Metabolism, ATP & Glycolysis

Question 1

What is energy used for in living organsims?

Answer 1

Energy is required to carry out life processes e.g.

• molecule synthesis
• establishing ion gradients
• mechanical work
• maintaining body heat

Question 2

Why is metabolism such a significant part of the whole body?

Answer 2

Integrates all the processes in the body

- often product of one process is substrate for another

Question 3

Explain why the study of metabolism is essential

Answer 3

Can study metabolic diseases
Can alter the way body uses food
Can use metabolite changes to aid diagnosis and follow treatment

Question 4

How does ATP transfer energy?

Answer 4

Acts as an energy donor and acceptor

is a short term energy reservoir

Question 5

Collectively what do we name the life processes?

Answer 5

This is our Metabolism

Question 6

Approximately how much energy is used during exercise?

Answer 6

0.5 kgmin⁻¹

Question 7

Outline the process of glycolysis

Answer 7

1. Glucose phosphorylated by 2Pi molecules
   
   • energy provided by ATP hydrolysis
2. Phosphorylated glucose split into 2 3C molecules
3. NAD reduced as 3C TP is oxidised
4. 2 Pyruvate molecules produced

Question 8

What enzyme is responsible for the conversion of glucose to G6P

Answer 8

Hexokinase using ATP

Question 9

What is Anabolism ?

Answer 9

Synthesis of new molecules from smaller less complex molecules

Question 10

Where in a cell does glycolysis occur?

Answer 10

In the mitochondria

Question 11

How much energy is available after ATP hydrolysis?

Answer 11

65Kjmol⁻¹

Question 12

What is the role of glucokinase in the liver?

Answer 12

Also converts Glucose -> G6P (same as hexokinase)

provides 95% of hexokinase activity in hepatocytes

Question 13

What are the products of glycolysis?

Answer 13

2ATP, 2NADH, 2 Pyruvate

Question 14

How much ATP does the body approximately contain?

Answer 14

100g of ATP

Question 15

Why is liver glycolysis regulation so much more complex than in muscles?

Answer 15

The liver has many more functions than muscles

Question 16

Why does a low pH not have a significant effect on the liver?

Answer 16

Lactate isn’t produced in the liver

Question 17

Which enzyme is responsible for the conversion of G6P to Fructose-6-Phosphate ?

Answer 17

Phosphofructokinase using ATP

Question 18

How is glycolysis regulated?

Answer 18

By the regulation of enzymes catalysing irreversible reactions

Question 19

Where do humans get their energy from?

Answer 19

All our energy is derived from the food we eat

Question 20

How is the activity of glycolysis irreversible enzymes regulated?

Answer 20

• reversible binding of allosteric effectors
• covalent modifications
• transcription

Question 21

How is the energy demands met by ATP in the body?

Answer 21

ATP resynthesised from ADP during oxidative phosphorylation in the mitochondria

Question 22

Define Catabolism

Answer 22

Breakdown of complex molecules to release energy or to carry out mechanical work

Question 23

How much energy is used at rest in 24hrs?

Answer 23

40Kg

Question 24

What factors inhibit the conversion of G6P to F6P in the liver and muscle?

Answer 24

High [ATP]
Low pH
inhibits phosphofructokinase
- lower F6P affinity

Question 25

How is ATP formed?

Answer 25

From ADP catalysed by Adenylate KInase enzyme

Question 26

What is the significance of glycolysis being inhibited by low pH in muscles ?

Answer 26

Protects muscle from excessive lactate production during anaerobic respiration

Question 27

Which step in glycolysis is the most significant regulatory point?

Answer 27

The conversion of G6P to Fructose-6-Phosphate by Phosphofructokinase (PFK)

Question 28

How is PFK inhibited in the liver?

Answer 28

High [ATP] inhibits PFK | Citrate inhibits PFK

Question 29

How do tumours and exercising muscles fulfill their energy needs?

Answer 29

Their energy requirements are met through anaerobic respiration

Question 30

What are the 2 major functions of glycolysis?

Answer 30

1. Degrades glucose to generate ATP | 2. Provides the building blocks for cellular component synthesis

Question 31

What happens to F6P in the liver when [blood glucose] is high?

Answer 31

F6P indirectly converted to F26BisP

Question 32

What is the role of pyruvate kinase in glycolysis?

Answer 32

Conversion of Phosphopenol pyruvate to pyruvate using ATP

Question 33

Write out the equation for the production of lactate in anaerobic conditions

Answer 33

Pyruvate + NADH -> Lactate + NAD

Question 34

What activates Pyruvate KInase activity?

Answer 34

Pyruvate KInase activity increases when energy charge is low (glycolytic intermediates accumulate)

Question 35

How is PFK stimulated in the liver?

Answer 35

Indirectly stimulated by the build up of F6P

Question 36

How does glycolysis occur in anaerobic conditions?

Answer 36

Oxidative phosphorylation reduces pyruvate -> lactate | NADH is oxidised producing NAD for glycolysis to continue

Question 37

Why do tumours use glycolysis?

Answer 37

Tumours outgrow their blood supply Oxygen delivery is reduced Therefore tumour cells metabolism reverts to glycolysis

Question 38

How is the production of NAD guaranteed for glycolysis to continue?

Answer 38

Glyceraldehyde-3-Phosphate continually oxidised to regenerate NAD

Question 39

What inhibits the activity of Hexokinase in the liver?

Answer 39

G6P inhibits hexokinase

Question 40

Explain what occurs in the liver when [glucose] increases?

Answer 40

Glucose increases F26BisP concentration | Activating PFK allowing glycolysis to occur

Question 41

What is activated due to a reduction in Oxygen?

Answer 41

Transcription Factor HIF 1ɒ activated in response to hypoxia

Question 42

What factors inhibit the activity of Pyruvate Kinase?

Answer 42

Alanine and ATP

Question 43

What is the role of the transcription factor HIF 1ɒ during hypoxia?

Answer 43

Regulates the expression of enzymes in the glycolytic pathway

Question 44

How does Fructose-2,6-bisphosphate regulate glycolysis?

Answer 44

Allosterically affects PFK and F16BisP activity to regulate glycolysis and gluconeogenesis

Question 45

How is an/aerobic respiration controlled?

Answer 45

The rate at which glucose is converted to pyruvate is regulated in 3 non reversible step: - Inhibition of PFK (by ATP and citrate) - PFK activation (by AMP and F26BisP)