GCSE AQA Biology - Bioenergetics

Photosynthesis balanced symbol equation

6CO₂ + 6H₂O →^light C₆H₁₂O₆ + 6O₂

What are the 5 uses of glucose in plants?

• For respiration

• To make cellulose which strengthens the cell wall

• To make amino acids for protein synthesis

• To store as fats and oils

• To store as starch

Why do plants store glucose as starch?

So it’s ready for when photosynthesis is not happening.

How do plants produce proteins? (2)

• They combine glucose with nitrate ions from the soil to make amino acids

• The amino acids are made into proteins

What are the three factors affecting rate of photosynthesis?

• Light intensity

• CO₂ concentration

• Temperature

Limiting factor

The factor that prevents photosynthesis from happening any faster

What is another factor which can affect rate of photosynthesis?

The amount of chlorophyll

Describe how light intensity affects rate of photosynthesis

• As light intensity increases, rate of photosynthesis steadily increases

• Up until light intensity has no effect, as another factor has become the limiting factor

Describe how carbon dioxide affects rate of photosynthesis

• As carbon dioxide concentration increases, rate of photosynthesis steadily increases

• Up until carbon dioxide has no effect, as another factor becomes the limiting factor

Describe how temperature affects rate of photosynthesis

• As temperature increases, rate of photosynthesis increases up until an optimum

• Past the optimum, enzymes will be denatured and rate of photosynthesis will decrease

The inverse square law

Light ∝ 1/distance²

If the distance from the pondweed is halved, what will be the effect on the light intensity?

Light intensity will be four times greater.

How can we accurately measure oxygen production from the pondweed?

• Collect the oxygen in the capillary tube

• Use the syringe to draw in gas bubble in the tube alongside a ruler to measure the length of the gas bubble

Describe the experiment to measure the effect of light intensity on photosynthesis

• Place a source of light at a specific distance from pondweed

• Leave the pondweed for a set amount of time

• Measure oxygen production

• Repeat twice and find a mean

How do greenhouses provide the ideal condition for plants?

They trap the sun’s heat, ensuring temperature does not become limiting.

How may a farmer keep temperature ideal during winter in a greenhouse?

Using a heater

How may a farmer keep temperature ideal during summer in a greenhouse if it’s too hot?

Shades and ventilation to cool things down.

How can farmers increase CO2 levels?

By using a paraffin heater, which makes CO2 as a bi-product

How can farmers provide light after the sun goes down?

By using artificial light

Why is it important that farmers keep conditions just right for plants?

So that plants grow faster and a decent crop can be harvested, without wasting money.

Respiration

The process of transferring energy from glucose that goes into every cell in the body.

Three examples of how organisms use energy transferred from respiration

• To form large molecules from smaller ones

• To allow muscles to contract

• To maintain body temperature

What are three examples of how glucose molecules are joined together?

• To form starch for storage in plants

• To form glycogen for storage in animals

• To form cellulose for plant cell walls

Metabolism

The sum of all the reactions that happen in a cell or the body.

Aerobic respiration symbol equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Anaerobic respiration

The incomplete breakdown of glucose, making lactic acid.

When is anaerobic respiration used?

During vigorous exercise, when your body can’t supply enough energy to your muscles.

How is anaerobic respiration in plant and yeast cells different from in muscle cells?

Ethanol and carbon dioxide are produced instead of lactic acid.

What do we call anaerobic respiration in yeast cells?

Fermentation

What is the economic importance of fermentation?

It’s used to make bread and alcoholic drinks.

Explains what happens when your muscles need more energy to contract? (3)

• There is an increased respiration

• To get enough oxygen for your cells, there is an increased breathing rate and breath volume

• Heart rate also increases to get oxygenated blood to the cells quicker

What is the problem with build up of lactic acid?

It can be painful

What is muscle fatigue?

After long periods of exercise, your muscles get tired and stop contracting efficiently.

Oxygen debt

The amount of extra oxygen your body needs to react with a remove build up of lactic acid.

Why do you need to keep breathing hard after you stop exercise?

To get more oxygen into your blood, to be transported to muscle cells to ‘repay’ oxygen debt.

What are the three ways you could measure breathing rate?

• Counting breaths

• Measure heart rate

• Measure pulse