Exam 3: Lectures 22-25 Flashcards
______ has glucokinase instead of hexokinase.
•liver, stores glucose
________ traps glucose in the cell and prevents it from diffusing across the membrane.
•Phosphorylation
What is the committed step in glycolysis?
•phosphofructokinase step
Most important regulatory enzyme in glycolysis?
•phosphofructokinase, committed step
At rest, muscle can get there ATP from oxidation of _______, and glycolysis is ________.
- Fatty acids
* inhibited
PFK II in liver is activated by _______.
- 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
Phosphorylated pyruvate kinase is ______ active than dephosphorylated pyruvate kinase.
- Less active
* when low blood-glucose levels, ATP phosphorylates it to conserve glucose
Major precursors of Gluconeogenesis are?
- lactate, amino acids, and glycerols
* Not fatty acids
_______ transports Oxaloacetate to the cytoplasm.
•Malate shuttle
Fructose 2,6-bisphosphate strongly stimulates _______ and inhibits ______.
- PFK
* Fructose 1,6-bisphosphatase
_______ is a major precursor for the net formation of glucose in the liver.
•Alanine
Glycogen phosphorylase
•Breaks a-1,4 bonds
Glycogen is stored in the liver, muscle, and other tissue as______.
•Granules
Glycogen degradation is also know as?
•Glycogenolysis
Pyridoxal 5’-phosphate (vit B6) is required to?
- phosphorylase glycogen (removal of glucose molecule)
* will remove glucose until it gets within 4 residues of a branch
Transferase
- 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
a-1,6-Glucosidase
•cleaves single glucose molecule left over after transferase moves other 3
Glucose 6-phosphatase is found in the _____ of the liver.
•ER
Glycogen synthesis is also know as?
•glycogenesis
Branching enzyme
- 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
3 Hormones control reversible phosphorylation
- 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
Signal Transduction
- 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”
Insulin
- Activates phosphorprotein phosphatase 1
- Dephosphorylates (activates) glycogen synthase
- Inactivates phosphorylase kinase, and glycogen phosphorylase
- released after meal because blood glucose levels are high
Binding of Ca to calmodulin…
•Activates non-phosphorylated phosphorylase kinase in skeletal muscles
