proteins 3.14

Question 1

what is a chain of amino acids called

Answer 1

a polypeptide chain

Question 2

what is the structure of an amino acid

Answer 2

carbon (C) attached to an amine (NH3), a carboxyl (COOH), and an R group (varient)

Question 3

how many different R groups/amino acids are there

Answer 3

20

Question 4

what bonds are in a polypeptide

Answer 4

peptide bonds

Question 5

where do the peptide bonds form

Answer 5

between N in amine group and C in carboxyl group

Question 6

what type of reaction forms a dipeptide

Answer 6

condensation

Question 7

what does a condensation reaction produce

Answer 7

H20

Question 8

what is the primary structure

Answer 8

sequence of amino acids in a polypeptide chain

Question 9

what can a change in the polypeptide amino sequence cause

Answer 9

may cause a change in the protein shape
may stop it from carrying out its function

Question 10

what is the secondary structure

Answer 10

either an alpha helix or a beta pleated sheet

Question 11

how does the secondary structure form

Answer 11

H of the amine group has overall positive charge
O of the carboxyl group has overall negative charge
hydrogen bonds can form between these 2 groups
causes the chain to be twisted into a 3D shape

Question 12

what bonds form the tertiary structure

Answer 12

hydrogen bonds
ionic bonds
disulphide bridges

Question 13

where do the tertiary structure bond forms

Answer 13

only between the R groups

Question 14

what is the relative strength of hydrogen bonds

Answer 14

weak

Question 15

what is the relative strength of disulphide bridges

Answer 15

very strong

Question 16

what are the features of ionic bonds (2)

Answer 16

strong and vulnerable to pH

Question 17

what is the purpose of the 3D tertiary structure

Answer 17

makes each protein distinctive and allows it to recognise and be recognised by other molecules.

Question 18

what feature defines a protein having a quaternary structure

Answer 18

protein has more than one polypeptide chain

Question 19

what are the 2 molecular shapes of proteins

Answer 19

fibrous or globular

Question 20

fibrous vs globular stability

Answer 20

fibrous stable
globular not stable

Question 21

fibrous vs globular bonds

Answer 21

fibrous mainly H bonds
globular many types of bonds

Question 22

fibrous vs globular shape

Answer 22

fibrous long and linear
globular coiled with depressions

Question 23

fibrous vs globular sequence

Answer 23

fibrous regular sequence
globular irregular sequence

Question 24

fibrous vs globular function

Answer 24

fibrous structural function
globular metabollic function

Question 25

fibrous vs globular solubility

Answer 25

fibrous insoluble globular soluble

Question 26

what is biuret solution made of

Answer 26

sodium hydroxide and copper (II) sulphate solution

Question 27

what colour is biuret solution originally

Answer 27

blue

Question 28

what colour is biuret solution in the presence of protein

Answer 28

purple

Question 29

what type of protein is an enzyme (2)

Answer 29

globular tertiary structure

Question 30

how is an enzyme substrate complex held together

Answer 30

weak non covalent interactions (H, ionic, hydrophobic)

Question 31

how do enzymes lower the activation energy of a reaction (2)

Answer 31

put stress on the bonds within a molecule hold molecules closer together

Question 32

what is the lock and key model

Answer 32

each substrate will only fit the active site of one particular enzyme

Question 33

what is the induced fit model

Answer 33

suggests the active site is flexible, the substrate doesn't only have to fit the active site, it also has to make the active site change in the right way.

Question 34

how does increasing temperature affect enzyme action

Answer 34

increasing temperature means more heat energy so more kinetic energy for enzyme and substrate. move faster so more collisions. more ES complexes formed. rate of reaction is increased.

Question 35

how does too high temperature affect enzyme action

Answer 35

too high temperature means more kinetic energy. enzyme molecules vibrate more, H bonds in tertiary structure break. changes shape of enzyme. active site changes shape so substrate cannot fit.

Question 36

how does optimum pH affect enzyme action

Answer 36

solution of optimum pH has H ions, does not disrupt ionic bonding. no change in shape of enzyme, no change in active site, ES complexes formed, rate of reaction is maximum.

Question 37

how does pH being too high or low affect enzyme action

Answer 37

ionic bonds in tertiary structure break, changes shape of enzyme, ES complexes not formed, rate is reduced.

Question 38

how does substrate concentration affect enzyme action

Answer 38

substrate concentration increasing means more chance of enzymes and substrates colliding. more ES complexes formed. increases rate of reaction.

Question 39

why is substrate concentration limiting

Answer 39

eventually all enzyme active sites are occupied, enzymes are working at maximum turnover rate.

Question 40

how does increasing enzyme concentration affect enzyme action

Answer 40

more enzymes so more active sites more ES complexes formed more products formed

Question 41

what are the two types of enzyme inhibitors

Answer 41

competitive and non competitive

Question 42

where do competitive inhibitors bind

Answer 42

the active site

Question 43

limitation of competitive inhibitors

Answer 43

when the inhibitor leaves the active site, substrates can then bind

Question 44

where do non competitive inhibitors bind

Answer 44

to the allosteric site

Question 45

what do non competitive inhibitors do

Answer 45

attach to allosteric site changes shape of the active site so further substrate molecules cannot enter and form ES complexes

Question 46

Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst. (3 marks)

Answer 46

Substrate binds to the active site Active site changes shape so it is complementary to substrate Reduces activation energy

Question 47

A competitive inhibitor decreases the rate of an enzyme-controlled reaction. Explain how. (3 marks)

Answer 47

inhibitor similar shape to substrate binds to active site Prevents/reduces enzyme-substrate complex forming