helped by DNA polymerase T

Question 44

what is ATP made from

Answer 44

Pentose sugar Adenine base 3 phosphate groups

Question 45

what is equation for ATP to ADP and what is the enzyme used?

Answer 45

ATP + H2O -> ADP + Pi + energy ATP hydrolyse hydrolysis reaction

Question 46

Why is ATP easily hydrolysed?

Answer 46

The 3 phosphate groups in ATP are unstable so have a low activation energy

Question 47

How does ATP get reformed from ADP

Answer 47

It is a reversibe reaction (condensation) It requires energy to Add the Phosphate back to the ATP It is catalysed by ATP synthase The phosphate is added back in plants by photophosphorylation The phosphate is added back in animals by oxidative phosphorylation,substrate level phosphorylation

Question 48

Why is ATP not stored in abundance?

Answer 48

It is an immediate energy source. Glycogen is a much better long term store This is because ATP is hydrolsed quickly to form energy wheras glucose requires a lot of reactions ATP also produced much less energy which is more manageble

Question 49

describe the uses of ATP?

Answer 49

active transport metabolic processes making starch from glucose movement (muscle contraction) secretion phosphorylate other molecules e.g glucose with the extra phosphate

Question 50

what are the features of water?

Answer 50

dipolar slighly positive hydrogen and negative oxygen this allows for hydrogen bonding This gives it a higher specific heat capacity Can therefore act as a buffer against sudden changes Also a higher latent heat for vaporisation this makes sweating a useful way to use energy to evaporate water They are cohesive can be pulled through xylem vessel surface tension strong enough to supprt small insects

Question 51

How is water in used in metabolism?

Answer 51

Hydrolysis reactions to break down bigger molecules

Question 52

how is water used as a solvent?

Answer 52

dissolves other substances e.g gases CO2 and O2 | wastes such as urea and ammonia