Term
| Nutrients can cross the intestinal lumen once they have been broken down into... |
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Definition
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Term
| The 'tight' cell junctions are most leaky in the ____ intestine |
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Definition
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Definition
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Term
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Definition
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Term
| (cations/anions) can cross easily between tight junctions of the cell intestine |
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Definition
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Term
True or False
All water secretion in the intestine is osmotic |
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Definition
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Term
| If osmolarity of the intestine > blood, water will (enter/exit) the lumen |
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Definition
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Term
| Why does loss if intestinal villi lead to diarrhea? |
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Definition
| less absorption of nutrients, greater osmolarity in intestine, water moves into intestinal lumen = get the runs gross |
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Term
| Paracellular tansport is (active/passive) |
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Definition
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Term
| Transcellular transport is (active/passive) |
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Definition
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Term
| Why is absorption of K+ greatest in the distal intestine? |
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Definition
-K+ is absorbed via paracellular transport (relies on concentration gradients)
-water needs to be absorbed in the proximal intestine first, leading to an increase in [K+] as you move down the intestine
-higher [K+] promotes diffusion from lumen into bloodstream |
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Term
| What is the difference between primary active transport pump vs uniporter vs symporter vs antiporter |
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Definition
Primary: uses ATP to pump ions against concentration gradients
Uniporter: passive diffusion down a gradient
Symporter: Na+ moves down gradient, driving a second molecule with it (may be with or against the second molecule's gradient)
Antiporter: Na+ moves down gradient, driving a second molecule in the opposite direction (with or against its concentration gradient) |
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Term
| How is sodium absorbed? (3) |
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Definition
1. Passive diffusion through symporters
2. Antiporters (Na/H+ exchanger, sodium moves into the cell driving H+ out)
3. Simple diffusion (minimal) |
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Term
| Main site of electrolyte absorption, other than Na |
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Definition
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Term
| Nutrients are absorbed via (paracellular/transcelluar) route |
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Definition
| transcellular (relies on active transport) |
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Term
True or False
Mucus is secreted throughout the digestive system |
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Definition
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Term
| What are the 3 types of GIT secretions? |
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Definition
1. Mucus
2. Specialized substances e.g. digestive enzymes
3. Water & electrolytes |
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Term
| How is water secreted into the intestinal lumen? |
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Definition
-Na/Cl symporter brings Cl from bloodstream into cell lumen against its concentration gradient
-Cl diffuses from cell lumen into intestinal lumen passiely
-Na+ is pumped actively out of cells into bloodstream via Na/K pump
-H2O follows Cl- osmotically |
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Term
| How is bicarbonate secreted into the SI (3) |
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Definition
-coupled with Na+ (no net change in pH)
-Cl bicarb antiporter (increases lumen pH)
-selective bicarb channels (increases pH) |
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Term
| What happens after bicarbonate is secreted into the SI? |
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Definition
-reacts with HCl to neutralize pH -> H2O & CO2
-H2O and CO2 are reabsorbed to maintain body acid/base balance |
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Term
| Absorption of water is (active/passive) |
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Definition
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Term
| Absorption of ions is (active/passive) |
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Definition
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Term
| Absorption of nutrients is (active/passive) |
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Definition
active
-mainly secondary active transport |
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Term
| 2 phases of nutrient digestion |
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Definition
Luminal (mechanic & enzymatic)
Membrane-bound (enzymatic) |
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Term
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Definition
Fiber (mainly cellulose)
Starch (long glucose polymers)
Sugars |
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Term
True or False
Mammals are not able to enzymatically digest fiber |
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Definition
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Definition
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Definition
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Term
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Definition
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Term
| What are the 3 simple sugars |
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Definition
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Term
| What enzyme breaks polysaccharides down into smaller polysaccharides? Where does this happen? |
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Definition
amylase
in intestinal lumen |
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Term
True or False
A specific enzyme is required to break each disaccharide/trisaccharide down into simple sugars in the brush border |
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Definition
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Term
| What happens during the membrane phase of CHO digestion |
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Definition
| Tri/disaccharides are broken down into monosaccharides |
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Term
True or False
Expression of membrane-bound enzymes varies with diet, age,
pancreatic activity, etc. |
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Definition
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Term
| How does glucose get absorbed? |
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Definition
Na+ symporter (SGLT-1)
trades 1 glucose for 2 Na |
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Term
| How does galactose get absorbed? |
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Definition
Na+ symporter (SGLT-1)
trades 1 galactose for 2 Na |
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Term
| How does fructose get absorbed? |
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Definition
| facilitated diffusion (uniporter) GLUT-5 |
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Term
True or False
Glucose absorbtion requires active transport in the distal SI |
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Definition
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Term
True or False
Glucose absorption is done via passive transport in the proximal SI |
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Definition
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Term
| What does the GLUT2 uniporter do? |
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Definition
| move ALL simple sugars from the lumen of enterocytes into the submucosa |
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Term
True or False
Luminal protein digestion starts in the stomach |
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Definition
true
pepsin initiates protein digestion |
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Term
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Definition
| proteolytic enzyme in ruminant abomasums, which digests kappa-casein causing milk to curdle |
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Term
| Pancreatic proteolytic enzymes are most active at pH |
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Definition
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Term
| Membranous phase of protein digestion |
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Definition
Membrane-bound peptidases in SI break down peptides into:
• Free amino acids
• Di- and tri-peptides |
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Term
| Why are neonates able to absorb intact proteins? |
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Definition
-low HCl secretion and pancreatic enzyme secretion means protein reach the intestine intact
-specialized enterocytes are able to absorb them for up to 24h after birth |
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Term
| Phases of lipid digestion |
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Definition
1. Emulsification
2. Hydrolysis via lipase/colipase
3. Incorporation into micelles
4. Diffusion through glycocaylx to apical membrane
5. Absorption via FA transporter protein, or diffusion if concentration is high enough
6. Re-synthesis of TGs, bundled into chylomicrons
7. Chylomicron exported to lacteals |
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Term
True or False
body temperature influences lipid emulsification |
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Definition
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Term
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Definition
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Term
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Definition
| bundles of TGs and cholesterol |
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Definition
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