Biology topic 4

Question 1

Photosynthesis and limiting factors

Answer 1

Photosynthesis
Changes Carbon Dioxide and Water into glucose and oxygen
it gets it’s energy through light
it is an endothermic reaction
plants use the glucose for respiration, making cellulose, making amino acids and it is stored as oil and fats and starch

Limiting factors
rate of photosynthesis is affected by the intensity of light, concentration of CO2 and temperature
the limiting factor is the factor that stops the reaction happening any faster

Question 2

Respiration and Metabolism

Answer 2

Respiration
respiration involves many reactions as it transfers the energy that the cell needs to do everything
its the process of transferring energy from the breakdown of glucose
the energy is used for things such as building larger molecules from smaller ones, allows the muscles to contract and allows them to maintain body temperature

Metabolism
In a cell there are lots of chemical reactions happening all the time controlled by enzymes many of which are linked
In some of these reactions larger molecules are made from smaller ones
In other reactions smaller molecules are made from breaking down larger ones.

Question 3

Aerobic and Anaerobic reactions

Answer 3

Aerobic reactions
They need oxygen as it was the most efficient way to transfer energy from glucose
It happens all the time in plants and animals
Most of the reactions in aerobic respiration happen in the mitochondria

Anaerobic reactions
If your body doesn’t have enough oxygen then it will go to Anaerobic reaction
It produces lactic acids when breaking down glucose
It does not transfer as much energy as aerobic respiration
plants and yeast can respire without oxygen yet they produce ethanol
anaerobic respiration in yeast cells is called fermentation

Question 4

Exercise

Answer 4

The more you exercise the more you respire
The muscles need more energy to work
if you exercise vigorously and your body cannot supply the oxygen you will start respiring Anaerobically

Oxygen debt
An oxygen debt is the amount of extra oxygen needed to remove the build up of lactic acid and get it out of the body
This means you have to breathe a while after you stop exercising to “repay” the oxygen debt
The lactic acid is transported to the liver and there it is converted back to glucose.