Metabolic Pathways

Question 1

Glycogenesis

Answer 1

Glucose->glycogen

Question 2

Glycogenolysis

Answer 2

breakdown of glycogen to form glucose

Question 3

Gluconeogenesis

Answer 3

de novo synthesis of glucose from metabolic precursors (lactate amino acids, glycerol)

Essentialy the reverse of glycolysis

ie synthesis of glucose within the body from precursor substrates

Question 4

Role of glycogen

Answer 4

main storage form of glucose in liver and muscle cells

Question 5

When is liver glycogen broken down?

Answer 5

Between meals

Question 6

Why is liver glycogen released?

Answer 6

To maintain blood glucose levels for RBC and the brain

Question 7

Role of muscle glycogen cells?

Answer 7

not for maintenance of blood glucose levels

provide energy via glycolysis and TCA during bursts of physical activity

Question 8

What is the primary source of glucose overnight when hepatic glycogen is depleted?

Answer 8

gluconeogenesis

Question 9

Structure of glycogen

Answer 9

polymer consisting of glucose molecules joined by alpha 1-4 glycosidic links

Branches introduced by alpha 1-6 glycosidic links

Question 10

Primer for adding glucose residue to a glycogen chain

Answer 10

glycogenin

Question 11

What causes glycogenolysis to fluctuate?

Answer 11

It fluctuates depending on meal times

Question 12

What can UDP-glucose be thought of as?

Answer 12

An active intermediate of glucose

Question 13

What happens to the phosphate ester linkage in a nucleotide sugar during hydrolysis?

Answer 13

It releases free energy

Question 14

Role of glycogen synthase

Answer 14

Rate limiting enzyme of glycogenesis

Makes glycogen from UDP-glucose

Question 15

Glycogen breakdown summary

Answer 15

Glycogen-> glucose-1-phosphate-> glucose-6-phosphate

Question 16

Role of glycogen phosphorylase

Answer 16

Rate limiting enzyme for glycogenolysis

Question 17

Enzyme involved in lysis of glucose-1-phosphate to form glucose-6-phosphate

Answer 17

Phosphoglucomutase

Question 18

Precursor substrates involved in gluconeogenesis

Answer 18

Lactate, amino acids, glycerol

Question 19

synthesis of lactate

Answer 19

made by skeletal muscle under anaerobic condtions

Question 20

Where are amino acids derived from?

Answer 20

muscle protein by proteolysis

Question 21

Where is glycerol derived from?

Answer 21

triglycerides by lipolysis in adipose tissue

Question 22

Where is energy for gluconeogenesis from?

Answer 22

oxidation of fatty acids released from adipose tissue

Question 23

where does gluconeogenesis occur?

Answer 23

Mainly in the liver, but small amounts in the kidneys

Question 24

Gluconeogenesis proceeds via the synthesis of _____ in the _____

Answer 24

Oxaloacetate

Mitochondria

Question 25

Oxaloacetate

Answer 25

TCA cycle intermediate which is important for accepting acetyl groups from fat break down

Question 26

Cori cycle

Answer 26

Lactate produced in muscle Blood transfers lactate to liver Liver converts lactate back to glucose Glucose released to bloodstream

Question 27

Why is fat required in the body?

Answer 27

energy source, essential polyunsaturated fatty acids (those needed but cannot be made by body) and absorption of fat soluble vitamins

Question 28

Different types of lipids

Answer 28

Simple lipids Compound lipids Steroids

Question 29

Features of lipids

Answer 29

- usually hydrocarbons - contain long chain fatty acids - insoluble in water

Question 30

Examples of simple lipids

Answer 30

fatty acids triglycerides waxes

Question 31

examples of compound lipids

Answer 31

phospholipids, glycolipids, lipoproteins

Question 32

examples of steroids

Answer 32

cholesterol, steroid hormones eg adrogens

Question 33

What is the main energy storage form in adipose tissue?

Answer 33

Triglycerides (triacylglycerols)

Question 34

Structure of triglycerides

Answer 34

Glycerol and 3 fatty acids

Question 35

Fatty acids are aliphatic. T/F?

Answer 35

True, they have no rings

Question 36

Double bonds of fatty acids are usually in trans configuration. T/F

Answer 36

False | Cis

Question 37

All fatty acids are liquid at room temperature. T/F?

Answer 37

False Liquid up to 8 C atoms, longer ones are solid

Question 38

Impact of presence of double bonds on melting point

Answer 38

Lowers melting point

Question 39

Why are plant acids liquid?

Answer 39

they contain large proportions of unsaturated fatty acids | animal fats are solid as they mostly contain palmitic and stearic acid

Question 40

Main products of fat digestion

Answer 40

Glycerol, fatty acids and monoglycerides

Question 41

Which cells absorb fat in the intestine?

Answer 41

Mucosal cells

Question 42

Chylomicrons

Answer 42

Lipoproteins coated with a layer of protein, phospholipid and cholesterol

Question 43

Enzyme involved in llipolysis

Answer 43

Hormone sensitive lipase, which release free fatty acids and glycerol

Question 44

What must happen before fatty acids can be oxidised to generate energy?

Answer 44

They must be converted to CoA derivatives

Question 45

Where does initiation of fatty acid oxidation occur?

Answer 45

in the cytoplasm | further oxidation occurs in the mitochondrial matrix

Question 46

The carnitine shuttle

Answer 46

Fatty acids in cytoplasm are transferred from Acyl-CoA to carnitine (a transporter in inner membrane) and moves acyl-CoA to mitochondrial matrix

Question 47

Beta oxidation

Answer 47

Cycle of reactions which occurs in the mitochondrial matrix Consists of four steps per cycle

Question 48

Products of each cycle of beta oxidation

Answer 48

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

Question 49

Breakdown of glycerol

Answer 49

glycerol kinase causes activation to glycerol-3-phosphate it is then dehydrogenated to dihydroxyacterone phosphate

Question 50

Where are ketone bodies formed?

Answer 50

In liver mitochondria from acetyl-CoA from B oxidation

Question 51

Role of ketone bodies

Answer 51

molecules of energy metabolism for heart muscle and renal cortex It is converted back to acetyl-CoA which enters TCA cycle

Question 52

Ketosis in starvation and diabetes

Answer 52

oxaloacetate is consumed for gluconeogenesis fatty acids are oxidised to provide energy acetyl-CoA is converted to ketone bodies high levels in blood too much for extrahepatic tissue (i.e. heart, brain, etc.) ketone bodies are moderate acids accumulation leads to severe acidosis (blood can’t buffer any more) impairs tissue function, particularly central nervous system smell of acetone can be detected in breath