Photosynthesis and Respiration (B8 & B9)

?
  • Created by: samnt2017
  • Created on: 07-10-17 17:27

Photosynthesis

Carbon dioxide + Water === Glucose + Oxygen

CO2 + H2O === C6H12O6 + O2

=== Light and chlorophyll are needed for carbon dioxide and water to react.

The energy needed to produce the glucose molecules through photosynthesis is supplied by sunlight. The chlorophyll (found in chloroplasts) traps the sunlight.

The reactions are endothermic (take heat in).

1 of 6

Photosynthesis

Factors affecting photosynthesis.

The limiting factor is where a particular factor stops the reaction going any faster.

These include:

  • Temperature - If it increases, so does the rate of photosynthesis, due to more energy being provided. - At 45 degrees celcius, the rate drops to 0 because the enzymes have been destroyed.
  • Carbon dioxide concentration - If it increases, so does the rate of photosynthesis, because CO2 is needed for the reaction.
  • Light intensity - If it increases, so does the rate of photosynthesis, because more energy is provided.
  • Chlorophyll concentration - Does not vary in the short term, but may change if plants are grown in soil without enough minerals to make chlorophyll.
2 of 6

Photosynthesis

Converting glucose.

May be changed into other products such as:

  • Insoluble starch, which is stored in the stem, leaves or roots.
  • Fat or oil, which is also stored, e.g. in seeds.
  • Cellulose, to strengthen cell walls.
  • Protiens, which are used for growth and for enzymes.

To produce protiens from glucose, plants also use nitarte ions, which are absorbed from the soil. (Amino acids contain nitrogen, but glucose does not).

3 of 6

Respiration

Respiration is an example of an exothermic reaction. It releases energy from glucose molecules for use by the body.

Organisms need this energy:

  • For chemical reactions to build larger molecules.
  • For movement.
  • To keep warm.

Aerobic Respiration: Glucose + Oxygen === Carbon dioxide + Water

Anaerobic Respiration (In animals): Glucose === Lactic acid 

Anaerobic Respiration (In plants & yeast): Glucose === Ethanol + Carbon dioxide 

In anaerobic Respiration, the glucose is not completely broken down. This means that is transfers much less energy than aerobic respiration. Anaerobic Respiration in yeast cells is called fermentation.

4 of 6

Respiration

Exercise and Respiration.

The heart rate, breathing rate and breath volume all increase to supply the muscles with more oxygen and glucose for the increase in aerobic respiration.

Anaerobic respiration starts to take place in the muscle cells, when the muscles aren't supplied with enough oxygen during vigorous activity. This causes a build up of lactic acid and creates an oxygen debt. The lactic acid causes the muscles to hurt and stops them contracting efficiently. 

Deep breathing for some time after exercise is used to pay back the oxygen debt.

After exercise, blood flowing through the muscles transports the lactic acid to the liver where it is broken down.

The oxygen debt is the amount of extra oxygen the body needs after exercise to react with the lactic acid and remove it from the cells.

5 of 6

Respiration

Metabolism - The sum of all the chemical reactions in a cell or in the body.

These reactions are controlled by enzymes and many need a transfer of energy.

This energy is transferred by respiration and used to make new molecules.

This includes:

  • The conversion of glucose to starch, glycogen and cellulose.
  • The formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids.
  • The use of glucose and nitrate ions to form amino acids, which are used to synthesise proteins.
  • The breakdown of excess proteins into urea for excretion.
6 of 6

Comments

Helloxx33

Report

Great:)

Similar Biology resources:

See all Biology resources »See all Photosynthesis and transpiration resources »