Metabolism

Question 1

function of acetyl coA carboxylase

Answer 1

adds a carbon to acetyl coA , forming malignly co A for fatty acid synthesis
key point of regulation

Question 2

PDH regulation

Answer 2

active = DE - phosphroylated by phosphatase enzyme 
inactive = phosphorylated by kinase

Question 3

PDH regulation

Answer 3

active = DE - phosphroylated by phosphatase enzyme 
inactive = phosphorylated by kinase

Question 4

ketolysis stages

Answer 4

beta hydroxybutyrate to acetoacetate (reversible)
acetoacetate -> acetoacetyl coA (coupled with succinyl coA -> succinate)
acetoacetyl coA -> 2 acetyl coA by thiolase

Question 5

acetyl CoA carboxylase regulation

Answer 5

active = DE phosphorylated, binding of citrate
inactive = phosphorylated (occurs with glucagon or adrenaline)

Question 6

pyruvate carboxylase reaction

Answer 6

pyruvate to oxaloacetate
first step of gluconeogenesis in the mt
also anaplerotic reaction in TCA

Question 7

pyruvate carboxylase regulation

Answer 7

increase = glucagon, glucocorticoids (cortisol)
decrease = insulin

Question 8

atp concentration in the cell is …

Answer 8

kept fairly constant

1-10 mmol/l

Question 9

relative ATP:ADP

Answer 9

10:1

Question 10

relative ATP:AMP

Answer 10

100:1

makes AMP a very good emergency signal

Question 11

adenylate kinase function

Answer 11

phosphotransferase enzyme

between AMP/ADP/ATP

Question 12

how are NADH and FADH2 re-oxidised

Answer 12

re-oxidised at the mt. by donating H+ and e- (OIL)

NADH is able to diffuse, FADH2 attached

Question 13

how does NADH from glycolysis enter the mt

Answer 13

malate aspartate shuttle

inner mt. membrane impermeable to NADH

Question 14

components of the malate aspartate shuttle

Answer 14

malate dehydrogenase on both sides of membrane
aspartate aminotransferase on both sides of membrane
malate-alpha-ketoglutarate antiporter on inner membrane
glutamate-aspartate antiporter in inner membrane

Question 15

process of malate aspartate shuttle

Answer 15

• in cytosol, malate dehydrogenase converts NADH and oxaloacetate to malate and NAD+
• malate antiporter imports into the matrix, and alpha KG goes in the other direction
• in matrix, reaction goes in reverse so malate and NAD+ goes back to oxaloacetate and NADH
• oxaloacetate then converted into aspartate and moved out with the second antiporter, glutamine moves in

Question 16

proteins in the inner membrane that dissipate the proton gradient

Answer 16

ANT and phosphate carrier
ANT: ADP into mt and ATP out
phosphate carrier: phosphate ions into the matrix

Question 17

effect of thyroxine on metabolism

Answer 17

increase basal metabolic rate

stimulate fat mobilisation and oxidation

Question 18

substrates of gluconeogenesis

Answer 18

lactate, alanine, glutamine, glycerol and other sugars

Question 19

transfer of ammonia from muscle cells (amino acid metabolism) to the liver

Answer 19

• free ammonia
• as glutamate
• as glutamine (majority I think)

Question 20

glutamine metabolism in intestines

Answer 20

enterocytes take up glutamine and release as alanine and ammonia

Question 21

what are amino acids separated into for metabolism

Answer 21

amino group -> ammonia -> urea

carbon skeleton for energy

Question 22

how is the amino group removed

Answer 22

transamination reaction
each amino acid has its own specific aminotransferase enzyme
amino acid a + keto acid b -> keto acid a + amino acid b

Question 23

most common acceptor of amino group

Answer 23

alpha keto glutarate
reaction forms glutamate
other acceptors are oxaloacetate or pyruvate

Question 24

deamination of glutamate

Answer 24

glutamate dehydrogenase

pooling of other aa into glutamate means that only one deamination pathway is required

Question 25

glutamate transamination produces

Answer 25

regenerates alpha ketoglutarate and a free ammonium

Question 26

glutamate dehydrogenase regulation

Answer 26

regulated by increases in ADP and GDP as signals of energy stress

Question 27

where does glutamate deamination take place

Answer 27

in mitochondrion of liver cells so ammonia can enter the urea cycle

Question 28

compartmentalisation of the urea cycle

Answer 28

occurs in both the mitochondrion and the cytosol

Question 29

where in the liver does the urea cycle occur

Answer 29

periportal hepatocytes

Question 30

examples of branched chain amino acids

Answer 30

leucine
isoleucine
valine

Question 31

branched chain amino acid metabolism requires the

Answer 31

branched chain alpha keto acid dehydrogenase complex

converted into acyl coA derivatives, then into acetyl coA or succinyl coA

Question 32

roles of endoplasmic reticulum (metabolism)

Answer 32

• smooth ER contains cyt P450
• SER site of elongation of FA over c16 in synthesis
• final step of gluconeogenesis
• protein synthesis
• synthesis of glycoprotein for secretion out of the cell

Question 33

lysosomes function (metabolism)

Answer 33

contains lytic enzymes
digestion of ingested macromolecules and turnover of intracellular components
- recycles building blocks of macromolecules, especially ECM components

Question 34

peroxisome function (metabolism)

Answer 34

peroxisome -> peroxide
contain enzymes involved in oxidative metabolism which use molecular oxygen and generate toxic H2O2
- also involved in substrate processing: very long chain FA, bile acid synthesis intermediates, also intermediates in branched chain amino acids and de novo lipogenesis

Question 35

protection of cells from reactive oxygen species

Answer 35

• peroxides are a highly reactive oxygen species that can damage the cell
• cells contain a high level of glutathione, kept in its reduced form
• enzyme SOD responsible for detoxifying superoxides (O2-), created hydrogen peroxide which can then be broken down

Question 36

how is H202 broken down

Answer 36

catalase

Question 37

antioxidant vitamins

Answer 37

C and E