control of metabolism

Question 1

what are the levels of regulation of cellular metabolism

Answer 1

intracellular region (cells)
intercellular region (whole body)

Question 2

intracellular regualtion

Answer 2

aim to maintain metabolic homeostasis

match rates of metabolic pathways to availability of substrates and requirement for ATP

Question 3

what influences intracellular regulation

Answer 3

concentration of substrates
allosteric activation and inhibition of metabolic enzymes
covalent modification of metabolic enzymes
substrate channeling

Question 4

what leads to the Michele’s mentalis curve

Answer 4

availability of substrates

rate of metabolic reactions is dependant on availability of substrates

Question 5

allosteric interations

Answer 5

binding of a substrate other than AS can have a postive/negative effect

Question 6

covalent modifications

Answer 6

e.g. phosphorylation

Question 7

substrate channeling

Answer 7

enzymes able to convert the same substrate into different products

Question 8

gene expression

Answer 8

enzyme levels can be increased by increased synthesis, decreased degradation ect

Question 9

intercellular regualtion

Answer 9

liver
adipose
brain 
muscle 
coodinate together to regulate the whole body

Question 10

what is intercellular regulation mediated by

Answer 10

hormones
nervous system
substrate availability

Question 11

hormone regulation in energy metabolism

Answer 11

insulin

glucagon

Question 12

insulin

Answer 12

two pp chains with disulphide bridges

Question 13

synthesis of insluin

Answer 13

preproinsulin to proinsulin to insulin
precursor has its signal sequence removed and exocytosis
C chain removed to form active form

Question 14

secretion of insulin increased by

Answer 14

glucose
amino acids
gastrointestinal hormones

Question 15

inhibition of insulin causes

Answer 15

fasting
stress
extreme exercise

Question 16

effect after a reduction in insulin secretion

Answer 16

release of glucose from liver

mediated by adrenalin released by adrenal medulla

Question 17

metabolic effects of insulin

Answer 17

carbohydrate metabolism - increased glucose uptake, increased glycogen synthesis
lipid metabolims - decrease in release of fatty acids, transport of glucose to adipocytes
protein synthesis - increase in uptake of aa into cells

Question 18

insulin mechanism of action

Answer 18

insulin binds to alpha subunit, dimerise
phosphorylation of beta subunit
phosphorylation of kinase enzyme (cascade)

also causes GLUT4 to move to membrane

Question 19

insulin receptor regulation

Answer 19

after binding, receptor internalised, blocks further signalling
receptor process in lysosome, recycled to cell surface

Question 20

glucagon

Answer 20

single pp chain

synthesised from precursor peptide

Question 21

mechanism of glucagon

Answer 21

binds to receptor
stimulate second messenger system
adenylate cyclase makes cAMP, activates protein kinase A
stimulates gluceoneogenesis and production of glucose from glycogen

Question 22

glycogen metabolic effects

Answer 22

carbohydrate metabolism
- increase breakdown of glycogen and gluconeogensis
protein metabolism
increased uptake of aa by liver

Question 23

what affects glucagon secretion

Answer 23

increase- low blood glucose, increase in aa, increased adrenaline
inhibit - blood glucose, insulin

Question 24

other hormones

Answer 24

adrenaline
norepinephrine
cortisol
oppose action of insulin

Question 25

other mechanisms of regualtion

Answer 25

cell to cell contact allows signalling

gap junctions allow passing of molecules across