Biochem Week 3 - Glycogenolysis, Glycolysis, Gluconeogenosis, Cori Cycle, etc. Flashcards
(32 cards)
Glycolyisis
What is the Function
Where tissues is it performed in?
Is it a cytosolic or mitochondrial process?
What are the inputs and outputs?
What are the regulatory enzymes/stemps and what modulates them?
Function: To degrade glucose for energy
Where (body): **LIVER, MUSCLE CELLS, **brain, kidney, RBCs, adipocytes
Where (cell): Cytosolic process
I_nputs/outputs:_ Glucose + 2 ATP –> 2 pyruvate + 4 ATP + 2NADH
Regulatory enzymes/steps and modulators:
- ) Hexokinase (glucokinase in liver) - converts glucose into G-6-P. Modulated by G-6-P (or F-6-P in liver)
- ) Phosphofurctokinase (PFK) - RATE LIMITING STEP - converts F-6-P into F-1,-6-BS. Inhibited by ATP (High energy) activated by AMP (low energy). Strong activation by F-2, 6-BS
- ) Pyruvate Kinase - modulated by
What is Hexokinase called in the Liver? How is it different?
What processes is it involved in?
Glucokinase
Indirectly -inhibited by F-6-P (NOT G-6-P like other hexokinases) to ensures that there is not a futile cycle between glycolyisis and gluconeogenesis w/o letting glycogen synthasis or degredation interfere.
Glycolysis and Gluconeogenesis
What are most hexokinases allosterically inhibited by?
What tissues?
Why?
Does it make or use ATP?
G-6-P
Muscle, adipose brain, RBCs. _NOT LIVER. _
Slows down hexokinase activity of converting Glucose –> G-6-P so that you don’t have more G-6-P hanging around then can be used.
What does Phosphofructokinase-1 (PFK-1) do?
Does it make or use ATP?
What activates it, what inhibits it?
What process is it involved in?
Converts F-6-P into F-1,6-BP.
It uses an ATP.
Activated by AMP and F-2,-6-BP. Inhibited by excess ATP.
Glycolysis
What does Phosphofructokinase-2 (PFK-2) do?
When is it activated?
Where would you not likely see as PFK-2 and why?
What process is it involved in?
Converts F-6-P into F-2,6-BP
Activated if there is too much F-6-P compared to F-1,6-BP. F-2,6-BP further stimulates PFK-1 to get the conversion of F-6-P to F-1-6-BF to go faster.
Wouldn’t see it in the liver as much as other tissues since the liver is trying not to use glucose so that it can be saved for other tissues.
Glycolysis
What is the rate limiting step in glycolysis?
PFK-1 converting F-6-P into F-2,6-BP
What does Pyruvate Kinase do?
What is it activated/inhibited by?
What process is it involved in?
Converts PEP to Pyruvate
Activated by F-1,6-BP and PEP. Inhibited by acetyle CoA and ATP.
Glycolysis
In the liver, how does glucagon and epinephrine affect pyruvate kinase and why?
Deactivates Pyruvate kinase by phosphorylating it.
Quick pathway: Glucagon + epinephrine signal through PKA-cAMP dependent kinase phophorylates and inactivates PK.
If NADH is converted to NAD+, what kind of reaction is it (reduction or oxidation)?
Oxidation!
It loses an election.
Generally what do kinases do?
What are some intermediates hat they use?
Phosphorylate another protein
NAD+/NADH
FADH/FADH2
Coenzyme A (eg. acetyl CoA)
Generally, what do phosphatases do?
Dephosphoralyates another protein.
Does the phosphorylation of pyruvate kinase activate or deactivate it?
Deactivates it.
This can be done in the liver through Glucagon and epinephrine.
Generally, what do Dehydrogenases do?
Where is GLUT 1 expressed?
Is it affected by insulin?
RBCs
Not affected by insulin.
Where is GLUT2 expressed?
Is it affected by insulin?
Liver
Not affected by insulin.
Where is GLUT4 expressed?
Is it affected by insulin?
Muscle cells and adipocytes.
YES! insulin causes it to be translocated to membrane.
Also, in skeletal muscle, contraction will cause it to be translocated to memebrane.
Glycogenesis
What is the Function
Where tissues is it performed in?
Is it a cytosolic or mitochondrial process?
What are the inputs and outputs?
What are the regulatory enzymes/stemps and what modulates them?
_Function: _To build glycogen from glucose
Where (body): LIVER and muscle
Where (cell): Cytosolic process
Inputs/outputs: Glucose + ATP –> Glycogen
Major Regulatory enzymes/steps and modulators:
- ) Hexokinase (glucokinase in liver) - converts glucose into G-6-P.
- ) Glycogen Synthase - Converts UDP-Glucose to glycogen. Must be dephosphorilated to work. Insulin and G-6-P stimulates activity; glucagon and epinephrine decreases activity.
Why does glycogen have branches?
Increases solubility.
Allows more than one site to be degraded at once.
Glycogenolysis
What is the Function
Where tissues is it performed in?
Is it a cytosolic or mitochondrial process?
What are the inputs and outputs?
What are the regulatory enzymes/stemps and what modulates them?
_Function: _To degrade glycogen into glucose
Where (body): LIVER and muscle
Where (cell): Cytosolic process
Inputs/outputs: Glycogen –> G-6-P
Major Regulatory enzymes/steps and modulators:
1.) Glycogen Phosphorylase - converts glycogen to G-1-6 which then becomes G-6-P. Activated by phosphorylase kinase (low energy molecules and glucogon). Inhibited by insulin and high levels of G-6-P, ATP,
What pathway is glycogen phosphorylase in?
What does it do?
Converts glycogen to G-1-6 which then becomes G-6-P.
Activated by phosphorylase kinase (low energy molecules and glucogon). Inhibited by insulin and high levels of G-6-P, ATP,
After pyruvate is made in glycolysis, what can happen to it?
1) Is oxidized by pyruvate dehydrogenase in mitochondria to enter the Triboxilate Citric Acid (TCA) cycle for further oxidation all the way down to CO2 and NADH/FADH.
2. ) Reduced to lactate by lactate dehydrogenase (LDH) and transported to the liver (Cori Cycle)
3. ) Carboxylated (oxidation) to oxaloacetate in mitochondria for replenishment of TCA intermediates.
What does the Pyruvate dehydrogenase (PDH) Complex do?
What does it need to work?
What is it inhibited by?
Simultaneously transports pyruvate into mitochondria while oxidizing and decarboxylating it into acetyl CoA.
Requires 5 cofactors: Thiamine, NAD+, FAD, CoA (All B vitamins), and Lipoate (Lipoic acid)
Inhibited by high energy signals (NADH, ATP, Acetyl CoA), stimulated by pyurvate and calcium.
What happens when the PDH complex is overwhelmed or inactive?
Is pyruvate oxidized or reduced?
in what tissues does this happen?
Where does it occur in the cell?
If there is too much pyruvate building up, Lactate dehydrogenase (LDH) converts pyruvate into lactate.
Reduced, because NADH is oxidized to NAD+.
Non-hepatic cells.
Occurs in cytosol.
Generally, what is the Cori Cycle?
What are some instances where it might occur?
A way for the liver to recycle pyruvate back into glucose in the event that there is a build up of pyruvate and it cannot be oxidized.
- ) The TCA cycle and PDH of the muscle are satruated.
- ) Not enough oxygen delivery (anarobic respiration)
3,) Few or no mitochondria around.
