The roles of ATP in living cells and the mechanisms of production 1

Question 1

Metabolism

Answer 1

Integrated set of enzymatic reactions comprising both anabolic and catabolic reactions

Question 2

Anabolism

Answer 2

Synthesis of complex molecules from simpler ones (necessary energy usually derived from ATP)

Question 3

Catabolism

Answer 3

Breakdown of energy rich molecules to simpler ones (CO2, H2O and NH3)

Question 4

Energy is required for:

Answer 4

Motion (muscle contraction)

Transport (of ions/ molecules across membranes)

Biosynthesis of essential metabolites

Thermoregulation

Question 5

Isothermal

Answer 5

Maintaining constant temperature

Question 6

3 important thermodynamic quantities

Answer 6

Enthalpy- the heat content of the reacting system

Entropy- the randomness or disorder in a system

Gibbs free energy- energy capable of doing work at constant temperature and pressure

Question 7

Exergonic reaction

Answer 7

Spontaneous

Free energy is defined as negative

Energy is liberated by the reaction

Catabolism

Question 8

Endergonic reaction

Answer 8

Unfavourable

Free energy is defined as positive

Energy input is required to start the reaction

Anabolism

Question 9

Coupling of reactions

Answer 9

Endergonic reaction driven in the forward direction by coupling it to an exergonic reaction through a common intermediate

Question 10

Adenosine triphosphate

Answer 10

ATP provides most of the free energy required

Energy currency of the cell

Achieved by phosphate group transfer

Question 11

Phosphate group transfer

Answer 11

Covalent participation by phosphate group transfer forms intermediate complex

Reaction between complex and another compound displaces the phosphate group to form product

Question 12

ATP/ ADP Mg2+ complexes

Answer 12

ATP in the cytosol is present as a complex with Mg2+

Mg2+ interacts with the oxygens of the triphosphate chain making it susceptible to cleavage in the phosphoryl transfer reactions

Question 13

Substrate level phosphorylation

Answer 13

Formation of ATP by phosphoryl group transfer from a substrate to ADP

Require soluble enzymes and chemical intermediates

Question 14

Respiration linked phosphorylation

Answer 14

Involve membrane bound enzymes and transmembrane gradients of protons and require oxygen

Question 15

Enzymes

Answer 15

Biological catalysts that accelerate the rate of chemical reactions

Create a new pathway for the reactions with a lower activation energy

Question 16

Oxidoreductases

Answer 16

Classification of enzymes that transfer electrons

Question 17

Transferases

Answer 17

Classification of enzymes that transfer functional groups

Question 18

Co-enzymes

Answer 18

Non-protein cofactors

Most coenzymes derived from vitamins

Participate in the enzymatic reaction

Have a loose association with their enzyme

Diffuse from one enzyme to the next carrying e-

Regenerated to maintain cellular concentration

Question 19

Prosthetic groups

Answer 19

Non-protein cofactor that is covalently bound to the enzyme

Not released as part of the reaction

Acts as a temporary store for e- or intermediates

Question 20

Redox coenzyme/ posthetic groups

Answer 20

Major redox coenzymes/ prosthetic groups involved in transudation of energy from dietary foods to ATP: NAD+, FAD, FMN

Electrons transferred from dietary material to these carriers so coenzymes are reduced

In each case two electrons are transferred but the number of H+ moved varies

Question 21

Nicotinamide adenine dinucleotide

Answer 21

NAD+ and NADP+ accept pairs of electrons to form NADH or NADPH

It is the nicotinamide that is the functional part of the molecule

NADH for ATP synthesis

NADPH for reductive biosynthesis

Question 22

Re-oxidation of redox coenzymes

Answer 22

Recycling of NADH and FADH2 is via the respiratory chain in the mitochondria

This is coupled to ATP synthesis- process of oxidative phosphorylation

Question 23

Glycolytic enzymes

Answer 23

Hexokinase- phosphorylation

PFK-1 - phosphorylation

Pyruvate kinase- phosphorylation

Question 24

The fate of pyruvate

Answer 24

Two possible fates:

• under aerobic conditions, oxidation and complete degradation
• in hypoxic conditions, it an be reduced to lactate