Lecture 2 Flashcards
(23 cards)
What is a monosacharide isomer?
Same formula but different arrangement of atoms. D and L
What is an asymmetrical carbon?
its also known as chiral carbon. it is carbon atom that is attached to four different types of atoms or groups of atoms.
What are epimers?
they are sugars differing in configuration at a single asymmetric center.
What are stereoisomers?
Isomeric molecules that have the same molecular formula and sequence of boned atoms but differ in the 3D orientations of their atoms in space.
What are Enantiomers?
Are two stereoisomers that are related to each other by reflection: they are mirror images of each other that are non-superimposable.
Diasteroisomers?
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.
How can you calculate the number of stereoisomers?
2^n= max # of stereoisomers.
N is the # of asyemmetrical carbons.
For example 2^2= 4 stereoisomers
What are the two main sources of glucose humans use?
1-Dietery starch and glycogen. Digested in the digested tract and then absorbed (transport).
2-Mobilization of intracellular stored polysaccharides (gylycogen) in cytoplasm.
How is starch and glycogen from the diet are digested (Cleaved and hydrolyzed)?
They’re digested by the sequential action of several hydrolases in the mouth and the gut.
What is the function of glycosidases?
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.
Salivary a-amylase:
a(1–>4) glycosidase; PH senseitive and incative in stomatch.
Pancreatic a-amylase
a(1–>4) glycosidase cleaves off maltose units.
Debranching enzyme:
a(1–>6) needed to act at banching points of amylopectin and glycogen; results in glucose and maltose.
Maltase in the brush border cells of small in small intestine
Hydrolases maltose with production of 2 glucose molecules
Lactase and surcase in the brush border cells of small in small intestine
Hydrolase lactose (gal/Glc) and surcose (Glc/Fru)
What are hexose transporters?
They help transport hexoses such as glucose, fructose and glactose because theyre important for energy but they cannot cross the cell memebrane.
What are the 2 distinct groups oh hexose transporters?
- Transporters down concentration gradient: GLUT1 to GLUT5.
- Transports against concentration gradients: SGLUT1 and SGLUT 2
SGLUT 1
-Major site of expression and characteristics
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.
GlLUT-1
-Major site of expression and characteristics
Its expressed in every tissue.
-Characterized as house keeping transporter; specific for Glc (High affinity) and Gal, not fru. Not found in hepatocytes.
GLUT-2
-Major site of expression and characteristics
- 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.
GLUT-3
-Major site of expression and characteristics
- Brain
- Primary Glc transporter for neurons.
GLUT-4
-Major site of expression and characteristics
- Muscle and adipose tissue.
- Hormone sensitive: Insulin-dependant translocation to PM. High affinity for GLC
GLUT-5
-Major site of expression and characteristics
- small intestines and sperm
- Specific for fructose.
