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52 Cards in this Set
- Front
- Back
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What are the 3 types of carbohydrates that we eat?
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Starch, Sucrose, Lactose. Carbs
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How many carbs do adults consume daily?
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300-350, makes up 45% of total caloric intake.
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All Starches are polymers of:
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alpha-D-glucose. They serve as the carbohydrate storage form in plants.
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What are the 2 structural classes of starch?
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Amylose and Amylopectin. Amylose consists of linear chains of LINEAR glucose linked by alpha 1-4 bonds, amylopectin has a branched character in which the linear chains are occasionally linked alpha 1-6.
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Starch is always a mixture of what two things?
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Amylose and Amylopectin.
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What are reducing sugars?
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If the hydroxyl group on the anomeric carbon of a cyclized sugar is not linked to another sugar by a glycosidic bond, the ring can open. The resulting aldehyde of the sugar can act as a REDUCING AGENT causing a reagent to be reduced and become colored while the aldehyde is oxidized. These are reducing sugars.
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What is the carbohydrate storage form in animals?
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Glycogen. It resembles amylpectin in structure, but is more highly branched.
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Where is Glycogen primarilyi stored?
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Liver and muscle. Present in minute quantities in our diet when we eat fish and meat.
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What is the chief constituent of the fibrous parts of plants?
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Cellulose.
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What makes provides bulk in our diet and is indigestible?
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Cellulose
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What types of glucose units make up the linear cellulose?
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Beta-D-glucose. Beta 1-4 linkage.
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What is Sucrose?
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Common table sugar, and is obtained commercially from cane or beet. It is composed of glucose linked to fructose by alpha, beta-1, 2 bonds.
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What is sucrose made of?
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Glucose and Fructose
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Is sucrose a reducing sugar?
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No. No open carbon.
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Lactose is only used by:
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Mammals.
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What is Lactose composed of?
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Galactose and Glucose with B-1,4 bonds.
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Is lactose a reducing sugar?
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YES!
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What disaccharide is found in mushrooms and fungi?
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Trehalose.
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What is Trehalose composed of?
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Two glucose lined by their anomeric carbons. Alpha,Alpha-1,1.
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Is Trehalose a reducing sugar?
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NO!
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What is Digestion catalyzed by?
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A family of enzymes known as glycosidases (glycoside hydrolases) that hydrolyze glycosidic bonds.
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What is another word for alpha 1-4 endoglucosidase?
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alpha-amylase. This means it will hydrolyze the interior alpha-1,4 bonds between glucose residues withing amylopectin, amylose, and glycogen, converting the large polysaccharides to smaller entities.
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What digestive enzymes are in the stomach?
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None. There may be some limited acid (nonezymatic) hydrolysis of sucrose to yield fructose and glucose.
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What happens in the Luminal Phase of Digestion?
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The exocrine pancreas secretions contain bicarbonate ion (HCO3) which neutralizes the HC1 from the stomach. It also contains pancreatic alpha amylase (similar to salivary alpha amylase) which continues the digestion of starch. Maltose, Maltotriose, and branched dextrins are the final products of alpha-amylase action on starch.
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What is secretin?
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Peptide hormone, acts on pancreas in order to release Bicarbonate.
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What is cholecystokinin?
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Stimulates production and release of digestive enzymes by pancreas, including pancreatic amylase.
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What happens in the Membrane Phase of digestion?
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Digestion of lactose, sucrose, maltose, maltotriose, and dextrins is carried out by glycosidases protruding form the brush-border membrane epithelial cells in the intestinal villi. these glycosidases include exoenzymes that cleave off one monosaccharide at a time from nonreducing end.
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What is B-galactosidase?
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Lactase, is specific for B-1,4 bond between galactose and glucose in lactose.
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What is Trehalase?
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Hydrolyzes trehalose (a, a-1 bond) to yield 2 molecules off glucose.
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What is Glucoamylase complex?
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(alpha-1,4-exoglucosidase) functions to cleave the alpha-1,4 linkages between glucose units in oligosaccharides, starting from the nonreducing end of the chains. It also hydrolyzes the alpha 1,4 bonds in maltose and maltotriose yielding glucose.
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What is Sucrase-Isomaltase?
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Is a complex which contains the following catalytic activites:
The sucrase site-hydrolyzes sucrose to glucose and fructose plus maltase activity. The isomaltase site-hydrolyzes the alpha-1,6 bonds between glucose residues plus maltase activity. |
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What is Dietary Fiber?
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Indigestible carbohydrates. They are of plant origin and cannot by hydrolyzed by digestive enzymes. They can be grouped by those that are soluble and those that aren't.
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What are the soluble fibers?
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Pectin, Mucilages and gums.
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What are insoluble fibers?
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Cellulose, Hemicelluloses, and lignin.
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How is Methane, short chain fatty acids, and lactic acids released into the gut?
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Bacterial flora in the fut may metabolize the more soluble dietary fibers.
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What are benefits of dietary fiber?
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Fiber softens the stool and reduces colonic wall in diverticular disease.
Pectins are thought to lower cholesterol levels by binding bile acids Pectins may slow rate of absorption of glucose and thus prevent high blood glucose levels after meals Fiber containing foods are useful for patients with IBS. |
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What is Raffinose?
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Oligosaccharides in beans and peas which are not digested in small intestine. Galactose units (1to 3) linked by 1,6 bonds to sucrose.
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What are the 2 transport mechanisms for Monosaccharides?
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1. Na+-Dependent Monosaccharide Cotransport System (Active transport)
2. Facilitated Diffusion (Na+-independent monosaccharide transport system) |
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What is SGLT-1
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is a Na+ dependent glucose symporter located on the luminal side of the intestinal epithelial cells.
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Fructose is taken out of the cell by:
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GLUT 5, and GLUT-2 on the contraluminal side.
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What tissue distribution is done by Glut-1
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RBCs, blood-brain barrier
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What tissue distribution is done by Glut-2
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Liver, Pancreatic B-Cells, Contraluminal membrane of intestinal epithelial cells. Accepts ALL 3 monosaccharides
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What tissue distribution is done by Glut-3
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Brain (neurons)
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What tissue distribution is done by GLUT-4
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Adipose tissue Skeletal muscle, Heart Muscle
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What tissue distribution is done by GLUT-5
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Intestinal epithelial cells, Sperm. Insulin-sensitive transporter.
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What tissue distribution is done by SGLT-1 and SGLT-2
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Intestinal epithelial cells for 1, Kidney for 2.
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What is the glycemic index?
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Indicative of how quickly blood glucose levels rise after consuming these foods. Not all are digested at same rate. Foods that slowly raise blood glucose over an extended period of time have a low Glycemic Index. The effect of 50g of carbohydrate in a particular food on blood glucose compared to 50g of glucose.
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What is the glycemic Load?
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The glycemic index times the amount of carbohydrate in a standard serving size of that food.
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What are the 3 classifications of Lactose Intolerance?
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1. Congenital lactase deficiency in infants and children
2. Temporary lactase deficiency in premature infants 3. Acquired isolated lactase deficiency or non-persistant lactase (late onset lactase deficiency, or adult hypolactasia) 4. Lactase deficiency secondary to intestinal diseases (secondary lactase deficiency) 5. Lactase deficiency secondary to insufficient mucosal contact time. |
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Which cultures have low prevalence of late onsent lactase deficiency?
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Danes and the Dutch.
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How do you diagnosis and treat lactose deficiency?
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Measure the amount of hydrogen that is exhaled after consuming a lactose containing meal. Reduce dairy use milk treated with lactase; or take tablets containing lactase before ingesting dairy.
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What is a normal glucose tolerance curve?
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Within 30-60 minutes teh blood glucose levers reach peak and then decrease to fasting in 2 hours.
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