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Advanced Metabolism > Week 4 > Flashcards

Week 4 Flashcards

1
Q

What two amino acids are both glucogenic and ketogenic?

A
  • threonine

- tyrosine

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2
Q

Is there a net loss of nitrogen?

A

There is not net loss of nitrogen, synthesis = degradation

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3
Q

What are the 3 different metabolic circumstances in which amino acid catabolism occurs?

A
  • normal synthesis and degradation of cellular proteins. those not recycles are oxidised to yield ATP
  • Dietary protein surplus is catabolised and oxidised to yield ATP
  • during starvation or in uncontrolled diabetes mellitus, carbohydrates are either unavailable or not properly used, cellular proteins will be oxidised to yield ATP
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4
Q

What proportion of dietary protein is endogenous?

A

half

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5
Q

What types of amino acids are sent to the muscles?

A

Branched-chain amino acids

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6
Q

What is the summary of dietary protein breakdown?

A
  • lots of proteases, beginning in the stomach followed by the absorption of free amino acids and transport to the liver (except branched chain AA that go to the muscle)
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7
Q

What do trypsin and chymotrypsin do in the small intestine?

A

They cut proteins and larger peptides into smaller peptides.

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8
Q

What do aminopeptidases and carboxypeptidases A and B do in the small intestine?

A

Degrade peptides into amino acids

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9
Q

Cleavage of dietary protein by proteases secreted from the pancreas starts by?

A

Enteropeptidase starts the activation by converting trypsinogen to trypsin

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10
Q

The release and activation of pancreatic zymogens is mediated by which hormones?

A

Cholecystokinin and secretin

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11
Q

How do neutral amino acids transport?

A

Across a concentration gradient - glucose transporters (GLUT)

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12
Q

How do basic amino acids transport?

A

Charge dependent transporters - cotransport

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13
Q

How do acidic amino acids transport?

A

Transported with sodium ions

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14
Q

What is Hartnup disease? (autosomal recessive metabolic disorder)

  • neurologic
  • diarrhoea
  • red scaly skin rash when skin is exposed to sunlight
A

This is where a person cannot absorb amino acids properly from the intestine and cannot reabsorb them properly from tubules in teh kidneys, particularly tryptophan

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15
Q

How is Hartnup diease tested?

A

A urine test that checks for high levels of neutral amino acids
SLC6A19 gene

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16
Q

What does the premature activation of trypsinogen lead to?

A

Results in the activation of trypsin and many other enzymes because trypsin is an activator for many proenzymes

17
Q

What can the premature activation of trypsinogen lead to?

A
  • pancreatic autodigestion

- detected by increased pancreatic amylase in serum

18
Q

What are some of the causes of trypsin and pancreatic autodigestion?

A
  • mutations within trypsinogen
  • mutations within normal trypsin inhibitor
  • clogged ducts, by gall stones.
19
Q

What two amino acids make up gluten?

A

Gliadin and glutenin

20
Q

What are some of the symptoms of cystinuria?

A
  • kidney stones that can block the urinary tract from unabsorbed cysteine
21
Q

How are most non-selective proteins degraded?

A

In the lysosomes, entry by macroautophagy that is the enclosure of a volume of the cytoplasm by an intracellular membrane

22
Q

Where are all proteins synthesised?

A

In the cytosol. They are synthesised on ribosomes attached to the ER

23
Q

Where is mRNA synthesised?

A

In the nucelus

24
Q

What are the 2 main pathways in which eukaryotic cellular proteins are degraded?

A
  1. ATP independent process - degrades proteins inside of lysosomes.
  2. ATP dependent pathway - targets specific proteins for degradation in proteosomes if they are attached to another protein, ubiquitin
25
Q

What are the 4 digestive processes mediated by the lysosome?

A
  • endocytosis
  • pinocytosis
  • phagocytosis
  • autophagy
26
Q

How are short lived regulatory proteins degraded? and where

A

Degraded in the cytosol by the ubiquitin system

27
Q

What is the ubiquitin-mediated degradation of amino acids?

A

It is the selective labelling of targetting proteins by ubiquitin molecules. Ubiquitin is a 76AA and binds covalently to available lysine residues on target proteins which are then recognised by proteases

28
Q

Describe ubiquitination?

A

Once one ubiquitin molecule joins, multiple join yielding a poly-ubiquitin chain
Some are modified, called multi-ubiquitination

29
Q

How many ubiquitin molecules must be attached to the lysine residues on the condemned protein in order for it to be recognised by the 26S?

A

4 molecules

30
Q

What is the role of E1 subunit in ubiquitin-protein degradation?

A

Activation protein by cysteine on E1

31
Q

What is the role of E2 in ubiquitin degradation?

A

Conjugation protein

32
Q

What is the role of E3 in Ubiquitin degradation?

A

Ubiquitin ligase - substrate recognition

33
Q

What is another example of proteolytic systems in cells?

A

Apoptosis

34
Q

What is the role of apoptosis?

A
  • eliminates unwanted or non-functional cells
  • involves activation of caspases
  • caspases have a cysteine at their active site and cleave target proteins at specific aspartic acids
35
Q

Is there advantage in the inhibition of protein degradation?

A
  • inhibition of proteosome in mammalian cells - induces apoptosis and sensitises cells to pro-apoptotic agents
  • chemotherapy
36
Q

What is an example of a proteosomal inhibitor used in chemotherapy?

A

Velcade, which is effective against multiple myeloma

37
Q

What is Liddle Syndrome?

A

A mutation in the subunit of the renal epithelial NA+ channel interferes with the binding of an E3 ligase that mediates its degradation. Channel accumulation leads to Na2+ reabsorption in excess and severe hypertension.

38
Q

What are 3 disorders with defects in cellular protein degradation regarding the E3 subunit of ubiquitin?

A

Liddle Syndrome
Juvenile parkinsonism
Breast and ovarian cancer
HPV induced cervical cancer

Advanced Metabolism (8 decks)

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