Exam 3: Lectures 22-25

Question 0

______ has glucokinase instead of hexokinase.

Answer 0

•liver, stores glucose

Question 1

________ traps glucose in the cell and prevents it from diffusing across the membrane.

Answer 1

•Phosphorylation

Question 2

What is the committed step in glycolysis?

Answer 2

•phosphofructokinase step

Question 3

Most important regulatory enzyme in glycolysis?

Answer 3

•phosphofructokinase, committed step

Question 4

At rest, muscle can get there ATP from oxidation of _______, and glycolysis is ________.

Answer 4

• Fatty acids

* inhibited

Question 5

PFK II in liver is activated by _______.

Answer 5

• Fructose 2,6 bisphosphate (F-2, 6-BP)
• allosterically increases the activity of PFK I, increases activity of enzyme in committed step
• inhibited by citrate

Question 6

Phosphorylated pyruvate kinase is ______ active than dephosphorylated pyruvate kinase.

Answer 6

• Less active

* when low blood-glucose levels, ATP phosphorylates it to conserve glucose

Question 7

Major precursors of Gluconeogenesis are?

Answer 7

• lactate, amino acids, and glycerols

* Not fatty acids

Question 8

_______ transports Oxaloacetate to the cytoplasm.

Answer 8

•Malate shuttle

Question 9

Fructose 2,6-bisphosphate strongly stimulates _______ and inhibits ______.

Answer 9

• PFK

* Fructose 1,6-bisphosphatase

Question 10

_______ is a major precursor for the net formation of glucose in the liver.

Answer 10

•Alanine

Question 11

Glycogen phosphorylase

Answer 11

•Breaks a-1,4 bonds

Question 12

Glycogen is stored in the liver, muscle, and other tissue as______.

Answer 12

•Granules

Question 13

Glycogen degradation is also know as?

Answer 13

•Glycogenolysis

Question 14

Pyridoxal 5’-phosphate (vit B6) is required to?

Answer 14

• phosphorylase glycogen (removal of glucose molecule)

* will remove glucose until it gets within 4 residues of a branch

Question 15

Transferase

Answer 15

• removes 3 glucose molecules from branch and add them to core
• gets rid of steric hinderance so more glucose molecules can be cleaved from glycogen

Question 16

a-1,6-Glucosidase

Answer 16

•cleaves single glucose molecule left over after transferase moves other 3

Question 17

Glucose 6-phosphatase is found in the _____ of the liver.

Answer 17

•ER

Question 18

Glycogen synthesis is also know as?

Answer 18

•glycogenesis

Question 19

Branching enzyme

Answer 19

• Breaks a 1-4-bonds and forms a 1-6 branch points by transferring 7 to 8 glucoses
• increases solubility, increases rate at which glycogen can be synthesized and degraded

Question 20

3 Hormones control reversible phosphorylation

Answer 20

• Insulin: triggers dephosphorylation in liver and muscles, high glucose levels promotes release
• Epinephrine: triggers phosphorylation in skeletal muscles (and liver)
• Glucagon: triggers phosphorylation in liver, released by alpha cells in pancreas

Question 21

Signal Transduction

Answer 21

• essential for maintaining homeostasis
• most hormones don’t enter the cells they affect, bind to membranes and act as “first messengers’
• trigger release of “second messengers”,
• formation/release of second in response to binding of hormones is “signal transduction”

Question 22

Insulin

Answer 22

• Activates phosphorprotein phosphatase 1
• Dephosphorylates (activates) glycogen synthase
• Inactivates phosphorylase kinase, and glycogen phosphorylase
• released after meal because blood glucose levels are high

Question 23

Binding of Ca to calmodulin…

Answer 23

•Activates non-phosphorylated phosphorylase kinase in skeletal muscles