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Flashcards in Combined Biology - 4.4 Deck (29)
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Write the word and symbol equations for photosynthesis.

carbon dioxide + water → glucose + oxygen

6CO2 + 6H2O → C6H12O6 + 6O2


Why is photosynthesis described as an endothermic reaction?

Energy is transferred from the environment to the chloroplasts, by light.


Name four factors that affect the rate of photosynthesis.

• Temperature

• Light intensity

• Carbon dioxide concentration

• Amount of chlorophyll


Higher Q. Describe how both temperature and light intensity affect the rate of photosynthesis.


*this is just an example, you have to be able to do this for any graph with interacting limiting factors

• As light intensity increases, the rate of photosynthesis increases, for both lines.

• When light is no longer a limiting factor, the lines level off.

• Temperature must have been a limiting factor at 10 oC as 20 oC levels off higher than 10 oC.


Higher Q. Suggest ways in which gardeners can optimise conditions for photosynthesis in greenhouses.

• Heater – to increase temperature (e.g. in winter)

• Shade/ventilation/opening windows – to decrease temperature (e.g. in summer)

• Artificial lights – to increase light intensity

• Paraffin heaters – to increase both temperature and carbon dioxide levels


List the 5 ways that plants use the glucose produced in photosynthesis.

• Respiration

• Converted into insoluble starch for storage

• Used to produce fat or oil for storage

• Used to produce cellulose, which strengthens the cell wall

• Used to produce amino acids for protein synthesis


As well as glucose, what else do plants need to produce proteins?

Nitrates (that they absorb from the soil)


Higher Q. Use the inverse square law to calculate the light intensity when a lamp is placed 20 cm from some pond weed.



*This is just an example,  you will need to be able to do this calculation when given the appropriate information.

Use the equation: light intensity ∝ 1/(distance (d)2)

Light intensity = 1/(20)2

Light intensity = 0.0025 arbitrary units


Is respiration an endothermic or exothermic reaction?

Exothermic reaction


Q. Which type of respiration releases most energy?

Q. Which type of respiration requires oxygen?

• Aerobic Respiration


• Aerobic Respiration


List three things that organisms need the energy from respiration for.

• Chemical reactions to build larger molecules

• Movement

• Keeping Warm


Write the word and symbol equations for aerobic respiration.

glucose + oxygen → carbon dioxide + water

C6H12O6 + 6O2 → 6CO2 + 6H2O


Write the word equation for anaerobic respiration in muscles.

glucose → lactic acid


Write the word equation for anaerobic respiration in plant and yeast cells.

glucose → ethanol + carbon dioxide


Name the process of anaerobic respiration in yeast cells.



Give the two main industrial uses of fermentation.

Bread making and alcoholic drinks


Explain how the human body reacts to the increased demand for energy during exercise.

• Heart rate increases

• Breathing rate increases

• Breath volume increases

• So the muscles receive more oxygenated blood


What type of respiration takes place if there is an insufficient amount of oxygen?

Anaerobic Respiration


What type of respiration involves the incomplete oxidation of glucose?

Anaerobic Respiration


What happens to muscles after long periods of exercise?

  • There is a build up of lactic acid.
  • This causes oxygen debt.
  • The muscles become fatigued.
  • Muscles stop contracting efficiently.


Higher Q. How do the muscles get rid of excess lactic acid?

• Blood transports lactic acid to liver.

• In the liver lactic acid is converted back into glucose.


Higher Q. What is ‘oxygen debt’?

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


What is ‘metabolism’?

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


List 5 processes involved in metabolism.

• Conversion of glucose to starch, glycogen and cellulose.

• Formation of lipid molecules from one molecule of glycerol and three molecules of fatty acids.

• Making amino acids (then proteins) using glucose and nitrate ions.

• Respiration

• Breakdown of excess proteins to form urea for excretion.


Sketch a graph to show how light intensity affects the rate of photosynthesis


Sketch a graph to show how carbon dioxide affects the rate of photosynthesis.


Sketch a graph to show how temperature affects the rate of photosynthesis.


Why does temperature affect the rate of photosynthesis?

• Because enzymes are needed for photosynthesis to work.

• There is an optimum temperature for the enzymes to work at.

• If the temperature is too low, the enzymes will work too slowly.

• If the temperature is too high, the enzymes will denature and not work.


Describe how you would use the following equipment to investigate how light intensity affects the rate of photosynthesis.

• Measure ‘10’ cm from pondweed using ruler and place lamp here.

• Turn lamp on and count the number of bubbles produced in one minute (or attach gas syringe and measure the volume of gas produced per minute).

• Repeat 2 more times at this distance.

• Repeat for different distances of lamp to pondweed (e.g. 5 cm, 15 cm, 20 cm).