UNIT 3 BIOCHEM: Carbohydrates

What are the two classes of carbohydrates?

ketones and aldehydes

T or F. Carbohydrates are a major portion of our caloric intake?

True. Carbohydrates are really important for many of our bodily functions. For example, carbohydrates are source of energy, a lubricant found between joints, and an adhesive found between cells

Which functional group is commonly found in carbohydrates?

alcohols

Draw d-glucose

What type of carbohydrate is glucose?

An aldohexose

Draw d-fructose

What type of carbohydrate is d-fructose?

a ketohexose

Epimer

isomers with different configurations of atoms around one of several asymmetric carbon atoms present

What are the epimers of glucose?

D-mannose and D-galactose

Draw d-mannose

Draw d-galactose

What structure is glucose in solution?

Glucose is cyclic in solution (but all 3 forms are present

Draw alpha and beta glucose

Polysaccharides

Carbohydrates made up of more than two monosaccharides

Monosaccharides

Single sugar molecules

Disaccharides

Carbohydrates made up of two monosaccharides; sucrose and lactose

What are two common polysaccahrides?

Starch and glycogen

What is glycogen made of?

glucose

What type of linkages are found in glycogen?

alpha 1,4 linkages and alpha 1,6 linkages

Draw an alpha 1,4 linkage

Draw an alpha 1,6 linkage

what is Glycogen; draw it

a polymer of glucose that is similar to amylopectin, but more extensively branched.

the storage form of carbohydrates

Why does glucose have to be stored as glycogen?

1) If glucose is stored freely in the cell, the concentration of glucose in the cell would be greater than the concentration of glucose out of the cell, meaning active transport would be needed to move glucose

2) If more glucose is in the cell than out of the cell, water will want to flood into the cell, causing the cell to burst

3) Free glucose will automatically enter glycolysis. Glycogen allows the body to regulate glycolysis

3)

Are glycogen synthesis and degradation simply the reversal of the pathway?

No, glycogen synthesis and breakdown have different pathways

What is glycogen synthesis and degradation controlled by?

hormones

Which enzymes are required for glycogen degradation?

1) Glycogen phosphorlyase

2) Debranching enzyme

What is the role of glycogen phosphorylase?

cleaves the alpha 1-4 linkages of glycogen, forming glucose 1-phosphate

What is the role of the debranching enzyme?

The debranching enzyme has two roles. It has a transferase activity, which exposes the alpha 1,6 linkage, and an alpha 1->6 glucosidase activity, which cleaves the alpha 1,6 linkage

Draw out glycogen degradation

Why is glycogen branched?

Since glycogen phosphorylase must start at the end of a branch, more branching means glycogen can be broken down and release glucose into the blood faster. effcientiy

What happens to glucose 1-phosphate?

is degraded by phosphoglucomutase into glucose 6-phosphate

What happens to glucose 6-phosphate in just the liver?

is degraded by glucose 6-phosphatase into glucose + Pi

What happens to glucose 6-phosphate in the muscle and liver (rare)?

glucose 6-phosphate enter glycolysis

Why is glucose 6-phosphate not degrade into glucose and Pi in the muscle?

the muscle does not have glucose-6 phosphatase

Where can epinephrine bind?

the muscle and liver

Where can glucagon bind?

the liver

Draw the epinephrine and glucagon pathways

explain and draw how cAMP activates PKA

explain how Gsa gets activated

inactive PKA has the 4 units that are bounded together. 4 cAMP breaks the units apart and 2 each bind to the 2 regulatory units which activates the catalytic domains.

GSa when inactive is bounded to GDP. when epipinerhine/glucagon binds to the specific receptor, the GDP gets replaced with GTP. this activates the GSA and moves it to adenyl cyclase which forms cAMP.

Draw out glycogen synthesis

explain and draw the different transporters with glucose being released in the bloodstream