UNIT 1 - KA6

Question 1

What are metabolic pathways

Answer 1

Metabolic pathways are interrogated and controlled pathways of enzyme - catalysed reactions within a cell

Question 2

What are anabolic reactions

Answer 2

Anabolic reactions build up large molecules from small molecules and require energy

Question 3

What are catabolic reactions

Answer 3

Catabolic reactions break down large molecules into smaller molecules and release energy

Question 4

What types of steps and routes can metabolic pathways have

Answer 4

Metabolic pathways can have reversible steps, irreversible steps and alternative routes

Question 5

What are metabolic pathways controlled by

Answer 5

Metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes

Question 6

What is the activation energy

Answer 6

The activation energy is the energy required to break chemical bonds during a chemical reaction.

Question 7

How much activation energy is needed with no enzymes

Answer 7

Higher activation energy needed with no enzymes :(

Question 8

How much activation energy is needed with enzymes

Answer 8

Lower activation energy is needed with enzymes :)

Question 9

Produce a graph of high and low activation energy

Answer 9

Check jotter

Question 10

What are the three key functions of enzymes

Answer 10

1) lower the activation energy (required for a reaction)
2) SPEED UP the rate of reaction
3) DO NOT change and can be reused

Question 11

What would not be able to proceed without enzymes

Answer 11

Enzymes are the body’s catalysts and without them the biochemical reactions essential for life would be unable to proceed at a fast enough rate to sustain life

Question 12

How many enzymes work for how many substrates

Answer 12

Enzymes are said to be specific which means that each enzyme only works on one substrate

Question 13

What is the substance and enzyme works on called

Answer 13

The substance and enzyme works on is called it’s substrate

Question 14

List three enzyme substrate and products

Answer 14

Amylase - starch - (Maltose/glusoce) simple sugars
Lipase - LIPDS (fats) - fatty acids and glycerol
Protease (eg pepsin) - protein - amino acids

Question 15

What is a model that explains how enzymes and substrates react

Answer 15

A model that explains how enzymes and substrates react when mixed is the INDUCED FIT model

Question 16

When does induced fit occur

Answer 16

Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds

Question 17

What are the steps of induced fit during an enzyme catalysed reaction

Answer 17

1- substrate with High affinity for active site binds to active site. Substrate becomes bound to active site

2- once the substrate binds induced fit occurs as the enzymes active site has changed shape to better fit the substrate (enzyme substrate complex formed).

3- substrate is broken down to end products

4- end products released

5- enzyme has returned to original shape. End products have low affinity allowing them to leave the active site

Question 18

Factors affecting the rate and direction of enzyme reactions

Answer 18

1 - temperature
2 - pH
3 - substrate concentration
4 - inhibitors

Question 19

What is the effect of substrate concentration on enzyme activity at W

Answer 19

• the reaction rate is lower at w because the substrate concentration is lower. So there are less substrate molecules to react with the available active sites. The reaction rate is quicker at x

Question 20

The effect of substrate concentration on enzyme activity at x-y and Z

Answer 20

• as substrate concentration increases from x-y more substrate is available to bind to free enzyme active sites so reaction rate increases. At z there are no free enzyme active sites available so even if substrate concentration is increased the reaction cannot go any faster

Question 21

Draw a graph of substrate concentration and reaction rate

Answer 21

Check jotter

Question 22

High substrate concentration

Answer 22

Substrate — ——> product
Enzyme

Question 23

Low substrate concentration

Answer 23

Substrate <——— product
Enzyme

Question 24

High product concentration

Answer 24

Substrate <——— product

Question 25

Low product concentration

Answer 25

Substrate ———> product

Question 26

What are metabolic path ways controlled through

Answer 26

Metabolic pathways are controlled through competitive, non - competitive and feedback inhibition of enzymes.

Question 27

What is an inhibitor

Answer 27

An inhibitor is a molecule that reduces or stops enzyme activity

Question 28

What type of molecular structure to competitive inhibitors have

Answer 28

Competitive inhibitors have a molecular structure similar to the substrate

Question 29

How do competitive inhibitors stop the substrate binding

Answer 29

They compete with the substrate blocking it from binding

Question 30

Produce a diagram to show how a competitive inhibitor works

Answer 30

Check jotter

Question 31

Where to non competitive inhibitors bind to

Answer 31

Non competitive inhibitors bind to the enzyme but not at the active site

Question 32

What do non competitive inhibitors do

Answer 32

They change the shape of the active site so the substrate no longer fits in

Question 33

Produce a diagram showing non competitive inhibition

Answer 33

Check jotter

Question 34

What is the effect of increasing substrate concentration on competitive inhibition

Answer 34

The substrates will fill more active sites and so increase reaction rate - REVERSIBLE

Question 35

Effect of increasing substrate concentration on non-competitive inhibition

Answer 35

The reaction rate will stay low even in a high substrate concentration (as most enzymes active sites have been changed) - NON REVERSIBLE

Question 36

Produce a series of diagrams showing induced fit during an enzyme catalysed reaction

Answer 36

Check jotter

Question 37

what is feedback / end product inhibition

Answer 37

End product inhibition is when the end product of a metabolic pathway reaches a critical concentration. This then inhibits an earlier enzyme, blocking the pathway preventing further synthesis of the end product

Question 38

What is the great benefit of feedback / end product inhibition

Answer 38

This conserves energy (ATP) in a cell

Question 39

What is another name of feedback / end product inhibition

Answer 39

Negative feedback control

Question 40

What is the activation energy reduced by

Answer 40

This is reduced by enzymes.