Carbohydrate Metabolism

Question 1

What is the critical blood glucose level?

Answer 1

2.5 mM

Question 2

What are the symptoms of hypoglycaemia?

Answer 2

Muscle weakness
Loss of coordination
Mental confusion
Sweating 
Hypoglycaemic coma and death

Question 3

What are the hyperglycaemic symptoms?

Answer 3

Non enzymatic modification of proteins which could lead to cataracts
Hyperosmolar coma

Question 4

What is glycogensis

Answer 4

Glycogen synthesis

Question 5

How much glycogenesis takes place (in grams) in the liver and skeletal muscle?

Answer 5

100g in liver

300-400g in skeletal muscle

Question 6

When does glycogenesis take place?

Answer 6

When blood glucose levels are high

Question 7

What is glycogen?

Answer 7

Branched polymer of glucose

Question 8

How is glycogen formed?

Answer 8

Alpha 1-4 and 1-6 glycosidic bonds

Question 9

Where is glycogen formed

Answer 9

On a protein primer called glycogenin

Question 10

What is glycogenesis regulated by?

Answer 10

Glycogen synthase

Question 11

How are the branched points formed?

Answer 11

by a branching enzyme

Question 12

What enzyme performs G6P-G1P

Answer 12

Phosphoglucomutase

Question 13

What enzyme performs G1P+UTP->UDP

Answer 13

UDP glucose pyrophosphorylase

Question 14

What enzyme adds more glucose residues to the glycogenin?

Answer 14

Glycogen synthase

Question 15

How long is the original glycogen chain before branching happens?

Answer 15

11 glucose residues

Question 16

Why is glycogen formed?

Answer 16

Glucose is osmotically active so it cant be stored (affects the water potential of the cells)

Question 17

What is glycogenolysis?

Answer 17

Glycogen breakdown

Question 18

Where does glycogenolysis happen?

Answer 18

Liver, muscle and (sometimes) kidney

Question 19

When does glycogenolysis happen?

Answer 19

When glucose levels are low

Question 20

What is glycogenolysis stimulated by?

Answer 20

Glucagon, Adrenaline, noradrenaline, growth hormone

Question 21

What enzyme breaks the 1-4 glycosidic bonds between the glucose residues?

Answer 21

Phosphorylase

Question 22

What does the breakdown of 1-4 glycosidic bonds produce?

Answer 22

G1P

Question 23

What does phosphoglucomutase facilitate?

Answer 23

G1P-G6P

Question 24

What enzyme removes the last 3 glucose residues on a branch?

Answer 24

Transferase

Question 25

Where do the last 3 glucose residues go when they are debranched?

Answer 25

Added to the non-reducing end of the chain

Question 26

What enzyme breaks the 1-6 glycosidic bonds?

Answer 26

Alpha 1-6 glucosidase

Question 27

What happens to the glucose when it is freed from the glycogen?

Answer 27

Phosphorylated by hexokinase in the muscle to form G6P

Question 28

What breaks down the glucose chains to produce G1P?

Answer 28

Phosphorylase

Question 29

In the liver what enzyme does the G6P->glucose reaction?

Answer 29

G6-phosphatase

Question 30

What are the products of glycolysis?

Answer 30

G1P, glucose

Question 31

What is glycogen phosphorylase?

Answer 31

Large multi-subunit enzyme that plays a key role in glycogenolysis

Question 32

What is glycogen phosphorylase regulated by?

Answer 32

Allosteric interactions that signal the energy state of the cell

Question 33

What are the two isoforms of glycogen phosphorylase?

Answer 33

Active - phosphorylase A | Inactive - phosphorylase B

Question 34

What is phosphorylase A phosphorylated by?

Answer 34

Phosphorylase B kinase

Question 35

What inhibits phosphorylase?

Answer 35

Insulin

Question 36

What stimulates phosphorylase in the liver?

Answer 36

Glucagon

Question 37

What stimulates phosphorylase in the muscle?

Answer 37

Adrenaline

Question 38

What weakly stimulates phosphorylase?

Answer 38

Cortisol

Question 39

In muscle what can glycogen phosphorylase B be activated by?

Answer 39

5’AMP

Question 40

What blocks 5’ AMP activation?

Answer 40

ATP and G6P

Question 41

In the liver what is phosphorylase A inhibited by?

Answer 41

Glucose

Question 42

When and how is glycogen synthase activated?

Answer 42

In times of plenty of glucose, by insulin

Question 43

When and how is glycogen phosphorylase activated?

Answer 43

When blood glucose is low, by glucagon, adrenaline and noradrenaline

Question 44

What does the pentose phosphate pathway start and end with?

Answer 44

Starts with G6P and ends with ribose 5 phosphate

Question 45

What is ribose 5 phosphate included in?

Answer 45

Nucleotide and Nucleic acid synthesis

Question 46

Where is NADPH formed?

Answer 46

In the pentose phosphate pathway

Question 47

What is GSH used in?

Answer 47

In the protective mechanism of the self and to oxidative stress

Question 48

What is NADPH important to?

Answer 48

The formation of GSH and fatty acids

Question 49

What molecules do gluconeogenesis?

Answer 49

Triglycerides Lactate Amino acids

Question 50

What is gluconeogenesis?

Answer 50

Creation of new glucose

Question 51

Where does gluconeogenesis take place?

Answer 51

Mainly in the liver and the kidney, but also a bit in the intestine

Question 52

When does gluconeogenesis take place?

Answer 52

When the blood glucose levels are very low (fasting or starving)

Question 53

What is gluconeogenesis the reverse of?

Answer 53

Glycolysis

Question 54

What enzyme takes pyruvate to oxaloacetic acid?

Answer 54

Pyruvate carboxylase

Question 55

What enzyme takes oxaloacetic acid to phosphoenol pyruvate?

Answer 55

Phosphoenol pyruvate carboxykinase

Question 56

What enzyme reverses phosphofructokinase?

Answer 56

Fructose 1-6 bisphosphate

Question 57

What enzyme reverses hexokinase?

Answer 57

Glucose-6-phosphatase

Question 58

Where are the fatty acids fed into the TCA cycle?

Answer 58

Glycerol components feed in where F1-6 bisphosphate is split

Question 59

Where is pyruvate synthesised?

Answer 59

In the cytosol

Question 60

Where does pyruvate carboxylase work?

Answer 60

In the mitochondria

Question 61

3 most important substrates are

Answer 61

Amino acids (Alanine) Lactate Glycerol from triglycerides

Question 62

What is gluconeogenesis used for?

Answer 62

To maintain blood glucose

Question 63

What is the daily requirement for blood glucose?

Answer 63

160g

Question 64

What is the daily requirement for blood glucose in the brain?

Answer 64

120g

Question 65

What are the total body reserves of glucose?

Answer 65

210g

Question 66

What does the gluconeogenic pathway do?

Answer 66

Pyruvate to glucose

Question 67

Where does the gluconeogenic pathway take place?

Answer 67

Mostly in the liver and a little in the kidney

Question 68

Where does the gluconeogenic pathway take place during starvation?

Answer 68

Kidney productions rise to 40% and a little in the liver