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Flashcards in Role of ATP I Deck (35)
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1
Q

Metabolism

A

Integrated set of enzymatic reactions comprising both of anabolic and catabolic reactions

2
Q

Anabolism

A

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

3
Q

Catabolism

A

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

4
Q

Metabolism summary [2]

A

Anabolism: Synthetic reactions - the pathways end in ‘genesis’
Catabolism: Breakdown reactions - the pathways end in ‘lysis’

5
Q

Energy required for [4]

A
  • Motion (muscle contraction)
    • Transport (of ions/molecules across membranes)
    • Biosynthesis of essential metabolites
    • Thermoregulation
6
Q

Free energy

A
Cells are isothermal systems 
Heat flow cannot be used as a source of energy (heat can only do work when it passes to an area or an object at a lower temperature) 
Free energy (energy available to perform work) is acquired from nutrient molecules
7
Q

Gibbs free energy [3]

A
  • Enthalpy (H): Heat content of the reacting system
    • Entropy (S): Randomness or disorder in a system
    • Gibbs free energy (G): Energy capable of doing work at constant temperature and pressure
8
Q

For the reaction A-> B

If the concentration of B > A at equlibrium

A
  • Spontaneous or exergonic reaction
    • Free energy is defined as negative DG < 0
    • Energy is liberated by the reaction
9
Q

For the reaction A-> B

If the concentration of A > B at equilibrium

A
  • Unfavourable or endergonic reaction
    • Free energy is defined as positive DG> 0
    • Energy input is required to start the reaction
10
Q

Adenosine Triphosphate

A
  • ATP provides most of the free energy required
    • ATP is the energy currency of the cell
    • Achieved by phosphate group transfer
    • Gibbs free energy: The energy derived from the oxidation of dietary fuels
    • Energy is conserved as ATP and is transduced into useful work
11
Q

ATP/ADP Mg2+ complexes [2]

A
  • ATP in the cytosol is present as a complex with Mg2+
    • Mg2+ interacts with the oxygens of triphosphate chain making it susceptible to cleavage in the phosphoryl transfer reaction
12
Q

Substrate level phosphorylation (SLP) [2]

A
  • Formation of ATP by phosphoryl group transfer from a substrate to ADP
    • SLPs require soluble enzymes and chemical intermediates
13
Q

Enzymes [3]

A
  • Biological catalysts that accelerates the rate of chemical reactions
    • Creates a new pathway for reactions, one with a lower activation reaction
    • Does not influence the Delta G of the reaction
14
Q

Coenzymes [6]

A
  • Non-protein cofactors - eg metal cation
    • Most coenzymes derived from vitamins
    • Participate in the enzymatic reaction
    • Have a loose association with their enzyme
    • Diffuse from one enzyme to the next carry e-
    • Regenerated to maintain cellular concentration
15
Q

Prosthetic groups [3]

A
  • 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 intermediate
16
Q

Redox coenzymes/prosthetic groups

[3]

A

• Major redox coenzymes/prosthetic groups involved in transduction of energy from dietary foods to ATP: NAD+/FAD/FMN
• Electrons are transferred from dietary material to these carriers -> coenzymes are reduced
• In each case two electrons are transferred but the number of H+ moved varies
E.g. NAD+ is reduced to NADH and FAD is reduced to FADH2

17
Q

Nicotinamide adenine dinucleotide (NAD)

[3]

A

NAD+ and NADP+ accept pairs of electrons to form NADH and NADPH
Nicotinamide is the functional part of the molecule
• NADH for ATP synthesis
• NADPH for reductive biosynthesis

18
Q

Re-oxidation of redox coenzymes

A

• Recycling of NADH and FADH2 is via the respiratory chain in the mitochondria
• This is coupled to ATP synthesis - process of oxidative phosphorylation
~ 2.5 molecules of ATP may be synthesised for 1 NADH re-oxidised [1.5 ATP for every FADH2 ]

19
Q

Respiration-linked phosphorylation

A

Respiration-linked phosphorylation involve membrane-bound enzymes and transmembrane gradients of protons and require oxygen

20
Q

FAD

A

Prosthetic group derived from from B2- riboflavin

Receives electrons from dietary material to be reduced.
- Receives 2 electrons and 2 protons to form FADH2

  • Reoxised in the respiratory chain during oxidative phosphorylation.
21
Q

FMN

A

Prosthetic group derived from from B2- riboflavin

22
Q

NAD+

A

Co-enzyme derived from vitamin niacin- - Functional group is nicotinamide

Receives electrons from dietary material to be reduced.

  • Receives 2 electrons (hydride ion) and 1 proton
  • Forms NADH

NADH is reoxidised in oxidative phosphorylation, via the respiratory chain or anaerobic respiration.

23
Q

NADPH

A

Reduced NADP

Involved in providing reducing power for reductive biosyntheses

24
Q

Glycolysis priming stages

  • include ATP
  • Include enzymes
A
  1. Glucose—> G6P (glucose 6-phosphate), hydrolyses ATP.
    - uses hexokinase (Hk)
  2. G6P—> F6P (fructose 6-phosphate)
    - uses isomerase
  3. F6P—> FBP (fructose 1,6-bisphosphate)
    - Uses ATP
    - PFK-1 enzyme
  4. FBP —> DHAP, G3P
    - aldolase
  5. DHAP—> G3P
    - isomerase

G3P continues in glycolysis

25
Q

What enzyme converts Glucose—> G6P (glucose 6-phosphate)

A

Hexokinase- HK

This process uses ATP

26
Q

What enzyme converts

G6P—> F6P (fructose 6-phosphate)

A

Isomerase

27
Q

What enzyme converts

F6P—> FBP (fructose 1,6-bisphosphate)

A

PFK-1

This process uses ATP and is the committed step- cannot be reversed.

28
Q

What enzyme converts

FBP —> DHAP, G3P

A

Aldolase

29
Q

What enzyme can convert DHAP into G3P and vice versa

A

Isomerase enzyme.

30
Q

Glycolysis payoff reactions

  • Include SLP steps
  • NADH formation
  • Enzymes
A
  1. G3P –> 1,3 BPG (1, 3 biphosphoglycerate).
    - G3P dehydrogenase
    - NAD+ reduced
  2. 1,3 BPG—> 3PG (3, phosphoglycerate)
    - SLP
    - PGK enzyme (phosphoglycerate kinase)
  3. 3PG–> 2PG
    - mutase
  4. 2PG–> PEP
  5. PEP —> pyruvate
    - pyruvate kinase (Py k)
    - SLP

Pyruvate enters link reaction. Payoff reactions happen twice.

31
Q

What enzyme converts

G3P –> 1,3 BPG (1, 3 biphosphoglycerate)

A

G3P dehydrogenase

  • Forms NADH from NAD+
32
Q

What enzyme converts

1,3 BPG—> 3PG (3, phosphoglycerate)

A

PGK (phosphoglycerate kinase)

  • SLP step
33
Q

What enzyme converts

3PG–> 2PG

A

Mutase

34
Q

What enzyme converts

PEP —> pyruvate

A

Pyruvate kinase (Py k)

  • SLP step
35
Q

Why has the system of lactate production evolved?

A

To recycle NAD+