Cellular Respiration & Oxygen Transport
Glycolysis is a process that converts glucose from a six carbon molecule and breaks it in half into two different three carbon molecules called pyruvic acid. Breaking glucose in half produces two molecules of ATP. This is a very fast conversion from glucose into two separate pyruvic acid (three carbon units) and ATP. The full process of aerobic respiration takes pyruvic and places it in the citric acid cycle, which produces high energy electrons that are sent to the electron transport chain. The electron transport chain uses the high energy electrons and creates ATP with them. The end products are CO2, H2O, heat, and 32-34 ATP. Aerobic respiration requires many more steps and time to convert pyruvate (three carbon units) into the end product of 32-34 ATP.
Aerobic respiration uses oxygen while anaerobic respiration does not use oxygen.
The advantage of a aerobic respiration is that it creates an abundant supply of ATP from one molecule of glucose. The disadvantage is that it takes time for the conversion. Glycolysis is much faster and quicker yielding two molecules of ATP for the breakdown of glucose with two byproducts of pyruvic acid that then become lactic acid. Many glucose molecules can be quickly converted to pyruvic acid.
Glycolysis is for fast energy. Glycolysis obtains a little energy quickly, but only happens for a short period of time. Think of a 100m dash. Aerobic respiration is for long bouts of exercise, think of a marathon.
Questions
When is it more efficient for aerobic respiration? ______________________________________
What are the goals of aerobic respiration? ___________________________________________
If you running as fast as you can for a short distance, would you use aerobic or anaerobic respiration? __________
Which system is more efficient at producing ATP?____________________________________
Since aerobic respiration is more efficient, why do we not always use it? __________________
Does speed and necessity for energy sometimes dictate the bodies decision on how it obtains energy? _________
If you were running from a grizzly bear, would you want quick energy? ____________________
Are you willing to be less efficient but quick under those circumstances? ___________________
If you are watching TV on your couch, would your body rather be efficient or quick with its synthesis of ATP energy? __________
Oxygen Transport
Hemoglobin is a molecule in which oxygen binds to for transport and storage. In the bloodstream hemoglobin is inside red blood cells. Low oxygen concentration causes hemoglobin to release oxygen into the cells and tissues. Active muscle cells are using oxygen and create an area of low O2 concentration in the blood adjacent to the muscle. As red blood cells enter this area, the low O2 concentrations stimulates hemoglobin to release increased amounts of O2.
– Stimulus for hemoglobin releasing oxygen is low oxygen levels.
Why does it make sense for the stimulus for releasing oxygen is low oxygen levels? ________________________
What happen if hemoglobin refuses to release oxygen ___________________________
Why is low blood concentration of O2 a great signal to hemoglobin to release O2? _______________
What would higher blood concentrations of O2 signal to hemoglobin? __________________________
Carbon monoxide will bind stronger than O2 to hemoglobin and refuse to let go under low O2.
What is Carbon monoxide poisoning and why is it deadly? ______________________________
_____________________________________________________________________________
What would be the treatment for carbon monoxide exposure? ___________________________
Myoglobin is a molecule inside of muscle fibers that bind and store oxygen. The myoglobin pigment is what gives muscle its distinctive color.
What is the purpose of myoglobin? ____________________________________________
Does hemoglobin pass its oxygen to myoglobin? _________________________________
When would muscle cell concentrations of O2 be lower than the bloodstream? _________
What would happen if the muscle had plenty of O2, would hemoglobin drop off more? __________________
What would happen if the muscle had an extreme shortage of O2, what would hemoglobin do? _________
Oxygen Debt
During rest or with mild activity there is enough oxygen to support aerobic respiration. However if the intensity and duration of activity increases it will require more ATP than is available. The body will shift to obtaining some of its energy from anaerobic respiration.
Will oxygen debt occur slowly when walking up a flight of stairs?_________________________
Would you produce an oxygen debt if you ran up 5 flights of stairs? _______________________
When have you experienced oxygen debt? ________________________________________
What is the hardest anaerobic activity you participated in and how long did it take to recover? _______________________
If you were in better physical condition, how would the activity and oxygen debt time changed? ______________________
Oxygen deficiency occurs during strenuous exercise along with the accumulation of lactic acid (as a product of anaerobic respiration from the conversion of pyruvic acid to lactic acid). Muscle cells do not have the enzymes capable of converting lactic acid back into glucose, unlike the liver. Lactic acid diffuses out of the muscle cell and into the bloodstream where it is carried to the liver. The liver will convert lactic acid molecules back into glucose (with the addition of a little energy) where it is then stored in the liver or transferred back to the muscle for storage.
Oxygen debt refers to the amount of oxygen the liver cells require to convert the accumulated lactic acid back into glucose, plus the amount of oxygen that the muscles need to resynthesize ATP and creatine phosphate back to their previous exercise levels. Repaying the oxygen debt can take anywhere from a few minutes to several hours depending on the intensity and duration of exercise, along with a person’s training levels. A well-trained individual has better enzymes for converting lactic acid back into glucose.
Would you expect a person to develop an oxygen debt if they ran 4 miles as fast as they could?
Compare that to a person walking 4 miles slowly?_____________________________________
Why does muscle have to transfer lactic acid to the bloodstream? _______________________
What does it feel like when lactic acid accumulates with exercise? _______________________
If a muscle cell is release lactic acid, would you expect it to have high or low cellular O2 levels? _____________
Muscle fatigue
Muscle fatigue is when a skeletal muscle loses its ability to contract during strenuous exercise. Muscle fatigue arises with a lowering of pH, a buildup of lactic acid, and accumulation of other substrates produced during anaerobic respiration and muscle contraction.
A muscle cramp occurs when there is a lack of ATP required to return calcium ions back to the sarcoplasmic reticulum. A muscle fiber is unable to relax and calcium remains inside the fiber causing contraction.
Contraction of skeletal muscle creates heat. Muscle contraction is an important source of heat for the body, especially if the body temperature drops in colder environments (shivering). Enzymatic processes also utilize energy (break ATP). The process of cellular respiration requires a significant amount of energy, resulting in a significant amount of energy lost as heat.