12.Glycolysis

Question 1

What is glycolysis?

Answer 1

the first step in the breakdown of glucose to extract energy for cellular metabolism

Question 2

What are the two polymers of glucose?

Answer 2

starch and cellulose

Question 3

Glucose

Answer 3

• the most important carbohydrate
• primary energy source
• oxidised to GOCOWE - glucose and oxygen to carbon dioxide, water and energy
• cells like erythrocytes, retina, Renal medulla use glucose as their only source of energy
• required for function of the brain

Question 4

Glycolysis reaction

Answer 4

C6H1206 +O2 → CO2 + H2O + energy

Question 5

State the two forms of glucose

Answer 5

straight chain and intermediate

Question 6

What is the difference between alpha-glucose and b-glucose?

Answer 6

alpha- glucose - OH on aldehyde group points down

beta- glucose - OH on aldehyde group points up

Question 7

What are the 3 stages of metabolism?

Answer 7

1. Glycolysis
2. Citric acid cycle
3. Electron transfer chain

Question 8

How can glucose be transported in the cell?

Answer 8

1. via Na+/glucose symporters in the gut.

2. passive-facilitated diffusion through glucose transporters.

Question 9

GLUT 1 tissue/characteristics

Answer 9

• brain

- low Km

Question 10

GLUT 2 tissue/characteristics

Answer 10

• liver/pancreatic B cells

- high Km/ insulin independent

Question 11

GLUT 3 tissue/characteristics

Answer 11

• brain

- low Km

Question 12

GLUT 4 tissue/characteristics

Answer 12

• muscle/adipose tissue

- insulin dependent

Question 13

GLUT 5 tissue/characteristics

Answer 13

• gut

- fructose transport

Question 14

Describe the action of GLUT 1

Answer 14

1. binding of glucose to the outside triggers a conformational change so that the binding site faces inwards
2. glucose can be released in the cell
3. conformational change regenerates binding site on the outside

Question 15

Glycolysis reaction (glucose to pyruvate)

Answer 15

Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 Pyruvate + 2 ATP + 2 H20 + 2 NADH and 2 H+

Question 16

Stages of Glycolysis

Answer 16

1. Energy investing - glucose is trapped and destabilised
2. Two 3 carbon molecules are formed
3. Generation of ATP

Question 17

What type of linkage is formed from the reaction between a-glucose and fructose? What product is formed and what is removed?

Answer 17

• a-1,2-glycosidic linkage (sucrose)

- water

Question 18

What type of linkage is formed from the reaction between a-glucose and b-glucose? What product is formed and what is removed?

Answer 18

• a-1,4-glycosidic linkage (maltose)

- water

Question 19

What type of linkage is formed from the reaction between b-glucose and b-glucose? What product is formed and what is removed

Answer 19

• b-1,4-glycosidic linkage (cellobiose)

Question 20

What are the two main cellular requirements in Glycolysis?

Answer 20

• production of ATP

- provision of building blocks for synthetic reactions

Question 21

What acts as control points In Glycolysis?

Answer 21

enzymes

Question 22

Hexokinase

Answer 22

Glucose + ATP → Glucose-6-phosphate + ADP + H+

ΔG°= -33.5 KJ mol-1

Question 23

Phosphofructokinase

Answer 23

Fructose-6-phosphate + ATP → Fructose-1,6- diphosphate + ADP +H+
ΔG°= -22.2 KJ mol-1

Question 24

Pyruvate kinase

Answer 24

Phosphoenolpyruvate + ADP + H+ → Pyruvate and ATP

ΔG°= -16.7 KJ mol-1

Question 25

What is the key enzyme in the control of Glycolysis?

Answer 25

phosphofructokinase

Question 26

Negative modulators

Answer 26

ATP and citrate
-early intermediate in citric acid cycle
-biosynthetic precursors are abundant
Hydrogen
-prevents excessive formation

Question 27

Positive modulators

Answer 27

AMP and fructose-2,6- bisphosphate

Question 28

What is energy change?

Answer 28

the ATP/AMP ratio

Question 29

If cell Is fully charged..

Answer 29

all adenyl nucleotides are in the shape of ATP

Question 30

If cell is discharged..

Answer 30

the cell only contains AMP and Pi

Question 31

What is AMP and not ATP the positive modulator?

Answer 31

• if ATP is rapidly used up…(ATP → ADP +Pi)

- adenyl kinase can salvage some of the energy in ADP (2 ADP → ATP + AMP)