Muscle proteins degradation and N Metabolism

Question 1

What are the mechanisms of muscle catabolism

Answer 1

• Ubiquitin-proteosome protein degrading system
• Autophagy via the lysosome
• Role for calcium activated proteases (calpains)

Question 2

What is it called when breakdown of muscle exceeds synthesis

Answer 2

Muscle atrophy

Question 3

When does cachexia occur

Answer 3

Late stages of cancer and HIV infection

Question 4

What happens in cachexia to increase muscle breakdown rate

Answer 4

• release of cytokines which cause increase in degradation

- Increase in enzymes involved in the ubiquitin-proteasome pathway

Question 5

What are amino acids broken down into

Answer 5

Ammonium ion, then urea

Question 6

How are amino acids converted to urea

Answer 6

Remove nitrogen groups from amino acids to form ammonium ion, then convert ammonium ion to urea

Question 7

How is ammonium ion converted to urea

Answer 7

urea cycle

Question 8

How many amino acids are there

Answer 8

20

Question 9

Can mammals synthesis all 20 amino acids?

-How do they get them

Answer 9

no

-can get the essential ones from diet and the non essential ones can be synthesized or inter-convereted

Question 10

What can amino acids be converted into

Answer 10

• ammonium ion
• Carbon skeleton to form pyruvate, alphaketogluterate, cuccinyl coa, fumarate oxaloacetate
• purines, creatine, porphyrins, pyrimidines

Question 11

What is nitrogen balance

Answer 11

Difference between nitrogen intake in the diet (protein) and nitrogen excreted (urea)

Question 12

Where are amino acids catabolised to urea

Answer 12

Liver

Question 13

How is nitrogen transported from the muscle to the liver

Answer 13

Amino acids converted to Alanine and Glutamine in muscle/other tissues which can be transported to the liver to form ammonium ion, then urea

Question 14

How is NH4+ formed

Answer 14

Transamination

Oxidative deamination

Question 15

What happens in transamination

Answer 15

alpha ketogluterate is reacted with an alpha amino acid using an aminotransferase as an enzyme to form glutamate an an alpha kept acid

Question 16

give an example of a transamination reaction

Answer 16

aspartate+alphaketoglutarate—– (aspartate aminotransferase)— oxaloacetat + glutamate

Question 17

what happens after glutamate is formed using transamination

Answer 17

Oxidative deamination happens to glutamate to form ammonium ion

Question 18

What happens in oxidative deamination of glutamate

Answer 18

Add NAD+ and h2o to glutamate to form ammonium ion, NADH and alpha ketoglutarate

Question 19

What is the enzyme used in oxidative deamination of glutamate

Answer 19

Glutamate dehydrogenase

Question 20

How Is the ammonium ion turned into urea (first step) and where does it take place

Answer 20

Urea cycle

-Co2+ion makes carbonyl phosphate in the mitochondrial matrix

Question 21

Second stage of urea cycle

Third stage of urea cycle

Answer 21

aspartate is added to the compound formed (adds on an amine group)
-water is added to form urea

Question 22

What are the two types of amino acids

Answer 22

GLucogenic

Ketogenic

Question 23

What are glycogenic amino acids

Answer 23

Carbon skeletons increase the concentration of glucose (TCA cycle, gluconeogenesis)

Question 24

What are ketogenic amino acids

Answer 24

Carbon skeletons increase the concentration of Ketone bodies

Question 25

What are the ketogenic amino acids

Answer 25

Leu | Lys

Question 26

What are both ketogenic and glucogenic amino acids

Answer 26

``` Iso Trp The Tyr Thr (all the remaining ones are glucogenic) ```