Proteins & Enzymes

Question 1

What are amino acids?

Answer 1

Monomers from which proteins are made from

Question 2

What elements are found in amino acids?

Answer 2

Carbon
Hydrogen
Oxygen
Nitrogen

Question 3

What differs in each amino acid?

Answer 3

R group

Question 4

How is a polypeptide formed?

Answer 4

Peptide bond forms between the carboxyl group of one amino acid and the amine group of another during a condensation reaction

Question 5

How are directives formed?

Answer 5

Condensation of 2 amino acids

Question 6

How are polypeptides formed?

Answer 6

Condensation of many amino acids

Question 7

What reaction digests proteins?

Answer 7

Hydrolysis reaction

Question 8

What is the primary structure of a protein?

Answer 8

The number and sequence of amino acids in a polypeptide chain

Question 9

What is the secondary structure of a protein?

Answer 9

The folding of the polypeptide into an alpha helix or beta pleated sheet which are held together by hydrogen bonds between the NH group of one amino acid and the C=Ongroup of another

Question 10

What is the tertiary structure of a protein?

Answer 10

The folding of a polypeptide chain into a specific 3D shape which is held together by hydrogen bonds, ionic bonds and disulphide bridges between the R groups of amino acids

Question 11

What is the quaternary structure of a protein?

Answer 11

More than 1 polypeptide chain joined together

Question 12

What is the denaturing of a protein?

Answer 12

The hydrogen bonds in the protein break which changes the shape of tertiary structure so the protein can no longer carry out its function

Question 13

What is the food test for protein?

Answer 13

Biuret

Question 14

How do you test for protein?

Answer 14

1. Add biuret solution to food sample
2. If protein is present, colour change from blue to lilac will occur

Question 15

What are enzymes?

Answer 15

Biological catalysts

Question 16

How do enzymes speed up recovery?

Answer 16

Lower the activation energy needed for a chemical reaction

Question 17

What is the structure of an enzyme?

Answer 17

They have a specific 3D shape with a specific active site complementary to the substrate

Question 18

What is the induced fit theory?

Answer 18

1. Substrate enters the enzyme’s active site
2. The active site changes shape to become fully complementary to the substrate
3. Enzyme-substrate complex forms
4. Pressure is put on the bonds in the substrate causing them to break more easily
5. Products are released from the active site and the active site returns to its original shape

Question 19

What factors affect enzymes?

Answer 19

Temperature
pH
Inhibitors
Substrate concentration
Enzyme concentration

Question 20

What is an optimum?

Answer 20

When the enzyme works best

Question 21

What effect does temperature have on enzymes?

Answer 21

As temperature increases the substrate molecules have more kinetic energy which will cause more frequent collisions forming enzyme-substrate complexes
If the temperature increases or decreases too much the hydrogen bonds, holding the tertiary structure if the enzyme together, break which causes the active site to change shape so it is no longer complementary to the substrate. The enzyme is denatured and can no longer catalyse any reactions

Question 22

What is the effect of pH on enzymes?

Answer 22

If the pH isn’t at the enzyme’s optimum, the charge groups on the R group of amino acids are altered causing the hydrogen bonds and ionic bonds to break. This changes the enzyme’s tertiary structure which changes the enzyme’s active site so it is no longer complementary to the substrate

Question 23

What is the effect of substrate concentration on enzymes?

Answer 23

As substrate concentration increases, the rate of reaction increases and then plateaus
The rate of reaction is low at low substrate concentrations because not all of the active sites are saturated. The reaction plateaus when all of the enzymes active sites are saturted

Question 24

What is the effect of enzyme concentration on enzymes?

Answer 24

Increasing the enzyme concentration increases the rate of reaction because the more enzymes there are the more likely they are to collide with a substrate.
If the amount of substrate becomes limiting, increasing the enzyme concentration will have no effect on the rate of reaction

Question 25

What effect do inhibitors have on enzyme reactions?

Answer 25

They decrease the rate of reaction

Question 26

What do competitive inhibitors do?

Answer 26

They have a similar tertiary structure to the substrate so bind to the active site of the enzyme
They prevent the normal substrates binding to the active site which slows the rate of reaction

Question 27

What do non-competitive inhibitors do?

Answer 27

Bind to the enzyme AWAY from the active site
They change the shape of the active site so it is no longer complementary to the substrate
NO enzyme-substrate complexes form and rate of reaction is decreased