Diestion And Absorption Of Proteins

Question 1

Are amino acids stored in the body?

Answer 1

NO

- quickly degraded if found in excess

Question 2

What forms are most proteins absorbed as?

Answer 2

Tripeptides/dipeptides or AA’s

- use either facilitative diffusion or active transport in the intestinal brush border (similar to carbs)

Question 3

Zymogen function

Answer 3

Pepsinogen = cleaved into pepsin spontaneously in acidic environments
- cleave peptides into smaller units in stomach

Tyrpsinogen = cleaved by enterokinase into trypsin

• cleaves and activates other proteolytic enzymes such as: (chymotrypsin, elastase, carbooxypeptidases)
• *also positive feedback on itself (cleaves activates itself and more of trypsinogen)

Question 4

What controls pancreatic zymogen release?

Answer 4

The presence of CCK

Question 5

Enteropeptidase

Answer 5

A serine protease that is found on the apical surface of brush border
- converts trypsinogen -> trypsin by removal of a hexapeptide From N-terminus

Question 6

Gastric digestion of proteins

Answer 6

Begins in the stomach

• HCl = cleaves/activates pepsin and also denatures proteins (makes it easier for pepsin to do its job)
• pepsin = cleaves a few AAs off polypeptides

Question 7

Celiac disease

Answer 7

Malabsorption disorder where an autoimmune reaction occurs in the presence of gluten
- triggers immune system to damage the brush border of the small intestine resulting in malabsorption of proteins and lipids, as well as some carbs

Question 8

What are examples of pathology that can cause pancreatic secretion dysfunction

Answer 8

Chronic pancreatitis

Cystic fibrosis

Pancreatectomy

results in poor digestion and absorption of fats and proteins = steatorrhea and undigested proteins in feces

Question 9

Aminopeptidase

Answer 9

Exopeptidase located on luminal surface of enterocytes

Cleaves N-terminal residue from oligopeptides

Question 10

How are free amino acids absorbed?

Answer 10

Mostly by enterocytes at apical surface
- via sodium dependent secondary active transport from SLC proteins**

ONLY free AAs are released into the portal system via facilitated diffusion

Question 11

How are Di and tri peptides absorbed

Answer 11

By proton-linked peptide transporters (pepT1)

Question 12

What is the only amino acid transport system that is sodium-independent?

Answer 12

L system

• branched and aromatic AAs
• His/Met/Leu/Ile/Val/Phe/Tyr/Trp

Question 13

Cystinuria

Answer 13

A disorder of the proximal tubule’s inability to reabsorbs cystine/arginine and lysine AAs as well as ornithine
- “COAL”

inability to reabsorption cysteine leads to accumulation and urinary tract stones

Question 14

Hartnup disease

Answer 14

A mutation in B0 membrane transport protein system

• cant reabsorption neutral amino acids in kidneys and intestines (especially Trp)
• cant synthesize proper NAD(P) levels

Symptoms:

• pellagra-like symptoms
• inflamed skin
• diarrhea
• dementia
• canker sores

Question 15

What is the function of a proteasomes?

Answer 15

Ubiquitylation of damaged, short lived proteins or excess AAs
- uses ATP hydrolysis to unfold proteins

Cleaves ubiquinated proteins into AAs

Question 16

Autophagy

Answer 16

The process of a cell to target long-lived, aggregated proteins and damaged organelles

• encases it in a double membrane vesicle for elimination
• also allows sometimes for reuse of basic molecular components for building blocks for cells

Question 17

How does nitrogen balance affect people?

Answer 17

(Nitrogen consumed - nitrogen excreted) = balance (+/-)

Positive balance = tissue growth

Negative balance = tissue damage

Question 18

Kwashiorkor vs marasmus

Answer 18

Kawashiorkor:

• Protein depreciation and chronic malnutrition disorder
• carbohydrate heavy/protein poor diets

Symptoms:

• stunted growth
• skin lesions
• depigmented, course hair
• bilateral pitting edema**
• distended abdomen**
• decreased serum albumin

Marasmus

• overall calorie deprivation
• deficiency in protien/carbs and calories

Symptoms:

• extreme muscle wasting and cachexia
• weakness
• anemia
• stunted growth
• NO edema or distention of abdomen**

Question 19

Vitamin A effects

Answer 19

Works for vision, growth and differentiation

deficiency = night blindness and xerophthalamia

Question 20

Vitamin D effects

Answer 20

Calcium metabolism

*deficiency = rickets/osteomalacia *

Question 21

Vitamin K primary effect

Answer 21

Blood clotting

deficiency = spontaneous bleeding

Question 22

Vitamin E primary effect

Answer 22

Oxidative protection

deficiency causes hemolytic anemia

Question 23

Difference between fat soluble and water soluble vitamins

Answer 23

Fat soluble: (DEAK)

• hydrophobic
• stored in fat
• slower onset
• toxicity more common
• steatorrhea causes malabsorption
• AD are most common to be toxic in high doses

Water soluble (all B vitamins and C)

• hydrophilic
• excreted in urine
• faster onset
• uncommon for toxicity
• NO deficiency relented to steatorrhea

Question 24

Deficency in niacin causes what?

Answer 24

Pellagra
- dermatitis, diarrhea and dementia symptoms

high doses of niacin inhibits lipolysis in adipose tissue

Question 25

What enzyme is auto analyzed for protein digestion?

Answer 25

Pepsinogen

- it auto cleaves itself in acidic conditions

Question 26

What does each micro mineral do as a function

Answer 26

Chromium -> insulin release

Copper -> enzyme cofactor

Fluorine -> bacteria resistance

Iron -> enzyme cofactor

Manganese -> enzyme cofactor

Zinc -> enzyme cofactor, compliment action, innate immunity

Iodine -> thyroid function

Selenium -> glutathione production

Potassium -> blood pressure

Cholride and sodium -> fluid balance and blood volume