T2 L1 Role of ATP in living cells

Question 1

What is the definition of metabolism?

Answer 1

An integrated set of enzymatic reactions comprising of both anabolic and catabolic reactions.
Energy is stored as ATP for later use in anabolic reactions.

Question 2

What is the definition of anabolism?

Answer 2

The synthesis of complex molecules from simpler ones
Requires energy usually derived from ATP
Synthetic reactions
Pathways end in ‘‘genesis’’

Question 3

What is the definition of catabolism

Answer 3

The breakdown of energy rich molecules to simpler ones

Pathways end in ‘‘lysis’’

Question 4

Give 4 things that energy is required for

Answer 4

Motion - muscle contraction
Transport - ions/molecules across membranes
Biosynthesis of essential metabolites
Thermoregulation

Question 5

What does an isothermal system mean?

Answer 5

It maintains a constant temperature
Cells are isothermal systems
Heat flow can’t be used as a source of energy
Heat can only do work when it passes to an area of lower temperature

Question 6

What is Gibbs free energy?

Answer 6

The energy capable of doing work at a constant temperature & pressure
Delta G = Delta H - T x delta S

Question 7

What is enthalpy?

Answer 7

The heat content of the reacting system

Question 8

What is entropy?

Answer 8

The randomness or disorder in a system

Question 9

What is delta H

Answer 9

The kinds & numbers of chemical bonds that are formed & broken
Positive when energy is absorbed from a reaction - endothermic reaction

Question 10

What is delta S

Answer 10

The formation of large complex molecules from smaller ones

Positive when randomness increases

Question 11

What is Gibbs free energy of a reaction?

Answer 11

Maximum amount of energy that can be obtained from a reaction at constant temperature & pressure

Question 12

What is an exergonic reaction?

Answer 12

Products have less free energy than the reactants

Formation of products is spontaneous

Question 13

What is an endergonic reaction?

Answer 13

Products have more free energy than reactants so are less stable

Question 14

Describe the coupling of reactions

Answer 14

Endergonic reactions can be driven in forward direction by coupling to an exergonic reaction through a common intermediate.

1) Glucose + Pi –> glucose-6-phosphate + H2O
2) ATP + H2O –> ADP + Pi
Sum) Glucose + ATP –> glucose-6-phosphate + ADP

Question 15

Describe Adenosine triphosphate

Answer 15

Provides most of the free energy required
Energy currency of the cell
Formed by phosphate group transfer
Gibbs free energy - energy derived from the oxidation of dietary fuels
Energy conserved as ATP is transducer into useful work

Question 16

Why is magnesium is present in the cytosol?

Answer 16

ATP is present as a complex with Mg2+
Mg2+ interacts with oxygens of the triphosphate chain & make it susceptible to cleavage in phosphoryl transfer reactions
Mg2+ deficiency will impair almost all metabolism & make the individual tired

Question 17

What is substrate level phosphorylation?

Answer 17

Formation of ATP by phosphoryl group transfer from a substrate to ADP
Requires soluble enzymes & complex intermediates
Respiration linked phosphorylations involve:
-membrane bound enzymes
-transmembrane gradients of protons
-oxygen

Question 18

What are enzymes?

Answer 18

Biological catalysts that accelerate the rate of chemical reactions
Create a new pathway for the reaction with a lower activation energy
Doesn’t influence delta G of a reaction

Question 19

How are enzymes classified?

Answer 19

Transfer of electrons

Transfer of functional groups

Question 20

Give examples of enzymes with transfer of electrons

Answer 20

Class: Oxioreductases

Important subclasses: dehydrogenase, oxidases, peroxidases, reductases, monoxygenases, deoxygenates

Question 21

Give examples of enzymes with transfer of functional groups

Answer 21

Class: transferases

Important subclasses: C1 transferases, glyosyltransferases, aminotransferases, phosphotransferases

Question 22

What are coenzymes?

Answer 22

Non-protein co factors
Most are derived from vitamins
Participate in enzymatic reactions
Have a loose association with their enzyme
Diffuse from one enzyme to the next carrying electrons
Regenerated to maintain cellular concentration

Question 23

What are prosthetic groups?

Answer 23

Non-protein co factor that is covalently bonded to the enzyme
Not released as part of the reaction
Acts as a temporary store for electrons or intermediates

Question 24

Give some examples of vitamins

Answer 24

B2- FAD or FMN. Prosthetic group
Niacin - NAD+. Co-substrate
Water soluble vitamins (B1, B2, B3, B6, C, biotin, folic acid & pantothenic acid) are readily absorbed from the diet unlike the fat-soluble vitamins (A,D,E & K)

Question 25

Describe redox coenzymes/prosthetic groups

Answer 25

Major redox coenzymes/prosthetic groups involved in transduction of energy from dietary foods to ATP:
Electrons are transferred from dietary material to these carriers causing the coenzymes to be reduced
NAD+ is reduced to NADH
FAD is reduced to FADH2
FMN is reduced to FMNH2

Question 26

Describe nicotinamide adenine dinucleotide

Answer 26

NAD+ & NADP+ accept electrons to form NADH or NADPH
Nicotinamide is te functional part of the molecules
NADH involved in ATP synthesis
NADPH involved in reductive biosynthesis

Question 27

How does re-oxidation or redox coenzymes occur?

Answer 27

Recycling of NADH & FADH2 occurs via the respiratory chain in the mitochondria
Process is coupled to ATP synthesis - process of oxidative phosphorylation

Question 28

What are the glycolytic enzymes used in the priming stage?

Answer 28

Priming stage uses 2 ATP & proceeds 2 C3 molecules, which are interconvertible
Hexokinase - phosphorylation reactions
PFK-1 - phosphorylation reactions
Phosphoglucose isomerase - isomerisation reactions

Question 29

What are the glycolytic enzymes used in the pay off stage?

Answer 29

Pay-off stage generates 4 ATP, 2 NADH & various intermediates
Pyruvate kinase - phosphorylation reactions
Enolase - dehydration reaction

Question 30

Describe pyruvate

Answer 30

Undergoes oxidation & complex degradation under aerobic conditions
Reduced to lactate in hypoxic conditions to allow NADH to be recycled

Question 31

Give the steps of glycolysis

Answer 31

Glucose to glucose-6-phosphate to fructose-6-phosphate to fructose-1,6-phosphate
Splits into DHAP or G-3-P
G-3-P goes to 1,3-BPG to 3PG to 2PG to PEP to pyruvate