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Endocrine > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

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

A

alpha cells
beta cells
delta cells
PP cells

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2
Q

What do each cell found in the islets of langerhans secrete

A

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

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3
Q

Where is insulin synthesised?

A

rough endoplasmic reticulum of pancreatic beta cells

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4
Q

What is the precursor for insulin?

A

larger single chain preprohormone called preproinsulin

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5
Q

Briefly describe the structure of insulin

A

two polypeptide chains linked by disulfide bonds

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6
Q

Name the other by-product of insulin cleavage

A

C Peptide

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7
Q

How are insulin preparations classified?

A 
Ultra fast/ultra short-acting
Short-acting
Intermediate-acting
Long-acting
Ultra long-acting
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8
Q

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

A

Within 15 minutes of beginning a meal

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9
Q

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

A

Must be used in combination with longer-acting preparation

unless used for continuous infusion

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10
Q

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

A

Ultra-long acting

Administered as a single bedtime dose

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11
Q

What transporter is responsible for glucose uptake into the cell?

A

GLUT 2

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12
Q

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

A

Glucokinase

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13
Q

Describe the physiology of insulin release

A 
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
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14
Q

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

A

blood glucose rising above 5 mM

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15
Q

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

A

hyperglyceamia takes glucose concentration outwith the Km of glucokinase

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16
Q

Describe the graphic nature of insulin release

A

Biphasic

First peak is higher than second

17
Q

What are the two pools in which insulin is released?

A

RRP – readily releasable pool (5 %)

Reserve pool

18
Q

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

A

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

19
Q

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

A
  • patients who have trouble injecting insulin

- patient has improved their glucose control and lessened the stress on the islet.

20
Q

What two subunits make up the K+ ATP channels?

A

Kir6.2 and SUR1

21
Q

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

A

Neonatal diabetes

22
Q

What is MODY?

A

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
Q

What are the functions of HNF transcription factors?

A
  • pancreas foetal development and neogenesis

- regulate b cell differentiation and function

24
Q

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

A

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

25
Q

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

A

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
Q

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

A

Lipolysis

Gluconeogenesis in liver

27
Q

What processes does insulin stimulate?

A 
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
Q

What type of receptor does insulin bind to?

A

Receptor Tyrosine Kinase

29
Q

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

A

PKB

Ras

30
Q

What is Leprechaunism/ Donohue Syndrome?

A
  • Rare autosomal recessive genetic trait
  • Mutations in the gene for the insulin receptor
  • Severe insulin resistance
31
Q

What developmental abnormalities can be present in Leprechaunism/ Donohue Syndrome?

A
  • elfin facial appearance
  • growth retardation
  • absence of subcutaneous fat, decreased muscle mass
32
Q

What is Rabson Mendenhall Syndrome?

A
  • Rare autosomal recessive genetic trait
  • Severe insulin resistance
  • hyperglycemia and compensatory hyperinsulinemia
  • Diabetic ketoacidosis can occur
33
Q

What developmental abnormality can be seen in Rabson Mendenhall syndrome?

A

Acanthosis nigricans (hyperpigmentation)

34
Q

When is Diabetic ketoacidosis a danger in Type 1 diabetes?

A

If an insulin dose is missed

Endocrine (24 decks)

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