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Flashcards by Eleni Cico, updated more than 1 year ago
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Created by Eleni Cico
almost 4 years ago
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| Question | Answer |
| Name three major groups of carbohydrates? | Monosaccharide’s, disaccharides or oligosaccharides and polysaccharides |
| Give two examples of each of these groups of carbohydrates? | . Fructose, galactose, glucose / lactose, maltose, sucrose / cellulose, glycogen, starch |
| Which monosaccharide has a slower rate of uptake from the digestive tract? | Fructose |
| The digestion of disaccharides occurs mainly in which location? | Upper small intestine |
| The digestive enzymes which achieve this are collectively known as ……… | Disaccharidases |
| What is the name of the key enzyme involved in the breakdown of polysaccharides? | Alpha amylase (glycosidase) |
| Which two places is this enzyme produced? | Mouth and pancreas |
| By which transport mechanism are monosaccharide’s taken over the basolateral border and into portal circulation? | Facilitated diffusion |
| Glucose is up taken into cells via ……… | Glucose transporters (GLUT) |
| What is the name of the transporter which is regulated by insulin? | GLUT 4 |
| In which locations are GLUT4 found? | Muscles and adipose tissue |
| Which three nutrients are required for the insulin receptor to function? | Chromium, glutamine and B3 |
| What is the name of the transporter in the brain? | GLUT 3 |
| Name two groups of simple lipids? | .Fatty acids, glycerols (triacylglycerols, diacylglycerols and monoacylglycerols) and waxes such as sterols esters (cholesterol) and nonsterol esters (Vit A) |
| Name two groups of compound lipids? | Phospholipids (phosphatidic acids, plasmalogens and sphingomyelins), glycolipids (CHO containing) and lipoproteins |
| .How are long-chained fatty acids assisted over the brush border and explain how this is accomplished? | Dietary fats with the help of enzymes (lipases) are hydrolyzed and bile salts help in emulsification and form micelles which are stabilized to allow the hydrophobic fats to diffuse through the hydrophilic brush border of intestine. |
| How are LC FAs transported through the enterocytes? | via chylomicrons |
| How do these larger lipids then travel through circulation and why are these necessary? | via lipoproteins such as VLDL’s, LDL’s and HDL’s, as the protein component stabilize the lipoproteins as they travel through the blood and allow them to be recognized by specific cell receptors |
| Which enzyme hydrolyses these particles, allowing the lipids to be released into tissues? | Lipoprotein lipase |
| How do short chained fatty acids travel through circulation? | Bound to albumin |
| What is the major storage site for triaclyglycerols? | Adipose tissue |
| What effect can insulin have on these stores? | Insulin accelerates the entry of glucose into the adipose cells and increases the availability and uptake of fatty acids by stimulating lipoprotein lipase. It also inhibits intracellular lipase which hydrolyses stored triacylglycerols. |
| Name four essential and four non-essential amino acids? | ESSENTIAL - Isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine; NON-ESSENTIAL – Alanine, aspartic acid, carnitine, cysteine, glutamic acid, glutathione, glycine, ornithine, praline, serine, taurine, tyrosine |
| Which are absorbed faster – peptides or free amino acids? | .Peptides |
| What two mechanisms are utilised to transport free amino acids across the basolateral border? What reason may designate the use of one transport over the other? | .Sodium dependent pathways are used when the amino acid concentrations in the gut are low, while diffusion is the mechanism at other times. |
| Within intestinal cells, amino acids may be used for the synthesis of what four compounds? | Apoproteins for lipoprotein formation, new digestive enzymes, hormones or nitrogen-containing compounds |
| What group of enzymes hydrolyse protein? | Proteases |
| .Name three types of protein hydrolyzing enzymes that function in the small intestine? | Trypsinogen/ trypsin, chymotrypsinogen/ chymotrypsin, procarboxypeptidases such as carboxypeptidase A & B, proelastase/ elastase, collagenase, ribonuclease and deoxyribonuclease |
| What syndrome allows small oligopeptides to enter circulation via paracellular or intercellular routes, which can cause inflammatory reactions? | Leaky gut |
| Name two carrier systems which transport amino acids into the liver? | .Diffusion; sodium dependent transport; hormones and cytokines or system A which induces glucagon and provides amino acid substrates for glyconeogenesis |
| Name 3 types of plasma proteins? | Albumin, transthyretin, retinol-binding protein, blood-clotting proteins or globulins |
| Name three nitrogen-containing compounds which the liver synthesizes from amino acids? | Glutathione, carnitine, creatine, carnosine and choline |
| Name two forms of vitamin C, one acid and one alkaline? | ACID – ascorbic acid; ALKALINE – calcium ascorbate or sodium ascorbate |
| What substance is necessary to reform ascorbate from dehydroascorbate and is essential for vitamin C metabolism? | Glutathione |
| Is the absorption of vitamin C influenced by intake concentrations? | Yes |
| Name 2 antagonists of vitamin C? | Pectin, zinc and high intakes of iron |
| Which cells have the highest concentration of vitamin C? | Adrenal and pituitary glands |
| Vitamin C is necessary to activate which enzyme responsible for energy production and collagen synthesis? | Hydroxylase |
| Name two co-enzyme forms of thiamine? | Thiamine diphosphate (TDP) and thiamin triphosphate (TTP) |
| Name three foods which contain anti-thiamine factors? | Raw fish and polyhdroxyphenols such as found in coffee, tea, betel nuts, blueberries, black currents, Brussels sprouts and red cabbage |
| .Name two substances which prevent the destruction of vitamin B1? | Vitamin C and citric acid |
| What are the group of enzymes which break the phosphate bonds with thiamine prior to absorption? | Phosphatases |
| In high concentrations of B1 ingestion, by what mechanism does transport over the brush border occur? | Passive diffusion |
| .By what mechanism does the uptake of B1 occur into cells? | Active transport (sodium dependent) |
| What are the two co-enzyme forms of riboflavin? | FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide) |
| Name three antagonists of vitamin B2? | Copper, zinc, iron, manganese and alcohol |
| Which protein carrier transports majority of B2 through circulation? | Albumin |
| The highest concentrations of B2 exist in which organs? | Liver, kidney and heart |
| Name the two active coenzyme forms of niacin? | NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate |
| Vitamin B3 may also be synthesized in the liver from which amino acid? | Tryptophan |
| By which two mechanisms do B3 get absorbed from the intestine? | Passive diffusion or sodium dependent active transport dependent on intakes |
| Is the absorption of mechanism of B5 concentration dependent? | Yes |
| What is the coenzyme form of pantothenate? | Coenzyme A |
| How is B5 mainly transported in circulation? | via red blood cells |
| In cells what is B5 typically used for? | To synthesize and re-synthesize CoA |
| Name the three phosphorylated coenzyme forms of pyridoxine? | PNP (pyridoxine phosphate), PLP (pyridoxal phosphate) and PMP (pyridoxamine phosphate) |
| These phosphorylated forms require hydrolysis prior to absorption into the enterocytes, what is the name of the enzyme responsible for this and which nutrient is it dependent on? | Alkaline phosphatase which is zinc dependent |
| What is the active form of B6 known as? | Pyridoxal-5-phosphate (PLP) |
| Which vitamin is an agonist of B6? | B2 |
| How is B6 absorbed across both the brush and basolateral border? | Passive diffusion |
| How is B12 released from peptide bonds in foods? | Pepsin and hydrochloric acid |
| What is the name of the substance which is found in saliva and gastric juice that can bind to B12 before it is released from food? | R proteins |
| What is the name of the glycoprotein synthesized by the gastric parietal cells, although functions in the small intestine to aid B12 absorption? | IF (intrinsic factor) |
| Describe the process by which these two substances aid B12 digestion? | B12 in stomach binds with R-proteins and travel to intestine, once in the SI, the B12- R protein complex is hydrolysed by proteases to release the B12. After, it is released then binds to IF where this complex then travels to the ileum, where specific B12 receptor sites (ileal receptor) are located and calcium helps in absorption at ileal receptors. |
| Which mineral is required for B12 absorption? | Calcium |
| Which 2 nutrients may antagonize B12 if supplemented at the same time? | Vitamin C and iron |
| What is the major storage form of B12 in the liver? | Adenosylcobalamin |
| B12 travels in circulation bound to what? | Transcobalamins |
| What are the three substances which make up folic acid? | Pteridine, PABA (para-amino-benzoic acid) and glutamic acid |
| Folate exists primarily in foods in polyglutamate forms which need to be hydrolysed into monoglutamate forms prior to absorption into enterocytes. Name the group of enzymes responsible for this and what nutrient are they dependent on? | Conjugases are zinc dependent |
| Name 3 factors which may inhibit the absorption of folate? | Alcohol, zinc deficiency due to diminished conjugase activity or conjugase inhibitors such as lentils, legumes, cabbage and oranges |
| .How does the majority of folate travel through circulation? | Bound to folate binding proteins (FBP’s) |
| Where is biotin endogenously produced? | Colonic bacteria |
| What substance can inhibit intestinal absorption of biotin? | Raw egg white or alcohol |
| Name three forms of vitamin A? | Retinol, retinal, retinoic acid, retinyl ester and provitamin A carotenoids such as β-carotene, α-carotene, lycopene and oxy-carotenoids such as lutein, canthaxanthin and zeaxanthin |
| How does the absorption of vitamin A take place over the brush border? | Active transport via micelle |
| Inside cells, which two proteins are required for vitamin A metabolism? | CRBP (cellular retinoid binding protein) and CRABP (cellular retinoic acid binding protein) |
| Inside the enterocyte, which B vitamin is needed to form retinol from beta carotene? | Niacin |
| Name two substances which may enhance vitamin A absorption? | Fat and vitamin E |
| Name two substances which may impair the absorption of vitamin A? | Fiber and vitamin E in large doses |
| Describe the process by which vitamin D can be synthesized by sunlight and subsequently transported to tissues? | Skin exposure to UV light in the presence of 7-dehydrocholesterol, a derivative of cholesterol, produces pre-vitamin D3. This is then converted to vitamin D3, also known as cholecalciferol or calcitriol, which is reabsorbed into the blood stream and transported to tissues via plasma transporter α2-globulin vitamin Dbinding protein (DBP). |
| .Via what other mechanism can vitamin D be transported to tissues? | Chylomicrons |
| Name two substances which can stimulate vitamin D metabolism? | PTH (parathyroid hormone), low calcium or low phosphorous |
| Name the two classes of vitamin E? | Tocopherols and tocotrienols |
| Once over the basolateral border, how is vitamin E transported to the liver? | Via the chylomicron remnants |
| How is vitamin E mainly transported through circulation, after leaving the liver? | via lipoproteins VLDL, LDL and HDL’s |
| What is thought to be vitamin E’s main function in these particles? | May prevent them from oxidation |
| Where does vitamin E exist mainly in cells? | Within cell membranes |
| .Name 2 types of vitamin K, one exogenous and one endogenous type and from where are they found or produced? | Phylloquinone (K1) exists in plants; menaquinone (K2) is synthesized by colonic bacteria |
| What is a known antagonist of vitamin K? | Warfarin |
| How is vitamin K transported over the basolateral border? | Active transport via chylomicrons |
| For what reason is the calcium present in foods and supplements relatively insoluble? | As calcium is present in its insoluble salts and need to be solubilised |
| Via which binding sites does calcium get up taken over the brush border? | Calbindin (calcium-binding protein) |
| What happens to these when there is low blood levels of calcium? Which vitamin regulates this process? | Calbindin transporters up regulate or increase in number, to draw in more calcium from the intestines Vitamin D |
| Name three substances which may bind calcium to be excreted in faeces? | Fibre, phytate, oxalate and fatty acids |
| .List two factors which may increase the absorption of calcium? | Food ingestion, lactose, other sugars, sugar alcohol and protein |
| List four factors which may inhibit calcium absorption? | Fibre and phytates bind calcium; oxalates chelate and increase excretion; magnesium competes for absorption with calcium; parathyroid insufficiency will decrease vitamin D absorption which decreases calcium absorption; unabsorbed fatty acids in high quantities bind to calcium and form fatty soaps |
| List three factors which decrease the absorption of magnesium? | Phytates and fibre decrease absorption; unabsorbed fatty acids binds to form soaps which are then excreted; iron and magnesium supplementation taken together decreases magnesium uptake |
| List two factors which may increase magnesium absorption? | Vitamin D increases absorption through active transport; lactose also appears to increase absorption |
| What are the two mechanisms of magnesium absorption and why would one method be utilised over another? | Concentration dependent passive diffusion with high intakes and carrier mediated active transport at low intakes |
| List two ways that magnesium may travel through circulation? | Free Mg2+; protein bound albumin or globulins; non-protein complexes to citrate, phosphate or sulphate. |
| What are the two mechanisms of phosphorus absorption and why would one method be utilised over another? | Concentration dependent passive diffusion with high intakes and carrier mediated sodium dependent active transport at low intakes |
| In what form is phosphorus usually found in the body? | PO4 2+ |
| List two ways sodium is up taken into enterocytes? | Sodium/ glucose transporter; sodium/ hydrogen exchange or sodium channel |
| How is chromium mainly transported through circulation? | Bound to transferrin |
| Name two other minerals which competitively bind to transferrin? | Copper, cadmium, manganese and iron |
| Which vitamin increases the plasma concentration of chromium? | Vitamin C |
| In foods, copper is bound to proteins. What is needed to free bound copper to allow its absorption? | HCl and pepsin in the stomach and proteases in the small intestine. |
| What is the name of the receptors which facilitate the transport of copper into cells from circulation? | Ceruloplasmin receptors |
| What is the name of the soluble intracellular proteins which bind to intracellular copper and deliver it to various locations in the cell? | Chaperones |
| Name three factors which decrease copper absorption? | Zinc, phytates, iron in large amounts, calcium and phosphorus, vitamin C and antacid ingestion due to these preventing copper being released from it’s bound amino acids |
| Name an iodine inhibitor? | Goitrogens (isothiocyanates) found in the cruciferous family of vegetables which include broccoli, kale, cauliflower, mustard, turnips, Brussels sprouts, cabbage etc |
| Which mechanism is utilised to allow iodine to enter and exit the enterocytes? | simple diffusion |
| How is iodine up taken into the thyroid? | active transport |
| Name two transport proteins which transport the thyroid hormones T3 and T4 through circulation? | Thyroxine binding globulins, albumin, transthyretin |
| What are the two forms of iron found in foods? | Ferric Fe3+ and ferrous Fe2+ |
| List three substances which may inhibit iron absorption? | Polyphenols such as tea and coffee; oxalic acid found in spinach, chard, berries, chocolate; phytates found in grains; EDTA preservative; phosvitin protein in egg yolks; nutrients such as calcium, zinc, manganese. |
| Iron travels in the blood bound to what? | Transferrin |
| Iron is stored bound to what? | Ferritin |
| Name two ways manganese is transported through circulation? | Bound to transferrin; free; bound to albumin or α-2 macroglobulin |
| Iron competes for absorption with manganese. Why may this be the case? | Use the same transporter DMT1 |
| Which two ways is molybdenum transported in circulation? | Albumin and a-2 macroglobulin |
| What are the two mechanisms of molybdenum absorption and why would one method be utilised over another? | Concentration dependent passive diffusion with high intakes and carrier mediated sodium dependent active transport at low intakes |
| What form of selenium is thought to be better absorbed? | Selenomethionein |
| Name two factors which increase absorption of selenium? | Vitamin A, C, E and the presence of reduced glutathione in the intestinal lumen |
| Name two ways selenium may be transported in circulation? | Either in free form or bound to albumin |
| By which mechanism is selenium taken into and out of circulation? | Passive diffusion |
| Are high or low concentrations of zinc absorbed? | Low concentrations |
| Name two substances which enhance zinc absorption? | Citric acid, picolinic acid, amino acids such as histidine and cysteine; glutathione, tripeptides and low zinc status |
| Name three substances which may inhibit zinc absorption? | Fiber, phytates, oxalates, polyphenols and some nutrients with divalent bonds such as magnesium, iron and calcium |
| Name four substances may zinc be bound to in the blood? | Albumin, transferrin, α-2 macroglobulin, and immunoglobulin g (IgG) |
| Name three other minerals are known to use the same transporter DMT1, as zinc? | Iron, manganese, copper |
| What substance is zinc incorporated into for storage inside cells? | Metallothionein |
| Boron is thought to move into and out of cells by which mechanism? | Passive diffusion |
| Where is boron found mainly in the body? | Bones, teeth, nails, hair |
| What is vanadium bound to for transport through circulation? | Transferrin |
| What is vanadium bound to for storage inside cells? | Ferritin |
| Vanadium mimics the action of which hormone? | insulin |
| . Which other nutrients use these same storage mechanisms? | iron |
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