ATP-PC/Glycolysis Flashcards
What is the purpose of the ATP-PC system?
to help us recreate ATP if we need it
What are the different names for the ATP-PC system?
phosphagen system, phosphocreatine system, creatine phosphate system
The ATP-PC system is a ____ reaction and is ____ at replacing ATP. This makes the duration ___ and ____.
coupled, fast, short, explosive
When does the ATP-PC system occur?
during active muscle contraction and glycolysis
Where does the ATP-PC system take place?
mitochondria and cytosol
Where is phosphocreatine found? Where is the most located?
Mostly in places with high energy fluctuating tissue like skeletal muscle, cardiac muscle and the brain. Skeletal muscle
Phosphocreatine is a ___ energy compound. What is it used for?
high. It’s used as a reservoir to replenish ATP
The amount of creatine you have depends on what?
how much muscle you have
Where do you get creatine from?
diet, supplementation, liver and kidney
What does phosphocreatine supply?
the phosphoryl group for ATP synthesis.
What happens when the cell has enough ATP?
The reaction reverses to replenish the reservoir
What is the key enzyme for the ATP-PC reaction?
creatine kinase
What are the reactants for the ATP-PC reaction?
ADP + PCr + Mg2+
What are the products for the ATP-PC reaction?
ATP + Cr
What has the most free energy in the ATP-PC system? Why?
Phosphocreatine because it supplies the phosphoryl group for ATP synthesis
What is the purpose of glycolysis?
carbohydrate breakdown and converting glucose into 2 pyruvates
Is glycolysis aerobic or anaerobic? Catabolic or anabolic?
anaerobic, catabolic
What does glycolysis produce?
ATP, NADH, pyruvate
What does fast glycolysis produce?
ATP, NADH, lactic acid and alanine
What happens to the pyruvate during slow glycolysis?
It gets sent to the mitochondria for aerobic metabolism
What types of cells only have glycolysis as a source of metabolic energy?
erythrocytes, renal medulla and sperm
Glycolysis is the precursor to what other pathway?
Krebs
Where does glycolysis occur?
cytosol of the cell
What is the fate of glucose?
to be converted into ATP and precursor molecules for aerobic metabolism
In general, what happens during the preparatory phase of glycolysis?
Glucose gets trapped into the cell my adding a phosphate to it, making it glucose-6-phosphate. It then gets changed into an energy rich sugar (fructose-1, 6-bisphosphate) so it can be broken in half to make ATP
In general, what happens during the pay off phase of glycolysis?
- Get ATP by splitting fructose-1,6-bisphosphate into into two molecules
- Set up large negative delta G reactions (exergonic)
- Use that free energy to re-create ATP
- Create an end product that can be further oxidized (pyruvate) in aerobic metabolism
What enzyme turns glucose into glucose 6 phosphate?
hexokinase/glucokinase
What occurs to trap glucose into the cell?
hexokinase adds a phosphate to glucose
What enzyme turns glucose 6 phosphate into fructose 6 phosphate?
phosphoglucose isomerase
What specifically does phosphoglucose isomerase do?
takes the aldehyde on glucose 6 phosphate and turns it into a ketone
What enzyme turns fructose 6 phosphate into fructose 1,6 bisphosphate?
Phosphofructokinase (PFK)
Which step is considered the rate limiting step?
PFK turning fructose 6 phosphate into fructose 1,6 bisphosphate
What turns fructose 1,6 bisphosphate into dihydroxyacetone phosphate and glyceraldehyde 3 phosphate?
Aldolase
What enzyme turns dihydroxyacetone phosphate into glyceraldehyde 3 phosphate?
triose phosphate isomerase
What turns glyceraldehyde 3 phosphate into 1,3-bisphosphoglycerate?
glucose 3 phosphate dehydrogenase
What enzyme turns 1,3 bisphosphoglycerate into 3 phosphoglycerate?
phosphoglycerate kinase
What enzyme turns 3 phosphoglycerate into 2 phosphoglycerate?
phosphoglycerate mutase
What enzyme turns 2 phosphoglycerate into phosphoenolpyruvate?
enolase
What enzyme turns phosphoenolpyruvate into pyruvate?
pyruvate kinase
Which reactions are irreversible?
glucose (hexokinase) glucose 6 phosphate
fructose 6 phosphate (PFK) fructose 1,6 bisphosphate
phosphoenolpyruvate (pyruvate kinase) pyruvate
What steps give us energy?
1,3 bisophosphoglycerate (phosphoglycerate kinase) 3 phosphoglycerate
phosphoenolpyruvate (pyruvate kinase) pyruvate
Describe hexokinase I, II, III
for energy production
makes glucose into glucose 6 phosphate
present in most tissues
high affinity for glucose
Inhibited by its product
won’t lock in more glucose than the cell can use
no membrane carriers
commits the glucose to metabolism
Describe hexokinase IV
also called glucokinase
for blood glucose homeostasis
liver and beta cells of pancreas contain hexokinase IV
makes glucose into glucose 6 phosphate
has a lower affinity for glucose to allow brain and muscle a greater opportunity to capture glucose
Describe glucokinase
high Km, used in liver, not inhibited by G6P, stimulated by insulin, high affinity for fructose, not much taken up during fasting, increased uptake for conversion to fat and glycogen
Describe hexokinase
low Km, used in muscle inhibited by G6P, stimulated by glucose, increased uptake during fasting, limited uptake when muscle is full
When is PFK inhibited?
when there is a significant drop in pH, lots of citrate, high energy charge
What enzyme is part of the first committed step in glycolysis?
PFK
Define allosteric enzyme
an enzyme that is inhibited when there is a high energy charge
What does PFK-1 do?
catalyzes the formation of F1,6BP
What does PFK-2 do?
catalyzes formation of F2,6BP in a different pathway
What is the most potent activator of PFK?
F2,6BP
What is PFK-2 stimulated by?
insulin
What does PFK-2 stimulate?
glycolysis, PFK in liver
What does PFK-2 inhibit?
gluconeogenesis
What decreases fructose 2,6 bisphosphate?
glucagon
Which enzyme catalyzes the third irreversible step in glycolysis?
pyruvate kinase
What is pyruvate kinase stimulated and inhibited by?
inhibited by alanine
stimulated by fructose 1,6 bisphosphate
What does glucagon do to pyruvate kinase and where?
phosphates and inactivates it in the liver
Once pyruvate kinase is inactivated, where does the excess reactant go?
Goes to gluconeogenesis
When is glucagon secreted? Why?
when blood glucose is low to elevate the blood glucose
What is glucagon’s primary target? Why?
The liver to stop burning glucose and stop storing glucose
There are not any receptors in the muscle for glucagon, true or false?
True
What is alanine?
An amino acid that is one reaction from being pyruvate
What does alanine inhibit?
pyruvate kinase
What happens when energy charge is low?
amino acids jump into Krebs cycle, which throws off ammonia.
What happens to the ammonia that is produced when amino acids are used in glycolysis?
pyruvate picks them up and turns them into alanine
Is the reaction for alanine a reversible reaction? When is it important?
Yes, it is important for gluconeogenesis and amino acid metabolism
What pathway is lactic acid a part of specifically?
fast glycolysis
What kind of reaction gives off lactic acid? Which enzyme is used?
Reversible reaction, lactate dehydrogenase
What does lactic acid regenerate? Why?
NAD+ because it is needed for glyceraldehyde-3-phosphate dehydrogenase so glycolysis can continue
What is the reaction for lactic acid?
Pyruvate + NADH –> Lactate + NAD+
What does a moderate amount of lactate do to glycolysis? Why?
moderate amounts speeds up glycolysis because its not enough to drop the pH to inhibit PFK. It also creates more NAD+ to stimulate G3P dehydrogenase
What does a large amount of lactate do to glycollysis? Why?
inhibits glycolysis because of a significant drop in pH, which inhibits PFK
