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Intro to Biochemistry > 30 and 31 - Nutrition and Hormones > Flashcards

30 and 31 - Nutrition and Hormones Flashcards

1
Q

What are three types of hormones (based on derivatives, eg. polypeptides)?

A

Polypeptides
Amino acid derivates (catecholamines)
Steroids

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2
Q

What three broad functions that hormones carry out through receptor signalling?

A
  • Maintenance of homeostasis across organism
  • Response to external stimuli
  • Follow cyclic programs, sleep wake cycle, menstrual etc.
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3
Q

What do endocrine cells do?

A

Secrete hormone molecules into the bloodstream to trigger target cells any distance away

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4
Q

What do paracrine cells do?

A

Secrete hormone molecules to peripheral cells, only affecting tissue around them

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5
Q

What do autocrine cells do?

A

Secrete hormone molecules to bind to receptors on same cell. They affect themselves.

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6
Q

What are four peripheral endocrine organs?

A

Pancreas
Gastrointestinal tract
Adrenal cortex
Adrenal medulla

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7
Q

What three types of cells are there in the pancreas and what do they secrete?

A
  • alpha cells secrete glucagon
  • beta cells secrete insulin
  • delta cells secrete somatostatin
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8
Q

What 5 hormones does the gastrointestinal tract secrete?

A
  • Gastrin and secretin (acid production)
  • Cholecystokinin (gallbladder emptying)
  • Gastric inhibitory peptide (GI motility)
  • Ghrelin (appetite stimulant)
  • GLP (crosstalk with pancreas)
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9
Q

What 3 hormones does the adrenal cortex secrete? Which type of hormone are they?

A

Adrenal cortex steroids

  • Glucocorticoids
  • Mineralocorticoids
  • Sex steroids
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10
Q

What 2 hormones does the adrenal medulla secrete? What type of hormones are these?

A

Adrenal Medulla Catecholamines

  • Epinephrine
  • Norepinephrine
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11
Q

What are the 5 types of hormon receptors?

A
  • Ionotropic receptors
  • G-protein coupled receptors
  • Cytokine receptors
  • Receptor tyrosine kinases
  • Nuclear hormone receptors
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12
Q

What are ionotropic receptors?

A

Gated ion channels, used by neurotransmitters often.

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13
Q

Which hormones use G-protein coupled receptors?

A

MANY, over 800 different receptors.

  • Adrenergic (epinephrine)
  • Glucagon
  • Used in vision, taste and smell
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14
Q

What do cytokine receptors do?

A
  • Respond to cytokines (Intracellular signalling molecules)
  • Respond to tumour necrosis factor, type of cytokine that causes apoptosis
  • Respond to interleukins (immune signalling from leukocytes)
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15
Q

What do receptor tyrosine kinases respond to?

A
  • Insulin

- Growth factors

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16
Q

What do nuclear hormone receptors do?

A

Class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules. In response, these receptors work with other proteins to regulate the expression of specific genes, thereby controlling the development, homeostasis, and metabolism of the organism. Can bind to DNA.

  • Respond to membrane-permeable ligands
  • Vitamins A and D
  • As well as some fatty acids and bile acids
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17
Q

What is slow signal transduction?

A

Involves altered protein synthesis by affecting gene expression. Takes minutes to hours.

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18
Q

What is fast signal transduction?

A

Intracellular signalling pathway that leads to altered protein function (often allosterically), leading to altered cytoplasmic machinery. This is quick and takes seconds to minutes

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19
Q

What are the steps of the G-protein cycle?

A
  1. Ligand binds to receptor
  2. G-protein activated by GTP exchanging with GDP
  3. Alpha subunit of G protein with GTP bound (active) dissociates and activates adenylate cyclase
  4. Adenylate cyclase synthesizes cAMP from ATP as long as GTP-Gα is bound.
  5. cAMP activates protein kinase A, which causes cellular effects.
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20
Q

How is a G-protein coupled receptor signal terminated?

A
  1. G protein has GTPase activity, it hydrolyzes GTP to GDP and inactivates itself.
  2. Additional regulatory proteins can hydrolyze the GTP and shorten the signal
  3. cAMP is hydrolyzed and removed by phosphodiesterase
  4. The receptor is endocytosed and can be degraded (fewer receptors on suface leads to less signal)
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21
Q

What type of hormone receptor is the insulin receptor?

A

Receptor tyrosine kinase, similar to other growth factor receptors.
- Dimer

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22
Q

What is the structure of a receptor tyrosine kinase?

A

It is a dimer

  • There are two α-subunits in the extracellular space
  • Each α-subunit is attached to a β-subunit, which is intracellular and contains the tyrosine kinase domains.
  • Ligands (like insulin) bind to the α-subunits
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23
Q

What are the steps of insulin receptor activation and termination? (receptor tyrosine kinase activation)

A

Activation

  1. Insulin binds to the α-subunits of the receptor
  2. Phosphorylation of tyrosine on receptor and IRS (insulin receptor substrate)
  3. Cellular response

Termination

  1. Dephosphorylation of receptor and IRS by a tyrosine phosphatase
  2. Internalization of receptor

PIP2 and PIP3 are special lipids in the membrane that are used in receptor tyrosine kinase signalling

24
Q

What are the 11 water-soluble vitamins?

A
  • ascorbic acid (vitamin C)
  • thiamine (vitamin B1)
  • riboflavin (vitamin B2)
  • Niacin (vitamin B3)
  • Biotin
  • Pantothenic acid
  • Folic acid
  • Vitamin B12
  • Pyridoxine (vitamin B6)
  • Pyridoxal
  • Pyridoxamine
25
Q

What are the four fat soluble (water insoluble) vitamins?

A
  • Vitamin A (retinal, beta-carotenes)
  • Vitamin D (cholecalciferol)
  • Vitamin K (phylloquinones, menaquinones)
  • Vitamin E (tocopherols)
26
Q

What is the non-B complex, water soluble vitamin?

A

Ascorbic acid (vitamin C)

27
Q

What are the 5 B-complex and water soluble, energy releasing vitamins?

A
  • Thiamine (vitamin B1)
  • Riboflavin (vitamin B2)
  • Niacin (vitamin B3)
  • Biotin
  • Pantothenic acid
28
Q

What are the two hematopoietic, B-complex, water soluble vitamins?

A
  • Folic acid

- Vitamin B12

29
Q

What is the only vitamin that is non B-complex and ALSO water soluble?

A

Ascorbic acid (vitamin C)

Vitamin A, D, K and E are all fat soluble (water insoluble). The rest of the water soluble vitamins are B-complexes

30
Q

What types of vitamins can accumulate in the body and therefore have an upper limit for daily intake?

A

Fat soluble vitamins can accumulate in the body.

31
Q

Which ‘vitamin’ is not really a vitamin at all? (it’s a hormone)

A

vitamin D, it can be synthesized in the body as cholecalciferol

32
Q

What is vitamin B1 (thiamine) used for? (hint, its derivative is thiamine pyrophosphate, TPP)

A

Cofactor in pyruvate dehydrogenase, ketoglutarate dehydrogenase and in a transketolase in the pentose phosphate pathway. Also oxidative decarboxylation.

33
Q

What is vitamin B2 (riboflavin) used for?

A

As a precursor for the redoxactive flavin cofactors FADH2 and FMN

34
Q

What is vitamin B3 (niacin, nicotinic acid) used for?

A

Niacin and nicotinamide are precursors for NADH and NADPH

35
Q

What is vitamin B5 (pantothenic acid) used for?

A

Component of coenzyme CoA, deficiencies very unlikely?

36
Q

What is vitamin B6 (pyridoxine) used for?

A

The active form is pyridoxal-phosphate or pyridoxamine phosphate, cofactor for over 100 enzyme systems: transaminations, deaminations, decarboxylations.

37
Q

What is vitamin B7 (biotin) used for?

A

Cofactor in carboxylations (acetyl carboxylase, pyruvate carboxylase)

38
Q

What is vitamin B9 (folate) used for?

A

Tetrahydrofolate (THF) is a cofactor in one-carbon metabolism (can hold donor group with one carbon atom) and amino acid metabolism

39
Q

What is vitamin B12 (cobalamine) used for?

A

Involved in one carbon metabolism like THF (vitamin B9, folate)

40
Q

What is the active form of vitamin B1 (thiamine)?

A

thiamine pyrophosphate. It acts as a cofactor in transketolases and oxidative decarboxylation.

Cereals are fortified with it to prevent deficiencies causing Beriberi or Wernicke Korsakoff

41
Q

What step of TCA cycle is thiamine pyrophosphate (active form of vitamin B1) involved in?

A

The dehydrogenation of alpha-ketoglutarate with alpha-ketoglutarate dehydrogenase to succinyl-CoA

42
Q

What vitamin is needed as a cofactor for the breakdown of propionyl-CoA (from odd chain fatty acids, some amino acids)?

A

Vitamin B7, biotin

43
Q

What is the cholesterol precursor for vitamin D? What is needed to convert it to cholecalciferol (vitamin D3) in animals?

A

7-dehydrocholesterol

- UV light is needed

44
Q

What happens to cholecalciferol and ergocalciferol in the liver and kidney?

A

Two hydroxylation steps, one takin place in the liver (first) and the second taking place in the kidney.

45
Q

What is the regulated step of vitamin D3 and vitamin D2 hydroxylation? Where does it take place in the body? What stimulates it?

A

Hydroxylation in the kidney is the regulated step. Stimulated by low phosphate and by parathyroid hormone

46
Q

What type of vitamin D is synthesized in animals?

A

Cholecalciferol (vitamin D3)

47
Q

What type of vitamin D is synthesized in plants?

A

ergocalciferol (vitamin D2)

48
Q

What does vitamin D do in animals?

A
  • Increases calcium in plasma through increased intestinal absorption, decreased kidney excretion of calcium
49
Q

What does parathyroid hormone do in animals?

A
  • Increases calcium mobilization from bones

- Increases production of vitamin D (kidney)

50
Q

What does calcitonin do?

A

Acts to reduce plasma calcium, reversing the effects of parathyroid hormone.

51
Q

What is an example of a glucocorticoid from the adrenal cortex?

A

cortisol

52
Q

What is an example of mineralcorticoid from the adrenal cortex?

A

aldosterone

53
Q

What is an example of an androgen from the adrenal cortex?

A

Testosterone

54
Q

What is an example of an estrogen from the adrenal cortex?

A

Progesterone
Pregnenolone
Estradiol

55
Q

What are all steroids derived from?

A

Cholesterol

Intro to Biochemistry (28 decks)

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