RESPIRATION Flashcards
Aerobic respiration
The chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
Anaerobic respiration
The chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
Most of the processes taking place in cells in the body need energy to make them happen. Examples of energy-consuming processes in living organisms are:
• the contraction of muscle cells, e.g. to create movement of the organism; • synthesis (building up) of proteins from amino acids; • the process of cell division (Chapter 17) to create more cells, to replace damaged or worn-out cells or to make reproductive cells; • the process of active transport (Chapter 3), involving the movement of molecules across a cell membrane against a concentration gradient; • growth of an organism through the formation of new cells or a permanent increase in cell size; • the conduction of electrical impulses by nerve cells (Chapter 14); • maintaining a constant body temperature in warm-blooded animals (Chapter 14) to make sure that vital chemical reactions continue at a steady rate even when the surrounding temperature varies.
This energy comes from
the food that cells take in. The food mainly used for energy in cells is glucose. Respiration, which produces the energy, is a chemical process that takes place in cells and involves the action of enzymes.
aerobic resp 1
In humans, energy is usually released by aerobic respiration. However, the cells must receive plenty of oxygen to maintain this process. The breakdown of one glucose molecule releases 2830 kJ of energy. It is possible to carry out experiments using invertebrates and germinating seeds and measure the oxygen uptake of the organisms: the faster the uptake, the faster the rate of aerobic respiration. Germinating seeds do not need energy for movement, so their respiration rate tends to be lower than that of animals.
Anaerobic respiration
This form of respiration does not require oxygen. When tissues are respiring very fast, the oxygen supply is not fast enough to cope, so tissues such as muscles start to respire anaerobically instead. However, this is a less efficient process than aerobic respiration, so much less energy is produced. The breakdown of one glucose molecule by yeast releases only 118 kJ of energy.
The word equation for anaerobic respiration in yeast is:
glucose → ethanol carbon dioxide energy
The word equation for anaerobic respiration in muscles is: glucose → lactic acid energy
balanced chemical equation for aerobic respiration is:
It is possible to carry out experiments using germinating seeds to investigate the effect of temperature on respiration rate.
Again, the rate of oxygen uptake of the organisms is used to indicate respiration rate. As temperature increases, so does the rate of oxygen uptake and, therefore, the respiration rate. This is because respiration is controlled by enzymes. An increase in temperature increases kinetic energy of the molecules, so reaction rate increases.
The balanced chemical equation for anaerobic respiration in yeast is:
Oxygen debt
Muscles respire anaerobically when exercising vigorously because the blood cannot supply enough oxygen to maintain aerobic respiration.
However, the formation and build-up of lactic acid in muscles causes cramp (muscle fatigue).
An oxygen debt is created
because oxygen is needed for aerobic respiration to convert lactic acid back to a harmless chemical (pyruvic acid). This happens in the liver. At the end of a race, a sprinter has to pant to get sufficient oxygen to the muscles to repay the oxygen debt.
Breathing remains deep
to supply enough oxygen and the heart rate remains fast to transport lactic acid in the blood from the muscles to the liver. A long-distance runner judges his or her pace, not running too fast, to prevent the muscles respiring anaerobically. Muscle cramp would stop the athlete running.
