Lec 15 - Glucose homeostasis

Question 1

why is glucose delivery to CNS vital

Answer 1

outside of neonatal period, CNS cant substitute glucose

Question 2

what enzyme catalyses glucose to glycogen

Answer 2

glycogen synthase

Question 3

what is the stored resovoir of glucose

Answer 3

glycogen

Question 4

normoglycaemia

Answer 4

4-6mmol/L

Question 5

gluconeogenesis: what and where

Answer 5

in liver
conversion of fat and protein derivatives to glucose

Question 6

hyperglycaemia

Answer 6

> 10mmol/L (sustained)

Question 7

what type of action does insulin

Answer 7

hyperglycaemic towards normal glycaemic range

Question 8

why might some tissues be more sensitive to insulin (and which)

Answer 8

liver
muscle
adipocytes
(more insulin receptors)

Question 9

how is glucose controlled when there are no inslin receptors

Answer 9

glucose transporters in cell membrane

Question 10

two main hormones in glucose

Answer 10

insulin and glucagon

Question 11

what cells is insulin released from

Answer 11

beta cells in islets

Question 12

what does low blood sugar trigger

Answer 12

release of glucagon

Question 13

what cells secrete glucagon

Answer 13

alpha cell in islets

Question 14

what is EGP

Answer 14

endogenous glucose production
which increases blood sugar levels
triggered by glucagon
and braked by insulin

Question 15

what are incretins

Answer 15

hormones that work to increase insluin secretion and switch off glucagon

Question 16

2 main incretin hormones

Answer 16

GIP
GLP-1

Question 17

2 types of diabetes mellitus

Answer 17

1 = autoimmune destruction of beta cells
2 = defects in insluin release, sensing and/or signalling

Question 18

where are the islets of langerhans

Answer 18

in pancreas
close to blood vessels (highly vascularised AND richly innervated)
1% of pancreatic tissue

Question 19

what do delta cells in islets of langerhans release

Answer 19

somatostatin

Question 20

what do epsilon cells release in islets

Answer 20

ghrelin

Question 21

what do pp cells in islets make hehe

Answer 21

pancreatic plypeptide

Question 22

insulin precursor

Answer 22

proinsulin

Question 23

what type of bonds between the 2 chains of insulin

Answer 23

disulphide

Question 24

what is the linker peptide in insulin

Answer 24

C peptide

Question 25

what enxyme converts proinsulin into insluin and c peptide

Answer 25

proenzyme convertase (PC)

Question 26

why is c peptide good to use clinically

Answer 26

has a longer half life than insulin

Question 27

what is insulin complexed with in secretory vesicles

Answer 27

zinc
forms multimeric crystals in the vesicles

Question 28

how many grnaules does each beta cell hold

Answer 28

~ 10,000 granules

Question 29

half life of insulin

Answer 29

3-5 mins

Question 30

where is inslouin metabolised

Answer 30

liver

Question 31

what pathways does insulin stimulate

Answer 31

glycolysis
glycogen synthase
glucose uptake
protein synth
gene expression

Question 32

what pathways does insulin inhibit

Answer 32

gluconeogenesis
lipolysis

Question 33

what type of receptor is insluin receptor

Answer 33

intrinsic tyrosine kinase

Question 34

what proteins does activation of insulin receptor activate

Answer 34

IRS and SH2 activation
activation of IRS-1

Question 35

what pathway does insluin binding activate

Answer 35

pi3 kinase pathway
and Ras/ref pathway

Question 36

what signalling molecule coordinates phosphorylation of downstream proteins in insulin signalling

Answer 36

AKT

Question 37

what gene synthesises glucagon

Answer 37

pre-proglucagon gene

Question 38

if pro-enzyme convertase 1 acts of pre-proglucagon, then what is it converted to

Answer 38

GLP-1

Question 39

what receptor is glucagon rec

Answer 39

GPRC
adenylate cyclase pathway
increase cAMP

Question 40

what is glucagon release stimulated by

Answer 40

• low glucose duh
• adrenaline
• amino acids
• acetylcholine
• GIP at low glucose conc

Question 41

what is glucagon inhibited by

Answer 41

• raised glucose
• somatostatin
• insulin, GABA, the zinc from beta cells
• GLP-1
• GIP at high glucose conc.

Question 42

EGP effects

Answer 42

• glycogenolysis (glycogen ->glucose)
• lipolysis (to increase circulating glycerol and fatty acids)
• gluconeogenesis (amino acids and glycerol -> glucose)

Question 43

how does insulin switch off glucagon production

Answer 43

inhibits alpha cells

Question 44

what else do beta cells secrete that suppress alpha cells

Answer 44

GABA

Question 45

effects of somatostatin

Answer 45

• inhibits insulin and glucagon by inhibiting alpha and beta cells
• acts locally, doesnt leave islet

Question 46

why do alpha cells also need to switch on the beta cells and delta cells

Answer 46

if goes unchecked, these cellls can raise blood sugar too much
acts as negactive feedback