Introduction to Metabolism

Question 1

Define the term : Metabolism

Answer 1

Mechanisms which couple the demand for energy, with the fuel supply

Question 2

Define the term : Anabolism

Answer 2

SYNTHESIS of new molecules to store energy

Question 3

Define the term : Catabolism

Answer 3

DEGRADATION of molecules to release energy

Question 4

Define the term : Oxidation

Answer 4

Gain of oxygen

OR

Loss of hydrogen

OR

Loss of electrons from molecules

Question 5

Define the term : Reduction

Answer 5

Loss of oxygen

OR

Gain of hydrogen

OR

Addition of electrons

Question 6

Function of ATP

Answer 6

Adenosine Triphosphate

The essential link between anabolism and catabolism
Energy currency

Question 7

How many stage of metabolism are there ?

Answer 7

3 stages

Question 8

Describe what happens in stage 1 of metabolism

Answer 8

Digestion in the GI tract
Absorption and Transport in the blood

Question 9

Describe what happens in stage 2 of metabolism

Answer 9

In the cell cytoplasm :

• Anabolic
• Catabolic

reactions occur

Question 10

Where does stage 2 of metabolism occur ?

Answer 10

In the cell cytoplasm

Question 11

Anabolic

Answer 11

Nutrients built into storage molecules

e.g. glycogen/protein/adipose

Question 12

Catabolic

Answer 12

Nutrients/ Storage molecules are broken down

e.g. pyruvate / acetyl CoA

Question 13

Where does stage 3 of metabolism occur ?

Answer 13

In the mitochondria

Question 14

Describe what happens in stage 3 of metabolism

Answer 14

IN mitochondria :

Catabolism requiring oxygen to completely break down food and generate ATP.

Question 15

State the 2 nutritional states

Answer 15

Absorptive (fed)
Post-absorptive (fasting)

Energy is stored in the absorptive state and released in the post-absorptive

Question 16

How do we capture energy release from food ?

Answer 16

The process of cellular respiration (stages 2+3) enables stepwise oxidation of food (e.g. glucose)

Captured as chemical energy, to store in high energy phosphate bonds of ATP.

Question 17

What is Redox ?

Answer 17

Reduction and Oxidation of molecules

Cellular respiration utilises these reactions to power the synthesis of ATP

Question 18

State the 2 key coenzymes involves in metabolism

Answer 18

NAD - Nictotinamide adenine dinucleotide
FAD - Flavin adenine dinucleotide

Question 19

How is NAD produced ?

Answer 19

Vitamin B3 - Niacin

Question 20

How is FAD produced ?

Answer 20

Vitamin B2 - Riboflavin

Question 21

State the stages of cellular respiration

Answer 21

Glycolysis
Citric acid cycle / Krebs cycle
Oxidative phosphorylation

Question 22

Where is energy stored in ATP ?

Answer 22

Energy is stored in phosphate bonds

Energy produced by catabolism is used to drive anabolism and other energy requiring processes.

Question 23

How much energy is released when ATP is hydrolysed to ADP + Pi ?

Answer 23

-30.5 kJ/mol of energy is released

Question 24

Describe the stages in cellular respiration

Answer 24

Stage 1 :

Digestion in the GI tract - absorption and transport to cells

Stage 2 : Glycolysis in the cell cytoplasm

Stage 3 : Citric Acid cycle and ox. phos. in mitochondria

… Ultimately yielding ATP

Question 25

Describe the 1st Law of Thermodynamics

Answer 25

The total energy of a system is constant

Energy can neither be created nor destroyed

Energy can be converted from one form to another

Question 26

State some types of energy

Answer 26

Kinetic energy
Potential energy

Question 27

What is Gibbs free energy ?

Answer 27

The energy needed to transform substrates into the transition state.

All reactions need to overcome the energy barrier

Question 28

Describe Gibbs free energy for a graph where free energy of substrate is equal to product

Answer 28

Delta G = 0

Question 29

Describe Gibbs free energy for a graph where free energy of substrate is higher than the product

Answer 29

Delta G = negative

So reaction is favourable

Question 30

Describe Gibbs free energy for a graph where free energy of substrate is lower than the product

Answer 30

Delta G = positive

So reaction is unfavourable

Question 31

Exergonic

Answer 31

Favourable
-delta G

Releases more energy than input

Question 32

Endergonic

Answer 32

Unfavourable
+delta G

Requires more energy input than it yields

Question 33

Explain how enzyme reactions can be coupled to utilise ‘free energy’

Answer 33

1st step of glycolysis : Phosphorylation of glucose : endergonic

Coupled to hydrolysis of ATP –> ADP + Pi :
exergonic

Question 34

State an example of a catabolic reaction

Answer 34

Breakdown of glucose to pyruvate

Mobilisation of fatty acids from lipid stores to feed into cellular respiration

Question 35

Metabolism is not 100% effective at capturing food energy.

What form of energy is most commonly lost in the process ?

Answer 35

Thermal energy