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Endocrine > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

Define euglycemia

A

normal concentration of glucose in the blood

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2
Q

What cells produce insulin?

A

Beta cells

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3
Q

Where are beta cells found

A

Pancreatic islets in the endocrine pancreas

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4
Q

Name the four different types of pancreatic islets cells and what they secrete

A

Beta cells - insulin Alpha cells - glucagon Delta cells - somatostatin Polypeptide cells - pancreatic polypeptide

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5
Q

Where is the insulin precursor synthesised?

A

rough endoplasmic reticulum

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6
Q

What other peptide is secreted with insulin, what is its function?

A

C-peptide, has no metabolic function

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7
Q

Describe the structure of insulin

A

Two polypeptide chains (alpha and beta) bound together by disulphide bonds

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8
Q

What do the disulphide bonds create?

A

3D structure which allows binding to receptors

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9
Q

Name the channel that glucose moves through to enter the beta cell

A

GLUT 2

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10
Q

What does glucose entry to the beta cell result in? What is the product?

A

Phosphorylation by glucokinase resulting in the production of 36ATP per glucose molecule

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11
Q

What is the purpose of the ATP produced during glycolysis in the beta cell?

A

It inhibits the ATP sensitive potassium channel preventing potassium from leaving the cell leading to depolarisation

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12
Q

Describe the beta cell response to depolarisation

A

Opening of voltage gated calcium channels stimulates insulin vesicles binding to the membrane and as a result insulin release

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13
Q

Explain the two phases of insulin release

A

1st phase - insulin is ready to go (readily releasable pool) 2nd phase - vesicles still need some manipulation (preparatory reactions) to become mobilised & available

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14
Q

What are the two subunits of the KATP channel?

A
  • inward rectifier pore subunit (KIR) - sulphonylurea regulatory subunit (SUR1)
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15
Q

Name two chemicals that inhibit KATP channels

A
  • ATP - Sulphonylurea
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16
Q

Name one chemical that stimulates KATP channels

A
  • diazoxide
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17
Q

What shape is the KATP channel?

A

Octomeric

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18
Q

When insulin in present, name six processes that increase

A

amino acid uptake DNA & Protein synthesis

Growth responses

Glucose uptake

Lipogenesis

Glycogen synthesis

(Gene expression)

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19
Q

When insulin is present, name two processes that decrease

A

lipolysis gluconeogenesis (gene expression)

20
Q

What type of receptor does insulin bind to?

A

Receptor tyrosin kinases (alpha unit)

21
Q

After insulin binding what happens to the receptor?

A

beta subunits dimerise & phosphorylate activating catalytic receptor activity

22
Q

What is autocrine regulation?

A

chemicals released from he cells bind to receptors on/in the cell that is releasing them

23
Q

What is paracrine regulation?

A

chemical released from the cell binds to receptors on adjacent cells

24
Q

What is endocrine regulation?

A

chemicals released from the secretory cells are transported via the circulatory system to target cells

25
Q

Describe negative feedback

A

product inhibits a intermediate pathway in order to maintain homeostasis and oppose change

26
Q

Describe positive feedback

A

initial stimulus produces a response that exaggerates the change

27
Q

Name two general regulatory mechanisms of homeostasis

A

Intrinsic - autocrine & paracrine

Extrinsic - nervous system & endocrine

28
Q

How does negative feedback control the hypothalamic pituitary adrenal axis?

A

Elevated cortisol inhibits intermediate steps to prevent more being produced

29
Q

What is the purpose of cortisol?

A
  • stimulate gluconeogenesis
  • protein breakdown & liberation of free fatty acids
  • immune system suppression
  • stress response
  • blood pressure maintenance
30
Q

Define hormones

A

any substance elaborated by one cell to regulate another cell

31
Q

How does the hypothalamus integrate nervous & endocrine systems?

A
  • secretion of regulatory hormones
  • synthesis of hormones
  • direct neural control (secretion of adrenaline & noradrenaline from adrenal medulla)
32
Q

Describe diurnal control

A

(curcaduab rhythm)

External cues (light/dark) evoke fluctuations in hormone secretions. Levels are also influenced by the rate at which hormones are eliminated by the body

33
Q

State three classes of hormones

A
  • Steroids
  • Amines
  • Peptide & protein hormones
34
Q

Where are steroids derived from and how are they transported?

A

Lipids derived from cholesterol, secreted not stored transported in the blood bound to carrier proteins

35
Q

Give examples of two steroids and where they are secreted from

A
  • cortisol - adrenal cortex involved in stress
  • testosterone & oestradiol - secreted from gonads involved in sexual characteristics
36
Q

Describe the mechanism of action of steroids

A

Bind to receptors & enter the nucleus (forming a complex), this binds to DNA & activates specific gens leading to the production of key proteins

37
Q

What are amines derived from & where are they secreted?

A

Amino acids, secreted from the thyroid & adrenal medulla

38
Q

How are amines transported in the blood?

A

Catecholamines - hydrophilic & transported free in the blood

Thyroid - bound to carrier proteins

39
Q

How do amines work?

A

Bind to receptors on the cell membrane to stimulate cellular responses

40
Q

What is the difference between peptide and protein hormones?

A

peptide - short chains

protein - larger molecules

41
Q

What is peptide/protein hormones polarity and how are they transported?

A

Hydophilic & transported ‘free’ in blood plasma

42
Q

How are peptide/protein hormones synthesised?

A

As precursor molecules, stored in vesicles and different end hormones are made by cleaving a common precursor using different enzymes

43
Q

Where are peptide & protein hormones secrected from?

A
  • pituitary
  • parathyroid
  • heart
  • stomach
  • liver
  • kidneys
44
Q

What do carrier protiens allow?

A
  1. Facilitation of hormone transport
  2. Increased half-life of hormone
  3. A reservoir for the hormone
45
Q

Name three important carrier proteins and what they carry

A
  • cortisol binding globulin (cortisol & aldosterone)
  • thyroxine binding globulin (thyroxine T4 & some T3)
  • sex steroid binding globulin (testosterone & oestradiol)

Endocrine (17 decks)

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