session 4-storage,glycogen,TAGS,chylomicrons,NH3 toxicity,PKU,homocystinuria,amino acids

Question 1

what is the second step of glycogen synthesis?

Answer 1

glucose 6 phosphate glucose 1 phosphate (note: is reversible) (note 2: catalysed by phosphoglucomuctase)

Question 2

what is the 3rd step of glycogen synthesis?

Answer 2

glucose 1 phosphate + UTP + H2O —> UDP-glucose + 2Pi

UTP is similar to ATP. UDP-glucose is highly active form of glucose

Question 3

what is the 4th step of glycogen synthesis?

Answer 3

glycogen (n residues) + UDP-glucose —> glycogen (n+1 residues) + UDP (glycogen synthase=1,4 glycosidic bonds)(branching enzyme=1,6 glycosidic bonds)

Question 4

what 2 enzymes are involved in glycogen degradation?

Answer 4

glycogen phosphorylase/debranching enzyme

Question 5

what enzyme do muscles lack?

Answer 5

glucose 6 phosphatase

Question 6

how do muscle glycogen stores differ from the liver?

Answer 6

glucagon has no effect on muscle stores as muscle does not have enzyme (glucose 6 phosphatase) to produce glucose

Question 7

what disease is characterised by glucose 6 phosphatase deficiency?

Answer 7

von Gierke’s disease

Question 8

what is the first step of glycogen synthesis?

Answer 8

glucose+ATP —>glucose-6-phosphate + ADP catalysed by……..(hexokinase and glucokinase in liver)

Question 9

what disease is characterised by (MUSCLE) glycogen phosphorylase deficiency?

Answer 9

McArdle disease

Question 10

name 3 ways in which gluconeogenesis can occur?

Answer 10

1. lactate (anaerobically)
2. amino acids
3. breakdown of TAG from adipose tissue to produce glycerol

Question 11

Some steps of glycolysis are used in gluconeogenesis…and even though some steps are irreversible,these can be bypassed by reactions catalysed by enzymes. What 2 enzymes are used to reverse step 10 in glycolysis from pyruvate—>oxaloacetate—>phosphoenolpyruvate

Answer 11

pyruvate—>oxaloacetate =(pyruvate carboxylase)

oxaloacetate—>phosphoenolpyruvate = PEPCK (phosphoenolpyruvate carboxykinase)

Question 12

after phosphoenolpyruvate, the reverse steps of 9,8,7,6,5,4 occur until step 3. what enzymes are used to convert fructose 1,6-bisphosphate–>fructose 6 phosphate , step 2 and then step 1 of glucose 6 phosphate–>glucose

Answer 12

1. fructose 1,6-bisphosphate–>fructose 6 phosphate =fructose 1,6-bisphosphatase
2. glucose 6 phosphate—>glucose =glucose 6 phosphatase

Question 13

what are TAGS (triacylglycerol) carried/transported in?

Answer 13

chylomicrons

Question 14

what is produced from acetyl CoA using a key regulator (acetyl CoA carboxylase) in the formation of fatty acids (lipogenesis)?

Answer 14

malonyl CoA

Question 15

fatty acid synthase complex builds fatty acids by sequential addition of 2 carbon units provided by malonyl CoA. What 2 molecules does lipogenesis require?

Answer 15

ATP and NADPH

Question 16

what does it mean if amino acids are ketogenic or glucogenic?

Answer 16

1. keto-produce acetyl CoA that can be used to synthesise ketone bodies
2. gluco-gluconeogenesis

Question 17

what enzyme converts alanine to glutamate?

Answer 17

ALT-alanine aminotransferase

Question 18

what enzyme converts glutamate to aspartate?

Answer 18

AST-aspartate aminotransferase

Question 19

how do you manage NH3 toxicity?

Answer 19

low protein diet and replace them with keto acids

Question 20

what test is used to detect SCD, CF and hypothyroidism?

Answer 20

heel prick test

Question 21

what enzyme deficiency causes PKU (phenylketonuria) and what type of inheritance is it?

Answer 21

phenylalanine hydroxylase

Autosomal recessive

Question 22

what builds up in the urine and has a musty smell when it comes to PKU?

Answer 22

-phenylketones build up in urine

Question 23

what happens to phenylalanine when it accumulates in the blood?

Answer 23

-transamination to phenylpyruvate and thus phenylketones

Question 24

name 3 symptoms of PKU

Answer 24

1. severe intellectual disability
2. hypo-pigmentation
3. seizures and microcephaly (small head)

Question 25

what amino acid has a defect in the condition homocystinuria?

Answer 25

methionine

Question 26

what enzyme is deficient in homocystinuria and what inheritance is it?

Answer 26

cystathionine beta-synthase

Autosomal recessive

Question 27

what role does CBS usually have?

Answer 27

converts homocysteine—>cystathionine—->cysteine

Question 28

what is the oxidised form of homocysteine?

Answer 28

homocystine

Question 29

what problems are associated with homocystinuria?

Answer 29

disorders of connective tissue, CNS and cardiovascular system

Question 30

in children, homocystinuria can be misdiagnosed to be…

Answer 30

marfans syndrome (long limbs, thin body) because symptoms are similar

Question 31

What 6 places in the body require glucose as an energy source?

Answer 31

• erythrocytes
• leukocytes
• renal medulla
• testes
• brain
• lens and cornea of eye

Question 32

Where are glycogen granules found in muscle and Liver?

Answer 32

Muscle-inter and intramyofibrillar

Liver-within hepatocytes

Question 33

Where does fatty acid synthesis occur?

Answer 33

Cytoplasm

Question 34

What are free fatty acids coupled with to be transported to muscle and other tissues to carry out beta oxidation?

Answer 34

Albumin

Question 35

Where does transamination occur and what do you measure to test liver function?

Answer 35

Liver

ALT and AST levels

Question 36

What is the treatment for phenylketonuria?

Answer 36

Low phenylalanine diet

No artificial sweeteners or high protein foods (eggs,meat,milk)