Aerobic respiration requires oxygen and fully breaks down glucose to release more energy in the form of ATP. It occurs in mitochondria. Anaerobic respiration does not require oxygen but produces less ATP. In humans, it occurs in muscles during intense exercise when oxygen demand outstrips supply, breaking glucose down to lactic acid. The lactic acid must later be oxidized to remove oxygen debt after exercise is complete. Anaerobic respiration in yeast produces ethanol through fermentation.

1. 7.1 The Respiratory Process in energy Production

2. What is Respiration? Respiration refers to the process of obtaining oxygen and delivering it to the cells for cellular respiration and removing carbon dioxide produced by the cells. Occurs in two main stages: External respiration Mechanical process that maintains a continuous exchange of gases between the respiratory surfaces of an organism and its environment. Internal respiration (cellular respiration) Biochemical process in which energy is made available to all living cells.

3. Energy requirement in living process Energy required in: Muscle contraction Active transport of biochemical substances Transmission of nerve impulses Synthesis of proteins Formation of new protoplasm for growth Cell division Heat released during cellular respiration helps maintain body temperature.

4. What is the main substrate to produce energy? Glucose. How is the chemical energy stored within glucose made available to living cells? The energy is released during cellular respiration. Two types of cellular respiration: AE robic respiration ANAE robic respiration

5. Aerobic respiration Requires continuous supply of oxygen which is obtained from the air during external respiration. Occurs in mitochondria in cells. Summary for aerobic respiration: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + 2898 kJ Release all available energy stored in glucose molecule. CO 2 and H 2 O are produced as waste products. glucose oxygen carbon dioxide water energy

6. Energy released is used to synthesize adenosine triphosphate (ATP) from adenosine triphosphate (ADP) and inorganic phosphate. ATP acts as an instant sources of energy which drives cellular processes as and when needed . ATP consists of phosphate bonds which can be easily broken down to release energy when required by the body.

7. How do cells overcome the shortfall in oxygen supply? Cells undergo ana erobic respiration, a process in which the cells continue to generate ATP without utilizing oxygen.

8. Anaerobic respiration Organisms that respire anaerobically known as anaerobes . Eg: bacteria, yeast Occurs in cytoplasm. Temporary anaerobic respiration may occur in our own body in the fast working skeletal muscles, as in fast running, walking, swimming etc.

9. Anaerobic respiration in human muscles During vigorous activity, blood cannot supply enough oxygen to meet demand for ATP. Muscles are in a state of oxygen deficiency and said to incur oxygen debt and obtain extra energy from anaerobic respiration. Glucose molecules break down partially into intermediate substance called lactic acid . Energy released much less than aerobic respiration.

10. When acid lactic concentration reach high level causing muscular cramps and fatigue. Body need to rest and recover. Getting rid of lactic acid: Lactic acid has to be oxidised to CO 2 and water after exercise but this step requires O 2 . Extra O 2 is absorbed from the air we breath in. Oxygen debt is the amount of O 2 needed to remove the lactic acid from the muscle cells . This is why we breath heavily after strenuous exercise.

11. Oxidation of lactic acid occurs in liver. Oxygen debt is said to “have been paid” when all lactic acid has been eliminated through increased breathing.

12. Anaerobic respiration in yeast Produces ethanol . Process known as fermentation and catalyzed by enzyme zymase . Application: Wine and beer production (production of ethanol) Bread making (CO 2 causes dough to rise)

13. Comparison between aerobic and anaerobic respiration