Nitrogen 2 Flashcards

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1
Q

What is the fate of nitrogen in aquatic vertebrates?

A

-Ammonia released to environment via passive diffusion from epithelial cells or active transport via gills

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2
Q

What is the fate of nitrogen in terrestrial vertebrates and sharks?

A

-Nitrogen excreted in the form of urea as urea is less toxic than ammonia and is highly soluble

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3
Q

What is the fate of nitrogen in birds/reptiles?

A
  • Excrete nitrogen as uric acid.

- Excretion as paste as uric acid is insoluble which allows for conservation of water

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4
Q

What do humans and apes excrete nitrogen as?

A
  • Urea from amino acids

- Uric acid from purines

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5
Q

In what form is ammonia safely transported in the bloodstream?

A

Glutamine

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6
Q

Where is excess glutamine processed?

A
  • Intestines
  • Kidneys
  • Liver
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7
Q

What do vigourously working muscles rely on for energy?

A

Anaerobic process of glycolysis

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8
Q

What does glycolysis yield?

A

Pyruvate which cannot be metabolised anaerobically and often builds up as lactic acid

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9
Q

How can pyruvate be converted to alanine?

A

Glutamate can donate ammonia to pyruvate to make alanine for transport to the liver

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10
Q

What is the glucose-alanine cycle?

A
  • Proteins broken down when exercising
  • Transported to liver as alanine/glutamine
  • Carbon skeleton toe pyruvate
  • Nitrogen is excreted as ammonia and converted to urea by the urea cycle
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11
Q

Why does glutamate have to be changed to alanine/glutamine to be transported to the liver?

A
  • Glutamate has a negative charge
  • Alanine/glutamine have NO charge
  • Charged molecules don’t pass through membranes easily hence converted to uncharged molecule to allow for easy transport
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12
Q

What happens to excess glutamate?

A

It is metabolised in the mitochondria of hepatocytes

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13
Q

What is the glutamate dehydrogenase reaction?

A

Two-electron oxidation of glutamate followed by hydrolysis

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14
Q

What is the net process of the glutamate dehydrogenase reaction?

A

Oxidative deamination of glutamate

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15
Q

Where does the glutamate dehydrogenase reaction occur?

A

In mitochondrial matrix of mammals

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16
Q

What can used as the electron acceptor in the glutamate dehydrogenase reaction?

A

NAD or NADP

17
Q

How is ammonia re-captured?

A

Via the synthesis of carbamoyl phosphate

18
Q

What is the first nitrogen- acquiring reaction?

A

Recapturing of ammonia

19
Q

What is the second nitrogen acquiring reaction?

A

Entry of aspartate into the urea cycle

20
Q

What happens to the nitrogen from carbomoyl phosphate?

A

It enters the urea cycle

21
Q

What happens to carbon atoms of degraded amino acids?

A

They emerge as major metabolic intermediates

22
Q

What happens to the carbon skeletons after amino groups are removed?

A

Either converted to glucose or oxidised as part of the citric acid cycle

23
Q

What are the 6 intermediate compounds?

A
  • Acetyl-CoA
  • Pyruvate
  • a-ketoglutarate
  • Succinyl-CoA
  • Fumarate
  • Oxaloacetate
24
Q

What is the primary role of carbs and fat?

A

To provide energy

25
Q

What is the primary role of amino acids?

A

Building blocks for proteins

26
Q

What are the 8 essential amino acids?

A
  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenlyalanine
  • Threonine
  • Tryptophan
  • Valine
27
Q

Glucogenic

A

Amino acids which feed in to gluconeogenesis and go on to produce glucose or glycogen in the liver

28
Q

Ketogenic

A

Amino acids which feed in to acetoacetate or acetyl CoA but cannot result in gluconeogenesis

29
Q

What amino acids are both glucogenic and ketogenic?

A
  • Isoleucine
  • Tyrosine
  • Phenylalanine
30
Q

Why can ketogenic amino acids not result in gluconeogenesis?

A

Pyruvate dehydrogenase reaction is irreversible and no NET synthesis of oxaloacetate through citric acid cycle

31
Q

What are ketone bodies?

A
  • Small water soluble
  • Produced by liver
  • Used by brain in absence of glucose