Biological Molecules : Proteins + Enzymes

Question 1

function of proteins : enzymes

Answer 1

biological catalysts that speed up reactions

Question 2

function of proteins : antibodies

Answer 2

immune response (kill pathogens)

Question 3

function of proteins : structural

Answer 3

e.g keratin for hair

Question 4

what are amino acids ?

Answer 4

basic monomer units which combine to make a polymer (polypeptide)

Question 5

structure of amino acids:order

Answer 5

monomer = amino acids 
dimer = dipeptide
polymer = polypeptide

Question 6

How are the two amino acids linked ?

Answer 6

peptide bond between C atom and N atom of amino acids

Question 7

how can a peptide bond be broken ?

Answer 7

hydrolysis reaction

Question 8

polypeptide

Answer 8

a chain of amino acids joined with peptide bonds via condensation reaction

Question 9

primary structure : what does the primary structure determine ?

Answer 9

determines the sequence of amino acids , shape and function

Question 10

primary structure : why is the shape of a protein important ?

Answer 10

the shape is specific to a function so a change in shape will make the function different

Question 11

secondary structure : what weak bonds are present

Answer 11

hydrogen bonds

Question 12

secondary structure : what do the hydrogen bonds do ?

Answer 12

initial folding of the polypeptide chain due to hydrogen bonds leads to an alpha helix or beta pleated sheet

Question 13

Tertiary structure : what does further folding of a polypeptide do ?

Answer 13

further folding leads to 3D shape due to more H , ionic and disulfide bonds.

Question 14

Tertiary structure : what does the 3D structure allow ?

Answer 14

make the protein distinctive and allows it to be recognized

Question 15

Quaternary structure : prosthetic groups + example

Answer 15

2 or more polypeptides chemically joined to form a non-protein prosthetic group like haem group in haemoglobin

Question 16

Test for Proteins

Answer 16

1. add biuret reagent to food sample

2. blue to lilac = postive result

Question 17

enzyme action : catalyst

Answer 17

alter rate of a chemical reactions without undergoing permanent changes themselves

Question 18

enzyme action : activation energy

Answer 18

minimum amount of energy needed to bring about a reaction

- enzymes lower a.e

Question 19

enzyme action : how do enzymes work ?

Answer 19

they work by lowering the activation energy

Question 20

enzyme action : what do chemical reactions require ?

Answer 20

kinetic energy

Question 21

enzyme action :how does formation of enzyme substrate complex increase ROR ?

Answer 21

puts strain on bonds making them more likely to collide

Question 22

Enzyme structure : what are active sites made up of ?

Answer 22

small number of amino acids

Question 23

Induced fit model : what happens when the active site is not complimentary to the substrate ? (1)

Answer 23

the active site changes shape to become complimentary

Question 24

Induced fit model : what happens when the product is released ? (2)

Answer 24

enzyme changes back to original shape

Question 25

Induced fit model : what can change the shape of enzyme ? (3)

Answer 25

enzymes environment

Question 26

Effect of temperature on enzymes (start)

Answer 26

• Rise in temp increases k.e so more E-S complexes
• molecules move around more rapidly and collide
• enzyme and substrate molecules come together

Question 27

Effect of temperature on enzymes (end)

Answer 27

• Enzyme denatures and changes to tertiary structure of active site
• no longer complimentary to substrate so fewer/ no enzyme substrate complexes

Question 28

What is denaturation ?

Answer 28

Permanent change to the enzyme so it doesn’t function again.

Question 29

Effect of PH on enzyme

Answer 29

• extremes of PH denature enzymes

- ionic bonds in tertiary structure breakdown

Question 30

PH inside organisms

Answer 30

• PH fluctuations inside organisms are small so they’re more likely to reduce enzyme activity than denature

Question 31

Effect of enzyme concentration on rate of reaction (start)

Answer 31

More enzymes so more E-S complexes

Question 32

Effect of enzyme concentration (end)

Answer 32

Maximum rate reached because there’s not enough substrate

Question 33

Effect of substrate concentration on rate of reaction (start)

Answer 33

As more substrate is added all active sites are working as fast as possible to there’s more E-S complexes
- this increases rate

Question 34

Effect of substrate concentration on rate of reaction (End)

Answer 34

When rate reaches a maximum level the rate levels off because there are not enough active sites to form E-S complexes

Question 35

Enzyme inhibition : what are enzyme inhibitors ?

Answer 35

Molecules that slow down enzyme catalysed reactions

Question 36

Enzyme inhibition : What are the two types of inhibitors ?

Answer 36

Competitive and non-competitive inhibitors

Question 37

Enzyme inhibition : competitive inhibitors binding

Answer 37

Bind to the active site of the enzyme

Question 38

Enzyme inhibition : Non-competitive inhibitors binding

Answer 38

Bind to enzyme at a position other than the active site

Question 39

Competitive inhibitors : how does their molecules shape help ?

Answer 39

• allows them to occupy the active site of an enzyme

Question 40

Competitive inhibitors : Shape of competitive inhibitor

Answer 40

Molecules shape similar to substrate

Question 41

Competitive inhibitors : Substrate conc increased ?

Answer 41

Effect of inhibitor reduced

Question 42

Competitive inhibitors : Greater conc of inhibitor ?

Answer 42

Longer for molecules to occupy an active site

Question 43

Competitive inhibitors : What do competitive inhibitors prevent ?

Answer 43

Prevent formation of E-S complexes

Question 44

Non-competitive inhibitors : what happens when attaching to the enzyme ?

Answer 44

• Inhibitor alters shape of enzyme + active site so substrate no longer fits
• no more E-S complexes

Question 45

Non-competitive inhibitors : Why does the effect on the inhibitor not decrease ?

Answer 45

The substrate and inhibitor are not competing for the same active site

Question 46

Non-competitive inhibitors : how do they affect tertiary structure ?

Answer 46

Changes the structure permanently