2.1 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

Define an anabolic reaction

Answer 2

Anabolic reactions build up large molecules from smaller molecules and requirers energy

Question 3

Define a catabolic reaction

Answer 3

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

Question 4

Give examples of catabolic reactions

Answer 4

Breakdown of…
Carbohydrates
Fats
Proteins

Question 5

Give examples of anabolic reactions

Answer 5

The synthesis of…
Starch
Fats 
Proteins 
Nucleic acids

Question 6

The importance of reversible and irreversible steps

Answer 6

They allow the process to be kept under control

Question 7

What controls metabolic pathways?

Answer 7

Enzymes

Question 8

Give three features of metabolic pathways

Answer 8

they can have reversible steps, irreversible steps and alternative routes.

Question 9

What type of reaction builds up large molecules from smaller molecules

Answer 9

Anabolic

Question 10

Describe the difference between anabolic and catabolic reactions

Answer 10

Anabolic reactions involve the building up of small molecules to larger more complex molecules - requires energy.
Catabolic reactions breakdown of large molecules into smaller simpler molecules - releases energy.

Question 11

Anabolic or catabolic;

Synthesis of protein from amino acids

Answer 11

Anabolic

Question 12

Anabolic or catabolic;

Aerobic respiration

Answer 12

Catabolic

Question 13

Anabolic or catabolic;

Digestion of fatty acids into glycerol

Answer 13

Catabolic

Question 14

Anabolic or catabolic;

Synthesis of glycogen from glucose

Answer 14

Anabolic

Question 15

Define the nucleus

Answer 15

Controls the activities of the cell

Question 16

Roll of the cell membrane

Answer 16

Controls the entry and exit of substances in the cell

Question 17

Roll of cytoplasm

Answer 17

Site of chemical reactions

Question 18

Roll of the vacuole

Answer 18

Maintains cell shape and contains cell sap

Question 19

Roll of the cell wall

Answer 19

Provides snd Maintains shape

Question 20

Roll of chloroplasts

Answer 20

Site of photosynthesis

Question 21

Roll of ribosome

Answer 21

Site of protein synthesis

Question 22

Roll of mitochondria

Answer 22

Site of energy synthesis

Question 23

What is active transport?

Answer 23

The movement of molecules or ions across the plasma membrane against a concentration gradient

Question 24

What are the two components of the plasma membrane?

Answer 24

Phospholipid and protein

Question 25

Funtions of pump - membrane

Answer 25

Recognise and transport specific ions across the membrane

Question 26

Functions of pores - membrane

Answer 26

Allow larger molecules to diffuse across a membrane

Question 27

How are metabolic pathways controlled?

Answer 27

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

Question 28

What is ‘induced fit’?

Answer 28

Induced fit and the role of the active site of an enzyme in affecting activation energy and the affinity of the substrate and products for the active site.

Question 29

List features of an enzyme

Answer 29

Speed up chemical reactions
lower the activation energy needed for a reaction to occur
are unchanged at the end
have an active site which is complementary to a particular substrate, are specific to their substrates

Question 30

Compare the infinity of a substrate and the affinty of a product for the active site

Answer 30

substrate has a high affinity and product has low affinity

Question 31

How will the presence of a substrate or the removal of a products affect reactions

Answer 31

Some metabolic reactions are reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction.

Question 32

Factors affecting enzyme action

Answer 32

Temperature
Ph
Supply of substrate

Question 33

Enzymes are biological catalysts, outline THREE features of catalysts

Answer 33

Speed up the rate of a chemical reaction

Take part in the reaction but remain unchanged at the end They lower the activation energy

Question 34

What determines the structure of an enzyme’s active site?

Answer 34

The sequence of amino acids

and the subsequent additional bonding between amino acids

Question 35

Define the infinity of the substrate to the active site

Answer 35

High

Question 36

Define the inifnity of the product to the active site

Answer 36

Low

Question 37

List how metabolic pathways are controlled

Answer 37

through competitive, non-competitive and feedback inhibition of enzymes.

Question 38

Define competitive inhibitors

Answer 38

Competitive inhibitors have a very similar shape to that of the substrate.
• They bind at the active site and prevent the substrate from binding. The rate of reaction is slows down.
• Competitive inhibition is reversed by increasing substrate concentration.

Question 39

Define non-competitive inhibitors

Answer 39

• A non-competitive inhibitor binds away from the active site of the enzyme molecule.
• This changes the shape of the active site and prevents the substrate from binding with the enzyme.
• An increase in substrate concentration has no effect on the rate of reaction as it is not competing with the substrate for the active site.
• Non-competitive inhibition cannot be reversed by increasing substrate concentration.

Question 40

When will feedback inhibition occur?

Answer 40

What the product concentration resches critical