B4

Photosynthesis limiting factors

Photosynthesis takes place in the chloroplasts as they use a green pigments called chlorophyll to absorb light and use it as energy to turn CO₂ and water into glucose and oxygen

Plants use glucose for

• Respiration: using energy from glucose for making other useful substances

• Making cellulose- This is for cell walls

• Making amino acids- Glucose + nitrates = amino acids which can make proteins

• Stored as fats- Glucose is turned into lipids for strong seeds

• Stored as starch- This is to store it for long periods of time when photosynthesis is inactive, such as winter

Limiting factors:

a resource or condition that constrains a population's growth or size

• CO₂ Concentration

• Light

• Temperature

• Chlorophyll

Light

• Light provides energy for photosynthesis

• As the amount light increases so does the rate of photosynthesis gradually

• Until it reaches a point where it no longer increases

• This is the point where light no longer becomes a limiting factor

• Leaving temperature and CO₂ concentration as the other limiting factors

Carbon dioxide

• CO₂ provides materials for photosynthesis

• As the amount CO₂ increases so does the rate of photosynthesis gradually

• Until it reaches a point where it no longer increases

• This is the point where CO₂ no longer becomes a limiting factor

• Leaving temperature and Light concentration as the other limiting factors

Temperature:

• Temperature provides materials for photosynthesis

• As the amount Temperature increases so does the rate of photosynthesis gradually

• Since the enzymes needed for photosynthesis are less active at low temperatures

• Until it reaches a point where it no longer increases

• This is the optimum temperature

• As the temperature increases further

• The enzymes need for photosynthesis get damaged

• Causing the rate of photosynthesis to decease.

You can use graphs to depict these using graphs as previously shown:

You can measure the rate of photosynthesis roughly using:

1. A source of white light places at varying distances from pond weed suspended in water

2. Leave it to photosynthesis for a set amount of time

3. Connected to a capillary tube that collects gas bubbles

4. At the end a syringe is used to measure the volume of gas measure

5. Repeat this changing either a limiting factor

• CO2 using sodium hydro carbonate

• Light intensity just vary the lamp’s distance

• Temperature use a heater

Light intensity is inversely proportional to distance:

You can artificially create ideal conditions for growing plants through green houses:

• By trapping heat from the sun

• Using ventilation so it doesn’t get too hot

• Using artificial lights at night

• Using paraffin heaters that automatically create CO₂ as a bi-product

• Keeping plants encased and away from pests

• All This costs money

Respiration and Metabolism:

Respiration is the process of transferring energy from glucose which goes on in every living cell

This transfer of energy can be for:

• Allowing muscles to contract

• Build up larger molecules like proteins from amino acids

• To maintain body temperature

Metabolism- this is the sum of all chemical reactions in an organism

Respiration

Aerobic respiration is the more efficient version of respiration that takes place using oxygen in the mitochondria:

Anaerobic respiration is the less efficient version of respiration that takes place when the body can’t supply cells with enough oxygen, leading to an incomplete break down glucose. this usually happens only during vigorous exercise.

• In plants this makes ethanol and carbon dioxide

• Which is called fermentation and is what makes alcohol

Exercise

• When you exercise you breathing rate and volume increases to supply your muscles with more oxygen

• And your heat rate increases to get this oxygenated blood around the body

• When you exercise vigorously you can’t supply your muscles with enough oxygen

• Leading to anaerobic respiration and muscle fatigue

• Making muscles not contract as efficiently

• During this exercise you build up an amount of lactic acid and oxygen debt

• Which is the amount of oxygen needed to complete the respiration reaction

• Turning the lactic acid into CO2 and water

• Which is done after just after exercise

• Lactic acid is also transported to the liver and converted to glucose again