Post-Ruminal Protein

Question 1

What is the most and least common way for proteins to be absorbed: whole proteins, peptides, or amino acids?

Answer 1

Most common: peptides
Least common: amino acids
(whole proteins too large, not absorbed)

Question 2

What is a zymogen?

Answer 2

It is an inactive pre-enzyme

Question 3

What are the types of protein digesting enzymes?

Answer 3

Endopeptidase (internal bonds)
Exopeptidase (terminal)
Carboxypeptidase (carboxyl group)
Aminopeptidase (amino group)

Question 4

How does HCl aid in protein digestion?

Answer 4

Activates pepsinogen to pepsin (endopeptidase)

Question 5

What hormone stimulate enzyme secretion?

Answer 5

secretin

Question 6

What are the pancreatic secretions?

Answer 6

Secrete the zymogens: Trypsinogen, chymotrypsinogen, procarboxypeptidase A/B, proelastase

Question 7

What is enterokinase

Answer 7

Is a membrane bound enterocyte secretion
Activates zymogens

Question 8

Where does proteolytic activity start in the ruminal intestine?

Answer 8

jejunum because it has little bicarb and pH is low (7-8)

Question 9

Where in the small intestine does most proteolytic activity occur, near the brush border or in the center?

Answer 9

at the brush border

Question 10

What is the difference between an endopeptidase and an exopeptidase?

Answer 10

Endopeptidase breaks peptide bonds within the primary structure
(proelastase, chymotrypsinogen, trypsinogen)
Exopeptidase cleaves amino acids off the terminal end
(procarboxypeptidase A & B)

Question 11

Where are trypsin inhibitors found?

Answer 11

soybeans, beans, peas
ruminant bacteria can break down

Question 12

How are intact proteins absorbed through the intestinal wall?

Answer 12

Absorbed through endocystosis and pinocytosis.
Only really happen in newborns with immunoglobulins. Adults will happen because of “leaky gut”

Question 13

How are peptides and amino acids absorbed through the intestinal wall?

Answer 13

Active transport, uses a carrier.
Peptide absorption more rapid.

Question 14

Where is the concentration of peptide and amino acid transporters in the small intestine the greatest?

Answer 14

Peptide transporters highest near the proximal SI
Amino acid transporters highest near the distal SI

Question 15

Enterocytes use much of the absorbed amino acids themselves. What do they use them for?

Answer 15

1. Transport into portal blood
2. Protein synthesis (digestive enzymes, structure, growth)
3. Energy

Question 16

What happens to amino acids once they enter the liver?

Answer 16

1. Synthesis of non-essential amino acids
2. Synthesis of proteins
3. Metabolized (de-aminated)
4. Escape the liver (circulation, tissues)

Question 17

What types of proteins does the body need amino acids for?

Answer 17

1. Structural proteins
2. Globular proteins (enzymes)
3. Immune proteins
4. Exportable/secreted proteins (ie. wool)

Question 18

What are 2 main ways that protein deposition can occur?

Answer 18

Gastrointestinal tract
Muscle

Question 19

Which organ is the most rapidly turning over organ in the body?

Answer 19

Small intestine

Question 20

Why do body organs turn over protein?

Answer 20

1. rapidly alter enzyme levels
2. mobilize proteins to redistribute amino acids
3. remove abnormal proteins
4. restructure cells and tissue during functional changes (ie. pregnancy)
5. coordinate whole body changes during different physiological states

Question 21

How do you get deposition? What do steroids and beta-agonists do?

Answer 21

synthesis must exceed degradation
Steroids increase synthesis
Beta-agonists decrease degradation

Question 22

What is metabolizable protein a measure of?

Answer 22

protein absorbed into the bloodstream