Chapter 23 Digestive System) Part 4 Flashcards
1
Q
Mechanisms of Digestion
A
- Digestion) catabolic process that breaks down macromolecules (large molecules) into monomers small enough for absoprtion
- Enzymatic Hydrolysis
- Enzymes) Break Down Food
- Hydrolysis) water added to a bond to breal it
- Mostly done in small intestine
- Pancreatic Enzymes (main source of lipases) and bile are both nessecary for fat breakdown and starting to break down macromolecules
- Brush borarder enzymes finish breaking down.
2
Q
Mechanisms of Absorption
A
- Absorption) Process of moving subatances from lumen of the gut into the body
- Enererocyte) Cell on Apical Side of Lumen mebrane that exits on Basil (basolateral) membrane and into interstital fluid on the other cide
- once here susbtences are able to diffuse into blood capillaries > tranported to hepatic portal vein in the lliver
- Some Lipid priducts enter the lacteal in the villus to be carried via lymphatic fluid
- Nonpolar substances = can passively diffuse through the phospolipid bilayer
- Most other nutrients = Absorbed through active transport processes driven directly or indirectly by metabolic energy.
3
Q
Digestion of Carbohydrates
A
- Only monosaccharides can be absorbed
- Glucose, Fructose, Galactose can be digested in the same form they were ingested in
- Breakdown of Complex Carbohydrates in Our digestive system
- We can break down disaccharides (sucrose, Lactose, maltose) and polysaccharides glycogen and starch
- Salivary Amylaase (saliva)
- Splits starch into Oligosaccharides (fragments of 2-8 linked glucose)
- Pancreatic Amylase (Small Intestine)
- Breaks down anything that secaped sailvary amylase.
- convert to oligosaccharides and disacharrides
- Brush Border Enzymes (villi)
- break down oligosaccharides and disacharrides to Monosacharides
- Brush border enxymes diretly break down disaccharides
- Monosacharides are tranported across apical membrane via enterocytete then exit basolateral membrane via facilitated diffusion
4
Q
Digestion of Proteins
A
- Proteins that can be digested
- Dietary proteins, digestive enxymes, mucosal cells
- digested down to amino acid monomers
- Begins with persin in stomach (ph 1.5-2.5)
- Inactive in high pH of duodenum
- Pancreatic Proteases
- Trypsin, Chymotrypsin, and Carboxypeptidase
- Brych Boarder Enzymes
- Aminopeptidase, carboxypeptidase, dipeptidase
- Amino acids are transported across apical membrane via enterocyte and leave basolateral side via facilitated diffusion
5
Q
Digestion of Lipids
A
- Triglycerides are most abundent fats in the diet.
- small intestine is primary site of lipid digestion
- Pancreases is major source of fat enzymes (lipases)
- Emulsification by Bile Salts
- Pretreat fats so they are more soluable in water
- increase surface area of fats by breaking globs into smaller droplets
- Nonpolar side of bile salt clings to fat droplet allowing the polar side to bind with water.
- Digestion
- Pancreatic Lipases break down to fatty acids and monoglycerides (glyceral with one fatty acid chain)
- Micelle Formation
- Bile Salts are essential for absorption of end products of digestion
- Mincelle) collection of fatty acid, monoglycerides, and bile salts
- Polar side of molecule faces the water.
- Diffustion
- Once the formation reaches the epitelial cells the lipid substances leace the mincelles and move through the lipid phase of the plasma membrane.
- Chylomicron Formation
- Smooth ER converts free fatty acids and monoglycerides from epiteliam back into Triglycerides
- Triglycerides are packed with other substances and proteins to form chylomicrons
- Chylomicron Transport)
- Moved out of epithlial cells via exocytosis
- Enter lacteals and are carried via lymph to venous circulation
- While in Bloodstream
- Triglycerides are hydrolyzed to free fatt acids and glycerol by lipoprotein lipase.
- Fatty acids/ glycerol can pass trhough the capillary walls and be used by tissue cells for enegy/ fat storage.
- Short Chain Fatty acids
- Simply diffuse into portal blood for disrtubution.
6
Q
Digestion of Nucleic Acids
A
- Enzymes that break down nucleic acids
- Pancreatic Nucleases) in pancreatic juice hydrolyze the nucleic acids to nucleotide monmers
- Brush Boarder Enzymes) break apart nuclotides to release nitrogenous bases, pentose sugars, and phosphate ions.
- Absoption of Nucletic Acids
- Active tranposport across the epithelium to the bloodstream
7
Q
Absorption of Vitamins
A
- In small intestine
- Fat-soluable vitamins (A,D,E, and K) carreid by Micelles; diffuse into absorptive cells
- Water-Soluable Vitamins (C and B) absorbed via diffusion, or passive. active transports
- Vitamin B12) binds with intrensic factor and absorbed via endocytosis
- LArge intesine
- Vitamins K and B from bacterial metabolism are absorbed.
8
Q
Absorbtion of Electrolytes
A
- Come from ingesteg foods and gastrointestinal secretions
- Most are actively absorbed along the lenght of the small intesine
- Iron and Calcium
- absorbed in duodenum
- Iron stored un mucosal cells and bind to ferritin and tranported in blood via tranferrin
- menstration causes women to loose more iron in their diets
- Ca2+ absorption regulated by vitamin D and parathyroid hormone (PTH)
- Na+) coupled with active absorption of glucose and amino acids
- HCO3-) excrted into lumen in exhange for Cl-
- K+) moves with concentration gradient of water.
9
Q
Absorption of Water
A
- Mostly dericed from GI tract secretions
- 95% in small intestion via osmosis
- Most of the rest is absorbed in large intstine
10
Q
Malabsortion of Nutritents
A
- Causes
- anything that interferes with delivery of bile or pancreatic juice
- Damaged intestinal mucosa
- Caliac Desiese (gluten-seneitive entropathy)
- Immune reation to gluten
- damages intestinal villi and brush border
11
Q
Aging of Digestive System
A
- Diverticulosis, fecal incontinence, and cancer of GI tract are common zs we age
- Stomach/colon cancer rarley has any early signs
