5. Citric Acid Cycle/ Oxidative Phosphorylation/ Glycolysis/ Gluconeogenesis

Question 1

Link reaction - Formation of Acetyl CoA

Answer 1

1C removed from (3C) pyruvate

by pyruvate dehydrogenase (PDH)

remaining 2C molecule combines with coenzyme A = acetyl coenzyme A

Question 2

Deficiency of pyruvate dehydrogenase (PDH)

Answer 2

Pyruvate shuttled into lactic acid

Congential Lactic Acidosis

Neurological problems

Question 3

Citric Acid Cycle

Answer 3

Question 4

Oxidative phosphorylation

Answer 4

per glucose molecule: 26 molecules of ATP

inner membrane of mitochondrion

Question 5

Glycolysis

Answer 5

glucose to pyruvate

Question 6

Gluconeogenesis

Answer 6

production of glucose in cells

For each molecule of glucose: Net energy gain 2NADH and 2ATP

Question 7

Transport of glucose in to cells

Answer 7

too hydrophilic to cross membranes

(sGLT)

Intestine and kidneys absorbs glucose

Question 8

sGLT 1 + sGLT2

Answer 8

intestinal mucosa

kidney tubules

Question 9

GLUT-1

Answer 9

Brain

erythrocyte

endothelial cells

fetal tissues

Question 10

GLUT-2

Answer 10

Liver

pancreatic cells

small intestine

kidney

Question 11

GLUT-3

Answer 11

Brain

placenta

testes

Question 12

GLUT-4

Answer 12

Skeletal and cardiac muscle

adipocytes (insulin-responsive)

Question 13

Insulin

Answer 13

Pancreatic β Cells

lowers blood glucose

Promotes Glycolysis

Suppresses Gluconeogenesis

Question 14

Glucagon

Answer 14

Pancreatic α cells

raises blood glucose

Promotes gluconeogenesis

Question 15

Glycolysis stage 1a

Answer 15

Glucose → Fructose 1, 6 Bisphosphate → Glucose 6 phosphate

Consumes 2 ATP molecules

Question 16

Hexokinase

Answer 16

High affinity for glucose

will phosphorylate glucose at any concentration

Question 17

Glucokinase

Answer 17

found in liver and β-cells

low affinity for glucose

only works when [glucose] above a threshold

Question 18

Glycolysis stage 1b

Answer 18

6C → 2 x 3C

DHAP

GAP

Question 19

Glycolysis stage 2

Answer 19

GAP → Phospho-enol pyruvate → Pyruvate

For each glucose we get 4 ATP and 2 NADH

key regulatory enzyme= Pyruvate Kinase

Question 20

Lactate Dehydrogenase (LDH)

Answer 20

pyruvate to lactate

Question 21

Cori cycle

Answer 21

Occurs when the oxidative capacity of OP chain is exceeded

Intense exercise, increase in lactate, intracellular pH drops, muscle cramps

Most of the lactate transpported to liver

Question 22

Lactic Acidosis

Answer 22

Over production of lactic acid

Lack of O2

Inhibition of oxidative phosphorylation

Net gain of 2x ATPs/glucose molecule

Question 23

3 irreversible reaction in Gluconeogenesis

Answer 23

Glucose → G-6-P

Fructose-6-P → Fructose-1,6-BP

Phospo-enol-pyruvate → pyruvate

Question 24

Summary of reactions in Gluconeogenesis:

Answer 24

Pyruvate → Oxaloacetate → malate → Oxaloacetate → PEP → glucose

Question 25

Final step in gluconeogenesis

Answer 25

Glucose-6-phosphate → glucose

Catalysed by Glucose-6-phosphatase

Question 26

Lactose intolerance (hypolactasia)

Answer 26

Missing enzyme “Lactase

Question 27

Galactose intolerance (Galactosemia)

Answer 27

Galactose 1-phosphate uridyl transferase missing

Question 28

Galactose intolerance symptoms

Answer 28

Vomiting, diarrhoea, cataract formation