Proteins and Enzymes

Question 1

what are proteins?

Answer 1

large polymers (polypeptide chain) made up of amino acids

Question 2

where are proteins made?

Answer 2

• created in the ribosome
• folded and modified in the golgi apparatus

Question 3

what’s the first structure that forms to make a protein?

Answer 3

polypeptide chain

Question 4

what is the primary structure of a protein?

Answer 4

the sequence of amino acids in a polypeptide chain

Question 5

what does DNA determine in the polypeptide chain?

Answer 5

the order of amino acids
- this will alter how the protein folds and bonds

Question 6

how many different amino acids are there?

Answer 6

20

Question 7

how is the polypeptide chain created?

Answer 7

condensation reactions between amino acids

Question 8

what is the secondary structure of a protein?

Answer 8

the sequence of amino acids cause parts of the protein to being bent into a helix or folded into b pleated sheets

Question 9

what bonds hold the secondary structure of a protein in place?

Answer 9

Hydrogen bonds between the carboxyl group (COOH) and the amine group (NH2)

Question 10

why are hydrogen bonds strong in the secondary structure?

Answer 10

because even though H bonds are weak there’s lots of them that provide collective strength

Question 11

what is a tertiary structure?

Answer 11

when the secondary structure is bent and folded further to form a precise 3D shape

Question 12

what bonds hold the tertiary and quaternary structure in place?

Answer 12

hydrogen, ionic and disulphide bonds

Question 13

what do disulphide bonds form between?

Answer 13

the R-groups of 2 amino acids that contain sulfur

Question 14

what is a quaternary structure?

Answer 14

a protein made up of 1 or more polypeptide chains

Question 15

what is the group called attached to a protein but not made up of amino acids?

Answer 15

prosthetic group

Question 16

what is a protein with a prosthetic group called?

Answer 16

a conjugated protein

Question 17

what are the properties of fibrous proteins?

Answer 17

• polypeptide chains form long twisted strands linked together
• stable structure
• insoluble in water
• strength gives structural function

Question 18

what shape do fibrous proteins form when folded?

Answer 18

long, rope-like shapes

Question 19

what are the properties of a globular protein?

Answer 19

• quite unstable structure
• soluble
• metabolic functions

Question 20

what shape do globular proteins form when folded?

Answer 20

spherical

Question 21

what forms fibrous and globular proteins?

Answer 21

the 3D folding in tertiary and quaternary proteins

Question 22

what is an enzyme?

Answer 22

a biological catalyst
- speed up a reaction without being used up

Question 23

how is the active site of an enzyme specific in shape?

Answer 23

unique in shape due to the specific folding and bonding in the tertiary structure of the protein

Question 24

are enzymes globular or fibrous?

Answer 24

globular

Question 25

how is the lock-and-key method different to the induced fit one?

Answer 25

• induced fit model suggests that the active site changes shape to be complementary to the substrate
• lock and key suggests enzymes are a fixed shape and the active site doesn’t change

Question 26

how does temperature affect enzyme activity?

Answer 26

• too low - not enough kinetic energy for successful collisions
• too high - enzymes denature so the active site changes shape so the enzyme substrate complexes can’t form

Question 27

how does pH affect enzyme activity?

Answer 27

the pH will interfere with the charges in the amino acids in the active site causing the enzyme to denature

Question 28

how can concentration affect enzyme activity?

Answer 28

• not enough substrate - fewer collisions so slower reaction
• not enough enzyme - active site will become saturated with the substrate and unable to work any faster

Question 29

what are competitive inhibitors?

Answer 29

• same shape as the substrate so can bind to the active site
• prevents substrate from binding and reaction occurring

Question 30

what are non-competitive inhibitors?

Answer 30

• bind to the enzyme away from the active site , allosteric site
• changes the shape of the active site
• substrate can no longer bind