Control of Metabolism & Biochemistry

Question 1

Which centres of the hypothalamus determine energy intake?

2

Answer 1

Feeding centre 
Satiety centre (insulin sensitive)

Question 2

Which 2 theory’s describe food intake drive?

Answer 2

Glucostatic (Blood Glucose Levels)

Lipostatic (Leptin peptide hormone being released from fat stores decreases feeding)

Question 3

What are the 3 classes of energy output?

Answer 3

Cellular work - Metabolism
Mechanical work - Movement / moving neurotransmitters
Heat loss - Associated with both above

Question 4

Anabolic pathways

Answer 4

Synthesis large molecules

Question 5

Catabolic pathways

Answer 5

Break down larger molecules

Question 6

How is glucose synthesised

Answer 6

Glycogen (glycigenisis) 
Amino acids (gluconeogensis)

Question 7

What is the normal blood glucose range

Answer 7

4.2-6.3mM

Question 8

Which are the 2 main hormones involved in the regulation of blood glucose levels

Answer 8

Insulin & Glucagon

Question 9

What percent of the pancreas has endocrine function?

Answer 9

1% (Islets of Langerhans)

Question 10

Whats are the cell types in Islets of Langerhans and what do they produce?

Answer 10

Alpha - Glucagon
Beta - Insulin
Delta - Somatostatin
F - Pancreatic polypeptide

Question 11

What are the actions of Insulin dominance over Glucagon?
(High Blood Glucose Levels)
(4)

Answer 11

Increase in:

• Glucose oxidation
• Glycogen synthesis
• Fat synthesis
• Protein synthesis

Question 12

What are the actions of Glucagon dominance over Insulin?
(Low Blood Glucose Levels)
(3)

Answer 12

Increase in:

• Glycogenolysis
• Gluconeogenesis
• Ketogenesis

Question 13

What type of hormone is Insulin

Answer 13

Peptide

Question 14

What is used to measure beta cell function (inline production)?

Answer 14

C-Peptide Levels

Question 15

What hormone other an insulin lowers blood glucose levels?

Answer 15

None

Question 16

How can glucose be stored?

Answer 16

Glycogen in the liver

Triacylglycerols in liver and adipose tissue

Question 17

What are the mechanisms of control of insulin secretion?

Answer 17

Increase of Blood glucose
Increases in glucose entering beta cells (GLUT)
Increase in metabolism
Increase in ATP
K+ ion channels in he beta cells are sensitive to ATP so close
Cells depolarise
Volted gated Ca channels open
Ca enters the cell triggering exocytosis of vesicles
Insulin is released

Question 18

What receptors does insulin bind to on muscle and adipose tissue?

Answer 18

Tyrosine Kinase Receptors

Question 19

What is the action of insulin binding to surface receptors

Answer 19

GLUT-4 transporters migrate from the cytoplasm to the cell membrane and becomes imbedded for the transport of glucose

Question 20

How does the GLUT-4 transport become attached to the cell membrane?

Answer 20

Insulin binds to receptors
Intracellular signalling cascade
GLUT4 migrates to membrane
GLUT-4 exocytosis into the cell membrane
Glucose enters the cell down the concentration gradient

Question 21

How do muscle and adipose tissues take up insulin in the absence of insulin?

Answer 21

Adipose - Can’t

Muscle - Can’t at rest but during exercise GLUT-4 transporters migrate independently of insulin

Question 22

Which tissues are insulin dependant?

Answer 22

Muscle (40% of body weight)

Fat (20-25% of body weight)

Question 23

What do other cells use to transport glucose?

Answer 23

Non insulin dependant GLUT transporters

Question 24

What cells use GLUT 1,2 & 3 transporters

Answer 24

GLUT-1 = Brain, Kidney, RBCs and other tissues
GLUT-2 = Beta cells of pancreas & Liver (insulin can still help in liver)
GLUT-3 = Similar to GLUT-1

Question 25

How does insulin help the hepatocytes absorp glucose ?

Answer 25

Insulin stimulates hexokinase in liver cells Signalling cascade Tuns glucose into Glucose-6-phosphate This reduces the concentration of glucose inside the cell Increases the concentration gradient More glucose enters the cell

Question 26

What are the additional actions of insulin?

Answer 26

Anabolic: Increases glycogen synthesis in muscle and liver cells Increases amino acid uptake (protein synthesis) Inhibits proteolysis (protein metabolise) Increases triacylglycerol synthesis in adipocytes Inhibits gluconeogenesis in the liver Hormones: Has a permissive effect on growth hormone Promotes K+ ion entry

Question 27

How does insulin increase glycogen synthesis?

Answer 27

Stimulates glycogen synthase and inhibits glycogen phosphorylase

Question 28

How long is Insulins half life?

Answer 28

5mins

Question 29

Where is Insulin broken down and by what?

Answer 29

Insulin bound receptors internalised by endocytosis and destroyed by insulin protease Insulinase in liver and kidneys

Question 30

What increases insulin release?

Answer 30

``` Increased BG Increased Amino Acids Increased Glucagon (for the uptake of glucose following gluconeagenisis) GI secretion & motility (CCK & secretin) Vagal nerve ```

Question 31

What inhibits insulin release?

Answer 31

Low BG Somatostatin Sympathetic alpha effects* Stress (hypoxia)* *results of the sympathetic nervous system

Question 32

Why is more insulin released as a result of oral glucose rather than IV glucose intake?

Answer 32

Vagus + Incretin response on top of the usual direct effect on Beta cells

Question 33

What is the half life of Glucagon?

Answer 33

5-10mins

Question 34

Where are most Glucagon using cells found?

Answer 34

Liver

Question 35

What are the Glucagon receptors?

Answer 35

G-Protein coupled receptors

Question 36

What would the brain switch to in the absence of Glucose?

Answer 36

Ketone Bodies

Question 37

What are the three processes caused by Glucagon?

Answer 37

- Glycogenesis (break down of Glycogen) - Glucaneogenasis (break down of amino acids) - Ketosis (Breakdown of adipose tissues)

Question 38

What would happen if Glucagon wasn't secreted in a rise of amino acids?

Answer 38

Insulin would rise to absorb amino acids Glucose would also be absorbed Hypoglycaemia would occur

Question 39

What are the 4 hormones which respond to a low Blood glucose level?

Answer 39

Glucagon - Glycogenolysis (liver) Epinehrine - Glycogenolysis (liver and muscle) Cortisol - Protein catabolism & Inhibition of glucose uptake Growth Hormone - Inhibition of glucose uptake All promote Lipolysis & Gluconeogensis

Question 40

What is the main function of Somatostatin?

Answer 40

Inhibits activity in GI tract (slows down gastric motility absorption of nutrients) Inhibits alpha and beta cells from secreting insulin and glucagon

Question 41

How does exercise effect insulin sensitivity?

Answer 41

Increases sensitivity for several hours post exercise