Biomolecular Interactions Exam 4

Relationship between Glucose and Galactose

Diastereomers (specifically C-4 epimers)

Relationship between Glucose and Fructose

Constitutional isomers

3 Carbon Aldose Example

Glyceraldehyde

5 Carbon Aldose Example

Ribose

6 Carbon Aldose Example

Glucose

Ketose

Ketone typically at the 2nd carbon

Aldose

Terminates with aldehyde

3 Carbon Ketose example

Dihydroxyacetone

5 Carbon Ketose example

Ribulose

6 Carbon Ketose example

Fructose

Stereoisomers

Same order, different spatial arrangement

Enantiomers

Non-superimposable mirror images; require inversion of every stereocenter

Relationship between D-Glyceraldehyde and L-Glyceraldehyde

Enantiomers

Diastereomer

Non-superimposable, non-mirror image stereoisomers

Epimer

Diastereomers that differ at only one stereocenter

Anomers

Type of diastereomer in cyclic carbohydrates that differ at the carbon atom that becomes asymmetric when the ring closes

Relationship between alpha-D-glucose and beta-D-glucose

Anomers

L carbohydrates

Rarely found in nature. The last hydroxyl group from the keto or aldehyde group is on the left side

D carbohydrates

Common in nature. The last hydroxyl group from the keto or aldehyde group is on the right side

Common monosaccharides include:

D-glucose, D-mannose, D-galactose, D-fructose

Pyran

6 membered ring w/ oxygen formed when aldehyde reacts with hydroxyl group

Furan

5 membered ring w/ oxygen formed when keto reacts with hydroxyl group

Ratio of cyclic to open chain carbs in solution

99:1

Ratio of alpha-D-glucose to beta-D-glucose

33:66

Which form/conformation of glucose is most stable and abundant?

Beta-D-glucopyranose

How are carbs modified

Hydroxyl group substituted for other groups

Oligosaccharides

Complex carb containing 3 to 10 monosaccharide units

Bonds between oligosaccharide monomers

O-glycosidic bonds at anomeric carbons

How are O-glycosidic bonds made

Condensation rxn between anomeric carbon of one sugar and hydroxyl group of another

Enzymes that catalyze formation of glycosidic bonds

Glycosyltransferases

Are disaccharides simple or complex carbs?

Simple

Simple carbs include:

Lactose, Sucrose, maltose

Lactose

Glucose + galactose

Sucrose

Glucose + fructose

Maltose

From hydrolysis of large oligosaccharides

Where are disaccharides digested

By enzymes on intestinal epithelium

Polysaccharides

More than 10 monomeric units

Homopolymers of glucose include:

Starch, glycogen, cellulose (fiber)

Starches include

Amylopectin (branched); amylose (straight chain)

Starches are found in

Plants

Glycogen is found in

Animals

Glycogen is

Highly branched

Glycosidic bonds linking monomers in straight chains of glucose in glycogen

alpha-1,4-glycosidic bonds

glycosidic bonds that create the branch points in glycogen

alpha-1,6-glycosidic bonds

Only place we see beta-1,4-glycosidic bonds in this class

Bonds between monomers in strands of cellulose

What types of bonds hold separate strands of cellulose together

Hydrogen bonds

How often does starch have a branch point

Every 30 glucose monomers

How often does glycogen have a branch point

Every 10 unitsWhic

Which branches more: starch or glycogen?

Glycogen

ATP is formed by the ___ of carbon fuels

Oxidation

How many phosphoanhydride bonds in ATP?

2

ATP hydrolysis releases:

Orthophosphate (Pi) and Pyrophosphate (PPi)

What type of phosphorylation uses phosphoryl transfer potential?

Substrate-level

What is the phosphoryl transfer potential of ATP

-30.5 kJ/mol or -7.3 kcal/mol

What happens to the electrons that are freed up during the oxidation of carbon fuels?

They are accepted by high energy electron carriers (NAD+ and FAD)

NAD+ gains what when it is reduced

2 electrons and one H+ ion

NAD stands for

Nicotinamide Adenine Dinucleotide

NAD is synthesized from which vitamin

Niacin (B3)

FAD gains what when it is reduced

2 electrons and 2 H+ ions

FAD stands for

Flavin adenine dinucleotide

FAD is synthesized from what vitamin

Riboflavin (B2)

What is the only fuel for the brain under non-starving conditions and red blood cells?

Glucose

Why is glucose primarily used for energy?

Most stable hexose; low tendency to modify proteins, available in primitive conditions

GLUT 1/3

Continuously transport glucose; found in all mammalian tissues; highest affinity for glucose

GLUT 2

When hyperglycemic; found in pancreatic beta cells and liver; lowest affinity for glucose

GLUT 4

Controlled by insulin; intermediate affinity for glucose; found in muscle and fat cells

GLUT 5

For fructose mostly; found in small intestine

Insulin release in pancreatic beta cells

(1) ATP from glycolysis closes ATP sensitive K+ channel (2) Membrane charge is altered (3) Ca2+ channels open (4) Insulin released from vesicles

Insulin receptor protein

Dimer with alpha and beta subunits

Insulin signaling on cell

(1) Insulin binds to receptor (2) Akt activated by phosphorylation (3) Increased trafficking of GLUT4 to cell surface and glycogen synthesis enzymes stimulated