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Biochemistry > Hormones and hormonal action > Flashcards

Hormones and hormonal action Flashcards

1
Q

Multicellular organisms depend on communication among cells for what 3 reasons

A

Regulation of metabolic processes

Control of cell growth and differentiation

Integration of normal physiological functions

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2
Q

what is a hormone

A

chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the body

hormones are carried via the blood circulation to target cells

they give specific changes in the metabolic behaviour of the target cell

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3
Q

what are some of the sites for hormone secretion

A

pineal gland, adrenal glands, pancreas, ovaries, testis etc

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4
Q

what does the pituitary gland regulate

A

regulates all other endocrine glands and releases growth hormone

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5
Q

what does the thyroid gland regulate

A

metabolism and body heat

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6
Q

what do the parathyroids regulate

A

use of calcium and phosphorus

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7
Q

what does the hypothalamus regulate

A

nervous and endocrine system

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8
Q

what does the adrenal gland regulate

A

response to emergency situations and salt balance

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9
Q

what does the pancreas regulate

A

blood glucose

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10
Q

what do the ovaries regulate

A

production of eggs and female characteristics

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11
Q

what does the testes regulate

A

production of sperm and male characteristics

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12
Q

what does the thymus regulate

A

immune system

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13
Q

what is the difference between nerve action and hormones

A

nerve action is quick and can be stopped quickly
hormone action is slower and lasts longer

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14
Q

what are the categories for hormone classification

A

Autocrine (act upon the secretory cell)

Paracrine (act on adjacent cells)

Endocrine (act on target cells at a distance)

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15
Q

what are autocrine hormones

A

hormones are released and act on the same cell that secreted them

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16
Q

what are paracrine hormones

A

act on adjacent cells, diffusing from the source to local target cell

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17
Q

what are endocrine hormones

A

travel from the source via the bloodstream to distant target cells

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18
Q

what are Eicosanoids

A

fatty acid derivatives

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19
Q

what is hydrophilic

A

proteins, peptide hormones and catecholamines and act through a second messenger system

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20
Q

what is lipophilic

A

steroids and thyroid hormones and activate genes on binding with receptors in the nucleus

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21
Q

what the structure of peptide hormones

A

Structure of one of the smallest peptide hormones – the tripeptide messenger thyrotropin releasing hormone (TRH).

The N-terminal glutamine is cyclized to pyro-glutamic acid, there is an amide on the C-terminus.

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22
Q

what are synthesised protein precursors known as

A

preprohormones

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23
Q

what is the prohormone is processed into

A

the active hormone and packaged into secretory vesicles.

Includes insulin and glucagon in this class.

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24
Q

what occurs in insulin biosynthesis

A
  1. preprohormone processing to the active form.
  2. The Preproinsulin is synthesised as a random coil on membrane associated ribosomes
  3. Disulphide bond formation occurs
  4. Connecting sequence (C-peptide) is cleaved out to leave the mature insulin molecule
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25
Q

where DOES INSULIN comes from

A

Insulin is produced in the beta-cells
of the islets of Langerhans in the
pancreas

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26
Q

where does insulin act

A

the liver, muscle and fat tissue

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27
Q

what does insulin do

A

causes cells to take up glucose from the blood, storing it in liver and muscle. Increases fat storage. It is an anabolic hormone.

28
Q

what condition is associated with issues with insulin

A

diabetes

29
Q

how does insulin effect carbohydrate metabolism

A
  1. Increases glucose uptake across cell membranes
  2. Increases rate of glycolysis in muscle + adipose tissue.
  3. Increases glycogen synthesis in muscle, adipose & liver.
  4. Decreases rate of glycogen breakdown in muscle & liver.
  5. Increases glucose oxidation in “Pentose Phosphate Pathway” in liver & adipose tissue.
30
Q

what are feedback mechanisms

A

they give rapid information on the systems being regulated

31
Q

what is direct negative feedback

A

where rate of hormone production/secretion is related to the blood concentration of metabolite e.g. insulin and blood glucose control.

Negative feedback means that when enough hormone is in the body, the body stops producing the hormone until it is needed again

32
Q

what is the effect of insulin on lipid metabolism

A
  1. Inhibits rate of lipolysis (lipid breakdown) in adipose tissue
  2. Stimulates fatty acid (FA) and triacylglycerol
    (TG) synthesis in adipose tissue & liver.
  3. May decrease rate of FA oxidation in liver.
33
Q

what is the effect of insulin on protein metabolism

A
  1. Increases transport of some amino acids
    (aa’s) into muscle, adipose, liver & other cells.
  2. Increases protein synthesis in muscle,
    adipose & liver cells.
  3. Decreases rate of protein breakdown in
    muscle.
34
Q

what does insulin encourage

A

protein synthesis

35
Q

what is positive nitrogen balance in normal subjects called

A

anabolic hormone

36
Q

what is the secretion of insulin stimulated by

A

amino acids, glucagon, GIT hormones and hyperglycaemia

37
Q

what is the secretion of insulin inhibited by

A

adrenaline and fasting

38
Q

what is the secretion of glucagon stimulated by

A

amino acids, fasting, hypoglycaemia

39
Q

what is the secretion of glucagon inhibited by

A

insulin

40
Q

what are steroid hormones

A

Steroid hormones are extracellular messengers derived from the gonads (ovary or testis), the adrenal cortex and the placenta in pregnancy.

They are not stored for release after synthesis.

Five major categories – progestins, glucocorticoids,
mineralocorticoids, androgens and estrogens.

41
Q

what occurs in steroid hormone synthesis

A

Cholesterol is converted first to pregnenolone by a 2 step process in the liver.

Pregnenolone is converted to progesterone by oxidation

42
Q

when and where is cortisol is synthesised

A

it is synthesised in the adrenal cortex in response to signals from adrenocorticotropic hormone (ACTH)

43
Q

when and where is cortisol is synthesised

A

it is synthesised in the adrenal cortex in response to signals from adrenocorticotropic hormone (ACTH)

44
Q

what is cortisol

A

it is called the “fight or flight hormone” and is involved in response to stress and anxiety. It comes from the cortex and outer part of the adrenal gland and acts in multiple tissues

45
Q

What are the two groups of hormones derived
from the amino acid tyrosine

A
  1. thyroid hormones (T4- thyroxine and T3- triiodothyronine)
  2. catecholamines
46
Q

How are thyroid hormones made

A

by modifying tyrosine residues in the protein thyroglobulin.

47
Q

How do thyroid hormones effect metabolism

A
  1. give a general increase in metabolism of carbs, fats and proteins
  2. increase oxygen consumption directly in heart, kidney and liver
48
Q

how do thyroid hormones effect growth and development

A

help skeletal bone development and growth and maturation of CNS

49
Q

What is thyroxine

A

it comes from the thyroid gland and acts in most cells of the body and controls the rate of metabolic processes

50
Q

what is hypothyroidism

A

People may not produce enough thyroxine

51
Q

what are amino acid derivatives known as

A

catecholamines

52
Q

what are catecholamines

A

they are produced in the adrenal medulla and the most common are adrenaline and noradrenaline

53
Q

how are catecholamines involved in the fight or flight response

A

they effect the heart by increasing heart rate and the force of contrition
they convert glycogen = glucose
they convert stored fat = free fatty acid

54
Q

what is adrenaline

A

it comes from the Adrenal Gland and acts in the heart, blood vessels, eyes. It stimulates heart rate, increases blood pressure, dilates pupils and is released in high stress conditions or in excitement or fear. e.g loud noise can trigger its release

55
Q

what processes does adrenaline increase

A

increase muscle and hepatic glycogenolysis, increase hepatic gluconeogenesis + glycolysis, increase lipolysis,
Increased glucagon and decreased insulin secretion

56
Q

what are eicosanoids

A

a special class of hormones that act like hormones but are distinctive in their extreme metabolic lability.

Act primarily on cells close to those that secreted them

57
Q

what do prostaglandins do

A

they stimulate the smooth muscle, regulate steroid biosynthesis, inhibit and stimulate platelet aggregation and give sensitisation to pain

58
Q

where do hormones travel through

A

the blood

59
Q

what can hormones influence

A

they only influence cells that have specific target receptors for the particular hormone

60
Q

what are membrane receptors

A

they are embedded in the cell membrane and are often are G-protein coupled receptors with 7- transmembrane domains and respond to neurotransmitters, peptides and proteins.

61
Q

what are intracellular receptors

A

they are in the cytoplasm or the nucleus and respond to steroids and thyroid hormones

62
Q

what are the 2 hormone modes of action

A
  1. the use second messengers
  2. direct action on the activation of specific genes
63
Q

what is involved in the use of second messengers

A

cAMP is a second messenger that mediates a cell-specific response.
An enzyme called phosphodiesterase breaks down cAMP, stops the signal.

64
Q

what is involved in the use of second messengers

A

cAMP is a second messenger that mediates a cell-specific response.
An enzyme called phosphodiesterase breaks down cAMP, stops the signal.

65
Q

what is involved in the direct action on the activation of specific genes

A

The hormone crosses the plasma membrane and
binds to specific receptor proteins in the cytoplasm. The receptor then moves to the nucleus where it interacts with
specific DNA sequences called hormone
responsive elements (HREs).

66
Q

how can hormones be removed from the bloodstream after achieving the desired effect

A

it can be removed at target tissue, secreted to bile and excreted in the faeces, can enter the bloodstream and excreted by the kidneys. The kidneys can inactivate hormones and excrete amino acids directly into the urine

67
Q

can steroid hormones be eliminated

A

they lack the ability to completely degrade

Biochemistry (20 decks)

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