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MD2002 > Using And Replenishing Metabolic Stores > Flashcards

Using And Replenishing Metabolic Stores Flashcards

1
Q

What is carbohydrate stored as in the body? And in which cells of the body?

A

Glycogen

In liver and muscle cells

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2
Q

What is the structure of glycogen?

A

Glycogen is a branched polymer of 3 and 6-7 units using a-1,4 linkages for length of 6-7 units and a-1,6 linkages for branching of 3 glucose units

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3
Q

What is glycogen broken down into?

A

90% broken down with phosphate into glucose-6-phosphate

10% broken down using H20 into glucose

(Conversion from glucose to glucose-6-phosphate uses 1ATP)

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4
Q

Why is glycogen broken down into glucose-6-phosphate rather than glucose?

A

G6P can’t pass through the cell membrane easily so is only for use in that particular cell

Direct conversation of glycogen to G6P saves the cell one ATP molecule per glucose

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5
Q

How many ATP gained when glycogen converted to G6P directly?

A

31-33 ATP (5 direct ATP)

Rather than 30-32 ATP (4 direct ATP)

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6
Q

What is the limited supply time of stored glucose?

A

3-5 hours

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7
Q

What is an alternative to glucose that weight for weight yields more energy?

How much more energy does it yield?

A

Lipids is an alternative
Weight for weight triglycerides produce 6x as much more energy

There are 135,000 kcal of energy stored as triglycerides in adipose tissue whereas there is only 1200 kcal of energy stored as glucose or glycogen in the muscle.

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8
Q

What is a triglyceride made up of

A

A glycerol unit and 3 fatty acid chains

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9
Q

What is the difference between triglycerides and omega 3

A

Triglycerides have double bond oxygens where as omega 3 has double bond between carbons in centre

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10
Q

What is fat stored as

A

Triglycerides which are esters of glycerol and fatty acid chains

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11
Q

How are triglycerides stored in body broken down?

A

Lipase breaks down triglycerides into glycerol and 3 fatty acids

Glycerol changed to Peruvate to acetyl coA and enters citric acid cycle

3 fatty acids are beta-oxidised where 2C Acyls are broken off and with addition of Coenzyme A are turned into acetyl coA and used in citric acid cycle

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12
Q

How does breakdown of fats produce atp?

A

Doesn’t directly

Hydrogens and electrons removed during fatty acid oxidation are used to generate atp and addition of acetyl coA from fatty acids and glycerol into Krebs

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13
Q

Where are fatty acids and glycerol metabolised

A

In liver

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14
Q

During starvation, what happens to citric acid cycle and how is it rectified by the body?

A

Oxaloacetate (binds with acetyl coA in Krebs) is depleted as liver uses it to make pyruvate to make glucose via gluconeogenesis

Acetyl coA builds up and is eventually changed into ketone bodies which is an alternative fuel for the brain

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15
Q

Examples of ketone bodies

A

Acetoacetate
3-hydroxybutrate
Acetone

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16
Q

Breakdown of proteins during metabolism?

A

amino acids formed by breakdown of protein can be

Incorporated into new proteins
Those not needed can’t be stored so used as metabolic fuel - can be

Deaminated (yields NH4+) a keto acid which can be used in citric acid or Krebs - only glutamic acid
Trans animated - can’t release NH4+ so passes amino group to keto acid such as alpha-ketoglutamate Keto acid then fed into Krebs as pyruvate, acetyl coA , a-ketoglutarate or oxaloacetate

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17
Q

What’s anabolism

A

Synthesis of complex molecules

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18
Q

What’s gluconeogenesis

A

Formation of glucose from non-carbohydrate sources

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19
Q

How does gluconeogenesis occur?

A

Pyruvate > g6p > glucose

Amino acids and lactate feed into pyruvate

Glycerol and AAs feed into pathway also

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20
Q

What is NH4+ and what is it converted to and where does it come from

A

Breakdown of proteins
Ammonium
Discarded in urea

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21
Q

How does lipid synthesis occur

A

Glycerol made during glycolysis
2C acyl units from Acetyl coA linked together by fatty acid synthase to form fatty acids

One glycerol plus 3 FA makes a triglyceride

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22
Q

Carbohydrates broken down into what and by which metabolic pathway

A

Glucose via glycolysis

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23
Q

Fats are broken down into what and by which metabolic pathway

A

Fatty acids and glycerol by beta-oxidation

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24
Q

Proteins broken down into what and by which metabolic pathway

A

Amino acids via transanimation

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25
Q

What happens to digested protein

A

Broken down to Amino acids which are transamination where amino acid is passed to keto acids
Can also be incorporated into new proteins
Or can be stored in muscle

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26
Q

Where is most protein stored and how much is stored there

A

In muscle 24,000kcal

27
Q

Transamination example during muscle breakdown

A

Amino acid pass amino group to pyruvate via transamination to form alanine which is transferred in the blood to the liver converted back to pyruvate and used to synthesis glucose so liver takes burden from muscle

28
Q

How much glucose does brain use

A

60%

29
Q

Why can’t brain use fatty acids as fuel

A

Can’t pass blood brain barrier

30
Q

What can fuel the skeletalmuscle

A

Glucose fatty acids and ketone bodies

31
Q

What does testing muscle use as fuel

A

Fatty acids

32
Q

What stores are used by skeletal muscle and the brain

A

The brain has no stores

The muscle stores glucose as glycogen (G6P)

33
Q

Rate of glycolysis and Krebs when muscle active? Lactic acid?

A

Rate of glycolysis outpaces rate of citric acid cycle so pyruvate is turned into lactate which is transferred to liver via blood where it can be converted back to glucose

34
Q

What is the function of adipocytes

A

Synthesis and store triglycerides

Release fatty acid and glycerol in times of need

35
Q

What does VLDL do?

A

Transports triglycerides proteins etc around the body

VLDL has high vol of triglyceride

36
Q

What ensures body / liver has access to nutrients absorbed by gut

A

Hepatic portal system

37
Q

What’s the role of the liver

A

Store and release glucose or make new glucose via glconeogenosus from constituents which aren’t from carbs

Synthesis fatty acids, esterifies and secrets into blood as VLDL

Fasting liver generates ketone bodies

38
Q

Where is glucagon from

A

Alpha cells

39
Q

Where is insulin from

A

Beta cells

As well as amylin

40
Q

Where is somatostatin from

A

D-cells

41
Q

What type of function is pancreas

A

Exocrine- to other tissues of the body via ducts etc

42
Q

What happens to the glucose (percentages)

A

30% absorbed via HPV
30% metabolised in liver
70% distributed to other tissues

43
Q

Fed state explained

A

Absorptive state
Shortly after meal when nutrients are available
Metabolism here is ANABOLIC

nutrient molecules used to provide energy stores of for growth and maintenance of cells and tissues and can provide energy for use immediately

44
Q

Fasted state explained

A

Postabsoprtive state
Body needs to draw upon reserves
Metabolism is CATABOLIC

Calls on stores and they become depleted

45
Q

How are metabolic pathways regulated?

A

Metabolic pathways are self regulated via the conc of substrates and products or via the rate of activity of enzymes (which can be affected by hormones such as insulin, glucoagon, adrenaline and noradrenaline)

46
Q

Insulin release explained

A

High conc of blood glucose and parasympathetic nervous system stimulate beta cells to release insulin.

This drives the fed state.

Stimulates the storage of fuels and anabolism to reduce levels of sugar in blood.

47
Q

What processes does insulin stimulate

A

Glycogen synthesis in liver and muscle
Formation of triglycerides in adipose tissue
Protein synthesis in muscle
Glycolysis and fatty acid synthesis in liver
Uptake of glucose to muscle and adipose

48
Q

Glucagon stimualtion explained

A

Low conc of blood glucose due to fasting state stimulates release of glucagon from alpha cells

Main target here is the liver.

49
Q

Glucagon stimulates which processes to occur

A

Release of glucagon G6P from glycogen
Gluconeogenesis but inhibits incorporation into glycogen
Breakdown of triglycerides

50
Q

What levels are glucagon and insulin in fed state and what does this do?

A

Glucagon is low and insulin is high in fed state

Causes synthesis of glycogen fat and protein
And glycolysis

51
Q

What levels are glucagon and insulin in fasted state and what does this do?

A

High glucagon low insulin

Causes glycogenolysis, gluconeogenesis and ketogenesis

52
Q

Amines (hormones) which regulate metabolism

A

Adrenaline and noradrenaline

53
Q

Where are adrenaline and noradrenaline secreted from m

A

Adrenal medulla and neurones of sympathetic nervous system when blood glucose drops

54
Q

What is the role of adrenaline and noradrenaline during metabolism

A

Similar to glucagon, they drive breakdown of glycogen and triglycerides BUT mainly on muscle rather than liver like glucagon

ALSO

increase glucagon secretion and inhibit insulin secretion

55
Q

Total available energy in the body

A

162000kcal approx

56
Q

How long do fuel stores last during starvation

A

1-3 months dependent upon level of exercise etc

57
Q

Range of blood glucose and normal

A

From 80mg/100ml to 120mg/100ml post meal

Normal is 80/100 which is 4-8mmol/litre

58
Q

Hypoglycaemia and hyperglycaemia ranges

A

<3 is hypoglycaemia and >11 is hyperglycaemia

59
Q

What happens durin the first days of starvation?

A

Glucose conc decreases
Proteins which yield glucose via gluconeogesis preserved
Muscle begins to use fatty acids as fuel
Liver uses fats, pyruvate, lactate and alanine from protein breakdown to make glucose for brain

60
Q

What happens during day 3 of starvation?

A

Increase in level of ketone bodies (formed in liver as consequence of breakdown of fatty acids and limits TCA )

Brain uses ketone bodies as fuel

Less glucose needed overall, less amjnoa cids needed for gluconeogenesis

61
Q

Fatty acids converted to ketone bodies by which process

A

Beta oxidation

62
Q

Type 1 vs type 2 diabetes

A

Type 1 is autoimmune where beta cells of pancreas rare damaged

10% of cases

Treated with insulin

Type 2 causes by lifestyle and genetics

90% of cases

Managed with exercise and weight loss

63
Q

What happens during diabetes

A

Blood glucose levels higher than normal which damages tissues, however, blood not taken up by insulin so body goes into fasting state.

Glycolysis is slow
Glucogenogenesis is stimulated from AAs via breakdown of protein muscle
Fatty acids make ketone bodies
Ketone bodies and glucose pass to blood

64
Q

Why do diabetics pee a lot

A

Transporters in kidney can’t remove all the glucose
It adds to osmotic strength of urine making it harder for kidney to reabsorb water
Ruins vol hence increases with glucose in

Severe- acidic ketone bodies in urine known as ketoacidosis

MD2002 (22 decks)

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