KA6 - Metabolic Pathways

Question 1

What are metabolic pathways?

Answer 1

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

Question 2

What 3 steps could a metabolic pathway have?

Answer 2

Reversible steps

Irreversible steps

Alternative routes

Question 3

What is the activation energy?

Answer 3

The activation energy of a reaction is the amount of energy required to make a reaction happen

Question 4

What happens to the activation energy of a reaction due to the binding of an enzyme to its substrate?

Answer 4

The binding of an enzyme to its substrate lowers the activation energy of a reaction

Question 5

If an enzyme is present, what happens to the amount of energy need to make a product?

Answer 5

Is an enzyme is present, the amount of energy needed to make a product is lowered

Question 6

What are the two types of metabolic pathways?

Answer 6

Anabolic

Catabolic

Question 7

What can anabolic pathways be referred to as?

Answer 7

Biosynthesis pathways

Question 8

What are anabolic pathways?

Answer 8

Anabolic pathways require energy. This energy is used to build up smaller molecules into larger ones

Question 9

Give two examples of anabolic reactions

Answer 9

DNA replication

Protein synthesis

Question 10

What can catabolic pathways also be referred to?

Answer 10

Degradation pathways

Question 11

What are catabolic pathways?

Answer 11

Catabolic pathways release energy. This release of energy occurs when large molecules are broken down into smaller ones

Question 12

Give two examples of catabolic pathways

Answer 12

Respiration

Digestiom

Question 13

Why must metabolic pathways be regulated and controlled?

Answer 13

In order to prevent the build up of an end product which is not needed

Question 14

How are metabolic pathways controlled?

Answer 14

A cell can control a metabolic pathway by the presence or absence of a particular enzyme or by regulation the rate of reaction of key enzymes

Question 15

What is the most effective way of regulating enzyme activity?

Answer 15

By changing the shape of the enzyme

Question 16

What is induced fit?

Answer 16

An induced fit occurs when the active site of an enzyme is changed slightly to better fit the substrate after the substrate binds

Question 17

What is affinity?

Answer 17

Affinity is the term used to describe the degree to which substances bind together

Question 18

What affinity does an enzymes active site have to the substrate?

Answer 18

An enzymes active site has a high affinity to the substrate as well as being specific to the substrate

Question 19

What happens as the products are made?

Answer 19

Their shape changes and they are no longer specific to the enzymes active site

Question 20

What affinity do the products have to the enzymes?

Answer 20

The products have low affinity to the enzymes and are released

Question 21

What then happens to the active site of an enzyme?

Answer 21

The active site of the enzyme then resumes its normal shape and the enzyme is free to attach to more substrate molecules

Question 22

What 4 factors affect enzymes?

Answer 22

Temperature

pH

Enzyme concentration

Substrate concentration

Question 23

What happens as substrate concentration increases?

Answer 23

The rate of the enzyme catalysed reaction increases until all of the active sites are occupied by the substrate

Question 24

What is the term used to describe the enzyme once all active sites are occupied?

Answer 24

Saturated

Question 25

What happens after the saturation point?

Answer 25

Adding more substrate will no long increase the reaction rate

Question 26

What else can stop an enzyme binding to its substrate?

Answer 26

Inhibitors

Question 27

What are the three types of inhibition?

Answer 27

Competitive inhibition Non competitive inhibition Feedback inhibition

Question 28

What is competitive inhibition?

Answer 28

Competitive inhibition occurs when a competitive inhibitor binds to the active site of an enzyme and therefore prevents the substrate from binding

Question 29

Why do competitive inhibitors compete with the substrate?

Answer 29

The competitive inhibitors compete with the substrate because they have a similar shape to the substrate and enzymes active site

Question 30

How can competitive inhibition be reversed?

Answer 30

By increasing the concentration of the substrate. This is because the increases substrate concentration dilutes the inhibitor so that the enzyme molecules bind to the substrate

Question 31

What is non competitive inhibition?

Answer 31

Non competitive inhibitors bind to a part of the enzyme that is not the active site but they still change the shape of the active site. This prevents the substrate from binding to the enzyme and therefore decreases the reaction rate

Question 32

Why can’t non competitive inhibition be reversed?

Answer 32

As the non competitive inhibitor does not bind to the enzymes active site, their effects cannot be reversed by increasing substrate concentration

Question 33

What is feedback inhibition?

Answer 33

Feedback inhibition occurs when the end product of a metabolic pathway reaches a critical concentration. The end product then binds to an enzyme at the start of the metabolic pathway, inhibits it an prevents any further synthesis of the ends product

Question 34

How does feedback inhibition stop the metabolic pathway?

Answer 34

Feedback inhibition stops the metabolic pathway and prevents further synthesis of the end product until the end product concentration decreases The higher the concentration of end product, the quicker the metabolic pathway stops

Question 35

What does feedback inhibition ensure?

Answer 35

That a cell does not produce more end product than necessary