Biochemistry Part 5

Question 1

What is our primary energy source?

Answer 1

Oxidised to CO2 and H20

Question 2

Which cell types require glucose?

Answer 2

Erythrocytes
Retina
Renal Medulla
Brain 
All cancer cells

Question 3

Name some dissacharides

Answer 3

Lactose
Maltose
Sucrose
Cellobiose

Question 4

Name some polysaccharides

Answer 4

Cellulose

Glycogen

Question 5

What are the fates of glucose?

Answer 5

Storage

• glycogen, starch, sucrose
• conversion to lipids

Oxidation through the pentose phosphate pathway

Fermentation by anaerobic glycolysis

Oxidation through aerobic glycolysis

Question 6

What is the outcome of the pentose phosphate pathway?

Answer 6

Formation of ribose-5-phosphate

Question 7

What is the outcome of oxidation though anaerobic glycolysis?

Answer 7

Formation or Pyruvate

Question 8

What is the outcome of fermentation by anaerobic glycolysis?

Answer 8

Formation of lactate

Question 9

What is ribose-5-phostphate?

Answer 9

Precursor for nucleotide synthesis and DNA repair

Essential for growth

Question 10

What is Lactate?

Answer 10

Rapid, inefficient ATP production

Question 11

What is pyruvate?

Answer 11

Efficient ATP production by oxidative metabolism

Question 12

How is glucose transported into cells?

Answer 12

Via Na+/glucose symporters

Via passive facilitated diffusion glucose transporters

Question 13

Where is GLUT 1 found?

Answer 13

Brain

Low Km

Question 14

Where is GLUT 2 found?

Answer 14

Liver B cells

High Km, insulin dependant

Question 15

Where is GLUT 3 found?

Answer 15

Brain

Low Km

Question 16

Where is GLUT 4 found?

Answer 16

Muscle
Adipose tissue
Insulin-dependant

Question 17

Where is GLUT 5 found?

Answer 17

Gut

Fructose transport

Question 18

Describe the action of GLUT 1?

Answer 18

Binding of glucose to the outside triggers a conformational change

Binding site faces inwards

Glucose can be released in the inside

Conformational change regenerates the binding site on the outside

Question 19

What is the overall reaction for glycolysis?

Answer 19

Glucose + 2ADP + 2 Pi + 2NAD+

=

2 pyruvate + 4ATP + 2 H2O + 2NADH + 2H+

Question 20

How many ATP is used in the conversion of Glucose to fructose-1,6-bisphosphate?

Answer 20

2

Question 21

How many ATP are generated in the conversion of 2 triode phosphates to 2 pyruvates?

Answer 21

4

2 NAD+ are degraded to 2NADH and 2H+

Question 22

Describe glycolysis stage 1?

Answer 22

Glucose is trapped and destabilised

Question 23

Describe glycolysis stage 2?

Answer 23

Two interconvertible three-carbon molecules are formed

Question 24

Describe glycolysis stage 3?

Answer 24

Generation of ATP

Question 25

What are the 3 control points in glycolysis?

Answer 25

1. Hexokinase- substrate entry 2. Phosphofructokinase- rate of flow 3. Pyruvate kinase- product exit

Question 26

What are the activators of phosphofructokinase?

Answer 26

AMP Fructose 2,6 bisphosphate

Question 27

What are the inhibitors of PFK?

Answer 27

ATP (will slow glycolysis if energy abundant) Citrate (TCA cycle intermediate. Slows downstream energy of pyruvate into TCA cycle if energy abundant) H+ (slows glycolysis if too much lactic acid is being produced)

Question 28

What is the energy charge?

Answer 28

The ATP/AMP ratio

Question 29

When is the cell fully charged and discharged?

Answer 29

Fully charged= all adenylate nucleotides are in the shape of ATP Discharged= if the cell only contains AMP and Pi

Question 30

Why is AMP and not ADP the positive regulator?

Answer 30

If ATP is rapidly used up then adenylate kinase can salvage some of the energy in ADP (2ADP = ATP + AMP)

Question 31

What is the fate of pyruvate?

Answer 31

Carbon to fuel TCA cycle in mitochondria

Question 32

What is the fate of electrons?

Answer 32

Electron transport chain and ATP synthesis

Question 33

What happens if mitochondrial metabolism is inhibited by lack of O2?

Answer 33

NADH is used to ferment pyruvate into lactic acid NADH is re-generated at beginning of stage 3

Question 34

What is the warburg effect?

Answer 34

Cancer cells produce energy by high rate of glucose metabolism to lactate (anaerobic glycolysis) -cancer cells have low Km Hexokinase

Question 35

What are the advantaged of the warburg effect?

Answer 35

>Rapid energy production ``` >Supports other pathways for nucleotide synthesis (needed for growth) ``` >Supports rapid cell growth (proliferation)

Question 36

What are the disadvantages of the warburg effect?

Answer 36

>Produces H+ and lactate as end products >Very inefficient ATP synthesis >High glucose consumption demand >Cancer patients lose weight

Question 37

What could be used to treat cancer by targeting glycolysis?

Answer 37

2-deoxyglucose 2-Bromopyruvate Dichloroacetate