Dietary Protein (Maris)

Question 1

What kind of reaction breaks polypeptides into amino acids?

Answer 1

Hydrolysis

Question 2

How do protein digestion and absorption work?

Answer 2

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.

Question 3

What does starvation always cause?

Answer 3

Wasting of lean body tissue in addition to fat loss.

Question 4

What is a zymogen?

Answer 4

Inactive enzyme precursor

Question 5

What is the major proteolytic enzyme of the stomach?

Answer 5

Pepsin

Question 6

How is pepsin produced and secreted?

Answer 6

It is produced and secreted as pepsinogen by gastric cells.

Question 7

How does protein digestion in the stomach occur?

Answer 7

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.

Question 8

Why do we have zymogens instead of enzymes in the digestive tract?

Answer 8

If enzymes were always active, they’d eat through the digestive tract.

Question 9

What neutralizes stomach acid?

Answer 9

Bicarbonate

Question 10

What activates trypsinogen to make what enzyme? Where does this occur?

Answer 10

Enteropeptidase to make Trypsin. Produced in pancreas.

Question 11

What activates chymotrypsinogen to make what enzyme? Where does this occur?

Answer 11

Trypsin to make Chymotrypsin. Produced in pancrease.

Question 12

What activates proelastase to make what enzyme? Where does this occur?

Answer 12

Trypsin to make elastase. Produced in pancreas.

Question 13

What activates procarboxypeptidase to make what enzyme? Where does this occur?

Answer 13

Trypsin to make carboxypeptidase. Produced in pancreas.

Question 14

What happens when you use protein for energy production?

Answer 14

1 - deamination. 2 - get ammonia & a keto acid as products.

Question 15

The liver combines ammonia, a toxic substance, with CO2 to produce what?

Answer 15

Urea and H2O

Question 16

What makes urea production increase?

Answer 16

Increased protein consumption

Question 17

Maximum urea production occurs when protein intake hits what level?

Answer 17

250 g/day

Question 18

In liver disease, what would you see in the blood?

Answer 18

Blood ammonia is high.

Question 19

In kidney disease, what would you see in the blood?

Answer 19

Blood urea is high.

Question 20

How much of your total caloric intake should come from protein? What are reasonable and high amounts?

Answer 20

10-35%; 30%, 50%

Question 21

What is Kwashiorkor?

Answer 21

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.

Question 22

In Kwashiorkor syndrome, why would you see changes in pigment and have edema, a damaged immune system, and rashes/sores that don’t heal?

Answer 22

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.

Question 23

What does creatinine clearance tell you?

Answer 23

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.

Question 24

What is Phenylketonuria (PKU)?

Answer 24

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.

Question 25

What is Maple Syrup Urine Disease (MSUD)?

Answer 25

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.