1.6 Cell Metabolism

Question 1

Definition of cell metabolism

Answer 1

All the enzyme controlled reactionsthat occur in a cell at the same time

Question 2

The two groups that reactions in a cell can be categorised into

Answer 2

• Catabolic

* Anabolic

Question 3

Explain an anabolic pathway

Answer 3

• Requires energy

* Involves biosynthetic processes (large molecules synthesised from small molecules)

Question 4

Explain a catabolic pathway

Answer 4

• Releases energy

* Involves the breakdown of large molecules into smaller molecules

Question 5

An example of a catabolic reaction

Answer 5

Aerobic respiration

Question 6

An example of an anabolic pathway

Answer 6

Protein synthesis

Question 7

Definition of a metabolic pathway

Answer 7

A series of chemical reactions that follow on, one after the other

Question 8

What each stage in a metabolic pathway is controlled by

Answer 8

Enzymes

Question 9

Example of a reversible metabolic pathway

Answer 9

The conversion of pyruvate into lactic acid in animal cells

Question 10

Example of an irreversible metabolic reaction

Answer 10

The conversion of pyruvate into ethanol and CO2 in plant cells

Question 11

What alternative routes do in metabolic reactions

Answer 11

Bypass steps in a pathways

Question 12

The two ways metabolic pathway can be controlled

Answer 12

• the presence or absence of particular enzymes in the pathway
• regulation of the rate of reaction of key enzymes within the pathway

Question 13

The result of the genes for some enzymes being continuously expressed

Answer 13

• the enzymes are always present in the cell

* their control involves the regulation of their rate of reaction

Question 14

The two molecules regulation of rate of reaction is controlled by

Answer 14

• intracellular

* extracellular

Question 15

Describe the work of extracellular signal molecules

Answer 15

Secreted by a particular cell but work elsewhere in the body

Question 16

Example of extracted signal molecules

Answer 16

Hormones which travel in the bloodstream to reach target tissues
eg. Insulin produced in the pancreas works on the liver

Question 17

Describe the work of intracellular signal molecules

Answer 17

Work inside the cell that produces them

Question 18

Where enzymes are found

Answer 18

Every living cell

Question 19

What an enzyme is

Answer 19

Biological catalysts made of protein

Question 20

What would happen if enzymes weren’t present in cells

Answer 20

Chemical reactions would occur in cells to slowly for life to exist

Question 21

What activation energy is

Answer 21

The energy needed to start a reaction

Question 22

Basic work of enzymes

Answer 22

Enzymes lower the activation energy needed to start a chemical reaction

Question 23

Symbol for activation energy

Answer 23

Ea

Question 24

Define what is ment by affinity

Answer 24

The active site having a chemical attraction to the substrate

Question 25

Explain the meaning of induced fit

Answer 25

• structural changes occur so that the active site fits precisely around the substrate
• the substrate induces the active site to change shape

Question 26

How enzymes reduce the activation energy required for the reaction to occur

Answer 26

Orientating and then holding the reactants close together

Question 27

Why the end products are released from the enzyme

Answer 27

The end products have a lower affinity for the active site

Question 28

What the direction and speed of an enzyme controlled reaction are controlled by

Answer 28

The concentrations of both the substrate and the end product

Question 29

In what direction does the increase in the substrate concentration drive to the reaction in

Answer 29

In the direction of the end product

Question 30

What drives a sequence of reactions in a particular direction

Answer 30

• presence of a substrate

* removal of a product

Question 31

What happens when enzymes act in groups

Answer 31

The product of one reaction acts as a substrate for the next

Question 32

What is ment by multi enzyme complexes

Answer 32

Where a number of enzymes work together at the same time on the same substrate molecule

Question 33

An example of a multi enzyme complex

Answer 33

DNA polymerase and RNA polymerase both working on a strand of DNA

Question 34

What an enzyme needs to function effectively

Answer 34

• suitable temperature
• appropriate pH
• adequate supply of substrate molecules

Question 35

Effects of inhibitors on the rate of reactions

Answer 35

• slow the rate of reaction down

* bring the reaction to a halt

Question 36

What happens when the genes responsible for the production of some enzymes are continuously expressed

Answer 36

The enzymes are always present in the cell

Question 37

How enzyme activity can be controlled

Answer 37

Regulation of the rate of reaction that the enzymes catalyse

Question 38

Explain the term enzyme inhibitor

Answer 38

• molecule that can affect the rate of reaction
• does this by blocking the active site of the enzyme
• or denaturing the enzyme

Question 39

Role of a competitive inhibitor

Answer 39

• competes with the substrate for the active site

* resembles the shape of the substrate

Question 40

How the effect of competitive inhibition can be reversed

Answer 40

By increasing the concentration of the substrate molecules so there is more of a chance that the substrate molecules occupy the active sites

Question 41

Effect of non competitive inhibition

Answer 41

Changed the shape of the active site on an enzyme

Question 42

How a non competitive inhibitor works

Answer 42

Binds to an area of the enzyme which is not the active site