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

what is gluconeogenesis?

Answer 3

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

Question 4

what is glycogen?

Answer 4

main storage form of glucose in liver and muscle cells.

Question 5

what does liver glycogen do?

Answer 5

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

Question 6

what does muscle glycogen do?

Answer 6

provides energy via glycolysis and the TCA during bursts of physical activity

Question 7

what does a glycogen ‘primer’ covalently attach to?

Answer 7

a protein called glycogenin

Question 8

what does glycogen synthase do?

Answer 8

• synthesises glycogen from UDP-glucose
• adds one glucose molecule to glycogen at a time
• can only extend the chains of glycogen

Question 9

what is the rate limiting enzyme of glycogensis?

Answer 9

glycogen synthase

Question 10

what is glycogenolysis catalysed by?

Answer 10

glycogen phosphorylase

Question 11

what is the rate limiting enzyme for glycogenolysis?

Answer 11

glycogen phosphorylase

Question 12

where does lactate as a precursor for gluconeogenesis come from?

Answer 12

synthesised by skeletal muscle under anaerobic conditions

Question 13

where does amino acids as a precursor for gluconeogenesis come from?

Answer 13

derived from muscle protein by proteolysis

Question 14

where does glycerol as a precursor for gluconeogenesis come from?

Answer 14

derived from triglycerides by lipolysis in adipose tissue

Question 15

what does gluconeogenesis require?

Answer 15

four unique liver enzymes.

Question 16

what happens during the cori cycle?

Answer 16

blood transports lactate to liver, liver converts lactate back to glucose, glucose is released into blood stream.

Question 17

when is lactate formed?

Answer 17

in fast-twitch muscle under conditions of heavy exercise

Question 18

what do high levels of AMP or ADP mean?

Answer 18

low energy

Question 19

what do high levels of ATP mean?

Answer 19

high energy

Question 20

what do high/low levels of fructose 2,6-bisphosphate mean?

Answer 20

high in fed state

low in starved state

Question 21

what do high levels of citrate, alanine, acetyl-CoA mean?

Answer 21

high when intermediates or building blocks abundant

Question 22

what are glycogen storage diseases?

Answer 22

group of diseases with increased glycogen deposits in liver or muscle or both

Question 23

what does increased fat intake without appropriate energy expenditure lead to?

Answer 23

• increase in number of adipocytes

- more fat in adipocytes

Question 24

what does control of energy balance depend on?

Answer 24

• genetically linked factors e.g. protein messengers regulating appetite
• environmental factors e.g. food abundance, fashionable foods

Question 25

what can a deficiency in essential fatty acids lead to?

Answer 25

membrane disorders, increased skin permeability and mitochondrial damage

Question 26

what are the fat soluble vitamins?

Answer 26

vitamins A,D,E and K

Question 27

what are triglycerides?

Answer 27

main energy storage form in adipose tissue

Question 28

what is the structure of triglycerides?

Answer 28

consist of glycerol and 3 fatty acids

Question 29

what does aliphatic mean?

Answer 29

no rings

Question 30

what are the main natural fatty acids?

Answer 30

palmitic acid, stearic acid and oleic acid

Question 31

what lowers melting point?

Answer 31

double bonds

Question 32

what are the main products of fat absorption?

Answer 32

glycerol, fatty aids and monoglycerides

Question 33

what is lipolysis?

Answer 33

breakdown of lipids

Question 34

what has to happen to fatty acids before they can be oxidised to generate energy?

Answer 34

they have to be converted to CoA derivatives

Question 35

how much energy does fatty acid oxidation require?

Answer 35

2 ATP

Question 36

where does fatty acid oxidation occur?

Answer 36

cytoplasm

Question 37

what is the carnitine shuttle?

Answer 37

in the cytoplasm, fatty acids are transferred from acyl-CoA to carnitine. net result - acyl-CoA located in mitochondrial matrix

Question 38

what does acyl-carnitine transporter in inner membrane do?

Answer 38

faciliates antiport of acyl-carnitine into the mitochondria and carnitine out

Question 39

where does beta oxidation occur?

Answer 39

mitochondrial matrix

Question 40

how many steps in beta oxidation?

Answer 40

four

Question 41

what are the products of each cycle of beta oxidation?

Answer 41

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

Question 42

what is glycerol broken down by/to?

Answer 42

activated to glycerol-3-phosphate by glycerol kinase

Question 43

what is glycerol dehydrogenated to?

Answer 43

dihydroxyacetone phosphate

Question 44

what are ketones formed from?

Answer 44

acetyl-CoA from beta oxidation

Question 45

where are ketones important?

Answer 45

energy metabolism for heart muscle and renal cortex

Question 46

what is the precursor of all new fatty acids called?

Answer 46

malonyl-CoA

Question 47

what happens to amino acids which are not used as building blocks?

Answer 47

they are degraded

Question 48

what is the major site of amino acid degradation?

Answer 48

liver

Question 49

what does amino acid breakdown produce?

Answer 49

ammonia and ammonium ions

Question 50

what amino acid product is toxic at high concentrations?

Answer 50

ammonium ions

Question 51

what are the major nitrogen-containing excretory molecule?

Answer 51

Urea, uric acid, creatinine and ammonium ions.

Question 52

where is urea formed?

Answer 52

liver

Question 53

what are the three steps in the synthesis of urea?

Answer 53

transamination, de-amination and urea (or ornithine) cycle

Question 54

what enzyme moves the amino group from alpha-amino acids to alpha-keta acids during transamination?

Answer 54

aminotransferases usually alpha-ketoglutarate

Question 55

During transamination what are the major carriers of nitrogen in the blood to liver?

Answer 55

alanine and glutamine

Question 56

How is alanine made during transamination?

Answer 56

amino group of glutamate is transferred to pyruvate, giving alanine

Question 57

How is glutamine made during transamination?

Answer 57

glutamine synthase adds NH4+ to glutamate giving glutamine

Question 58

where does deamination/urea cycle happen?

Answer 58

in the liver

Question 59

what happens during deamination/urea cycle?

Answer 59

amino group of glutamate is converted to free ammonium ion and then urea is synthesised in a complex series of reactions

Question 60

What are ketogenic amino acids degraded to?

Answer 60

acetyl-CoA or acetoacetyl-CoA, can give rise to ketone bodies or fatty acids

Question 61

what are glucogenic amino acids degraded to?

Answer 61

degraded to pyruvate or TCA cycle intermediates, can be converted into phosphoenolpyruvate and then into glucose

Question 62

what happens during alcaptonuria?

Answer 62

degradation of phenylalanine and tyrosine is blocked

Question 63

what is maple syrup urine disease?

Answer 63

degradation of phenylalaine and tyrosine is blocked, urine smells like maple syrup, mental and physical retardation and prevented by appropriate diet

Question 64

what is phenylketonuria?

Answer 64

phenylalanine accumulates in all body fluids, leads to severe mental retardation if untreated, as therapy must go as low phenylalanine diet

Question 65

what happens during a defect in a urea cycle enzyme?

Answer 65

- accumulation of urea cycle intermediates - glutamine levels increase in the circulation - alpha-ketoglurarate is no longer regenerated - alpha- ketoglurarate levels become too low to fix more free ammonium ion

Question 66

how do you treat urea cycle disorders?

Answer 66

treatment with low-protein diet, drugs which remove nitrogen