proteins and enzymes

Question 1

Describe how a peptide bond is formed between two amino acids

Answer 1

condensation reaction
between amine and carbonyl group of separate amino acids

Question 2

What is the primary structure of a protein?

Answer 2

number and sequence of amino acids

Question 3

What is the secondary structure of a protein?

Answer 3

hydrogen bonding between amino acids form beta pleated sheets or alpha helixes

Question 4

What is the tertiary structure of a protein?

Answer 4

The 3d shape determined by the placement of ionic, hydrogen and disulphide bonds between different R groups from amino acids in the polypeptide chain

Question 5

What is the quaternary structure of a protein?

Answer 5

two or more polypeptide chains bonded together

Question 6

What happens if you change the sequence or number of amino acids?

Answer 6

different sequences or number of amino acids form ionic/hydrogen/disulphide bonds, between R groups, in different places

Question 7

describe the lock and key model and how an enzyme acts as a catalyst

Answer 7

-named Enzyme has a specific shaped active site which is complementary to only name substrate.
-Substrate binds to active site forming an enzyme-substrate complex.
-lowering activation energy by stressing bonds within substrate.

Question 8

describe the induced fit model and how an enzyme acts as a catalyst

Answer 8

Active site not complementary
active site changes shape as substrate binds so it is complementary to substrate. Enzyme-substrate complex forms Stressing (or forming) bonds in substrate Reducing activation energy

Question 9

explain why enzymes only catalyse one reaction/ why a -named- enzyme cant catalyse reaction of -named- molecule

Answer 9

Active site of named enzyme is specific shape
Only one named substrate fits active site
named molecule is different shape so no Enzyme-substrate complex
forms. .

Question 10

explain how a competitive inhibitor works

Answer 10

-inhibitor is a similar shape to substrate
-inhibitor binds to the active site
-fewer enzyme-substrate complexes because less substrate can bind
-so less product is produced

inhabitation can be overcome by adding more substrate / max product will eventually form

Question 11

explain how a non-competitive inhibitor works

Answer 11

-inhibitor is not a similar shape to substrate
-inhibitor binds at allosteric sire
-changes the shape of active site so no longer complementary to substrate
-fewer enzyme-substrate complexes as substrate cannot bind
-less product formed

inhabitation cannot be overcome by adding more substrate / max product will never be produced