Chapter 7: Proteins and Amino Acids (Oct 15 lec) Flashcards
Why is it that herbivores can digest animal protein and carnivores can digest animal protein?
both plant and animal proteins are made up of the same 20 amino acids
- same bonds and structural themes, different amino acid profiles
peptides=
chains of amino acids joined by peptide bonds
proteins and polypeptides
both are chains of amino acids joined by peptide bonds
- polypeptides= a long chain
- proteins= an even longer chain
Water is ___ when a peptide bond is formed. Is this process reversible?
lost
Yes! water molecule required to break down peptide bonds
primary protein structure
a sequence of a chain of amino acids
secondary protein structure
h-bonding of the peptide backbone causes the amino acids to fold in a repeating pattern
- alpha helix or pleated beta sheet
tertiary protein structure
3D folding pattern of a protein due to side chain interactions
- lowest energy configuration spontaneously forms
- this tertiary structure can be the fully functional protein
quaternary protein structure
protein consisting of more than 1 amino acid (polypeptide) chain
- tertiary not always fully functional by themselves, but when put together it’s functional
- compact structure limits where enzymes can be active (hard to get peptide bonds to break them)
How does cooking denature protein?
disrupts the tertiary structure- protein folding
T/F
cooking is necessary for the digestion of protein
false- it’s possible to digest protein that’s not denatured
a denatured protein is
more stretched out, more susceptible to enzyme degradation
- allows access to peptide bonds by pepsin in stomach
If ingested protein is not denatured, it is denatured in the ___ by ____
stomach HCl (does not break down the protein itself, just denatures it)
zymogen=
an inactive precursor of an enzyme
peptidase/ protease=
an enzyme that catalyzes the breakdown of proteins
In the small intestine and pancreas, pH is near ____ and peptidases are secreted by _____
neutral
zymogens
Trypsin is an enzyme that aids with ____. _____is the precursor of trypsin and is stored in the ___.
digestion
Trypsinogen
pancreas
How does trypsinogen get activated into trypsin?
Enterokinase (an enzyme secreted by mucus in the intestine) cleaves trypsinogen to trypsin.
Once active, trypsin can go back and activate trypsinogen and other zymogens
match the terms
- Enterokinase, trypsin, trypsinogen
- active enzyme, cleaving enzyme, zymogen
cleaving enzyme= enterokinase
zymogen= trypsinogen
active enzyme= trypsin
why are proteins secreted as proteins?
To prevent the enzymes from digesting proteins in the cells in which they’re synthesized (b/c it’s an inactive precursor)
What do endopeptidases do?
Where do they work?
takes a long chain and chops it up into shorter chains (not yet amino acids)
more chains= more carboxy ends for exopeptidases to work
small intestine
What do exopeptidases do?
hydrolyze the ends of a chain (either carboxy or amino end)
- carboxypeptidase
- aminopeptidase
T/F
active enzymes cleave specific peptide bonds.
Give ex
true
ex. Chymotrypsin –> basic amino acids
Why does the intestine block absorption of intact protein?
the immune system would go crazy… reacting to foreign protein (lots of things that can hurt us are proteins, so the body attacks it)
exceptions: when can the body absorb intact proteins?
- newborns: first 24hrs after birth (gut closes to intact proteins after this)
- purpose= passive immunity - Adults:
- paracellular routes- tight junctions b/w cells (leaky gut)