Bioenergetics Flashcards Preview

MIMS > Bioenergetics > Flashcards

Flashcards in Bioenergetics Deck (249)
Loading flashcards...
1

What are the standard conditions for ΔG

pH 7
One atmosphere
298K

2

ΔG is a state function. What does this mean?

ΔG will be the same regardless of the path taken

This also means reactions can be coupled

3

Why is the hydrolysis of ATP so exothermic

Phosphate and ADP have more resonance stabilisation than ATP

Electrostatic repulsion. At pH7, ATP has ~4 negative charges in close proximity, weakening the bridging P-O-P bonds in ATP

Stabilisation due to hydration. More water can bind to ADP and Pi than ATP

4

What is phosphorylation potential

The free energy of ATP hydrolysis

5

What is the ATP turnover in humans during exercise

0.5kg/min

6

What is ATP often buffered by in mammals

Phosphocreatine

7

Give 3 examples of ATP hydrolysis

1. Phosphorylate glucose to provide enough energy to prime the molecule to be broken down to pyruvate

2. Peptides are unstable thermodynamically so ATP can be used to build long chains

3. To join 2 nucleic acids at the start of DNA synthesis

8

What are the 4 main carrier molecules and what does each carry

What do they all have in common structurally

ATP - phosphoryl-
NADH and NADPH: e-
FADH2 and FMNH2: e-
Coenzyme A: acyl

An adenine base is present

9

What do biotin and uridine diphosphate glucose carry respectively

B: CO2
UDG: glucose

10

What is the main redox system for energy producing pathways

What is it for biosynthesis

NAD+/NADH

NADP+/NADPH

11

What does the phosphate group act as in NADP+

A tag allowing recognition of this redox system by biosynthetic enzymes

12

What does Coenzyme A provide

The activated form of acetate

13

Why is blood important for fuel economy

It is a fuel pipe as far as metabolism is concerned, carrying glucose, fructose, lipoproteins, fatty acids, ketone bodies, and amino acids

14

Why is the small intestine important for fuel economy

Absorbs glucose, fructose and amino acids and transfers them to blood
Fats are packed and transferred to lymph and then blood

15

Why is the liver important for fuel economy

Central role in glucose control
‘Fat factory’ in terms of synthesis and export of triglycerides to adipose tissue
Also partially oxidises fats to produce ketone bodies and is central to amino acid metabolism

16

Why is the heart the ‘dustbin’ of the body

It will metabolise a wide variety of substrates left over from other metabolic processes

17

Why is adipose tissue important for fuel economy

Fat storage and energy store
Secretes hormones etc

18

Why is the brain important for fuel economy

Largely uses glucose to maintain neuronal cell function but can use ketone bodies during fasting

19

What are the beginning and end products of gluconeogenesis

Pyruvate to glucose-6-phosphate

20

What are the beginning and end products of glycolysis

Glucose 6 phosphate to pyruvate

21

What are the beginning and end products of glycogen synthesis

Glucose 1 phosphate to glycogen

22

What are the beginning and end products of fat synthesis

Acetyl CoA to fatty acid

23

What are the beginning and end products of glycogen breakdown

Glycogen to glucose 1 phosphate

24

What are the beginning and end products of fat breakdown

Glycogen to glucose-1-phosphate

25

Why is control necessary in metabolic processes (3)

1. To avoid uncontrolled substrate (futile) cycles
2. To link energy production to energy usage
3. To respond to physiological changes

26

How are enzyme activities controlled

Change in the amount of enzyme

Metabolic control of enzyme

27

How can you change the amount of enzyme

Altering rate of synthesis or rate of destruction

(Slow long term response)

28

Describe metabolic control of an enzyme

Rapid response for quick control of a pathway eg when products of a pathway inhibit steps at the start preventing accumulation of intermediates

29

What are the mechanisms for controlling enzyme reaction rates

Allosteric regulation: binding of an allosteric effector which changes the affinity of the enzyme for its substrates

Covalent modification: usually phosphorylation causing a conformational change

30

Catabolic vs anabolic

Catabolic is degradation
Anabolic is biosynthesis