Biochemistry Week 3

Front 1

carbohydrates

Back 1

-most abundant biomolecules on earth
-provide major portion of daily caloric requirement
-oxidation of carbs is the central energy yielding pathway in most cells

Front 2

starch

Back 2

-nutritional store of glucose in plants
2 Forms:
-amylopectin (branched) --> alpha (1,4) & alpha (1,6) glycosidic linkages
-amylose (unbranched) --> alpha (1,4)glycosydic linkages

Front 3

monosaccharides

Back 3

-only monosaccharides will be transported into cells to be used as an energy source
-disaccharides & polysaccharides need to be broken down into monosaccharides in order to be absorbed

Front 4

lactose vs. lactate

Back 4

-lactose --> disaccharide (galactose + glucose)
-lactate --> product of glycolysis

Front 5

salivary amylase

Back 5

-enzyme in mouth that is an alpha (1,4)-glucosidase
-limited breakdown of starch & glycogen
-products are unbranched oligosaccharides (limit dextrins) & maltose
-it breaks alpha (1,4) linkages

Front 6

pancreatic amylase

Back 6

-an alpha (1,4)-glucosidase secreted by the pancreatic duct into the duodenum
-products are maltose, matotriose, and dextrins

Front 7

brush border of mucosal epithelium

Back 7

-final hydrolysis of di- and oligosaccharides to monosaccharides is carried out by enzymes on the surface of the small intestine epithelial cells

Front 8

di-, oligo-, and ploysaccharides that aren't broken down

Back 8

-cannot be absorbed
-broken down by bacteria in lower portions of small intestine
-produce short-chain fatty acids, lactate, hydrogen gas, methane, and CO2
-leads to increased fluid secretion, increased intestinal motility, & cramps

Front 9

microvilli

Back 9

-in brush border
-increase surface area
-greater possibility for absorption

Front 10

SGLT1

Back 10

-active transporter for galactose & glucose
-Na+ dependent (drives reaction of sugar against conc. gradient)

Front 11

GLUT5

Back 11

-facilitated diffusion
-moves fructose down conc. gradient (Na+ independent)

Front 12

good test questions

Back 12

1)comparing fructose & glucose means of transport across membrane (ie. down vs. against conc. gradient)
2)contrast this process with lipids (carbs have to be broken down to cross membrane) (III-5)

Front 13

GLUT2

Back 13

-facilitated diffusion of glucose, galactose, & fructose
-Na+ independent

Front 14

rate of absorption

Back 14

-enhanced by the presence of microvilli in the lumenal surface of epithelial cells

Front 15

rate of monosaccharide absorption

Back 15

-increased by the existence of specific transport systems located in the plasma membrane of mucosal cells
1) a Na+ monosaccharide cotransporter --> catalyzes active transport of D-glucose & D-galactose into cell at expense of Na+ gradient (SGLT)
2) Na+ facilitated diffusion monosaccharide system with specificity for D-fructose (GLUT5)

Front 16

carbohydrate maldigestion diseases

Back 16

1) congenital asbsence of a particular enzyme --> ex. lactase deficiency in children
2) hereditary, delayed onset deficiency --> ex. delayed onset lactase deficiency
3) acquired deficiency --> caused as a result of intestinal disease (ex. temp lactase dificiency resulting from destruction of brush border tissue)

Front 17

lactose intolerance

Back 17

-common condition that leads to abdominal cramps & diarrhrea upon ingestion of lactose
-caused by absence of lactase
-lactose broken down into toxic products by enzymes present in large intestine

Front 18

glycolysis (Embden-Meyerhof pathway)

Back 18

1)represents the central pathway for catabolism of gluscose & other monosaccharides
2)nearly univerwal pathway that occurs in vitually all tissue
3)the liver is the principal organ in the maintenance of blood glucose levels (functional state of liver profoundly influences carbohydrate metabolism)
4)D-glucose is oxidized to pyruvate (which may be converted to lactate in anaerobic conditions)

Front 19

glycolysis under anaerobic conditions

Back 19

-consists of 11 couple reactions
-Net Reaction:
D-glucose + 2Pi + 2ADP --> 2 lactate + 2H+ + 2ATP + 2H20

Front 20

glycolysis under aerobic conditions

Back 20

-10 coupled reactions
-Net Reaction:
D-glucose + 2Pi + 2ADP + 2NAD+ --> 2 pyruvate + 2H+ + 2ATP +2NADH + 2H20

Front 21

stage 1 of glycolysis

Back 21

-the preperatory phase
1)transport sugars to liver
2)phosphorylate these sugars
3)convert the sugars
-2 ATP consumed

Front 22

stage 2 of glycolysis

Back 22

-conversion of glyceraldehyde 3-phosphate to pyruvate (or lactate) in a series of oxidation-reduction steps
-formation of 4 ATPs (net of 2 at this point)
-5 or 6 enzymes used