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Endocrine physiology > hormone regulation of metabolism > Flashcards

hormone regulation of metabolism Flashcards

1
Q

what are the different energy reserves in humans & where are they located?

A
  • fat (adipose tissue)
  • protein (muscle)
  • glycogen (muscle)
  • glycogen (liver)
  • glucose (ECF)
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2
Q

in what organs or tissues is glycogen stored?

A

the liver and muscle

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3
Q

can glycogen be rapidly metabolised?

A

yes - it can be ‘instant’ glucose

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4
Q

what kind of energy reserve are fatty acids?

A

they are medium to long term energy reserves

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5
Q

what occurs as a result of endogenous fatty acid synthesis exceeds the energy requirements?

A

the stores expand over time and lead to obesity

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6
Q

Describe glucose as a metabolic fuel?

A
  • excellent fuel
  • yields a significant amount of energy upon oxidation
  • can be utilised by virtually all cells
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7
Q

How does the brain utilise glucose?

A
  • the brain consumes 25% of all the glucose that is oxidised in the body
  • glycogen is not stored in the neurons so it requires a constant supply of glucose
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8
Q

what are the main sources of glucose?

A
  • through diet
  • glycogen reserves (180-200g) - 1 day supply
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9
Q

what are the 4 major pathways of glucose metabolism?

A
  1. glycogenesis
  2. glycogenolysis
  3. gluconeogenesis
  4. glycolysis
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10
Q

what is glycogenesis?

A

making glycogen from glucose for storage

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11
Q

what is glycogenolysis?

A

breaking down glycogen to use for energy

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12
Q

what is gluconeogenesis?

A

making new glucose from non carbohydrate sources eg fatty acids

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13
Q

what is glycolysis?

A

breaking down glucose for energy

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14
Q

is glycogen a short term or long term energy reserve?

A
  • short term energy reserve
  • plays essential role in maintaining blood glucose between meals
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15
Q

what is the main enzyme that activates glycogenesis?

A

glycogen synthase

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16
Q

what is the main enzyme that controls glycogenolysis?

A

glycogen phosphatase

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17
Q

Describe the** opposing effects that phosphorlyation by protein kinases** has on glycogen synthase and glycogen phosphotase

A
  • **phosphorylation of GS inactivates it **/ dephosphorylation activates it
  • phosphorylation of GP activates it/ dephosphorylation inactivates it
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18
Q

What hormone stimulates glycogenesis?

A

insulin

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19
Q

what does insulin signal?

A

energy abundance - ie too much energy

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20
Q

how does insulin stimulate glycogenesis?

A
  • activates protein phosphatase
  • this phosphatase** activates glycogen synthase** and dosent activate glycogen phosphatase
  • **decreases the activity of phosphorylase kinase **
  • therefore the** net effect of insulin stimulation **causes an increase in glycogen synthesis and a decrease in glycogenolysis
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21
Q

what 2 hormones stimulate glycogenolysis?

A
  1. glucagon
  2. epinephrine
22
Q

what does glucagon signal to the body?

A

glucagon signals that glucose is running low

23
Q

what does epinephrine signal to the body about glucose?

A

it signals that glucose is** urgently needed**

24
Q

how does glucagon and epinephrine stimulate glycogenolysis?

A
  • activates glycogen phosphatase - by activating phosphorylase kinase
    * inhibits glycogen synthase - mediated by protein kinase A
  • therefore the net effect is an** increase in glycogenolysis **and a decrease in glycogenesis
  • opposite effect to insulin
25
Q

when is gluconeogenesis most active?

A
  • it is most active in fasting state
  • during prolonged exercise
  • conditions of carbohydrate starvation
26
Q

where does gluconeogenesis mainly occur?

A
  • organs that rely least on glucose for energy - the liver
27
Q

what are the raw ingredients that the liver uses to synthesise glucose and what is an example?

A
  • supplied by the muscle and other tissues
  • eg RBC’s
28
Q

what is the starting molecule of gluconeogenesis?

A

pyruvate

29
Q

what is a** critical enzyme that allows glucose to leave the cell and that is not found in muscle**?

A
  • glucose 6 phosphatase
30
Q

During fasting what 2 hormones are prevalent and what actions do they have?

A
  • glucagon and cortisol
  • they induce gluconeogenic enzymes and inhibit glycolytic enzymes - ie they favour gluconeogenesis
31
Q

during the feeding stage, what hormone is prevalent and what actions does it have?

A

insulin
* insulin induces glycolytic enzymes
* inhibits gluconeogenic enzymes
* favours glycolysis

32
Q

what are fatty acids?

A

they are a long hydrocarbon chains (C10-24) with a terminal COO- group

33
Q

how are fatty acids mainly stored in the body?

A

triglycerides

34
Q

where does Beta oxidation ( FA metabolism) occur?

A

occurs in mitochondria

35
Q

what occurs in beta oxidation?

A
  • FA chains broken down to a 2C compound - acetyl CoA
  • when glucose and FA metabolism are balanced, acetyl Co A is oxidised in the TCA cycle
  • if acetyl CoA is in excess, the surplus is converted to ketone bodies
36
Q

what is an important enzyme involved in fatty acid synthesis?

A

acetyl CoA carboxylase

37
Q

What 2 hormones regulate ACC by controlling the activity of protein kinases and phosphatases?

A
  • glucagon
  • insulin
38
Q

how does glucagon influence ACC?

A
  • glucagon activates protein kinases which phosphorlyate and therefore inhibit acetyl CoA carboxylase
  • glucagon signals that energy is low and lipid metabolism should switch from FA synthesis to oxidation
39
Q

How does insulin influence ACC?

A
  • insulin activates** protein phosphatase** which dephosphorylates (ie activates) ACC
  • insulin** signals energy abundance** and lipid metabolism **should switch from FA oxidation to synthesis **
40
Q

what hormones stimulate lipolysis & why?

A
  • epinephrine - energy needed immediately
  • glucagon - no more glucose, switch to fatty acids as energy source
41
Q

how do epinephrine and glucagon stimulate lipolysis?

A

they activate** hormone sensitive lipase **which hydrolyses TG’s to FA’s and glycerol

42
Q

what hormone inhibits hormone sensitive lipase and what does it favour?

A

insulin
* favours triglyceride synthesis

43
Q

what is the anorexigenic pathway in the brain?

A

a pathway which leads to a feeling of being full - and signals that you should stop eating

44
Q

what is the orexigenic pathway in the brain?

A

a pathway in the brain that stimulates appetite

45
Q

what hormone stimulates the anorexigenic pathway? (ie the pathway that leads to the feeling of fullness)

A

insulin

46
Q

what** hormone produced in the stomach **stimulates the orexigenic pathway (ie favours appetite)?

A

GHRELIN

47
Q

what is GLP-1 and what is it’s** function**?

A

glucagon like peptide 1
* function : causes the glucose induced secretion of insulin from the pancreatic beta cells

48
Q

what pathway does GLP-1 favour?

A

the anorexigenic pathway

49
Q

what is leptin?

A

hormone predominantly made by** adipose cells** and enterocytes in the small intestine that helps to** regulate energy balance** by inhibiting hunger, which in turn diminishes fat storage in adipocytes

50
Q

what pathway does leptin favour?

A

the anorexigenic pathway

51
Q

what is the 1st metabolic priority in prolonged starvation?

A
  • to provide sufficient glucose to brain and other tissues that are dependent on it
52
Q

what is the 2nd metabolic priority in prolonged starvation?

A
  • a shift from the utilization of glucose to utilization of fatty acids/ ketone bodies & preserve protein

Endocrine physiology (19 decks)

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