Metabolism Overview

Question 1

What is catabolism?

Answer 1

Metabolic breakdown of complex substances into smaller products

(Food –> building blocks + energy + heat)

Question 2

What is anabolism?

Answer 2

Energy-requiring transformation of simpler substances into more complex ones

Question 3

Why are substances broken down step-wise rather than all in one go?

Answer 3

Step-wise releases small, usable packages of energy

Each step has a smaller activation energy (all in one go = lots of energy wasted as heat and high Ea)

Question 4

Why are forward and reverse pathways not direct opposites of each other?

Answer 4

Allows separate regulation

Prevents ‘futile cycle’

Question 5

What is another term for activated carrier molecules?

Answer 5

Cofactors

Coenzymes

Question 6

Why is energy stored at each step of an energetically favourable reaction?

Answer 6

To be used in energetically unfavourable reactions

Question 7

What bonds in ATP are broken to release energy?

Answer 7

Phosphoanhydride

Question 8

What properties make ATP suitable for energy storage in humans?

Answer 8

Chemically stable at physiological pH (6-9)

Structural features can be recognised by specific proteins, enzymes, etc

Hydrolysis releases energy

Question 9

What does ΔG mean?

Answer 9

Change in free energy

Question 10

What does it mean when ΔG is negative?

Answer 10

Energy released

Question 11

What is the ΔG of ATP hydrolysis?

Answer 11

-31 to -50kJ/mol

Question 12

Why is ATP hydrolysis energetically favourable?

Answer 12

Relieves electrostatic repulsion between phosphate groups (unstable molecule)

Released phosphate ion is resonance stabilised (electron delocalisation)

Increase in entropy

Question 13

How much energy is release when ATP is hydrolysed to AMP + PPi?

Answer 13

Almost twice as much as ATP to ADP hydrolysis

As PPi spontaneously breaks down into two Pi

Question 14

What is PPi called?

Answer 14

Pyrophosphate

Question 15

Give some of the functions of ATP

Answer 15

Cell motility and muscle contraction

Active transport

Metabolic control by regulating enzyme activity

Activate/phosphorylate molecules

Question 16

What UTP used for?

Answer 16

Synthesis of complex sugars

Question 17

What is GTP used for?

Answer 17

Protein synthesis (translation)

Microtubule elongation

Question 18

Which activated energy carriers carry electrons and protons?

Answer 18

NAD(H)

NADP(H)

FAD(H2)

Question 19

What does acetyl coenzyme A carry?

Answer 19

Acetyl

Question 20

Which activated energy carrier carries a carboxyl group?

Answer 20

Carboxylated biotin

Question 21

What activated energy carrier carries a methyl group?

Answer 21

S-adenosylmethionine

Question 22

What activated energy carrier carries a glucose?

Answer 22

Uridine diphosphate glucose (UDP-glucose)

Question 23

What does NAD stand for?

Answer 23

Nicotinamide adenine dinucleotide

Question 24

What are the main differences between NAD+ and NADP+?

Answer 24

NADP+ has a phosphate group

NADP+ replaces NAD+ in anabolic reactions

Question 25

What happens molecularly when NAD+ is reduced?

Answer 25

Nicotinamide group accepts one H and an electron (leaving a spare proton)

Question 26

What does FAD stand for?

Answer 26

Flavin adenine dinucleotide

Question 27

What happens molecularly when FAD is reduced?

Answer 27

Flavin group accepts two H (added to nitrogens) | Originally neutral so no spare protons

Question 28

What type of bonds does coenzyme A form with carboxylic acids?

Answer 28

Thioester

Question 29

How do we write the structure of coenzyme A?

Answer 29

CoA-SH

Question 30

What are the three main stages of catabolism of sugars, fats and amino acids?

Answer 30

Conversion to acetyl unit Krebs/TCA cycle Oxidative phosphorylation

Question 31

What is pyruvate converted to in anaerobic respiration?

Answer 31

Lactate/lactic acid

Question 32

What is the structure of pyruvate?

Answer 32

-OOC--CO--CH3

Question 33

What enzyme catalyses anaerobic respiration?

Answer 33

Lactate dehydrogenase

Question 34

What is the purpose of anaerobic respiration?

Answer 34

Regenerate NAD+ so glycolysis can continue

Question 35

By what process is glucose converted to the acetyl unit?

Answer 35

Glycolysis

Question 36

By what process is a fatty acid converted to the acetyl unit?

Answer 36

Beta oxidation

Question 37

How is an amino acid converted to the acetyl unit?

Answer 37

Transamination

Question 38

How can regulation of metabolic pathways be achieved?

Answer 38

Changes in amount of enzyme (gene expression) Changes in enzyme activity

Question 39

How can enzyme activity be altered?

Answer 39

Allosteric regulation/binding of allosteric regulators Phosphorylation and dephosphorylation

Question 40

What kind of alteration to enzyme activity is instantaneous and local?

Answer 40

Allosteric regulation