Protein Metabolism (Lab) Flashcards
T/F - Amino acids are not stored by the body (unlike fats and carbohydrates)
T
T/F - Amino acids must be obtained from the diet, synthesized de novo or produced from normal protein degradation
T
1st phase of AA catabolism
Removal of α-amino groups
Formation of ammonia and corresponding α-keto acid
Ammonia excreted in the urine or used to synthesize urea
2nd phase of AA catabolism
α-keto acids
common intermediates of energy producing metabolic pathways
(can be metabolized to CO2 and water, glucose, fatty acids, or ketone bodies)
Protein digestion starts in the ___
stomach
Dietary protein present in the stomach
stimulates the release of ___
gastrin
promotes secretion of pepsinogen and HCl/hydrochloric acid (has 3 functions)
Gastrin
FUNCTIONS OF HCL
- Antiseptic properties kill most bacteria
- Denaturing action “unwinds” globular
proteins - Acidic property leads to activation of
pepsinogen
affects the hydrolysis of 10% peptide bonds
Pepsin
Production of ____ is stimulated by the passage
of small amounts of acidic protein content into the
small intestine
secretin
Secretin stimulates ____ production, which in turn helps neutralize acidified gastric content
bicarbonate (HCO3-)
Promotes secretion of pancreatic digestive
enzymes trypsin, chymotrypsin, and
carboxypeptidase in their inactive forms
secretin
also have their zymogen forms
Proteolytic Enzymes
Specific to N- and C-terminal cleavage of Phe and Leu
Pepsin (pH 1.3)
Specific to C-terminal cleavage of Lys and Arg
Trypsin
Specific to C-terminal cleavage of aromatic amino acids
Chymotrypsin
T/F - N terminal side - <amino> - C-terminal side</amino>
T
are transported into the bloodstream via active transport process
Liberated amino acids
The passage of polypeptides and small proteins across the ____ is uncommon in adults
intestinal wall
In _____, the transport of polypeptides allows the passage of proteins such as antibodies in
colostrum milk from a mother to a nursing infant to build up immunologic protection in the
infant
infants
Protein Digestion and Absorption Pathway
- Mouth - Saliva (No effect on digestion)
- Stomach - HCl (denatures protein; Pepsin (Hydrolyzes peptide bonds)
–> Large Polypeptides - Small Intestine - Trypsin, Chymotrypsin, Carboxypeptidase, Aminopeptidase (all hydrolyzes peptide bonds)
- Intestinal Lining - Active transport
total supply of free amino acids available for use in
the human body
The Amino Acid Pool
Amino Acid Utilization
SOURCES
- Amino acid degraded of body
proteins - Amino acids derived from dietary
protein - Synthesis of non-essential AA from
intermediates of metabolism
Amino Acid Utilization
ROUTES OF DEPLETION
- Synthesis of body protein
- AA consumed for the synthesis of
essential nitrogen-containing
molecules - Conversion of AA to glucose,
glycogen, fatty acids, ketone
bodies, or H2O + CO2
The repetitive process in which proteins are degraded and
resynthesized.
Protein Turnover
T/F - The rate of protein synthesis is just sufficient to replace the protein being degraded
T (Leads to hydrolysis and resynthesis of 300-400 g of body protein each day)
Biosynthesis of non-essential amino acids in the liver
the state that results when the amount of nitrogen taken into the
human body as protein equals the amount of nitrogen excreted from the body in waste
materials
Nitrogen balance
Protein degradation exceeds protein synthesis; Amount of nitrogen in urine exceeds consumed amount; Results in tissue wasting
Negative nitrogen imbalance
Rate of protein synthesis (anabolism) is more than
protein degradation (catabolism); Indicated by the synthesis of large amounts of tissue
Positive nitrogen imbalance
Uses for Amino Acids (4)
Protein synthesis
Synthesis of non-protein nitrogen-containing compounds
Synthesis of non-essential amino acids
Production of energy