Unit 1- Enzymes + factors effecting enzymes

Question 1

What are enzymes?

Answer 1

Proteins which speed up the rate of chemical reactions

Question 2

How do enzymes speed up chemical reactions?

Answer 2

By acting as a biological catalyst

Question 3

What type of reactions do they catalyse?

Answer 3

-Metabolic
Both:
-cellular level (eg. respiration)
-the organism as a whole (eg. digestion in mammals)

Question 4

What do ezymes effect ?

Answer 4

-Function and structure

Question 5

Where can enzyme action take place?

Answer 5

-Intracellular (inside the cell)
-Extracellular (outside the cell)

Question 6

What is the active site?

Answer 6

The part of the enzyme where the substrate molecules bind to

Question 7

What are substrate molecules?

Answer 7

The substance that the enzyme interacts with

Question 8

Why are enzymes highly specific?

Answer 8

Due to their tertiary structure

Question 9

Define activation energy

Answer 9

The minimum amount of energy needed to be supplied to the chemicals before a reaction can start

Question 10

How is activation energy usually supplied?

Answer 10

As heat

Question 11

How do enzymes speed up the rate of reaction?

Answer 11

-They lower the amount of activation energy needed
-Often make reactions happen at a lower temperature than they would without an enzyme

Question 12

Why do enzyme-substrate complexes lower activation energy?

Answer 12

-If two substrate molecules need to be joined, being attached 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 strain on the bonds in the substrate so the substrate molecule breaks up more aesily

Question 13

Define catalyst

Answer 13

A substance which speeds up a chemical reaction without being used up itself

Question 14

Describe the lock and key theory

Answer 14

-The substrate fits into the active site the same way a key fits in a lock
-The active site and substrate are complementary to each other
-Enzyme-substrate complex is formed
-Enzyme is unchanged after reaction

Question 15

Describe the induced fit model

Answer 15

-The substrate needs to be the right shape for the active site and needs to make the active site change into the right shape
-After the products are released the active site returns to its original shape and binds to the next substrate molecule

Question 16

Explain how enzymes can catalyse synthesis reactions

Answer 16

-Two substrate molecules go into the active site
-Bind to form enzyme-substrate compex
-One product produced

Question 17

Explain how enzymes can break down substrates

Answer 17

-One substrate molecule goes into the active site
-Enzyme substrate complex formed ]
-2 products produced

Question 18

What are enzyme properties such as active sites related to?

Answer 18

-Their tertiary structure

Question 19

Why may a reaction not be catalysed?

Answer 19

-If the active site and substrate do not have complementary shape
-The substrate can not fit into the active site
-As the enzyme’s active site is determined by the tertiary structure

Question 20

What happens if the tertiary structure of a protein is altered in any way?

Answer 20

-The shape of the active site will change
-The substrate will not be complementary to the active site
-No enzyme-substrate complex formed
-Enzyme no longer able to carry out its function

Question 21

Why may the tertiary structure of an enzyme change?

Answer 21

-Ph
-Temprature

Question 22

Why else may the tertiary structure be altered?

Answer 22

-The primary structure (amino acid sequence) is determined by a gene
-A mutation can occur in that gene

Question 23

How can we measure enzyme activity?

Answer 23

How fast the product is made- different molecules are present at the end of a chemical reaction than there are at the beginning, by measuring the amount of end product at different points in the experiment the rate of reaction can be calculated

How fast the substrate is broken down- to produce end products, substrate molecules have to be used up, by measuring the amount of substrate molecules left at different times in a reaction rate of reaction can be calculated

Question 24

Rate of reaction 1.___ when tempraturate increases

Answer 24

1. Increases

Question 25

How does temperature increase the rate of reaction?

Answer 25

-More heat= more kinetic energy
-More kinetic energy molecules moving faster
-Substrate molecules more likely to collide with active sites
-Energy of collisions increase
-Higher energy collisions = more chance for successful collisions

Question 26

Why does the reaction stop if the temperature is too high?

Answer 26

-Rise in temperature makes molecules vibrate more
-If the temp is too high then the vibration can make bonds that hold the enzymes’ shape break
-The active site changes shape and the enzyme substrate no longer fits together
-Enzyme denatures
-No longer functions as a catalyst

Question 27

Is denaturation usually permanent?

Answer 27

Yes

Question 28

What is the optimum temprature for human enzymes?

Answer 28

37c

Question 29

What pH do most human enzymes work best at?

Answer 29

7 (neutral)

Question 30

What happens if the Ph is below/above optimum?

Answer 30

-The H+ and OH- ions found in acids and alkalis can disrupt the ionic/hydrogen bonds that hold the enzyme tertiary structure in place
-Enzyme becomes denatured, active site changes shape
-

Question 31

The higher the 1.____ _____ the faster the reaction

Answer 31

1. Substrate concentration

Question 32

How does substrate concentrationj effect rate of reaction?

Answer 32

-More substrate molecules= more collisions between substrate and enzyme, more likely active sites will be occupied

Question 33

What happens after the saturation point?

Answer 33

There are too many substrate molecules and the enzymes have enough to cope with as all the active sites are full so adding more will not make a difference

Question 34

The more 1_____ _______ there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme-substrate complex

Answer 34

1. Enzyme molecules

Question 35

What happens when the amount of substrate is limited?

Answer 35

More than enough enzyme molecules for the number of substrates so adding more enzymes has no effect

Question 36

How do competitive inhibitors prevent enzyme activity?

Answer 36

-They have a similar shape to the substrate
-They compete with the substrate molecules to bind with the active site
-They block the active site so no substrate molecules can fit in

Question 37

What does the enzyme inhibition depend on?

Answer 37

-The relative concentrations of the inhibitor or substrate
-If there is a high concentration of the inhibitor the inhibtor will take up most of the active sites
-If there is a higher concentration of the substrate they will take up most of the active sites

Question 38

Increasing the concentration of 1____ will increase the rate of reaction (up to a point)

Answer 38

1. Substrate

Question 39

Where do non-competitive inhibitors bind to? What does this cause?

Answer 39

-The enzyme away from its active site
-The active site changes shape so the substrate molecules can no longer bind to it

Question 40

Increasing the concentration of substrate 1____ make a difference

Answer 40

1. Will not