Dietary Protein (Maris) Flashcards
What kind of reaction breaks polypeptides into amino acids?
Hydrolysis
How do protein digestion and absorption work?
Enzymes mediate hydrolysis of proteins into single amino acids for absorption. Specific transport proteins transport AAs into intestinal cells (some stay, most go to liver via blood). AAs are then used to make proteins.
What does starvation always cause?
Wasting of lean body tissue in addition to fat loss.
What is a zymogen?
Inactive enzyme precursor
What is the major proteolytic enzyme of the stomach?
Pepsin
How is pepsin produced and secreted?
It is produced and secreted as pepsinogen by gastric cells.
How does protein digestion in the stomach occur?
In the digestive tract, dietary protein is broken down into amino acids by digestive enzymes, especially by pepsin. HCl produced by parietal cells induces a conformational change in pepsinogen that enables it to cleave itself, producing active pepsin.
Why do we have zymogens instead of enzymes in the digestive tract?
If enzymes were always active, they’d eat through the digestive tract.
What neutralizes stomach acid?
Bicarbonate
What activates trypsinogen to make what enzyme? Where does this occur?
Enteropeptidase to make Trypsin. Produced in pancreas.
What activates chymotrypsinogen to make what enzyme? Where does this occur?
Trypsin to make Chymotrypsin. Produced in pancrease.
What activates proelastase to make what enzyme? Where does this occur?
Trypsin to make elastase. Produced in pancreas.
What activates procarboxypeptidase to make what enzyme? Where does this occur?
Trypsin to make carboxypeptidase. Produced in pancreas.
What happens when you use protein for energy production?
1 - deamination. 2 - get ammonia & a keto acid as products.
The liver combines ammonia, a toxic substance, with CO2 to produce what?
Urea and H2O
What makes urea production increase?
Increased protein consumption
Maximum urea production occurs when protein intake hits what level?
250 g/day
In liver disease, what would you see in the blood?
Blood ammonia is high.
In kidney disease, what would you see in the blood?
Blood urea is high.
How much of your total caloric intake should come from protein? What are reasonable and high amounts?
10-35%; 30%, 50%
What is Kwashiorkor?
Acute malnutrition due to lack of dietary protein; common in very poor countries. Seen in cases of severe neglect/abuse in US. Fatal if left untreated.
In Kwashiorkor syndrome, why would you see changes in pigment and have edema, a damaged immune system, and rashes/sores that don’t heal?
Pigment - not getting enough protein, so you won’t have enough tyrosine. Edema - decreased plasma protein, thus fluid leaves and goes into interstitial spaces. Damaged immune system - antibody proteins have been dismantled to create energy. Rashes/sores - don’t have protein building blocks for healing.
What does creatinine clearance tell you?
Compares creatinine level in urine with level in blood. Creatinine is a breakdown product of creatine, which is an important part of muscle, which always breaks down in cases of starvation-induced malnutrition.
What is Phenylketonuria (PKU)?
Inability to break down phylalanine due to lack of phenylalanine hydroxylase (PAH). Leads to decrease in tyrosine, which causes delayed mental and social skills, jerking extremities, skin rashes, etc. Following a phenylalanine-free diet, if followed closely, can lead to good prognosis.
What is Maple Syrup Urine Disease (MSUD)?
Inability to break down branched chain amino acids. Autosomal recessive disorder that gives infants a characteristic sweet odor. Symptoms: poor feeding, vomiting, lethargy, developmental delay.
