section 4: enzymes - topic 1: action of enzymes

Question 1

what biological molecule are enzymes?

Answer 1

proteins.

Question 2

what do enzymes do?

Answer 2

they speed up chemical reactions by acting as biological catalysts.

Question 3

what is a catalyst? what makes an enzyme a biological one?

Answer 3

a substance that speeds up a chemical reaction without being used up in the reaction itself.

because they are found in living organisms.

Question 4

what do enzymes catalyse?

Answer 4

metabolic reactions.
both at a cellular level (i.e. respiration) and for the organism as a whole (i.e. digestion in mammals).

Question 5

what can enzymes affect?

Answer 5

structures and functions.

Question 6

enzymes are involved in the production of …?

Answer 6

collagen - an important protein in the connective tissues of animals.

Question 7

what can enzyme action be?

Answer 7

intracellular or extracellular.

Question 8

what is an example of an intracellular enzyme?

Answer 8

catalase.
it works inside cells to catalyse the breakdown of hydrogen peroxide to oxygen and water.

hydrogen peroxide is the toxic by-product of several cellular reactions, and can kill cells if left to build up.

Question 9

what are examples of extracellular enzymes?

Answer 9

amylase and trypsin - work outside cells in the digestive system.

amylase - found in saliva, secreted into the mouth by salivary glands, catalyses the hydrolysis of starch into maltose in the mouth.

trypsin - produced by cells in the pancreas, secreted into the small intestine, catalyses the hydrolysis of peptide bonds (turning big polypeptides into smaller ones which then get broken down into amino acids by other enzymes).

Question 10

what kind of proteins are enzymes?

Answer 10

globular proteins.

Question 11

what is the active site?

Answer 11

the part of the enzyme where the substrate molecules bind to.

Question 12

what determines the active site’s specific shape?

Answer 12

the enzymes tertiary structure.

Question 13

what forms when a substrate binds to an enzyme’s active site?

Answer 13

an enzyme-substrate complex.

Question 14

how do enzymes speed up reactions?

Answer 14

they reduce the amount of activation energy needed (often provided as heat), often making reactions happen at a lower temp than they could without an enzyme - this speeds up the rate of reaction.

Question 15

what specifically lowers the activation energy?

Answer 15

the enzyme-substrate complex.

Question 16

why does the enzyme-substrate complex lower the activation energy?

Answer 16

if 2 substrate molecules need to be joined, attaching to the enzyme holds them close together, reducing any repulsion between the molecules, so they can bond more easily.

if the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate - this strain means the substrate molecule breaks up more easily.

Question 17

what are the two models of enzyme action?

Answer 17

the lock and key model.
the induced fit model.