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Flashcards in Biochemistry Deck (34)
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1

What are the various types of cells which are found in the pancreatic islets of langherhans?

alpha cells
beta cells
delta cells
PP cells

2

What do each cell found in the islets of langerhans secrete

beta cells - insulin
alpha cells - glucagon
delta cells - somatostatin
PP cells - pancreatic polypeptide

3

Where is insulin synthesised?

rough endoplasmic reticulum of pancreatic beta cells

4

What is the precursor for insulin?

larger single chain preprohormone called preproinsulin

5

Briefly describe the structure of insulin

two polypeptide chains linked by disulfide bonds

6

Name the other by-product of insulin cleavage

C Peptide

7

How are insulin preparations classified?

Ultra fast/ultra short-acting
Short-acting
Intermediate-acting
Long-acting
Ultra long-acting

8

How long after a meal should Insulin Lispro be injected into the body?

Within 15 minutes of beginning a meal

9

Should ultra-fast acting insulin be used in Type 1 diabetes management?

Must be used in combination with longer-acting preparation
**unless used for continuous infusion**

10

What classification of insulin is glargine and when should this be administered?

Ultra-long acting
Administered as a single bedtime dose

11

What transporter is responsible for glucose uptake into the cell?

GLUT 2

12

What enzyme is responsible for the phosphorylation of glucose to Gluco-6-phosphate once it enters the cell?

Glucokinase

13

Describe the physiology of insulin release

Glucose into cell
Glucose metabolism = ATP generation
ATP inhibits K+ into cell
Membrane depolarises (closer to 0)
Opens Voltage Gated Ca2+ Channel
Ca2+ In
Vesicles fuse with membrane
Release insulin

14

What threshold must be met for Beta cells to release insulin?

blood glucose rising above 5 mM

15

What is meant by "the cells lose the ability to sense glucose?"

hyperglyceamia takes glucose concentration outwith the Km of glucokinase

16

Describe the graphic nature of insulin release

Biphasic
First peak is higher than second

17

What are the two pools in which insulin is released?

RRP – readily releasable pool (5 %)
Reserve pool

18

What type of drug is used in Type 2 Diabetes to stimulate insulin secretion from beta cells

sulphonylurea drugs mimic the action of ATP to depolarise beta cells.

19

What patients are sulphonylurea drugs most appropriate for in Type 2 Diabetes treatment

- patients who have trouble injecting insulin
- patient has improved their glucose control and lessened the stress on the islet.

20

What two subunits make up the K+ ATP channels?

Kir6.2 and SUR1

21

What can mutations in either of the two K+ ATP channel subunits result in?

Neonatal diabetes

22

What is MODY?

Maturity-onset diabetes of the young (MODY)

- genetic defect in beta cell function (6 mutations)
- Familial form of early-onset Type 2 diabetes
- defect in insulin secretion not damaged beta cells

23

What are the functions of HNF transcription factors?

- pancreas foetal development and neogenesis

- regulate b cell differentiation and function

24

Why must screening to differentiate between Type 1 diabetes and MODY be robust?

Allows treatment of MODY with sulphonylurea rather than insulin (as they usually have some b-cell function available)

25

Describe the difference between Type 1 diabetes, Type 2 Diabetes and MODY

Type 1 Diabetes – Loss of insulin secreting beta cells

MODY- defective glucose sensing in the pancreas and/or loss of insulin secretion

Type 2 Diabetes- Initially hyperglycemia with hyperinsulinemia => reduced insulin sensitivity in tissues

26

What processes does insulin turn OFF (as an anabolic hormone)?

Lipolysis
Gluconeogenesis in liver

27

What processes does insulin stimulate?

Amino acid uptake in muscle
DNA/Protein synthesis
Glucose uptake in muscle and adipose tissue
Lipogenesis in adipose tissue and liver
Glycogen synthesis in liver and muscle

28

What type of receptor does insulin bind to?

Receptor Tyrosine Kinase

29

What are the two main pathways via which insulin can signal?

PKB
Ras

30

What is Leprechaunism/ Donohue Syndrome?

- Rare autosomal recessive genetic trait
- Mutations in the gene for the insulin receptor
- Severe insulin resistance