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BIOC1301 > Control Of Metabolism > Flashcards

Control Of Metabolism Flashcards

0
Q

Name the cells signalling pathways?

A

Single signal to single response.
Single signal to different responses.
Different signals to the single response.

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1
Q

How many types of cell signalling pathways are there?

A

3

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2
Q

Give the two major receptor types?

A

G-protein coupled and bound (use enzymes)

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3
Q

Explain how the two receptors ‘switches’ work?

A

G-protein coupled is switched on by GTP binding and off by hydrolysis.
Bound is switched on by phosphorylation and off by phosphate release.

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4
Q

What removes the phosphate in bound receptors and what adds the phosphate?

A

Phosphatases and kinase.

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5
Q

How are phosphatases and kinase regulated?

A

By phosphorylation (usually)

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6
Q

Describe the three ranges of cell signalling?

A

Autocrine- same cell
Paracrine- near by cell
Endocrine- long distance in remote tissue

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7
Q

Give three aspects of the endocrine system?

A

Ductless glands release hormones, hormones regulate all aspects of metabolism, a wide variety of messengers are used.

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8
Q

Give the 6 functions of hormones?

A

Regulation of: growth, maturation, body mass, reproduction, behaviour and substrate/mineral balance.

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9
Q

What to a) alpha b) beta and c) delta cells of the pancreas secrete?

A

A) glucagon
B) insulin
C) somatostatin

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10
Q

What are the 4 types of hormones?(give examples)

A

Peptide/protein (insulin or growth hormone)
Steroids (cortisol, testosterone or oestrogen)
Lipids (eicosanoids)
Amino acid derivatives (adrenalin, thyroxin)

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11
Q

Give a brief description of a steroid hormones structure? And what are they derived from?

A

Three 6-membered rings and one 5-membered ring joint.

Cholesterol

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12
Q

What are the 5 classes of steroid hormones?

A 
Glucocorticoids- cortisol.
Mineralcorticoids- aldosterone. 
Androgens- testosterone. 
Oestrogens- estradiol and oestrone. 
Progestogens/progestins- progesterone.
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13
Q

Where are steroid hormones made?

A

In the mitochondria and smooth ER.

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14
Q

When are steroid hormones released?

A

Immediately

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15
Q

Steroid hormones are …… and are stored in …….?

A

Hydrophobic, blood bound protein carriers

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16
Q

How do lipid soluble hormones act?

A

Diffuse through bilayer and into the cell, binds to receptors, turns on/off specific genes, new mRNA is formed and new proteins alters cell’s activity

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17
Q

What is the most common hormone type?

A

Peptide

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18
Q

Give two features of peptide hormones?

A

Water soluble and lipophobic

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19
Q

What hormones are usually hydrophilic and act like peptides?

A

Amines

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20
Q

Give two examples of hormones?

A

Adrenaline and noradrenaline- released in response to acute stress
Insulin and glucagon- regulate blood glucose levels

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21
Q

What is a) a pre hormone b) a pro-hormone and c) a peptide-hormone receptor complex?

A

A) large and inactive hormone
B) a post translational modified hormone
C) a signal transduction system.

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22
Q

Describe peptide hormone synthesis?

A

mRNA binds amino acids into a pre-hormone. The pre-hormone is directed into the ER lumen by amino acids. Enzymes chop of the sequence creating a pro-hormone. The pro-hormone is passed from the ER through the Golgi complex. Buds of pro hormone and enzymes bud off the Golgi and the enzymes chop the pro hormone. Hormone are released bio exocytosis

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23
Q

How are peptide hormones stored?

A

In secretory vesicles until the intracellular signal prompts release

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24
Q

Do peptide hormones require transport proteins?

A

No they circulate in the blood

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25
Q

Which steroid or peptide hormones can diffuse through the plasma membrane?

A

Peptide can’t. Steroids can.

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26
Q

What receptors do peptides hormones acces?

A

Cell surface receptors and initiate signal transduction cascades

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27
Q

Do peptide or steroid hormones have a quicker response time?

A

Peptide

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28
Q

What are the thee methods of control of hormone secretion?

A

Feedback- negative and positive (negative most common)
Neural control- neural stimuli evoke or suppress hormone secretion
Chronotropic control- rhythm directed hormone secretion

29
Q

What are bound receptors often?

A

Tyrosine-kinase receptors

30
Q

Give the flow of a tyrosine kinase receptor?

A

Autophosphorylation, then either:

  • ras, MAPK, effectors or
  • PIK3, PIDK, effectors
31
Q

Give the flow of a g-protein coupled receptor?

A

Either cAMP, PKA, effector.
Or DAG, PKC, effector
Or IP3, Ca2+, effector

32
Q

What does the phosphorylated tyrosine bind?

A

SH2 domain

33
Q

What does the SH2 domain do?

A

Couples tyrosine phosphorylation to protein binding

34
Q

What does the SH3 domain often do?

A

Binds down stream proteins via a pro-rich sequence

35
Q

Describe g-protein coupled receptors?

A

7-transmembrane helices, ligand binds in the middle. 3 alpha subunits anchored to embrace via fatty acids.

36
Q

What are the second messengers in g-protein coupled receptors?

A

Ca2+ and inositol-1,4,5-triphosphate (PI3)

37
Q

Give an example for a hormone that uses a) tyrosine-kinase pathway, b) a g-protein cAMP/PKA and c) a g-protein IP3/Ca2+

A

A) insulin
B) glucagon and adrenaline at ß-adrenergic receptors
C) adrenaline at a-adrenergic receptors

38
Q

What does high blood glucose cause?

A

ß-cells to release insulin

39
Q

What does low blood glucose trigger?

A

Alpha-cells to release glucagon

40
Q

What does adrenaline do?

A

Stimulates glucagon release and inhibits insulin release

41
Q

What does insulin do?

A

Facilitates glucose entry into cells, stimulates glucogenesis, inhibits gluconeogenesis and glycogenolysis

42
Q

What does insulin release cause?

A

A fall in release of free fatty acids and glucose, glucose use and uptake rises, blood glucose levels fall, excess sugars are stored as glycogen or fat

43
Q

Why can fatty acids not be used as brain fuel?

A

As they cannot be oxidised fast enough

44
Q

What adrenaline receptors do a) muscle cells and b) liver cells express?

A

A) ß-adrenergic

B) both alpha and beta

45
Q

What does the activation by glucagon or adrenalin of protein kinase A cause?

A

Gluconeogenesis and glycogen breakdown

46
Q

In absorptive state what does nutrients supplied to the gut do?

A

Stimulates insulin to cause glucose use and storage

47
Q

In post-absorptive state what does the lack of nutrients do?

A

Causes glucagon to maintain glucose levels by mobilising stores and limiting usage

48
Q

What regulates fuel use?

A

AMP kinase

49
Q

After 48 hours of starvation what happens?

A

Gluconeogenesis using muscle mass and fuel, liver converts acetyl-CoA to ketone bodies

50
Q

What to peptides studies are involves in weight gain?

A

Leptin and adiponectin

51
Q

Describe Leptin?

A

A satiety factor of 146 residues, a peptide hormone produced by adipocytes. It activates nerves that reduce the expression of neuropeptide y- tells the body to eat less

52
Q

When and where is adiponectin released?

A

When fat stores are full from adipocytes

53
Q

What is resisten?

A

A peptide releases by adipocytes to block insulins activity

54
Q

What does adiponectin do?

A

Promotes glucose disposal, works with insulin, up regulates AMP kinase

55
Q

At what levels can metabolic regulation occur?

A

Genetic, transcriptional, translational, protein or by ligands which proteins directly.

56
Q

Describe myoglobin?

A

A monomeric, all helical protein with an iron ion which is coordinated by N2. Contains a cofactors haem group.

57
Q

Is the binding of oxygen to haem reversible?

A

YES

58
Q

What does the iron ion have?

A

Two oxidation states 3 and 2

59
Q

What is YO2?

A

The fractional saturation (equals one when saturated)

60
Q

What is PO2?

A

The oxygen concentration partial pressure in torr

61
Q

Why is there a lower partial pressure in venous compared to arterial?

A

To ensure the brain is supplied with oxygen

62
Q

What are the similarities and differences of Hb and Mb?

A

Both similar tertiary structure and 18% identical amino acid residues. Mb is a monomer and Hb is a tetramer of 2 alpha and 2 beta

63
Q

Does Hb or Mb find it harder to bind oxygen at low pressure?

A

Hb

64
Q

What does oxygen binding in Hb trigger?

A

Conformational change of all four subunits

65
Q

What is the lever principle?

A

In Hb. No oxygen his is in direct contact with iron ion. When oxygen binds electrons go form low to high spin and the iron drives I to the porphyrin rings causing it to be flat. Amplified movement due to alpha helices on a lever. Interfaces between subunits are effected.

66
Q

What is the differences between the hill plot for Mb and Hb?

A

Mb is a straight line and Hb is a asymptote

67
Q

What are examples of control of catalytic activity?

A

Enzymes availability, allosteric activation/ inhibition by small molecules, allosteric activation/ inhibition by phosphorylation

68
Q

What is the fastest type of control?

A

Inhibition by small molecules

69
Q

Why might an organism alter site metabolism?

A

To produce ATP form FA when glucose is unavailable.

To make FA when glucose is plentiful.

To use gluconeogenesis to make glucose for the brain.

BIOC1301 (6 decks)

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