Nitrogen

Question 1

What is the process in which nitrogen is converted to Ammonium?

Answer 1

Fixation

Question 2

What is nitrification?

Answer 2

NH4+ to nitrite and nitrate

We can get our Nitrogen from nitrate/nitrate

Question 3

What amino acid is central to nitrogen entering our body?

Answer 3

Glutamate

Question 4

What process is central to us conserving the nitrogen in our bodies?

Answer 4

Transamination

• transferring amino acids between molecules

Question 5

Give a general equation for transamination.

Answer 5

Amino acid 1 + keto acid 2 —-> Keto acid 1 + amino acid 2

Question 6

What is formed when glutamate undergoes transamination with a keto acid?

Answer 6

Alpha-Ketoglutarate

Question 7

Transamination reactions are readily reversible.

Why is this useful, in terms of how our body processes amino acids.

Answer 7

Can take part in both synthesis and degradation of amino acids

Question 8

Pyridoxal phosphate cofactor is needed by what type of enzyme?

Answer 8

Aminotransferases

transamination enzyme

Question 9

Pyridoxal phosphate cofactor (PLP) is derived from what essential vitamin?

Answer 9

B6

Question 10

Amino acids undergo oxidative catabolism under 3 conditions.

What are they?

Answer 10

Leftover amino acids from normal protein turnover

Excess from diet

Stored proteins are broken down when carbohydrates are in short supply

Question 11

What is pepsin and where does it function?

Answer 11

Enzyme - hydrolyses protein chains

Stomach

Question 12

Trypsin and chymotrypsin cut proteins and larger peptides into smaller peptides, but where do they do this?

Answer 12

Small intestine

Question 13

What enzymes hydrolyse peptides into amino acids, and where do they do this?

Answer 13

Aminopeptidase
Carboxypeptidases A & B

Small intestine

Question 14

True or false

Peptides/proteins must be degraded to amino acids before they can cross through the epithelial cells and into the blood.

Answer 14

False

Amino acids, dipeptides and tripeptides can cross into the epithelial cells

But only single amino acids can go into the blood

Question 15

What is ubiquitin used for?

Answer 15

Marks proteins that need to be degraded

Question 16

Why are excess proteins/amino acids degraded and not stored like fats/sugars?

Answer 16

No storage for excess protein

Question 17

How do humans excrete nitrogen?

Answer 17

Urea + uric acid

Question 18

Ammonia is kinda toxic n stuff

How is it safely transported in the blood?

Answer 18

As glutamine or alanine

Question 19

Where is excess glutamine processed?

3

Answer 19

Intestines
Kidneys
Liver

Question 20

Ammonia + pyruvate = ?

Answer 20

Alanine

Question 21

Muscles exercising vigorously work anaerobically.

This would cause a problem in the muscles if it was not for glutamate. What is the problem, and how does glutamate solve it?

Answer 21

Anaerobic ∴ glycolysis

∴ pyruvate produced which cannot be broken down anaerobically

∴ lactate would build up

glutamate can donate ammonia, to make alanine from the pyruvate

alanine transported to liver ∴ no lactate build up

Question 22

Proteins can be broken down in exercising muscles if needed.

What cycle is central to protein break down?

Answer 22

Glucose - alanine cycle

Question 23

In the glucose - alanine cycle, why is glutamate converted to glutamine/alanine, only to be converted back to glutamate later on?

Answer 23

Glutamate is negatively charged

∴ can’t be transported to the liver

Question 24

What happens to excess glutamate?

Answer 24

Metabolised in mitochondria of hepatocytes

Question 25

When excess glutamate is metabolised, what happens to ammonia/nitrogen?

Answer 25

Re-captured via synthesis of carbamoyl phosphate

Carbamoyl phosphate then goes into the urea cycle

Question 26

Through processes such as the glucose - alanine cycle, carbon skeletons are produced from amino acids.

How are these carbon skeletons used?

Answer 26

Converted to glucose

Oxidised in CAC

Converted to ketones/fats

Question 27

Why are amino acids useful in terms of the citric acid cycle?

Answer 27

Enter as intermediates

Carbon skeletons

Question 28

Describe what the terms glucogenic and ketogenic mean.

Answer 28

Some amino acids ‘feed’ into gluconeogenesis (glucogenic) and some ‘feed’ into the acetyl CoA (ketogenic)

Some amino acids are both glucogenic and ketogenic

Question 29

Describe the fates of ketogenic amino acids.

Answer 29

CAC

Ketone bodies

Question 30

What nitrogen containing molecule is used in the second nitrogen acquiring reaction of the urea cycle?

Answer 30

Aspartate

Question 31

What are the possible fates of carbon skeletons produced from amino acid degradation?

Answer 31

Citric acid cycle - catabolism

Gluconeogenesis

Ketogenesis

Question 32

What are the possible fates of ammonia produced by amino acid degradation?

Answer 32

Biosynthesis

Excretion via Urea cycle

Question 33

Why are molecules like glutamate and aspartate not suitable for tranpsort in the blood?

Answer 33

They are charged

Glutamine and alanine are uncharged so are much more suitable