Intro to Metabolism

Question 1

Definition of metabolism

Answer 1

The totality of the chemical reactions and physical changes that occur in living organisms, comprising anabolism and catabolism
The enzyme reactions of synthesis, breakdown and
interconversion of essential biomolecules

Question 2

What is Catabolism?

Answer 2

The metabolic breakdown of complex substances into smaller products - including the breakdown of
carbon compounds with the liberation of energy for use by the cell or organism

Question 3

What is Anabolism?

Answer 3

The energy requiring part of metabolism in which simpler
substances are transformed into more complex ones as in growth or other biosynthetic processes.

Question 4

Difference between Anabolism and Catabolism?
With Examples?

Answer 4

Catabolism Vs Anabolism
1. names end in ‘lysis’ names Vs end in ‘genesis’
2. glycolysis Vs gluconeogenesis
3. lipolysis Vs lipogenesis
4. glycogenolysis Vs glycogenesis
5. generate ATP & NADH Vs Use ATP, GTP, UTP
6. (mitochondria) Vs mostly in cytosol

Question 5

Describe how seperate regulation?

Answer 5

Activating enzyme 1 (and/or enzyme 2) would speed up forward and reverse
pathways – a ‘futile cycle’

However …
Activating enzyme 1 speeds up forward pathway
Activating enzyme 3 speeds up reverse pathway

Question 6

Explain the concept of controlled release of energy in enzyme catalysed metabolic pathways?

Answer 6

• Stepwise breakdown releases energy in useable small ‘packages’
• Pathways can be regulated by regulation of specific enzymes

Question 7

What are activated carrier molecules?

Answer 7

Activated carriers are molecules that can be split (C → A + B) to release free energy but only if there is an excess of C relative to its equilibrium concnetration.

Question 8

How is the energy stored?

Answer 8

Energy released at each step is stored in activated carrier
molecules

Question 9

What are the activated carrier molecules used in metabolism?

Answer 9

1. ATP
2. NADH, NADPH, FADH2
3. Acetyl CoA
4. Carboxylated biotin
5. S-adenosylmethionine
6. Uridine diphosphate glucose

Question 10

Group carried in high-energy linkage in Uridine diphosphate glucose?

Answer 10

Glucose

Question 11

Group carried in high energy linkage of S-adenosylmethionine?

Answer 11

Methyl group

Question 12

Examples of other ‘high energy’ nucleotides

Answer 12

1. UTP drives the synthesis of complex sugar
2. GTP drives the synthesis of proteins

Question 13

Group carried in high-energy linkage in carboxylated biotin?

Answer 13

Carboxyl group

Question 14

Group carried in high-energy linkage in Acetyl CoA?

Answer 14

Acetyl group

Question 15

Group carried in high-energy linkage in NADH,NADPH,FADH2?

Answer 15

electrons and hydrogens

Question 16

Group carried in high-energy linkage in ATP?

Answer 16

Phosphate group

Question 17

What is ATP?
Structure?

15

Answer 17

• Energy currency of the cell
• Adenosine triphosphate
• Chemically stable at pH 6-9

Question 18

Products of Hydrolysis of ATP?

Answer 18

Hydrolysis gives
* ADP
* H+
* O=P–O-–OH O- top and bottom pf P and -OH of P
+ ‘energy’

Question 19

What makes the hydrolysis of ATP energetically so
favourable?

Answer 19

• Relieves electrostatic repulsion between phosphate groups
• The released phosphate ion is resonance stabilised: increased entropy
  (ΔS +ve)
• Concept of a high energy bond’ or ‘high energy phosphate group’

Hydrolysis of ATP to AMP and PPi realeases almost twice as much free energy as ATP to ADP hydrolysis

Question 20

Breakdown of ATP to ADP

Answer 20

ΔG is - 31 to -50 kJ mole-1

Question 21

Functions of ATP

Answer 21

1. Used directly in cell motility and muscle contraction (motor proteins)
   ATP ———> ADP + Pi myosin/dynein
2. Used in active transport systems e.g. Na+ / K+ pumps
3. Used in metabolic control – regulates enzyme activity
4. Used in metabolism to add Pi to metabolic
   intermediates

Question 22

What can ATP act as?

Answer 22

High energy cofactor for kinase enzymes
ATP breakdown releases 32 kj of energy per mole

ATP ——» ADP. + Pi

Question 23

What do metabolic reactions require?

Answer 23

1. Fuel molecules (substrates/intermediates)
2. Enzyme catalysts
3. Cofactors

Question 24

Overview of the 3 stages of catabolism of:
1. Glucose
2. Fatty acids
3. Amino acids

Answer 24

Glucose

1. Glycolysis (cytosol) - pyruvate ——> CH3 - C
2. Kerbs cycle (mitochondria) - produces 2CO2 and 2H
3. Oxidative phosphorylation (mitochondrial membrane) - 2H + O —-> H20 + ATP

Fatty acids
1. B- oxidation
2. Kerbs cycle
3. Oxidative phosphorylation

Amino ac

Question 25

Where does each stage of metabolism occur?

Answer 25