Old Test 3

Question 1

In glycoproteins, a monosaccharide or an oligosaccharide is joined to a peptide chain through O-linkage or N-linkage. A) what is the amino acid involved in N-glycosidic linkage?

Answer 1

Asn- Aspargine

Question 2

What is the last enzyme of the ten enzymes in glycolysis is high regulated?

Answer 2

Pyruvate Kinase

Question 3

The activity of the enzyme Pyruvate Kinase is increased by its own substrate and is increased by fructose 1,6-bisphosophate. What is the purpose of this type of regulation

Answer 3

This is feedforward allosteric activation -the purpose is to make sure the complete reaction of glycolysis intermediates to pyruvate

Question 4

Answer 4

Km shifts to smaller values

Vmax does not change

curve is still sigmoidal

Question 5

Glucagon treatment shifts the curve of this enzyme as shown in the figure. However, glucagon is a hormone and odes not even enter the cell to have this affect. How is this regulation carried out?

Answer 5

One of the mechanisms for regulating pyruvate kinase is by covalent modification. Glucagon activates adenylyl cyclase and cAMP is made. cAMP induces PKA. PKA phosphorylates pyruvate kinase-this inhibits its activity

Question 6

Insulin is secreted by the pancrease in response to elevated blood glucose levels. Describe two ways in which insulin works to decrease blood glucose levels.

Answer 6

Insulin activates phosphoprotein phosphatase-1. This removes phosphate from glycogen and reverses the production of glucose from glycogen

-Phosphoprotein phosphatase-1 also removes phosphate from glycogen synthase,a nd this induces production of glycogen from glucose

Question 7

If cosubstrate are involved in either or both of the reactions write the abbreation fo rthe co-substrate and co-product

Answer 7

Question 8

The short name description of turanose is alpha-D-Glcp-(1->3)-B-D-fruf. Where Glcp is glucopyranosyl, Fruf is fructofuranoside)

Draw the haworth projections

Answer 8

Question 9

If you eat a fruit sald with grapes and apples (containing fructose) and apricots and pineapples(contain sucrose). Why will you metabolize the sucrose faster than the glucose that is derived from the sucrose

Answer 9

Fructose enters the cell and is phosphorylated to fructose 6-phosphate. This is isomerized to glucose 6-phosphate which will inhibit the use of glucose

Question 10

what is the goal of insulin

Answer 10

lower blood glucose levels

Question 11

What is the goal of glucagon signaling?

Answer 11

increasing blood glucose levels

Question 12

describe the role of the effector Fructose 2,6-bisphosphate on the regulation of glycolysis

Answer 12

it activates PFK-1 which increases glycolysis