respiration Flashcards
define respiration
respiration is the process where glucose is broken down to release energy in the form of ATP in all living cells.
aerobic respiration is more efficient pathway in generating ATP where oxygen is used. Most eukaryotic cells and some prokaryotic cells can carry out aerobic respiration.
anaerobic respiration generates less amount of ATP without the use of oxygen. although carbohydrates, fats and proteins can be used for respiration, glucose is the fuel that cells most often use.
aerobic respiration
it is the complete breakdown of glucose in the presence of oxygen with the release of 38 ATP molecules. carbon dioxide and water is also released as waste products.
glycosis takes place in cytosol. one glucose molecule is broken down to form 2 molecules of pyruvate and 2 ATP molecules.
if oxygen is present, the molecules of pyruvate would enter the mitochonfrion where they are completely oxidised into carbon dioxide and water. each pyruvate molecule yields 18 atp molecules.
including glycosis, a total of 38 atp molecules are produced from each molecule of glucose during aerobic respiration
anaerobic respiration
it is the breakdown of glucose in the absence of oxygen resulting in the release of lesser energy than aerobic respiration.
glycosis takes place in the cytosol where one glucose molecule is broken down in 2 pyruvate and 2 ATP molecules.
in the absence of oxygen, pyruvate will not enter the mitochondrion. instead it is converted into lactic acid or ethanol and carbon dioxide which are removed as metabollic waste.
in yeast, this process is known as alcoholic fermentation where pyruvate is converted into ethanol and carbon dioxide. Yeast is used for beer brewing, bread making where carbon generated allows dough to rise
during lactic acid fermentation, pyruvate is converted lactic acid with no release of carbon dioxide. lactic acid fermentation by certain fungi and bacteria can result in the formation of cheese and yoghurt
in human muscle cells when there is insufficient oxygen in muscle cells, lactic acid fermentation occurs to produce atp which supplements the amount of energy produced by aerobic to sustain vigorous activity
describe production of lactic acid in muscles during vigorous activity
during vigorous activity, muscles first respire aerobically.
breathing rate increases to take in oxygen and remove carbon dioxide at a faster rate. heartbeat also increases so that oxygen can be transported to the muscles at a faster rate. however there is a limit to the increase in breathing rate and heartbeat resulting in insufficient oxygen to meet the demands of the vigorous muscular contractions
in such cases, muscle cells also respire anaerobically for short durations in order to meet the energy demand of vigorous activity
extra energy released by anaerobic respiration supplements energy released by aerobic respiration to allow the muscles to continue contracting vigorously
when anaerobic respiration occurs, there is a build up of lactic acid in the muscle cells. since there is insufficient oxygen to meet the demands of vigorous muscular contractions, the muscles are said to incur an oxygen debt
describe the recovery period
during period of rest, the breathing rate continues to be high for some time as this is to provide extra oxygen to repay the oxygen debt
lactic acid is removed from the muscles and transported to the liver where some lactic acid is oxidised to release energy which is used to convert remaining lactic acid back into glucose
when all lactic acid has been converted to glucose, the oxygen debt is repaid
glucose then transported back to the muscles and the body is now ready for another race
