Exam 2 Peng Flashcards
<p>what are the nonessential AA?</p>
<p>all of the ones that start with A, C, or G AND proline, serine, tyrosine (Probably Sleeping Tymorrow)</p>
<p>what are pyrimidines?</p>
<p>thymine, cytosine, uracil</p>
<p>what are purines?</p>
<p>adenine and guanine</p>
central dogma
T
what are the four most abundant elements?
oxygen, carbon, hydrogen, nitrogen
what is our primary source of nitrogen? how do we uptake it?
AA
bacteria in soil > plants > animals/us
(we can’t break down N in air bc of strong triple bond)
what are our two methods of protein degradation? why do we need this?
1) dietary protein degradation -by digestive system
2) cellular protein degradation -in cells already
- -proteins are too large and need to be hydrolyzed or broken down, need proteins for AA we can’t make
where are protelytic enzymes found?
SI, stomach, pancreas
Point: to get free AA
what is the first step in deitary degradation?
hydrochloric acid in the stomach
1) kills bacteria 2) denatures proteins 3) activate proenzymes pepsinogen
what activates proenzyme pepsinogen?
hydrochloric acid
what happens to pepsinogen once it is activated?
turns into pepsin to digest large proteins
why can;t cell produce active pepsin? What happens instead?
it’ll damage the cell. so they produce inactive enzyme (zymogen) and later it’ll get activated when in correct location. HCL changes pepsinogen to become partially activated, and then pepsinogens interaction together to become active pepsin
inactive form of pepsin?
pepsinogen
what further cleaves peptides produced by pepsin?
pancreatic protease
how is pancreatic protease different from pepsin? How are they the same?
pancreatic protease exhibits substrate AA specificity. They both are secreted as inactive proenzyme (zymogens) and are activated through proteolytic activity (cascade effect)
what is a common pancreatic protease activator?
trypsin
what is aminopeptidase? found where?
found in luminal surface of the intestine. it is a exopeptidase that repeatedly cleaves N-terminus from oligopeptides to produce free AA
Big difference between aminopeptidase andpepsid or pancreatic proenzyme?
they cut from the END of a small protein at the N-terminus and NOT from within
what is the main goal or outcome from all peptidases?
to produce free AA
abnormaliites in protein degradation?
deficiency in pancreatic enzymes due to cystic fibrosis, removal or inflammation, celiac disease in SI, diabetes, or other digestive/kidney diseases
Main site for AA metabolism?
liver
what takes up AA and small proteins in the intestine? then what?
enterocytes. then absorbed into the blood or metabolized in liver
why is active transport required to move AA into a cell?
bc concentration of free AA in the cell is higher than outside it, requires hydrolysis of ATP for active transport to go against gradient
what is cystimuria?
the inability to reabsorb cystein, ornithine, arginine or lysine which means they accumulate in urine due to a genetic mutation. BUT CYSTEINE is fairly INSOLUBLE and resutls in KIDNEY STONES
what is the most common inherited diseases for dietary protein degradation?
cystimuria
what is protein turnover?
the rate at which proteins are constantly being synthesized and degraded; roughly 300-400g per day
what is the net amount of protein determined by?
the rate of both protein synthesis and degradation; varies per person and protein
what are the two ways that cellular proteins are degraded?
1) lysosomal degradation- degrade IN lysosome bc proteins SENT there
2) ubiquitin mediated degradation- like driving a car around trying to find proteins
lysosomal degradation is ____ dependent? contains? two types of lysosomal degradation?
ATP dependent and uses acid hydolases to degrade proteins; heterophagy and autophagy
heterophagy vs autophagy lysosomal degartion
- *heterophagy- degrades extracellular substrates via endocytosis (defense)
- *autophagy- degrade intracellular proteins (in own cell)
What is lysosomal storage disease?
defects in lysosomes resulting in inherited metabolic disorders such as developmental delay, deafness, blindness, organ probs
*diagnosed by enzyme assay and treatment is symptomatic or bone marrow transplant
how does ubiquitin mediated degradation for cellular protein degradation work?
proteins that are being degraded are first “tagged” with ubiquitin and THEN recognized by proteolytic enzymes responsible for degrading ubiquitinated cellular proteins
how is ubiquitin added onto a protein?
the C-terminus glycine residue ON UB is added to the lysine residue of the target protein
at least how many Ub need to be added for degradation? If not, what occurs?
you need at least FOUR UB tages (only a chain can degrade a protein); if less than 4 (monoubiquitnation) than only the function of the protein is modified and not degraded
what are the steps in protein ubiquitination? Is it ATP dependent? What creates variation?
1) Ub acitvating enzyme (E1)
2) Ub conjugating enzyme (E2)
3) Ub ligase
* ATP DEPENDNET aka needs energy, enzyme catalyzed
* there are MANY E1 and E2 enzymes to give this process specificity
what are defects for Ub- dependent proteolysis?
cancer, neurodegenerative diseases, metabolic disorders
treatment of Ub defects?
drugs that target proteolytic machinery are potentially valuable
*if protein degradation is blocked it causes a lot of toxicity in the cell which is an advantage to treat cancer cells
what is the N-terminal rule for degradation?
AA present at amine terminus influences turn-over rate
Met= stable
Arg or Leu = degrade rapidly at N-terminus
why degrade AA?
1) downregulation for quantitiy control
2) renewal for quality control
3) providing materials for synthesis of other molecules
4) providing energy (10-15%)
what is the obligatory step for all AA catabolism?
the removal of alpha-amino group
what happens to AA carbon skeletons during degradation?
they are degraded to intermediate products
catabolism
breakdown (large to small), makes energy, makes pre-cursers
