Nutritional Biochemistry Exam 1 – Flashcards
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What are the characteristics of lipids?
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1. large energy content (9 kcals/g) 2. Can be hydrophobic, hydrophilic or amphiphilic
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What are the 5 functions of lipids?
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1. Energy 2. Structure 3. Steroid hormones 4. Insulation 5. Fat soluble vitamin absorption
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What is the Omega nomenclature system?
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# of carbons:# of double bonds (omega) 1st double bond is at (#) from the methyl end (furthest point from glycerol) of fatty acid
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What is the Delta nomenclature system?
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# carbons: # double bonds (Delta) double bonds located at (insert locations here) from carboxyl end (Closest point from glycerol) of fatty acid
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How does each fatty acid behave at room temp?
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Saturated: solid monounsaturated: liquid at room temp, solid at lower temp Polyunsaturated: liquid at all temps
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What are the 3 disaccharides
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1. Sucrose 2. Maltose 3. Lactose
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What disaccharide digestion occurs in the mouth?
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None
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What disaccharide digestion occurs in the stomach?
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None
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What disaccharide digestion occurs in the small intestine?
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None
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What disaccharide digestion occurs in the brush border?
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1. Sucrase cleaves sucrose into a fructose and glucose 2. Maltase cleaves maltose into two glucoses 3. Lactase cleaves lactose into galactose and glucose
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How are the monosaccharides absorbed?
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1. Glucose and Galactose- are actively transported into intestinal epithelial cell through the transport protein sodium glucose transporter 1 (SGLUT 1), leave the cell through GLUT 2 by means of facilitated diffusion 2. Fructose enters intestinal epithelial cell by means of facilitation diffusion through GLUT 5, exit through GLUT 2 by means of facilitated diffusion
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What types of lipids do we consume?
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1. Triacylglycerols 2. Phospholipids 3. Cholesterol
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What lipid digestion occurs in the mouth?
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Lingual lipase acts on the ester bonds connecting fatty acids to glycerol. Specifically the fatty acid in the third position forming 1,2 diacylglycerols
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What lipid digestion occurs in the stomach?
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Gastric lipase breaks ester bonds between glycerol and fatty acids at the third position turning TAGs into 1,2 diacylglycerol. Specifically targets short and medium chain fatty acids that can be directly absorbed through the stomach.
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What lipid digestion occurs in the small intestine?
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1. Sodium bicarbonate neutralizes acidic chyme so bile and pancreatic lipase may do their work 2. CCK stimulates gall bladder to release bile which emulsifies the lipid droplet thus increasing the surface area that pancreatic lipase may work with. Amphiphilic bile surrounds the lipid allowing it to separate from the blob 3. Pancreatic lipase breaks the ester bonds of the DAGs and TAGs between the fatty acid at the one and 3 position creating a free fatty acids and 2 monoacylglycerol
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How does bile affect lipids?
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Bile affects lipids by emulsifying them thus increasing the surface area that pancreatic lipase can work on. Bile is amphiphilic and surrounds a lipid with it's hydrophobic end facing the lipid and the hydrophylic end facing out making it hydrophilic. Bile also aids in the formation of Micelles which assist in the transport of lipid digestive end products.
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How does pancreatic lipase act on the droplet of TAGs and DAGs?
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Pancreatic lipase, with the assistance of colipase, breaks the ester bonds of the DAGs and TAGs between the fatty acid at the 1 and 3 position creating a free fatty acids and 2 monoacylglycerol
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What is colipase?
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Colipase is the coenzyme that assists pancreatic lipase by anchoring it to the DAGs and TAGs so that it may cleave ester bonds at the 1 and 3 position
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What are the final end products of lipid digestion?
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1. 2-monoacylglycerol 2. Free fatty acids 3. Lysolecithin 4. Cholesterol
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How are the end products of lipid digestion absorbed
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a micelle formed from bile salts creates a hydrophilic vessel to transport the end products of lipid digestion across the water layer between the intestinal lumen and the intestinal epithelial cells. The end products of lipid digestion are then diffuse into the intestinal epithelial cell through either facilitated or regular diffusion.
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What is a micelle?
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a transport mechanism consisting of bile salts that assists the end products of lipid digestion (lysolecithin, monoacylglycerol, free fatty acids and cholesterol) to cross the unstirred intestinal water layer so that they may be absorbed into the intestinal epithelial cells.
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What happens to free fatty acids once in the cell?
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once in the cell the free fatty acids are acted upon by the ligase based enzyme fatty acyl-CoA synthetase to form the product fatty acyl-CoA. This reaction requires ATP
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What happens to 2-monoacylglycerol once in the cell?
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Once in the cell 2-monoacylglycerol is acted upon by acyl CoA monoacylglycerol acyl transferase. This enzyme takes fatty acyl-CoA and attaches it to the one position on the glycerol backbone to form 1,2 diacylglycerol
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What happens to 1,2 diacylglycerol once formed in the cell?
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1,2 diacylglycerol is acted upon by acyl CoA diacylglycerol acyl transferase which takes a fatty acyl CoA and attaches it to the three position on the glycerol backbone to form a full triacylglycerol
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What happens to cholesterol once in the cell?
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Cholesterol is acted upon by acyl CoA cholesterol acyl transferace which takes a fatty acyl CoA and attaches it to the cholesterol to form a cholesteryl ester
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How do lipids exit the intestinal epithelial cell?
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Triacylglycerols, cholesteryl esters, phospholipids and fat soluble vitmins enter a chylomicron which then enters the lymphatic system to join general circulation later
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What is a chylomicron?
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A transport lipoprotein formed in intestinal cells that aids in the transport of triglycerides, cholesterol, phospholipids and fat soluble vitamins. These lipoproteins enter the lymphatic system which then enters the bloodstream later.
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What are the 3 principal polysaccharides?
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1. Starch 2. Glycogen 3. Cellulose
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What is starch?
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The immediate fuel source for the body, consists of amylose and amylopectin
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What is amylose?
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A type of starch that contains alpha 1,4 linkages that make it linear
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What is amylopectin?
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a type of starch that contains both alpha 1,4 linkages and alpha 1,6 linkages making it both linear and branched
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What is cellulose?
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an indigestible, insuluble polysaccharide that humans lack the enzymes to break do to their beta 1,4 linkages
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What is glycogen?
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The storage form of glucose in the body consisting of alpha 1,4 and alpha 1,6 linkages making it both linear and branched
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What starch digestion occurs in the mouth?
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Salivary alpha amylase starts to break alpha 1,4 glycocytic linkages to form starch dextrins, maltose and isomaltose.
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What starch digestion occurs in the stomach?
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None, salivary amylase is deactivated due to the acidic nature of the stomach
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What starch digestion occurs in the lumen of the small intestine?
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Sodium bicarbonate neutralizes chyme so pancreatic alpha amylase can break down starch dextrins into maltose and isomaltose.
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What starch digestion occurs on the brush boarder of the small intestine?
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Enzymes maltase and isomaltase break down maltose and isomaltase into two glucoses
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How is starch absorbed?
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Glucose is actively transported into the epithelial cells of the small intestine through the protein SGLUT 1 which requires sodium be bound to the glucose and ATP. Glucose either remains in the cell or is diffused through either facilitated or regular diffusion into general circulation through the protein GLUT 2
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What is the first step of HCl production?
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H20 osmoses and C02 diffuse into the gastric parietal cells
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What is the enzyme that acts on H2O and CO2 in HCl production?
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carbonic anhydrase
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What is the product of the combination of H2O and CO2?
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carbonic acid (H2CO3)
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What happens to carbonic acid in HCl production?
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Carbonic acid spontaneously breaks into 2H+ and bicarbonate (CO3)
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What happens to 2H+ in HCl production?
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The 2H+ is actively transported, using a transport protein and ATP, into the gastric lumen. 2H+ is replaced by potassium which is actively transported into the parietal cell.
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What happens to bicarbonate (HCO3) in HCl production?
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Bicarbonate exits the parietal cell into the blood stream by means of facilitated diffusion. Bicarbonate is replaced by Cl which enters the parietal cell by means of facilitated diffusion.
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What happens to Cl in HCl production?
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Chlorine enters the parietal cell by means of facilitated diffusion, it then exits the cell by means of active transport to join with 2H+ to form hydrochloric acid
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What are the functions of HCl?
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1. Necessary to activate pepsinogen to pepsin for protein digestion 2. protects the stomach against bacteria and toxins
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What happens to protein in the stomach?
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HCl denatures protein structure by breaking hydrogen bonds, pepsin works on peptide bonds , End products: polypeptides, oligopeptides and free amino acids
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What is the cascade activation of pancreatic protease zymogens?
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duodenal enterocytes secrete enteropeptase which activates trypsinogen into trypsin by cleaving the inactive side chain. Trypsin then activates chymotrypsinogen, proelastase, procarboxypeptididase A and procarboxypeptidase B into chymotrypsin, elastase, carboxypeptidase A and carboxypeptidase B by also cleaving the inactive side chain.
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What are the 5 pancreatic protease zymogens?
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1. Trypsinogen 2. Chymotrypsinogen 3. Proelastase 4. Procarboxypeptidase A 5. Procarboxypeptidase B
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What are the 5 active pancreatic protease enzymes?
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1. Trypsin 2. Chymotrypsin 3. Elastase 4. Carboxypeptidase A 5. Carboxypeptidase B
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What do the pancreatic protease enzymes act on?
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1. Polypeptides 2. Oligopeptides
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What do the brush border enzymes act on?
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1. Oligopeptides 2. Tripeptides
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What happens to protein at the brush boarder?
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3 peptidase based enzymes act on the oligopeptides and tripeptides to break them into the final end products of protein digestion: tripeptides, dipeptides and free amino acids
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What are the final end products of protein digestion?
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1. Free amino acids 2. Tripeptides 3. Dipeptides
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How are amino acids absorbed into epithelial cells?
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Amino acids enter the intestinal epithelial cells by means of facilitated diffusion through an unnamed sodium dependent transport protein. Na binds to transport protein, altering it's structure, to allow the amino acid and sodium into the cell. The amino acids are then used within the cell or leave the cell through either facilitated or regular diffusion into the bloodstream to be transported to the liver.
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How are peptides absorbed into epithelial cells?
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The peptides enter the intestinal epithelial cell by means of facilitated diffusion through the protein PEPTI 1 which requires hydrogen.
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What happens to peptides within the cell?
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di and tripeptides are acted upon by cytosolic peptidase based enzymes and broken down into free amino acids.
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What is an enzyme?
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A catalyst for biochemical reactions within the body. Enzymes are highly specific to their active site, they do not change, their reactions can be either reversible or irreversible.
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What are the functions of enzymes?
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To catalyze biochemical reaction
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What is a rate limiting enzyme?
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An enzyme that stimulates a metabolic pathway in one direction thus exceeding the reaction in the other direction.
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What is the substrate, enzyme, product equation?
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A substrate binds to an enzyme, the enzyme acts on the substrate to create a product
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What is a cofactor?
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A substance other than the substrate that is essential for the enzyme to function. Usually a metal ion.
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What is a coenzyme?
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A nonprotein substance necessary for the functioning of an enzyme. Usually vitamins.
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How are enzymes regulated?
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1. Competitive inhibition 2. Noncompetitive inhibition 3. Allosteric control 4. Covalent Modification 5. Induction and Repression
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What is competitive inhibition of an enzyme?
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A substance binds to the active site of an enzyme thus preventing it's specified substrate from binding. Can be reversible or irreversible.
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What is non-competitive inhibition of an enzyme?
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An external agent binds elsewhere on an enzymes besides the active site. This alters active site so it's specified substrate cannot bind.
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What is allosteric control of an enzyme?
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A modulator binds to an enzyme somewhere other than its active site that can either up regulate (speed up) or down regulate (slow down) the rate of an enzymatic reaction. Ex. ATP, citrate, AMP
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What is covalant modification of an enzyme?
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Phosphoralation or dephosphoralation to either up regulate (speed up) or down regulate (slow down) the rate of an enzymatic reaction
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What is induction or repression of an enzyme?
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Molecular communication to either up regulate (speed up) or down regulate (slow down) enzyme production. Ex. hormones
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What are the enzyme classifications?
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1. Oxidoreductases 2. Transferases 3. Hydrolases 4. Lyases 5. Isomerases 6. Ligases
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What is the mechanistic action of oxidoreductase enzymes?
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Perform oxidation/reduction reactions by transfering H+ to a coenzyme.
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What is the mechanistic action of transferase enzymes?
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Transfer functional groups from one substance to another Ex. Acyl CoA monoacylglycerol acyl transferase
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What is the mechanistic action of hydrolase enzymes?
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Break bonds using water. Ex. Trypsin
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What is the mechanistic action of lyase enzymes?
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Break bonds without the use of water but with the transfer of H+
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What is the mechanistic action of isomerase enzymes?
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Enzymes that rearrange molecules to create optical or geometric isomers
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What is the mechanistic action of ligase enzymes?
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Form bonds using ATP Ex. Fatty Acyl CoA synthase
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Where is bile made?
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The Liver
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Where is bile stored?
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The Gallbladder
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How is bile released?
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CCK stimulates the gallbladder to release bile into the common bile duct that leads into the duodenum of the small intestine.
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Where is bile reabsorbed?
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The Ileum of the small intestine
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How is bile reabsorbed?
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Bile is actively transported into the intestinal epithelial cells within the ileum.
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Where does bile go once absorbed?
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Bile then attaches to albumin and is then transported in the hepatic portal vein to the liver.
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Once bile is recycled what happens?
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Bile acids are reconjugated to amino acids to be used again.
