Respiration

Lactic acid fermentation

-During lactic acid fermentation, pyruvate is converted into lactic acid, with no release of carbon dioxide -Lactic acid fermentation by certain fungi and bacteria are used in production of cheese and yoghurt -In human muscle cells, when there is insufficient oxygen during vigorous exercise, lactic acid fermentation occurs to produce ATP. Supplements aerobic respiration in order to sustain vigorous muscle contractions

Effect of lactic acid in muscles during exercise (anaerobic respiration in muscle cells)

-During vigorous muscle contractions, muscle cells first respire aerobically. -Breathing rate increases to take in oxygen and remove carbon dioxide at a faster rate. Heart rate also increases to transport oxygen to heart muscles at a faster rate. -However, there is a limit in the increase of breathing rate and heart rate thus there is insufficient oxygen to meet the demands of vigorous muscle contractions -Muscle cells then respire anaerobically for short durations in order to meet the energy demands -extra energy released by anaerobic respiration supplements energy released by aerobic respiration to allow muscles to continue contracting -when anaerobic respiration occurs, there is a build-up of lactic acid in muscle cells -since there is insufficient oxygen to meet the demands of vigorous muscle contractions, the muscles incur an oxygen debt. Lactic acid concentrations slowly build up in the muscles, and may eventually be high enough to cause fatigue and muscular pain. body then needs to rest and recover

Glycolysis in anaerobic respiration

-Glycolysis of 1 glucose molecule yields 2 molecules of pyruvate and 2 ATP molecules -In absence/low concentration of oxygen, pyruvate will not enter the mitochondrion -Instead, pyruvate is converted into lactic acid/ethanol/carbon dioxide, which are removed as metabolic waste products

Mitochondria in aerobic respiration

-Glycolysis, takes place in the cytosol. 1 glucose molecule is broken down into 2 molecules of ATP and 2 molecules of pyruvate -In the presence of oxygen, the 2 molecules of pyruvate would enter the mitochondrion, where they are completely oxidised into carbon dioxide and water. Each pyruvate molecule yields 18 ATP molecules -Each glucose molecule produces 38 molecules of ATP during aerobic respiration

use of energy in humans

-Muscle contraction -Protein synthesis -Cell division -Active transport -Growth -Passage of nerve impulses -Maintenance of constant body temperature

Alcoholic fermentation

-Occurs in yeast whereby pyruvate is converted into ethanol and carbon dioxide -Yeast is used in beer brewing and breaad making, where carbon dioxide produced allows dough to rise

recovery period

-during period of rest, breathing rate continues to be fast for some time. -this is to provide sufficient oxygen to repay the oxygen debt -Lactic acid is removed from the muscles and transported to the liver. -In the liver, some of the lactic acid is oxidised to release energy. this energy is used to oxidise the remaining lactic acid to release glucose. -When all the lactic acid has been oxidised into glucose, oxygen debt has been paid -Glucose is transported back to muscle cells and the body is now ready for another race

Aerobic respiration is the more efficient pathway in generating ATP where oxygen is used in the process

-most eukaryotic and some prokaryotic cells can carry out aerobic respiration -smaller amount of ATP is generated from anaerobic respiration without using oxygen at all

Anaerobic respiration

Breakdown of glucose in the absence of oxygen, anerobic respiration releases less energy than aerobic respiration

Aerobic respiration

breakdown of glucose in the presence of oxygen with the release of 38 ATP molecules. Carbon dioxide and water are released as waste products

definition of respiration

the breakdown of glucose, in the form of ATP, from glucose in all living cells