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Biochemistry MBS > Protein Digestion > Flashcards

Protein Digestion Flashcards

1
Q

sources of amino acids

A
  • body protein (major source)
  • dietary protein
  • digestive enzymes
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2
Q

uses for amino acids

A
  • synth of nitrogen containing compounds
  • degradation for energy to make glucose
  • protein synth
  • poop production
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3
Q

what concentration are amino acids maintained at in the blood

A

-high for use all over the body

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4
Q

two sources of blood protein

A
  • 3/4 body breakdown

- 1/4 dietary

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5
Q

dietary protein digestion

A
  • glands of the stomach secrete acid and pepsinogen
  • acid denatures proteins and pepsin produces peptides
  • peptides eneter the small intestine, pancreas secretes bicarb and zymogens
  • activated enzymes in the duodenum digest long peptides into short ones
  • enzymes of intestinal lumen and villi produce mostly amino acid for absorption
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6
Q

pepsinogen

A
  • is not active at neutral ph
  • at higher ph, a pro-peptide is blocking the active site
  • at lower ph, autoactivtion happen and the site is exposed
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7
Q

regulation of digestion in the small intestine

A
  • acid chyme passes to duodenum
  • mucosal cells release of secretin and CCK into the blood
  • gall bladder contracts and pancreas releases juices
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8
Q

what does the pancreas secrete

A
  • bicarb

- inactive zymogens (these are activated by enzymes from the duodenum)

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9
Q

trypsinogen

A
  • activated by enteropeptidase which starts off the process of digestion. made into trypsin
  • trypsin acts on trypsinogen to turn it into trypsin
  • activates chymotrypsinogen, proelastase, and procarboxypeptidase
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10
Q

degradation of digestive enzymes

A
  • they degrade themselves as they run out of dietary amino acids to work on
  • degradation = production (70g/day)
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11
Q

uninhibited trypsin in pancreatic cells

A

-leads to pancreatitis
-could be from a mutation
-

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12
Q

carboxypeptidase produces

A

mostly amino acids

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13
Q

aminopeptidases and dipeptidases produce

A

amino acids

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14
Q

absorption uptake in and out of cells occurs via

A
  • transporters
  • there is a high aa concentration in cells so you must use energy to move amino acids in,
  • you can just use facilitated transport to move amino acids out
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15
Q

where does amino acid transport occur

A
  • intestines from the lumen
  • refiltered from urine in the kidney for reuse
  • across mitochondrial membranes
  • solute carrier transporters are a diverse group
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16
Q

characterization of amino acid transporters

A
  • often sodium linked transporters that use energy to pump sodium out of the cell in order to establish a sodium gradient that is used to pump the amino acids in (NA/K ATPase)
  • one transporter will carry many aa’s that have similar characteristics
17
Q

where is the first place amino acids go

A

-liver via portal vein

18
Q

defective kidney transport for cystine

A
  • can cause cystinuria
  • carrier rate of 1:50
  • resorption rate rises
  • results in high cystein in urin and it is of limiited solubility so it results in stones
  • also high lysine
19
Q

niacin (VB3)

  • pellagra
  • hartnip
A
  • made from tryptophan
  • deficiency disease, pllagra causes its victims to experience dermatitis, dirrhea, and dementia
  • clinical features of hartnup disease are nearly identical to thos of pellagra, although more intermittent and slightly less than pellagra
20
Q

hartnup disease

A
  • abnormal excretion of tryptophan into the urine and deficient in absorption in the intestine
  • patient is characterized by intermittent attacks of dermatitis, diarrhea, and dementia
  • tryptophan can be converted into niacin, a precursor to NAD
  • affects occur in the brin and skin
21
Q

cathepsins

A
  • lysosomal proteases

- effective for degrading extracellular proteins

22
Q

sources for amino acids from protein degradation oustide of dietary proteins

A
  • lysosomal system (cathesins)
  • digestive enzyme turnover
  • the ubiquitin/proteasome pathway (UPP): major pathway for degradation of intracellular proteins (muscle)
23
Q

degradation rate of proteins

A
  • varies

- proteins that shouldnt be around for a long time such as cell cycle proteins will degrade more quickly

24
Q

what happens to proteins that are destine for the ubiquitin pathway

A
  • enzymes E1,2, and 3 add ubiquitin to the target which tags it for degradation
  • final product is polyubiquitinated
25
Q

the proteasome

A
  • present in the cytoplasm
  • composed of two regulatory particles and a core particle an
  • end product is amino acids
  • processing is upregulated when needed
26
Q

regulatory particle

A
  • selects substrates
  • remoives Ub for recycling
  • edits wrongly tagged proteins
27
Q

core particle

A

-this is where proteins are digested into peptides of 7 to 10 aa’s

28
Q

ubiquitin signals in the protein sequence and not variable

A
  • N end rule: methionine is the slowest
  • PEST sequence
  • destruction boxes
29
Q

ubitquitin signals that are external and variable

A
  • phosphoryltaion
  • denaturation/damage
  • facilitators/chaperons
30
Q

HPV E6

A
  • faciliates the degradation of p53
  • this protein forma complex with its target and makes it more likely to be ubiquinylated
  • this is a viral protein which upregulates the cell cycle by degrading p53, a powerful tumor supressor
  • certain forms of the virus are assoicated with cervical cancer
31
Q

parkinsons

A
  • lewy bodies (protein deposits in the brain)
  • causes a loss of neurons, dopamine
  • L dopa is the most common treatment
32
Q

parkin and E6AP

A

-examples od E3 type ubitquitin ligases that are associated with parkinsons and HPV induced disease

33
Q

plasma

A
  • this is how proteins are transported in the blood

- alanine and glutamine are in the highest concentration due to the way they are metabolized

34
Q

free amino acids

A

levels are low compared to that of polymerized aa’s

-95% is turned over every ten mins

35
Q

essential amino acids

A

-must be obtained from the fiet
-if something is too hard to make, we eat it
-

36
Q

list the essential amino acids

A
  • arg
  • val
  • phe
  • his
  • thr
  • met
  • iso
  • lys
  • leu
  • tryp
  • are valuable phor his thriving metabolism in lyfes leunatic tryp
37
Q

inadequate protein in the diet

A
  • kwashiorkor
  • marasmus
  • bloated stomachs due to loss of plasma protein and fatty liver
38
Q

quality sources of protein

A
  • animal proteins is of much higher percentage and is broken down much easier
  • animal has complete amino acid sources
  • chemical score for animal is high

Biochemistry MBS (36 decks)

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