Biological Molecules

Question 1

describe how a peptide bond is formed between two amino acids to form a dipeptide

Answer 1

condensation reaction between amine and carboxyl

peptide bond formed between c and N

Question 2

how is the secondary structure of a polypeptide produced by bonds between amino acid

Answer 2

hydrogen bonds
between NH and C=O
forming a helix

Question 3

two proteins have the same number and type of amino acids but different tertiary structure, explain why

Answer 3

different sequences of amino acids which cause different primary structures
this forms ionic/hydrogen/disulphide bonds in different places

Question 4

compare and contrast the processes by which water and inorganic ions enter

Answer 4

comparison :
• both move down a concentration gradient
• both move throught protein channels in membrane
contrast :
• ions can move against a concentration gradient by active transport

Question 5

how to test for lipids

Answer 5

dissolve in alcohol and then add water

white emulsion shows presence of lipid

Question 6

describe the structure of glycogen

Answer 6

polysaccharide of α glucose

joined by glycosidic bonds with branched structure

Question 7

how is glycogen used as a source for energy in animals

Answer 7

hydrolysed into glucose

glucose used in respiration

Question 8

how is glycogen used as a source for energy in animals

Answer 8

hydrolysed into glucose

glucose used in respiration

Question 9

difference between phospholipid and triglyceride

Answer 9

in phospholipid a fatty acid is replaced by a phosphate

Question 10

difference between saturated and unsaturated fatty acids

Answer 10

saturated only has single bonds between carbon and unsaturated has single and double bonds between carbons

Question 11

why wouldn’t a fat substitute be digested by lipase

Answer 11

Enzymes are specific, the fat substitute isnt complementary so is unable to bind to lipase

Question 12

Give ways ATP is a suitable source for cells to use

Answer 12

NOTICE IN CONTEXT OF STORAGE

1. releases relatively small amount of energy (small manageable bursts)
2. releases energy instantaneously
3. phosphorylates other compounds, making them more reactive
4. can be rapidly synthesized
5. is not lost from cells

Question 13

does anaerobic reaction occur in organelles?

is electron transport chain involved?

Answer 13

no

Question 14

does aerobic reaction and photosynthesis occur in organelles?
is electron transport chain involved?

Answer 14

yes

Question 15

write a simple equation to show how ATP is synthesized from ADP

Answer 15

ADP + Pi -> ATP

Question 16

Give two ways that the properties of ATP make it a suitable source of energy in biological processes

Answer 16

NOTICE tHAT THE qUESTION IS ASKING IN CONTEXT OF RELEASE NOT STORAGE

1. Energy released in small suitable amounts
2. Soluble
3. involves a simple/single reaction

Question 17

why is it necessary for them tp synthesise such a large amount of ATP

Answer 17

1. ATP can not be stored (bc its an immediate store of energy)
2. ATP only releases a small amount of energy af a time

Question 18

why would you suspend a mitochondria in an isotopic solution

Answer 18

prevent damage to mitochondria caused by differences in water potential/osmosis/water

Question 19

when glucose is released what happens to energy not incorporated into ATP

Answer 19

released as heat

Question 20

when one mole of glucose is respired anaerobically, only 2 moles of ATP are produced,
explain why less energy is released

Answer 20

glucose is only partly broken down

only broken down to lactate

Question 21

at the end of a sprint race, a runner continues to breathe rapidly for some time, explain the advantage of this

Answer 21

lactis acid has been built up

oxygen used to break down lactic and convert it back to glucose

Question 22

name the substance that muscles use as their immediately energy source

Answer 22

ATP

Question 23

cats are lactose intolerant, lactase is used to hydrolyse lactose, making milk hydrolysis lactose free
why used lactase coated beads instead of direct lactase

Answer 23

1 beads are reusable
2 no need to remove lactase afterwords
3 allows continuous process 
4 enzyme is more stable 
5 avoid end product inhibition

Question 24

suggest why does lactose-free milk (galactose is hydrolysed) tastes sweeter after than the cows milk with lactose

Answer 24

lactose is hydrolysed to glucose and galactose so more sugar molecules present

Question 25

suggest why does lactose-free milk (galactose is hydrolysed) tastes sweeter after than the cows milk with lactose

Answer 25

lactose is hydrolysed to glucose and galactose so more sugar molecules present

Question 26

give two ways the structure of starch is similar to cellulose

Answer 26

1 are polymers 
2 contain glucose/carbon/hydrogen and oxygen
3 contain glycosidic bonds
4 have 1-4 links 
hydrogen bonding

Question 27

give two ways starch is different from cellulose

Answer 27

1 starch contains α glucose and cellulose contains β glucose
2 starch is branched and coiled while cellulose is unbranched and straight
3 starch also has 1-6 branching
4 starch doesn’t have hydrogen bonds berween moleculess
5 starch has glucose/monomers same way up
6 starch doesn’t have fibres

Question 28

explain difference between the structure of statch molecule and cellulose molecule

Answer 28

1 starch formed from α glucose but cellulose formed from β glucose
2 position of hydrogen and hydroxyl groups on carbon atom 1 inverted

Question 29

explain one way in which starch molecules are adapted for their function in plant cells

Answer 29

1 insoluble 
2 so dont affect water potential
or
1 helical
2 compact
or
1 large molecules 
2 can not leave cells

Question 30

explain how cellulose moelcules are adapted for their function in plants

Answer 30

long straight chains
become linked together by many hydrogen bonds to form fibrils
provide strength to cell wall

Question 31

when wheat ia hydrolysed what sugars would you sugar would you expect and why?

Answer 31

maltose

salivary amilase breaks down starch

Question 32

using the ides of water potential, explain why adults that can not digest lactose get diarrhoea when they drink milk

Answer 32

SOLUBLE lactose isnt hydrolysed
lowers water potential in the lumen
causing water to enter lumen by osmosis

Question 33

explain the difference of effect of chewing vs chopping on the digestion in wheat

Answer 33

some strach is already digested when chewing in mouth
faster digestion of chewed starch
same amount of digestion at the end of time

Question 34

describe competitive and non competitive inhibition of enzymes

Answer 34

1 inhibitors reduce binding of enzyme to substrate/prevent formation of enzyme substrate complex

2 competitive inhibition, inhibitor similar shape to substrate
3 binds in to active site
4 inhibition can be overcome by more substrate
5 non competitive inhibition, inhibitor binds to site on enzyme other than active site
6 changes shape of active site
7 cannot be overcome by adding more substrate

Question 35

explain how sports drinks could provide an energy boost when running

Answer 35

1 drink contains carbohydrates so raises blood glucose concentration quickly
2 contains salt so glucose more rapidly absorbed
3 increases glucose to muscles for respiration
4 faster energy release

Question 36

for enzyme related reactions how could you set up a control experiment?

Answer 36

boil the enzyme

Question 37

describe the structure of proteins

Answer 37

polymers of amino acids
joined by peptide bonds
formed by condensation
primary structure is sequence of amino acids
secondary structure is folding of polypeptide chain due to hydrogen bonding to form alpha sheet or beta pleated sheet
tertiary structure is 3D folding due to hydrogen bonding, ionic bonding and disulphide bonds
quarternary structure is two or more peptide chains

Question 38

describe how proteins are digested in the human gut

Answer 38

hydrolysis of peptide bonds
endopeptidaeses break polypeptides into smaller peptide chains
exopeptides remove terminal amino acids;
dipeptidaeses hydrolyse/break down dipeptides into amino acids

Question 39

what sugars do you expect to produce when chewing and why

Answer 39

maltose

salivary enzymes breaks down starch