Biochemistry

Question 1

What is glycogenesis?

Answer 1

Synthesis of glycogen from glucose

Question 2

What is glycogenolysis?

Answer 2

Breakdown of glycogen to form glucose

Question 3

Where is glycogen stored in the body?

Answer 3

Liver
Muscle cells

Question 4

When enough glucose is present, glycogen synthesis begins: glucose-6-phosphate is converted to what?

Answer 4

Glucose-1-phosphate

Question 5

What is formed from glucose-1-phosphate in glycogen synthesis?

Answer 5

UDP-glucose

Question 6

What is UDP-glucose?

Answer 6

Essentially an active form of glucose

Question 7

When does glycogenolysis occur?

Answer 7

Between meals to maintain blood glucose levels

Question 8

Which enzyme catalyses glycogenolysis?

Answer 8

Glycogen phosphorylase

Question 9

What are the 2 regulatory actions of glucagon upon glycogenolysis?

Answer 9

Stimulates glycogen breakdown
Inhibits glycogen synthase

Question 10

What is gluconeogenesis? When does it occur?

Answer 10

Synthesis of glucose from non-carbohydrate precursors
Occurs when glycogen stores are completely depleted

Question 11

Where does gluconeogenesis mainly occur?

Answer 11

Liver

Question 12

Which TCA cycle intermediate is needed for gluconeogenesis? Why is it needed?

Answer 12

Oxaloacetate (4C)
Accepts acetyl groups from fat breakdown

Question 13

Describe the Cori Cycle

Answer 13

Blood transports lactate to liver
Liver converts lactate to glucose
Glucose is released into blood

Question 14

What effect do insulin and glucagon have on gluconeogenesis?

Answer 14

Insulin inhibits gluconeogenesis
Glucagon stimulates gluconeogenesis

Question 15

What happens when increased fat intake is not coupled with appropriate energy expenditure?

Answer 15

OBESITY
Increase in number and size of adipocytes

Question 16

Fat provides us with 2x more energy than carbohydrates. True/False?

Answer 16

True

Question 17

What are essential fatty acids?

Answer 17

Fatty acids required by, but cannot be synthesised by, the body

Question 18

What are the main products of lipid digestion?

Answer 18

Glycerol
Fatty acids
Monoglycerides

Question 19

What must happen to long-chain fatty acids to make them transportable?

Answer 19

Resynthesised to triglyceride and coated into a chylomicron, which enters the lymph

Question 20

What happens to chylomicrons at muscle and adipose tissue?

Answer 20

Cleaved by lipoprotein lipase into free fatty acids

Question 21

What happens to free fatty acids at muscle and adipose tissue?

Answer 21

Resynthesised into triglyceride or oxidised to provide energy

Question 22

Where does further oxidation of fatty acid occur?
Why is this a problem for acyl-CoA?

Answer 22

Oxidation occurs in the mitochondrial matrix
acyl-CoA is formed in the cytoplasm!

Question 23

What transports acyl-CoA into the mitochondrial matrix?

Answer 23

Carnitine shuttle

Question 24

How is acyl-carnitine formed in the cytoplasm?

Answer 24

Fatty acids are transferred from acyl-CoA to carnitine to form acyl-carnitine

Question 25

How does acyl-carnitine get across the inner membrane into the matrix? What happens to the carnitine?

Answer 25

Via a transporter Carnitine is cleaved off, leaving acyl group

Question 26

In the matrix, what happens to the free acyl- group?

Answer 26

Combines with CoA again to form acyl-CoA Net effect: acyl-CoA ends up in the matrix!

Question 27

What happens to acyl-CoA in the matrix?

Answer 27

Shortened by 2C to form acetyl-CoA and a new acyl-CoA

Question 28

What are the products of one round of B-oxidation of fatty acid?

Answer 28

1 acetyl-CoA 1 acyl-CoA, shortened by 2C 1 FADH2 1 NADH + H

Question 29

How and where are ketone bodies formed?

Answer 29

Formed from acetyl-CoA during B-oxidation in liver mitochondria

Question 30

What is lipogenesis?

Answer 30

Synthesis of fatty acids

Question 31

Lipogenesis is a reductive process (electrons are required). True/False?

Answer 31

True

Question 32

What transports acetyl-CoA from mitochondrial matrix into cytoplasm?

Answer 32

Citrate

Question 33

What is the vital first step in lipogenesis from acetyl-CoA?

Answer 33

Activation of acetyl-CoA by acetyl-CoA carboxylase into malonyl-CoA

Question 34

Which enzyme catalyses synthesis of long chain fatty acid from malonyl-CoA, acetyl-CoA and NADH?

Answer 34

Fatty acid synthase

Question 35

Which component of fatty acid synthase carries the growing fatty acid chain during synthesis?

Answer 35

Acyl-carrier protein (ACP)

Question 36

When a fatty acid chain length of __C is reached, the fatty acid is released

Answer 36

16C

Question 37

Synthesis of fatty acids is maximal when carbohydrate is scarce. True/False?

Answer 37

False Synthesis occurs when carbohydrate is in plentiful supply + fatty acids are scarce (otherwise lipolysis would occur)

Question 38

Amino acids which are not used for proteins are stored in the liver. True/False?

Answer 38

False Amino acids cannot be stored and are degraded if not used as building blocks

Question 39

Where is the major site of amino acid degradation?

Answer 39

Liver

Question 40

What does amino acid degradation primarily produce?

Answer 40

Ammonia (NH3) and ammonium ions

Question 41

What are the 3 steps by which urea is formed?

Answer 41

Transaminiation De-amination Urea cycle

Question 42

Which organ is albumin secreted from?

Answer 42

Liver

Question 43

Name the main liver-derived plasma proteins (4), in order of increasing molecular weight

Answer 43

Albumin alpha-globulins beta-globulins gamma-globulins

Question 44

What characteristic of plasma proteins enables them to maintain osmotic pressure which increases fluid movement out of the tissues into the blood?

Answer 44

They are insoluble - they do not diffuse into the interstitial fluid and only circulate in the blood

Question 45

List some hydrophobic substances that are carried in the blood by plasma proteins (4)

Answer 45

Steroid hormones Free fatty acids Bilirubin Cholesterol

Question 46

Give 2 examples of alpha-globulin plasma proteins

Answer 46

Ceruloplasmin Retinol-binding protein

Question 47

Give 2 examples of beta-globulin plasma proteins

Answer 47

Transferrin Fibrinogen

Question 48

Transferrin transports Fe2+ (ferrous iron). True/False?

Answer 48

False Transports Fe3+ (ferric iron)

Question 49

What is the most abundant plasma protein in the blood?

Answer 49

Albumin

Question 50

Insulin inhibits production of albumin. True/False?

Answer 50

False Insulin stimulates production of albumin

Question 51

Are albumin levels low or high in liver disease?

Answer 51

Low

Question 52

Iron is transported in the ferrous/ferric state bound to ____, and is stored in the ferrous/ferric state bound to ____

Answer 52

Iron is transported in the ferric state bound to transferrin, and is stored in the ferrous state bound to ferritin

Question 53

Which plasma protein does copper bind to for transport?

Answer 53

Ceruloplasmin

Question 54

Which disease results due to accumulation of copper due to deficiency of ceruloplasmin?

Answer 54

Wilson's disease