Biochemistry

Question 1

definition of glycogenesis

Answer 1

synthesis of glycogen from glucose

Question 2

definition of glycogenolysis

Answer 2

breakdown of glycogen to form glucose

Question 3

definition of gluconeogenesis

Answer 3

de novo synthesis of glucose from metabolic precursors

Question 4

what is liver glycogen

Answer 4

broken down between meals and released to maintain blood glucose levels for red blood cells and brain

Question 5

what is muscle glycogen

Answer 5

provides energy via glycolysis and the TCA during bursts of physical activity. not availale for maintenance of blood glucose levels

Question 6

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

Answer 6

gluconeogenesis

Question 7

what does UDPG stand for?

Answer 7

uridine diphosphate glucose

Question 8

what enzyme synthesises glycogen from UDP-glucose

Answer 8

glycogen synthase

Question 9

can glycogen synthase start new molecules of glycogen?

Answer 9

no, it can only extend the chains of glycogen and cannot introduce new branches

Question 10

what enzyme catalyses glycogenolysis?

Answer 10

glycogen phosphorylase

Question 11

what happens in the liver during glycogenolysis?

Answer 11

glucose-6-phosphate can be de-phosphorylated and the resulting glucose is released into the blood stream

Question 12

what happens in (skeletal) muscle during glycogenolysis?

Answer 12

glucose-6-phosphate cannot be de-phosphorylated but instead is used to provide energy via glycolysis and the TCA cycle

Question 13

what are the precursors of gluconeogenesis?

Answer 13

• lactate
• amino acids
• glycerol

Question 14

what is the cori cycle?

Answer 14

lactate (as a precursor of gluconeogenesis) produced by anaerobic glycolysis in the muscles moves to the liver and is converted to glucose, which is then released into bloodstream

Question 15

what are lipids?

Answer 15

a collection of different compounds, predominantly hydrocarbons that contain long fatty acids and are insoluble in water

Question 16

examples of simple lipids

Answer 16

fatty acids, triglycerides, waxes

Question 17

examples of compound lipids

Answer 17

phospho-, glyco-lipids, lipoprotein

Question 18

examples of steroids

Answer 18

cholesterol, steroid hormones

Question 19

what are triglycerides

Answer 19

= triacylglycerols
main storage form in adupose tissue
hydrophobic
consist of glycerol and 3 fatty acids

Question 20

what is the structure of fatty acids?

Answer 20

straight chains, aliphatic, usually contain an even number of C atoms
can be saturated, unsaturated or polyunsaturated
double bonds are usually in cis formation

Question 21

how long are fatty acids that are liquid at room temperature?

Answer 21

up to 8 carbon atoms

Question 22

are plant fats liquid or solid?

Answer 22

liquid

they contain large proportions of unsaturated fatty acids

Question 23

are animal fats liquid or solid?

Answer 23

solid

they contain mainly palmitic and stearic acid

Question 24

what are the main products of fat digestion?

Answer 24

• glycerol
• fatty acids
  monoglycerides

Question 25

how is fat absorbed?

Answer 25

- short and medium length fatty acids enter portal blood - long chain FAs and monoglycerides are re-synthesized to triglycerides - coated with a layer of chylomicrons

Question 26

what are chylomicrons?

Answer 26

a layer of protein, phospholipid and cholesterol

Question 27

what is the function of Chylomicrons?

Answer 27

transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are hydrolyzed by the activity of the lipoprotein lipase, allowing the released free fatty acids to be absorbed by the tissues.

Question 28

what is lipidolysis?

Answer 28

breakdown of lipids

Question 29

what initially cleaves fatty acids and glycerol during lipidolysis when energy is needed

Answer 29

hormone sensitive lipases

Question 30

where does fatty acid conversion to CoA derivatives initially occur?

Answer 30

the cytoplasm

Question 31

where does further oxidation of fatty acids occur?

Answer 31

mitochondrial matrix

Question 32

how do fatty acids get from the cytoplasm to the mitochondria?

Answer 32

the carnitine shuttle | - acyl-carnitine transporter facilitates antiport of acyl-carnitine to the mitochondrion and carnitine out

Question 33

where does beta oxidation take place?

Answer 33

mitochondria

Question 34

how many times is beta oxidation repeated?

Answer 34

8 times

Question 35

what is the net yield of beta oxidation?

Answer 35

120 ATP

Question 36

what reactions occur in the breakdown of glycerol?

Answer 36

activated to glycerol-3-phosphate by glycerol kinase then dehydrogenated to dihydroxyacetone

Question 37

how and where are ketone bodies formed?

Answer 37

formed in liver mitochondria from acetyl-CoA from beta oxidation

Question 38

what happens to ketones in starvation or diabetes?

Answer 38

high levels in blood, accumulation leads to severe acidosis