Lecture 2

Question 1

What is a monosacharide isomer?

Answer 1

Same formula but different arrangement of atoms. D and L

Question 2

What is an asymmetrical carbon?

Answer 2

its also known as chiral carbon. it is carbon atom that is attached to four different types of atoms or groups of atoms.

Question 3

What are epimers?

Answer 3

they are sugars differing in configuration at a single asymmetric center.

Question 4

What are stereoisomers?

Answer 4

Isomeric molecules that have the same molecular formula and sequence of boned atoms but differ in the 3D orientations of their atoms in space.

Question 5

What are Enantiomers?

Answer 5

Are two stereoisomers that are related to each other by reflection: they are mirror images of each other that are non-superimposable.

Question 6

Diasteroisomers?

Answer 6

Occur when two or more stereoisomers of a compound have a different configurations at one or more(But not all) of the equivellent stereocenters.
-They are not howver mirror images, They are designated D/L and D-form predominates.

Question 7

How can you calculate the number of stereoisomers?

Answer 7

2^n= max # of stereoisomers.
N is the # of asyemmetrical carbons.

For example 2^2= 4 stereoisomers

Question 8

What are the two main sources of glucose humans use?

Answer 8

1-Dietery starch and glycogen. Digested in the digested tract and then absorbed (transport).
2-Mobilization of intracellular stored polysaccharides (gylycogen) in cytoplasm.

Question 9

How is starch and glycogen from the diet are digested (Cleaved and hydrolyzed)?

Answer 9

They’re digested by the sequential action of several hydrolases in the mouth and the gut.

Question 10

What is the function of glycosidases?

Answer 10

The attack the non-reducing end of the plysaccharide and cleave the glycosidic bon by adding a water molecule in a reaction reverse to condensation.

Question 11

Salivary a-amylase:

Answer 11

a(1–>4) glycosidase; PH senseitive and incative in stomatch.

Question 12

Pancreatic a-amylase

Answer 12

a(1–>4) glycosidase cleaves off maltose units.

Question 13

Debranching enzyme:

Answer 13

a(1–>6) needed to act at banching points of amylopectin and glycogen; results in glucose and maltose.

Question 14

Maltase in the brush border cells of small in small intestine

Answer 14

Hydrolases maltose with production of 2 glucose molecules

Question 15

Lactase and surcase in the brush border cells of small in small intestine

Answer 15

Hydrolase lactose (gal/Glc) and surcose (Glc/Fru)

Question 16

What are hexose transporters?

Answer 16

They help transport hexoses such as glucose, fructose and glactose because theyre important for energy but they cannot cross the cell memebrane.

Question 17

What are the 2 distinct groups oh hexose transporters?

Answer 17

• Transporters down concentration gradient: GLUT1 to GLUT5.

- Transports against concentration gradients: SGLUT1 and SGLUT 2

Question 18

SGLUT 1

-Major site of expression and characteristics

Answer 18

Its expressed in intestinal mucosa (Luminal) and kidney tubules.

• Its a symport, one molecule of Glc/Gla along with 2 Na+ Ions.
• Uses Natural Na+ to move Glc against the concentration gradient but it does not transport fructose.

Question 19

GlLUT-1

-Major site of expression and characteristics

Answer 19

Its expressed in every tissue.
-Characterized as house keeping transporter; specific for Glc (High affinity) and Gal, not fru. Not found in hepatocytes.

Question 20

GLUT-2

-Major site of expression and characteristics

Answer 20

• liver, pancreas beta cells, small intestines and kidney.
• Low affinity, high capacity glucose transporter.
• transports Glc, Gal and fructose out of cell into blood.
• “glucose sensor” in pancreatic beta cells.

Question 21

GLUT-3

-Major site of expression and characteristics

Answer 21

• Brain

- Primary Glc transporter for neurons.

Question 22

GLUT-4

-Major site of expression and characteristics

Answer 22

• Muscle and adipose tissue.

- Hormone sensitive: Insulin-dependant translocation to PM. High affinity for GLC

Question 23

GLUT-5

-Major site of expression and characteristics

Answer 23

• small intestines and sperm

- Specific for fructose.