Lactate
What does the enzyme Lactate Dehydrogenase do?
converts lactate to pyruvate and back
What is the rate limiting enzyme of glycolysis?
Phosphofructokinase (pfk)
What process only occurs in the liver and not in the skeletal muscles?
gluconeogenesis
What does the process of glycolysis start with and what is the end product of the process?
glucose (from the liver) or glucose 1-phosphate (from SM)
the end product is two pyruvates
What does the enzyme Glucose-6-phosphatase do? Where is this enzyme located?
removes phosphate from glucose because glucose 1-phosphate cannot travel into the bloodstream. This enzyme is located in the liver, but not in skeletal muscles.
True or False: Lactic Acid is formed due to a lack of oxygen.
Explain your answer.
False. There is always enough oxygen for maximal ATP synthesis even during maximal intensity exercise. Lactate is formed due to an overproduction of NADH.
What is the difference between starting with blood glucose and glucose 1-phosphate?
Blood glucose will require the use of an ATP molecule to add the phosphate to the glucose, therefore starting with blood glucose only nets 2 ATP. Starting with glucose 1-phosphate nets 3 ATP.
Should glycolysis be happening in the liver during exercise? Why or why not?
No, because any free glucose should be saved for the skeletal muscle to use for making ATP. The liver can rely on other forms of energy.
What are the byproducts of glycolysis?
2/3 ATP and 2 NADH
What is the rate limiting enzyme of the citric acid cycle? How is that enzyme activated?
isocitrate dehydrogenase
activated by an increase in ADP and Calcium and a decrease in ATP
heart, liver, inactive muscles
used in small amounts in the brain, kidneys, urine and type 1 SM fibers
How would an increase in Myokinase affect phosphofructokinase and the process of glycolysis?
Myokinase takes two ADP and makes one ATP and one AMP. That AMP helps to increase pfk because pfk is activated by an increase in AMP. PFK is the RLE, so an increase in this enzyme will speed up the process of glycolysis.
What does the enzyme fructokinase do? Where is this enzyme absent in the body?
breaks down fructose
absent in skeletal muscles, therefore fructose cannot be used to make energy and has to be processed by the liver, which is difficult.
How many ATP does one glucose molecule net?
30 ATP if starting with blood glucose
31 ATP if starting with muscle glycogen
What does the enzyme phosphorylase do? What process is this enzyme a part of? How is this enzyme activated and deactivated? When do you want this enzyme deactivated and activated?
Phosphorylase breaks down straight chains of glycogen only, which is a part of glycogenolysis (glycogen to glucose). This enzyme is activated by phosphorylase kinase and deactivated by PP1. This enzyme should be active when exercising.
Is Lactic Acid the cause of Delayed Onset Muscle Soreness? Explain why or why not.
No. DOMS occurs around 48 to 72 hours after exercise and the half life of lactate is 12 minutes.
What does the enzyme pyruvate kinase do? How is this enzyme activated?
Helps to create pyruvate
increased by a decrease in ATP and phosphocreatine an an increase in ADP
Does the process of gluconeogenesis require energy? If so, how many ATP does this process cost?
Yes, six ATP are required to take pyruvate and turn it into glucose
What are the byproducts of the Citric Acid Cycle?
3 NADH, 1 GTP (ATP) and 1 FADH2 per pyruvate
What does the complex pyruvate dehydrogenase do? How is that complex activated and deactivated?
Pyruvate dehydrogenase helps make pyruvate into acetyl CoA. It is activated by pyruvate dehydrogenase phosphatase and deactivated by pyruvate dehydrogenase kinase.
Is lactate the only cause of the increase in acidity during exercise? Explain your answer.
No. Every time ATP is hydrolyzed, a proton is created; NADH frees a proton also. Exercise increases the amount of ATP broken down, which increases the number of protons. Lactate may contribute to the increase in acidity, but is not the sole cause.
How would a decrease in phosphorylase affect the process of glycolysis?
Phosphorylase helps breakdown straight chains of glycogen into glucose, which is the starting product of glycolysis. With less substrate, the process of glycolysis will also decrease.
What is the name of the enzyme in the liver that removes phosphate from glucose? Why is this enzyme not in skeletal muscle?
glucose-6-phosphatase
glucose cannot enter into the bloodstream when a phosphate is attached to a molecule. We want glucose leaving the liver to go to the skeletal muscle to be used to make ATP. We do not want glucose leaving the skeletal muscle.
List the processes in order from glycolysis to oxidative phosphorylation. State what each process begins and ends with when appropriate.
Glycolysis- glucose to pyruvate
Pyruvate oxidation- pyruvate to acetyl CoA
Citric Acid Cycle- Acetyl CoA
Electron Transport chain- NADH and FADH2
Oxidative phosphorylation
Explain how the bifunctional enzyme- PFK 2/ fructose 2,6 Bisphosphatase works.
Purpose of this enzyme is to help regulate gluconeogenesis in the liver. The phosphatase side is activated when exercising, which results in a decrease in fructose 2,6-biphosphate and a decrease in pfk to increase glucose levels.