Section 2 f) Summary

Respiration is the chemical breakdown of sugars to release energy in living cells.
This is very important, without it we wouldn't have the energy for any of the other life processes. Notable everyday energy-requiring processes include:

• nerve impulses
• cell division
• muscle contraction
• homeostasis and thermoregulation
• protein synthesis
• active transport

Aerobic respiration is releasing energy from glucose by reacting it with oxygen:

Glucose + Oxygen --> Carbon dioxide + Water (+ Energy)

C6H12O6 + 6O2 --> 6CO2 + 6H2O (+ Energy)

Anaerobic respiration is releasing energy from glucose without oxygen. It releases different toxic by-products in plants and animals, and less energy than aerobic respiration:

Plants: Glucose --> Carbon dioxide + Ethanol (+ Some energy)

Animals: Glucose --> Carbon dioxide + Lactic acid (+ Some energy)

The rate of respiration is affected by enzymes and their optimum temperature and pH. 

We can investigate respiration through the following experiments:

Rising dough (yeast):

1. Place dough into oiled measuring cylinders, and record their height. 
2. Place each measuring cylinder into a water bath (regular intervals of 10℃), with three cylinders in each bath so an average for each can be found.
3. Measure the height of the dough every 10 minutes, for 30 minutes.
4. Record the average heights in a table, then find the average percentage change in height. 

Seeds:

1. Fill one vacuum flask with living seeds, and thee other with surface-sterilised seeds. Place a thermometer in each and seal the top with cotton wool.
2. Record starting temp, then wait 30 minutes. 
3. The flask containing the living seeds will have increased in temperature, and the one with dead seeds will not. 

Heat is a by-product of the use of the energy for respiration. 

Humans: 

You can see that we produce carbon dioxide by blowing into a straw in a boiling tube containing lime water - it goes cloudy - or hydrogen carbonate indicator - it goes from red to yellow.