3: Insulin production, secretion and action Flashcards Preview

Endocrine Week 1 2017/18 > 3: Insulin production, secretion and action > Flashcards

Flashcards in 3: Insulin production, secretion and action Deck (50)
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1

Insulin helps with homeostasis of what?

Blood glucose concentration

2

What is the normal blood glucose concentration?

5mmol/L

3

What cells in the pancreas produce insulin?

Beta cells

4

What cells in the pancreas produce glucagon?

Alpha cells

5

The majority of pancreatic cells are acinar cells which secrete ___ enzymes.

digestive enzymes

6

Where specifically in a beta cell is insulin produced?

Rough ER

7

The precursor of insulin is a large chain polypeptide called ___.

preproinsulin

8

What activates insulin?

Cleavage of C peptide which is found in the middle of preproinsulin

9

Which bonds connect the two polypeptide chains of activated insulin?

Disulphide bonds

10

Which structure connect the two polypeptide chains for inactive proinsulin?

C peptide

11

Depending on the position of amino acids, insulin can be ___-acting or ___-acting.

short acting

long acting

12

Which type of insulin acts ultra-quickly and is injected by T1 diabetics 15 minutes before meals?

Lispro

13

Which type of insulin acts over an ultra-long period and is injected by diabetics at bedtime to maintain their blood glucose level overnight?

Glargine

14

What activates the secretion of insulin by beta cells?

Presence of glucose

15

By which transporter do glucose molecules enter beta cells?

GLUT2

16

Within beta cells, glucose is phosphorylated by ___ to form what?

glucokinase

Glucose-6-phosphate

17

In Type 1 diabetes, what happens to beta cells?

Destroyed by immune system

18

In Type 2 diabetes, why does insulin resistance develop?

Beta cells fail to sense glucose because they are constantly surrounded by it (hyperglycaemia), no longer produce insulin

19

What is produced by the metabolism of one molecule of glucose?

36 ATP molecules

20

When ATP is produced in a beta cell, what happens to

a) Potassium channels

b) Calcium channels

Kchannels close

Beta cell depolarises

Ca2+ channels open

Triggers secretion of insulin by exocytosis

21

Beta cells release insulin in response to blood glucose concentration rising above __ mM.

5 mM

22

In hyperglycaemia, the blood glucose concentration is (below / above) the KM of glucokinase.

What does this cause?

above KM of glucokinase

Over time, Type 2 diabetes:

hyperglycaemia hyperinsulinaemia insulin resistance hyperglycaemia causing complications via Poyol pathway in a vicious cycle

23

Release of insulin occurs in ___ phases.

two phases

24

What percentage of insulin vesicles are immediately available for release from beta cells?

About 5%

25

The other 95% of insulin is released in the (first / second) phase of insulin release.

second phase

26

What type of drug mimics ATP to depolarise beta cells and trigger insulin release?

Sulphonylureas

-amides and -azides

27

What channel do suphonylurea drugs bind to?

Potassium channels

cause them to close - depolarisation due to lack of K efflux - Ca influx - insulin release

28

What drug has the opposite effect on potassium channels to sulphonylamides and is used to treat functional tumours like insulinomas?

Diazoxide

29

Mutations in the genes for the potassium channels of beta cells can lead to what type of diabetes?

What drug is used to treat this?

Neonatal / congenital diabetes

Sulphonylureas

30

What disease is caused by mutations affecting beta cell function and presents like T2 diabetes i.e problems with insulin secretion in young people?

MODY

maturity-onset diabetes of the young