Control Of Glucose/glycogen

Question 1

Why in muscle cells is glycogen and glucose controlled

Answer 1

For muscle energy needs, if more energy needed glucose increases

Question 2

What happens in muscle cells when exercise occurs

Answer 2

Increased glucose uptake into cells

Increased glycogenolysis

Decreased glycogenesis

Increased glycolysis for atp

Question 3

Why does liver respond to high or low glucose eg after meal or at rest

Answer 3

To control blood glucose and also supply for other cells

Question 4

What happens to liver cells after a meal (high glucose)

Answer 4

Increase glucose uptake by liver cells

Increased glycogenesis for storage

Decreased glycogenolysis

Question 5

Which 3 hormones control glucose blood conc

Answer 5

Epinephrine

Insulin

Glucagon

Question 6

Where is epinephrine produced and when is it released

Answer 6

Produced by chromaffin cells in the adrenal medulla

Released in emergency low glucose conc levels

Increases blood glucose

Question 7

What cells does adrenaline act on for glucose increase in blood

Answer 7

Muscle and liver (causes contraction and also for general increase in blood)

Question 8

What happens when epinephrine/adrenaline binds to GPCR on muscle or liver cells

Answer 8

Activates the G protein

G protein activates adenylate cyclase

ATP converted into cAMP

Camp activates PKA

PKA activates phosphorylase kinase

Activates phosphorylase A (glycogen phosphorylase) from B by phosphorylation

Phosphorylase A causes glycogenolysis (removes glucose from glycogen via phosphorylation)

Question 9

What happens to glycogen synthase when glucagon or adrenaline bind

Answer 9

It’s inactivated (phosphorylation of it) via pKA

Stops glycogen synthesis

Question 10

Where is glucagon produced

Answer 10

Alpha cells in the pancreas islets of langerhans

Question 11

Where is insulin produced and secreted

Answer 11

Beta cells in pancreas

Question 12

Why is it important that pancreas is highly vascularised

Answer 12

For glucose and o2 level sensing

Needs to secrete hormones when sensing glucose levels in blood

Question 13

Where does glucagon bind to to increase BGC

Answer 13

Liver cells

Question 14

What 4 effects does glucagon have

Answer 14

Decrease glucose uptake in liver cells

Increase gluconeogenesis

Increase glycogenolysis (via camp pka)

Decrease glycogenesis

Question 15

Where does insulin act on when B cells detect high BGC

Answer 15

Liver and muscle cells receptors

Question 16

How is glycogen synthase deactivated by PKA

Answer 16

Phosphorylation of it

Question 17

What kind of receptors does insulin bind to on liver or muscle cells

Answer 17

RTK

Receptor tyrosine kinase (enzyme linked receptors)

Question 18

How is glycogen phosphorylase A activated by PKA

Answer 18

Addition of a phosphate

Question 19

Explain how insulin causes glycogenesis when bound to RTK

Answer 19

Causes auto phosphorylation on the receptor domains

IRS becomes phosphorylated

Activates Protein kinases

PK inactivate glycogen synthase kinases (by phosphorylation)

This activates glycogen synthase because glycogen synthase kinase no longer phosphorylates glycogen synthase

= active glycogen synthase

Question 20

Which enzyme keeps glycogen synthase phosphorylated (inactive) which is then inactivated by insulin binding

Answer 20

Glycogen synthase kinase

Question 21

What is IRS

Answer 21

Insulin receptor substrate

Question 22

Why does glucose need glut uniporters for transport

Answer 22

It’s hydrophilic

Question 23

Which GLUT receptor channels are found on all cells

Answer 23

Glut 1 and 3

Question 24

Where is glut 2 found

Answer 24

Liver and pancreas

Question 25

Why is GLUt2 important at the Bcells in pancreas

Answer 25

It regulates the release of insulin

Question 26

Explain the steps of what happens when high glucose levels flow into Bcells down glut2 receptor channel

Answer 26

Causes glycolysis within the B cell

Releases ATP

ATP is used to block K+ channels

This causes depolarisation which causes ca2+ channels to open

Ca2+ flooding into Bcell causes insulin release

Question 27

Why is glut 2 important in liver cells

Answer 27

Allows uptake of glucose when too high in blood

Question 28

Where is GLUT 4 located and controlled by

Answer 28

In fat (adipose) cells and muscle cells

Controlled by insulin

Question 29

How does insulin binding to muscle cells cause uptake of glucose

Answer 29

When insulin binds to muscle cells it causes glut 4 transporters to be released from the recycling endosome

They are embedded into the plasma membrane for glucose uptake into muscles when exercise is high

Question 30

What is type 1 diabetes caused by

Answer 30

Insulin deficiency

Autoimmune attack on Bcells so insulin can’t be released

Question 31

What do type 1 diabetics rely on

Answer 31

Insulin injection

Question 32

What was type 2 thought to be caused by first

Answer 32

Increased insulin in the blood due to food intake

Caused peripheral resistance to insulin in liver and muscle cells
Glucose levels can’t decrease

Question 33

Apart from peripheral resistance of liver and muscle cells to insulin, what else was thought to cause diabetes

Answer 33

B cell death due to exhaustion from continuous insulin release

Question 34

What was found recently to cause diabetes 2 which now shows it is reversible

Answer 34

Beta cell hiding to avoid death

B cells hide from the lipids and fat which overspill from the liver

B cells therefore hide from the lipids and aren’t active

Question 35

How can diet reverse diabetes 2

Answer 35

B cells stop hiding from the overspill of fats and lipids

Question 36

Because of the inability of diabetics to store glucose as glycogen, what happens

Answer 36

Renal excretion of glucose form the kidneys in urine , the reabsorption channels become saturated with glucose

Causes water loss in urine too due to high osmolarity in the blood (high glucose)