Biochem Fo Life

Question 1

Salivary amylase

Answer 1

An enodnuclease meaning it only cleaves INTERNAL alpha 1,4 bonds between glucose residues
Forms alpha-dextrins
Inactivated by stomach acidity

Question 2

Alpha amylase

Answer 2

Secreted by the pancreas along with bicarbonate
Bicarbonate neutralizes acid so that the amylase can work
Continues hydrolysis of dextrine to maltose, maltotriose, and oligosaccharides

Question 3

Glucoamylase

Answer 3

Highest activity in the intestinal ileum

Exoglucosidase specific for alpha 1,4 bonds at the nonreducing end of a polysaccharide or limit dextrin

Question 4

Sucrase-isomaltase complex

Answer 4

Highest activity in the jejunum

Hydrolzes the alpha 1,6 bond - only way to do this

Question 5

Trehalase

Answer 5

Hydrolyzes the alpha 1,1 bond of trehalose

Question 6

Beta-glycosidase complex

Answer 6

Lactase-glucosylceramidase

Hydrolyzes the beta 1,4 bond connecting glucose and galactose in lactose

Question 7

GLUT2

Answer 7

Located in the liver and only imports glucose in when levels are high

Question 8

GLUT1

Answer 8

In RBC and brain to import glucose in

Question 9

GLUT4

Answer 9

In muscles and adipose tissues

Insulin-sensitive receptor

Question 10

Pepsinogen

Answer 10

Released from chief cells and converted to pepsin by the low pH of the stomach
Has endopeptidase activity
Autocatylitic - once active, can go activate more pepsinogen to become pepsin

Question 11

Brush-border enteropeptidase

Answer 11

Cleaves trypsinogen to trypsin when its released from the pancreas
Trypsin is then able to activate other pancreatic zymogens

Question 12

Serine proteases

Answer 12

What trypsin, chymotrypsin, and elastase are

They also function as endopeptidases

Question 13

Trypsin

Answer 13

Very specific for cleavage site next to lysine or arginine

Question 14

Exopeptidase

Answer 14

Take over where the endopeptidases leave off
Carboxypeptidase A: prefers hydrophobic AA’s
Carboxypeptidase B: prefers hydrophilic AA’s

Question 15

Na-dependent transport

Answer 15

Way to get amino acids into the cell

Question 16

Essential fatty acids

Answer 16

Include linoleic and alpha-linolenic acid as well as eicosapentaenoic acid and docosahexaenoic acid

Question 17

Lingual/gastric lipase

Answer 17

Prefer short and medium chain FA’s

Babies have less pancreatic lipase, so thought to be more important with them

Question 18

Colipase

Answer 18

Secreted along with pancreatic lipase in response to CCK levels
Helps with putting TAG in the lipase active site

Question 19

Pancreatic lipase

Answer 19

Bile salts can inhibit it by coating the substrate and blocking access to the active site - collapse helps with this
Hydrolyzes fatty acids from positions 1 and 3 on TAGs to leave 2-monoacylglycerol

Question 20

Micelle

Answer 20

Contain fatty acids and 2-monoacylglycerols packaged with bile salts for formation (requires critical concentration of bile salts for formation so if don’t have that, bad news bears)
Micelles are absorbed by microvilli on intestinal epithelial cells, but bile salts remain for reabsorption elsewhere

Question 21

Portal blood

Answer 21

WHere short and medium-chain fatty acids wind up - they don’t need micelles to be absorbed, just go directly into epithelium

Question 22

Smooth ER

Answer 22

In intestinal epithelial cells, fatty acids and MAGs are converted back to TAGs in the sER
fatty acids are activated to fatty acyl coA to do this

Question 23

Folate

Answer 23

Enters proximal third of intestine where folate conjugates remove glutamate residues into a mono glutamate form that is readily absorbed
Within the intestine, it is converted to N5-methyl FH4 and this is then transported to the liver
Used as a methyl carrier for the body

Question 24

Cyanocobalamin

Answer 24

Form of B12 found in supplements

Question 25

Cobalamin

Answer 25

Free cobalamin binds to haptocorrins (R-binders/transcobalamin I) within the stomach (these are secreted by salivary glands and gastric mucosa)
The cobalamin then travels to the intestine bound to these haptocorrins where pancreatic proteases degrade the R-binders so that B12 is able to bind to intrinsic factor
B12-intrinsic factor is then absorbed by binding to receptors in the ileum
In the enterocyte, B12 binds to transcobalamin II which is then released into the circulation for it to be delivered to tissues with transcobalamin II receptors (i.e. liver)

Question 26

Pyridoxal phosphate (PLP)

Answer 26

Cofactor needed for transamination reactions

Question 27

NADPH

Answer 27

Generated by the pentose phosphate pathway and required by cells in the liver for glutathione reductase activity

Question 28

Glucokinase

Answer 28

Enzyme that phosphorylates glucose and “traps” it inside the cell so that it can be utilized