Unit 1 KA6 Metabolic Pathways

Question 1

Define metabolism

Answer 1

All the chemical reactions that occur within the human body

Question 2

What are anabolic pathways?

Answer 2

Enzyme pathways that require energy and involve biosynthetic (building up small molecules to larger ones) processes

Question 3

What are catabolic pathways?

Answer 3

Enzyme pathways that release energy and involve the breakdown of molecules to smaller ones

Question 4

What is activation energy?

Answer 4

The energy require to break chemcial bonds in the reactants to start a chemical reaction

Question 5

What is the state at which chemical bonds become unstable due to absorbing too much energy called?

Answer 5

The transition state

Question 6

What is a catalyst?

Answer 6

A substance that:
*Lowers the activation energy of a reaction by providing an alternative reaction pathway
* Speeds up the reaction rate
* Takes part in the reaction but remains unchanged by the end of it

Question 7

What is a biological catalyst?

Answer 7

An enzyme

Question 8

What are enzymes made of?

Answer 8

Protein

Question 9

Why do enzyme active sites only bind to specific substrates?

Answer 9

The active site has a specific shape

due to the structure and bonding of the amino acids in the polypeptide chain

Question 10

**

Substrate molecules have high ____ for the active site

Answer 10

affinity

Question 11

The products have a ____ affinity for the active site

Answer 11

low

Question 12

What does affinity mean?

Answer 12

The strength of attraction between the molecules.

Question 13

What is induced fit?

Answer 13

When the enzyme’s active site changes shape to better fit the substrate

Question 14

How does induced fit help the reaction?

Answer 14

It insures that the active site is very close to the substrate and thus increases the chance of the reaction taking place

Question 15

How are the reactants’ orientation determined in enzyme reactions with multiple reactants?

Answer 15

The shape of the active site determines the orientation

This holds the reactants tightly together, in a way that ensures the reaction can take place

Question 16

What factors affect enzyme reactions?

Answer 16

1. Temperature
2. pH
3. Substrate concentration
4. Enzyme concentration

Question 17

What do inhibitors do to the reaction rate?

Answer 17

slow it down or bring it to a halt

Question 18

What happens to the reaction rate as substrate concentration increases?

Answer 18

Increases, then eventually remains constant as the active sites are all occupied, meaning the enzyme concentration is now the limiting factor

Question 19

How can metabolic pathways be controlled?

Answer 19

1. Presence of an enzyme
2. Absence of an enzyme
3. Key enzymes regulating the rate of a reaction within a metabolic pathway

Question 20

How are enzymes who’s genes are continually expressed controlled?

Answer 20

regulation of their rate of reaction

Question 21

Most enzyme reactions are reversible

What determines the direction of reaction?

Answer 21

The concentration of the substrates and products

Question 22

What is an inhibitor?

Answer 22

A substance that decreases the rate of an enzyme controlled reaction

Question 23

What is a competitive inhibitor?

Answer 23

An inhibitor that competes with the substrate for the enzyme’s active sites

It binds to the enzyme’s active site, preventing the substrate from binding to the active site, reducing enzyme activity and thus the rate of reaction

Question 24

What is the structure of competitive inhibitors?

Answer 24

Similar molecular structure to the enzyme’s substrate

Question 25

How can the effect of competitive inhibitors be reversed?

Answer 25

By increasing the substrate concentration

Question 26

What is a non-competive inhibitor?

Answer 26

An enzyme inhibitor that does not compete with the substrate for the active site

The inhibitor instead competes for the allosteric (non-active) site

Question 27

What is the site where non-competitive inhibitors bind to on an enzyme?

Answer 27

The allosteric (non-active) site

Question 28

Once a non-competitive inhiitor has binded to the allosteric site, what is the effect on the enzyme?

Answer 28

The active site’s shape changes, so it no longer fits the substrate, thus preventing it from binding

Question 29

If substrate concentration is increased, what happens to the effect of the non-competive inhibitors?

Answer 29

Nothing, as they do not compete with the subtrate for the active site

They bind to the allosteric site, instead of the active site