Digestion and absorption of macronutrients

Question 1

Calories come from carbs, proteins and lipids, gastric and pancreatic secretions review

Answer 1

mucous neck cells- mucus and HCO3
Parietal cells- HCL and intrinsic factor (B12)
Cheif cells - pepsinogen (protein digestion
ECL- histamine

Pancreas
Active enzymes- Lipases, amylae, DNAses
Zymogens- proelastase, carboxy, trypcinogen

Question 2

Pancreatic exocrine insufficiency

Answer 2

Most commonly caused by:
Chronic pancreatitis- chronic alcoholism, autoimmune diseases, gallstones

Cystic fibrosis
Type 1 and 2 diabetes (50% of type1 and 40% type 2)

Symptoms- Wt loss, steatorrhea, diarrhea, abdominal discomfort fat-soluble vitamin deficiencies (ADEK), other nutrient deficiencies (B12, folate, iron, calcium

Diagnosis- fecal elastase test, fecal fat test, direct pancreatic function tests

Question 3

Protein digestion and Absorption in stomach

Answer 3

In the stomach:
Parietal cells secrete HCL- stimulated by Ach, gastrin, histamine, inhibited by Somatostatin

Chief cells secrete pepsinogen-stimulated by HCl, Ach, secretin, ph optimum low, endopeptidase w/ specificity for aromatic AA peptide bonds, denatures above ph 5

Question 4

Protein digestion and and absoprtion - small intestine

Answer 4

Enterokinase- activates Trypsin, and duodenal zymogens
Pancreatic enzymes: trypsin, chymotrypsin, elastase, carboxypeptidase A and B (as proenzymes that are activated by trypsin)
Aminopeptidases cleave from enterocytes

Brush borer peptidases- Tetra, Tri, and di peptidases. At tri peptides is when you satart absorbind

Aminoacid transporters- Amino acids are class specific, di and tripeptided transporters, Luminal Absorb of AA, D and Tri- peptidases

Question 5

lipid digestion and absorptions

Answer 5

Dietary lipids:
Triacylglycerols (TAGs), approx 90% of all diatary fat (butter oil), Saturated (animal), vs Unsaturated

Phospholipids- 5% of dietary fat
Sterols- Cholesterol ester (animal), unesterified cholesterol

Fat soluble vit (ADEK)
Hydrophobic (lipophili phytochemicals)

Usually a TAG is digeste to 2FAs and a sn2-Monoacylglycerol

Phospholipids- to lysophospholipid and FA
Cholesterol Ester-> Cholesterol and FA

Question 6

lipid digestion and absorptions enzymes

Answer 6

Lingual lipase- from serous glands of the tongue, commences hydrolysis of sn 3 Fa from Tgs

Gastric lipase- preferentially dydrolyzes TGs containing SCFAs

Pancreatic lipase- secreted into duodenum, requires bile salts, co lipase )anchors lipase

Bile salts- synthesized in liver from cholesterol–> stored / concentrated in gallbladder– micelle

Most potent stimulus for CCK secretion is lipid in duodenum (CCK- contracts gall bladder

Small and medium can be directly absorbed

Dietary lipids slows rate of gastric emptying, feel fuller for longer, need fat to absorb the nutrients

Question 7

Carbohydrate digestion and absorption

Answer 7

Complex CHOs- Starches, glycogen, Fiber
Oligosaccharides- Inulin frucoligosaccharide
Simple CHOs- Disaccharides (Sucrose- Glucose and Fructose, Maltose- Glucose and Glucose, Lactose- Glucose and galactose

Amylase
Brush border enzymes- Sucrase, maltase, lactase

in duodenum and jejunum

Transporters SGLT1 for glucose and galactose, GLUT for fructose

Question 8

Lactose intoletace

Answer 8

inadequate lactase enzyme production
Lactose is undigestd and not absorbed–> its then metabolized by the large intestine bacteria, gas bloating nausea and abdomina cramps and discomfort

Primary lactose intolerance (most common)- Lactase production declines in late childhood or adulthood, more common in persons with African, Asian, hispanic, Nat Am ancenstory
Seconndary Small intestine injury, celiac disesase, Crohns, bacterial overgrowth
Congenital/dev- complete absence of lactase

H breath test

Question 9

Where are macronutrientes absorbed

Answer 9

Lipids, monosaccharides, amino acid, small peptides in the duodenum

Lipids, monosaccharides, amino acids, small peptides in the jejunum

Short chain fatty acids- in the large intestine

Question 10

Protein energy malnutriotion

Answer 10

Inadequate CALORIE and PROTEIN intake

Irreversible effects on cognitive and immune function esp for 2 yos
Common micronutrient deficiencies0 iron, iodine, vitA zic and Mg K
Dev countries

dev- post bariatric surgery, cf, cRf, chronic alcoholism
elderly

Question 11

kwashiorker

Answer 11

severe protein deficiency- lakcing all dietary, essential amino acids- diet can be adequate in calories from carbohydrates and fats, poor plant heavy diets can lack all 9 essential AAs

edema, anemia, fatty liver- big belly

Question 12

marasmus

Answer 12

total calorie deficiency