Term
| Glucose, Fructose and Galactose are all examples of ? |
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Definition
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Term
| Sucrose, Lactose and maltose are all examples of ? |
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Definition
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Term
| T/F: There is only receptors in the S.I. for monosaccharides so all other sugars have to be broken down into monomers. |
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Definition
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Term
| List the different types of Carbohydrates. |
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Definition
1. Sugar
2. Sugar EtOH
3. Starches
4. Dietary Fiber |
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Term
| Starches are large polysaccharides. Give the name of the branched chain polymers and the straight chains that make up starch. |
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Definition
Branched = Amylopectin
Straight = Amylose |
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Term
| T/F: Dietary fibers are starchy polysaccharides. |
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Definition
| False; they are non-starchy. Made of cellulose that humans cannot digest |
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Term
| What does bacteria in the colon do to dietary fibers? |
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Definition
| They ferment it and create short fatty acids. The short FAs can then supply energy to the cells in the colon. |
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Term
| What process causes the digestion of carbohydrates? |
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Definition
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Term
| Digestion of Carbs in the mouth occurs because |
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Definition
| Saliva contains alpha amylase which is the enzyme that breaks starch down into simpler structures like maltose and glucose |
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Term
| In the _______________ there is minimal amount of digestion. |
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Definition
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Term
| _____________% of food swallowed is of starch hydrolyzed to maltose. In the stomach it mixes with ___________. |
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Definition
30-40%
Stomach secretions |
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Term
| What inactivates Salivary Amylase? |
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Definition
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Term
| Where does the majority of digestion of carbohydrates occur? And by which enzyme? |
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Definition
| In the SI by pancreatic amylase |
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Term
| Which enzymes can be found lining the microvilli brush border of Enterocytes? |
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Definition
1. Lactase
2. Maltase
3. Sucrase
4. Alpha Dextrinase |
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Term
| What is the function of enterocytes in digestion of carbs? |
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Definition
| They allow absorption of Gluc. |
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Term
| Describe the absorption of Glucose. |
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Definition
| Glucose enters enterocyte via a Na+ dependent Gluc co-transporter. It exits the enterocyte via GLUT 2 on the basolateral membrane and now enters the blood capillary. |
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Term
| What is different about the absorption of Fructose by the enterocytes? |
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Definition
| Instead of using the Na+/Gluc Co-transporter to enter the enterocyte, Fructose uses GLUT5. |
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Term
| T/F: The digestion of proteins occur via dehydration. |
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Definition
| False; it occurs via hydrolysis. Removing water will create peptide linkages whereas adding water breaks these bonds. |
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Term
| What causes the digestion of proteins in the stomach? |
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Definition
Pepsin
Digests about 10-20% of dietary protein
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Term
| What causes the digestion of proteins in the SI? |
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Definition
Proteolytic enzymes that are secreted from the pancreas. Those include:
1. Trypin and Chymotrypsin
2. Carboxypolypeptidase
P3. roelastase--->Elastase |
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Term
| What causes digestion of peptides in the Enterocytes? |
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Definition
| In the Duodenum and Jejunum, the brush border has microvilli that contains peptidases in the membrane. These include Aminopolypeptidase and dipeptidase. |
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Term
| 99% of digest protein results into _______. |
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Definition
Amino Acids
(can hae some small peptides) |
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Term
| Describe the absorption of A.A by the enterocytes. |
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Definition
| Enterocytes has a Na+/A.A. co transported on the Apical membrane. Once Na+ binds then A.A. will bind and both get transported into the cell. The A.A. will leave via an A.A. only transporter located on the B.M.. Goes to the blood. |
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Term
| Describe the absorption of Peptides by enterocytes? |
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Definition
| Peptides enter the enterocyte cell via a H+/Peptide Co-transporter called PepT1. Once inside the cell peptidases break down the peptides into A.A. Which then exit on the B.M via A.A. only transporter. Now goes to the blood. |
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Term
| What 2 things can emulsify fats? |
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Definition
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Term
| How does bile salts accelerate fat digestion? |
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Definition
| They form michelles which then transport the digested fat products to the brush border of enterocytes for absorption. |
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Term
| T/F: Digestion of fats can start in the mouth. |
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Definition
| True, there is lingual lipase that can breakdown some fats. |
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Term
| Emulsification of fat begins in the ________________, but most of it occurs in the _______________. |
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Definition
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Term
| Digestion of fats use lipolytic enzymes that are secreted from the pancreas. What are these enzymes and what do they do? |
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Definition
1. Pancreatic lipase = Hydrolyzes TG to FFA and 2-MG
2. Cholesterol Esterase Hydrolase = Hydrolyzes FA from Cholesterol esters
3. Phospholipase A2 = Hydrolyzes FA from Phospholipids |
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Term
| Describe the absorption of lipids by the enterocytes. |
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Definition
| The majority of lipids are in FA and MG form. They enter the enterocyte by simple diffusion. Once inside it goes to the ER where it makes more TGs. The TGs become surround by apolipoprotiens thus forming a Chylomicron. The Chylomicron goes to the golgi, and eventually exits the enterocyte via exocytosis. It does not go to the blood immediately. It first goes into the lymphatic system then to the blood system. |
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Term
____________ mL of H2O enter the GI a day.
_____________ mL is lost in feces and
______________ mL must be absorbed. |
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Definition
9200 mL
50-100 mL
9100 mL |
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Term
| What are the 3 mechanisms that absorb Na+ and Cl-? |
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Definition
1. Active electrogenic transport of Na+
2. Na+ coupled to water soluble organic solutes such as Glucose or A.A.
3. Neutral Na/Cl co-transporter |
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Term
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Definition
| Indirect absorption in the duodenum and jejunum |
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Term
| T/F: All HCO3- gets absorbed |
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Definition
| False; the HCO3- that makes up the gastric mucus layer is localized to the stomach and will not leave to get absorbed. It protects us from excoriation of pepsin and HCl so we dont want it to get absorbed. |
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Term
| Absorption of Ca2+ occurs actively in all segments. Which channels allow for the absorption of Ca2+? |
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Definition
Transient Receptor Potential Vanilloid Type 6
(TRPV6 Channels) |
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Term
| What sequesters Ca2+ into enterocyte and increases the transport across the cell to the B.M? |
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Definition
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Term
| What increases the Ca2+ absorption from the intestine? |
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Definition
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Term
| How does Ca2+ exit the B.M. of the enterocyte? |
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Definition
| Leaves via a Ca-ATPase or a Na+/Ca2+ exchanger. |
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Term
| Describe the absorption of Iron by the enterocytes. |
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Definition
1. Fe3+ is reduced to Fe2+ via Reductase located in brush border of enterocyte.
2. Fe2+ cotransported with H+ into cell via Divalent Metal Transporter (DMT1)
3. If there is an high # of Fe, then it gets incorporated to Ferritin and will not reach the blood. Instead the enterocyte dies and sheds, so lose Iron.
4. If there is a low # of Fe it will exit the BM via Ferroportin transporter.
5. Hephaestin first binds to Fe2+ and converts it back to Fe3+ then exits thru B.M
6. Fe3+ binds to Transferrin for transport throughout body |
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Term
| Which kinds of foods provide us with Heme? |
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Definition
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Term
| Describe the absorption of Vit B12. |
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Definition
| Vit B12-R protein complex are in the gatric lumen. So Pancreatic proteases degrade the R proteins and leave free Vit. B12. The B12 then binds to intrisinc factors that is needed for absorption. The brush border receptor binds the B12-IF complex and allows absorption in the ileum. |
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Term
| Which vitamines are fat soluble and what do they need for absorption? |
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Definition
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Term
| How are water soluble vitamins absorbed? |
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Definition
| By carriers that are Na+ co-transporters |
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Term
| T/F: If not bound to intrinsic factor, Vit. B12 can still be absorbed just to a smaller extent. |
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Definition
| False; if there is no intrinsic factor bound to Vit. B12 then it will not get absorbed. It is very important for its absorption. |
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Term
| The Large intestine reabsorbs water and electrolytes. This occurs in the ________________ (proximal). the Large intestine can also store feces, this occurs in the ___________________(distal). |
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Definition
Absorbing colong
Storage colon |
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Term
| What gives feces its brown color? |
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Definition
Derivatives of bilirubin
(Sterocobilin and Urobilin) |
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Term
| Feces is ____________water and ___________ solid material. |
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Definition
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Term
| What things make up the solid material of feces? |
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Definition
1. 30% dead bacteria
2. 10-20% of undigested fats
3. 2-3% protein
4. 10-20% inorganic material
5. 30% of undigested roughage |
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