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Semester 2 Year 1 > Metabolic Stores > Flashcards

Metabolic Stores Flashcards

1
Q

How are carbohydrates stored in the body?

A

as glycogen mainly in liver and muscle

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2
Q

How much glycogen is stored in the body?

A

For about 3-5 hours of moderate exercise

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3
Q

What is glycogen?

A

A branched glucose polymer

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4
Q

When glycogen is broken down what is it converted into?

A

most is converted directly to glucose-6-P without consuming ATP

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5
Q

Why is converting glucose-6-P in the bloodstream for use in cells a shit idea?

A

Glucose-6-P cannot easily pass through the cell membrane

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6
Q

What happens when glucose is required in an area of the body that doesn’t have any?

A

Glucose is transported there and then phosphorylated after entering the cell, using ATP

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7
Q

After glycogen stores run out during extended periods of exercise/starvation what fuel does the body use?

A

Lipids

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8
Q

Why are lipids important?

A

weight-for weight, triglycerides (= triacylglycerols) can produce about six times as much energy as
glycogen

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9
Q

What is fat stored as?

A

Much is stored as triglycerides (=triacylglycerols)

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10
Q

What are triglycerides (=triacylglycerols)?

A

esters of glycerol and fatty acids

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11
Q

What’s an ester?

A

chemical compound derived from an acid (organic or inorganic) in which at least one –OH (hydroxyl) group is replaced by an –O–alkyl (alkoxy) group

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12
Q

What is a triglyceride?

A

a triacyl glycerol

esters in which three molecules of one or more different fatty acids are linked to the alcohol glycerol

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13
Q

How are esters named?

A

according to the fatty acid components; e.g., tristearin contains three molecules of stearic acid, and oleodistearin, one of oleic acid and two of stearic acid

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14
Q

What are fatty acids linked to to begin lipolysis?

A

Coenzyme A

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15
Q

What occurs to fatty acids that are linked to coenzyme A?

A

they are oxidized and 2-carbon fragments cleaved off (as acetyl-CoA)

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16
Q

How may the breakdown of fatty acids by coenzyme A generate ATP?

A

Although no ATP is generated directly by this process, hydrogen and electrons removed during fatty acid oxidation are passed along the respiratory chain, so indirectly producing ATP

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17
Q

What releases fatty acids and glycerol?

A

Adipose tissue

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18
Q

Where in the body are fatty acids and glycerol metabolised?

A

The liver

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19
Q

What does the breakdown of fatty acids lead to?

A

the formation of chemicals known as ketone bodies

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20
Q

What are the main ketone bodies in the body?

A

acetoacetate, 3-hydroxybutyrate

and acetone

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21
Q

Why are ketone bodies made?

A

Ketone bodies are made because acetyl-CoA formed in the breakdown of fatty acids cannot enter the citric acid cycle since oxaloacetate becomes depleted because the liver converts it to pyruvate to produce glucose (gluconeogenesis)

Acetyl-CoA, therefore, is converted to ketone bodies

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22
Q

What is a way to identify if there are a significant number ketone bodies present in a patient?

A

Ketone bodies smell fruity, so they

can often be smelled on the breath of people who have been fasting for some time

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23
Q

Under what circumstances on the metabolic level are ketone bodies produced?

A

Formed in the liver when Acetyl CoA production exceeds the needs of the citric acid cycle

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24
Q

Discuss proteins in the metabolism

A

Amino acids produced by the breakdown of dietary proteins can be incorporated into new proteins

However, amino acids not needed to make new proteins cannot be stored, so they are used as metabolic fuel

Some amino acids can be deaminated, yielding NH4 + a keto acid
that are intermediates of the glycolytic pathway or of the citric acid cycle

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25
Q

Why are excess amino acids used as fuel or broken down for use as intermediates?

A

They cannot be stored

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26
Q

Why are only some excess amino acids broken down for use as intermediates and others not?

A

Some amino acids cannot release their amino groups as NH4+

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27
Q

What occurs to excess amino acids that cannot release their amino groups as NH4+?

A

they have to pass their amino group to a keto acid (mainly
alpha-ketoglutarate) in the process known as transamination
(A new amino acid and a new ketogenic acid are formed, its literally only a change in the R groups functionally)

28
Q

What occurs to the ketogenic acid formed as a result of transamination? (and resulting amino acid)

A

The resulting keto acid can then be fed into glycolysis or the citric acid cycle (as pyruvate, acetyl-CoA, a-ketoglutarate or oxaloacetate), while the resulting amino acid can then be deaminated and used similarly

29
Q

What occurs to the NH4+ released when amino acids release their amino groups?

A

It is converted into urea

30
Q

Why is NH4+ converted into urea instead of just hanging about?

A

The NH4+ which is formed is very toxic, so the body rapidly converts it to urea, which is far less toxic

31
Q

What two reactions occur to convert amino acids to provide fuel molecules? (and another reaction to do with these)

A 
Transamination (AA + KA -> KA + AA)
Oxidative deamination (AA(glutamic acid) -> NH3 +KA)

Also I guess CO2 is combined with NH3 (ammonia) to produce urea

32
Q

What is anabolism?

A

Synthesis of more complex molecules

33
Q

What is gluconeogenesis?

A

Formation of glucose from non carbohydrate sources

34
Q

What is the difference between gluconeogenesis and just doing glycolysis backwards?

A

Some enzymes are different:

  1. Pyruvate carboxylase (mitochondria)
  2. Phosphoenol pyruvate carboxykinase (PEPCK) (mito + cyto)
  3. Glucose 6-phosphatase (G6-Pase) (endoplasmic reticulum)
35
Q

What are the enzymes present in gluconeogenesis?

A
  1. Pyruvate carboxylase (mitochondria)
  2. Phosphoenol pyruvate carboxykinase (PEPCK) (mito + cyto)
  3. Glucose 6-phosphatase (G6-Pase) (endoplasmic reticulum)
36
Q

What molecules found in cells can feed into the pathway of gluconeogenesis?

A

Glycerol (from triglycerides) and the

carbon backbone of amino acids

37
Q

Where does the bulk of gluconeogenesis occur?

A

The liver

38
Q

Give an example of an anabolic reaction

A

Lipid synthesis

39
Q

What is the process of lipid synthesis?

A

1 - Glycerol can be made from glucose through glycolysis

2 - Two-carbon acyl units from acetyl coenzyme A are linked together by fatty acid synthesise to form fatty acids

3 - One glycerol plus 3 fatty acids makes a triglyceride

40
Q

Where is fatty acid synthetase (essential for reaction of Acetyl CoA and acyl unit to form fatty acid) found in the cell?

A

In the cytoplasm

41
Q

Provide a brief summary of the strengths and weaknesses of fatty acids v glycerol

A

Although fats are efficient for storage, they are not used as effectively as fuel as carbohydrate

42
Q

What is an issue arising from the use of less efficient fatty acids for fuel?

A

energy production cannot be as high when we are using lipids as fuel rather than carbohydrate

43
Q

What do athletes do to get around the lacking efficiency of lipid fuel?

A

endurance athletes carbohydrate (carbo) load by eating foods like pasta before an event

44
Q

How are amino acids sourced in the body?

A

Some amino acids must be provided in the diet, while others can be made by transferring amino groups to keto acids

45
Q

How are amino acids incorporated into proteins that we eat?

A

the normal way (DNA, mRNA, tRNA and ribosomal RNA……………)

46
Q

What is the largest potential source of external protein by tissue type?

A

Muscle

47
Q

What fuel(s) does the brain use?

A

Normally glucose is the only fuel the brain can use

48
Q

How much glucose does the brain use?

A

Brain accounts for about 60% of all glucose used by the body (approx 120 g per day)

49
Q

Where does the brain get its fuel?

A

It cannot store glucose or glycogen, so needs a constant supply in the blood
In times of starvation it can use ketone bodies (mainly acetoacetate and 3-hydroxybutyrate) formed in other tissues

50
Q

Why can the brain not use fatty acids as fuel?

A

Because a special barrier (blood-brain barrier) that protects the brain from other potentially dangerous chemicals prevents fatty acids getting into brain tissue

51
Q

What fuel(s) do the skeletal muscle use?

A

Muscle can use glucose, fatty acids and ketone bodies

Resting muscle mainly uses fatty acids as fuel

52
Q

Where does the muscle get its fuel?

A

Muscle differs from brain in having large glycogen reserves (3⁄4 of body glycogen)
In muscle, glucose-6-P is formed from glycogen
-Like brain, muscle cannot convert this to glucose, so neither tissue can export glucose

53
Q

Which can export glucose to the body: the brain or the skeletal muscle?

A

neither

54
Q

What occurs to the metabolic process in the skeletal muscle during activity?

A

When muscle is active the rate of glycolysis far outpaces the citric acid cycle

Therefore, pyruvate must be converted to lactate

The lactate passes into the blood and to the liver, where it is converted back to glucose

55
Q

What occurs when muscle protein is being broken down?

A

many amino acids pass their amino group to pyruvate (transamination) to form alanine
Alanine enters the blood and in the liver can be converted to back to pyruvate, which is used to synthesize glucose
So, this shows that the liver takes some of the metabolic burden away from muscle

56
Q

What is fat (adipose) tissue made of?

A

Adipocytes, each of which has a fat droplet that occupies most of the cell

57
Q

What is the main function of the fat (adipose) tissue?

A

To synthesize and store triglycerides (=triacylglycerols) and release fatty acids and glycerol in times of need

58
Q

What determines the rate at which fatty acids are esterified?

A

Availability of glucose

59
Q

What may effect the activity of the lipase that hydrolyses triglycerides?

A

Hormones

60
Q

What cool vascular system ensures the liver has access to nutrients absorbed by the gut?

A

The hepatic portal system

61
Q

When fuel supplies are available what does the liver do?

A

Synthesizes fatty acids, esterifies them and then secretes them into the blood as very low density lipoprotein (VLDL)

62
Q

In fasting what does the liver do?

A

Generates ketone bodies for use in other tissues

63
Q

What functions does the liver have relevant to the fuelling of other systems?

A

The liver can readily store and release glucose and can make new glucose (gluconeogenesis) from lactate, alanine and glycerol in the diet or released by other tissues

64
Q

Where is pyruvate carboxylase found in the cell?

A

In the mitochondria

65
Q

Where is phosphoenol pyruvate carboxykinase (PEPCK) found in the cell?

A

In the mitochondria and cytoplasm

66
Q

Where is glucose 6-phosphatase (G6-Pase) found in the cell?

A

In the endoplasmic reticulum

Semester 2 Year 1 (82 decks)

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