Biology - B4

  • Created by: abbiedye
  • Created on: 20-06-18 19:18

What is photosynthesis?

carbon dioxide + water -----> glucose + oxygen

- It takes place in chloroplasts in green plant cells - they contain pigments like chlorophyll that absorbs light

- Photosynthesis is endothermic

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What do plants use glucose for?

For respiration - plants can convert the rest of the glucose into useful substances

Making cellulose - for making strong plant cell walls

Making amino acids - combined with nitrate ions to make amino acids, then made into proteins

Stored as oils or fats - turned into lipids for storing in seeds

Stored as starch - stored in roots, stems and leaves - ready for when photosynthesis isn't happening

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What are the limiting factors of photosynthesis?

- Light intensity, concentration of carbon dioxide and temperature

Depends on environmental conditions:                                                                                                - night - light intensity                                                                                                                          - - winter - temperature                                                                                                                          - warm and bright enough - carbon dioxide

Chlorophyll - affected by disease and lack of nutrients  

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How do es light, temperature and CO2 effect photos

- Not enough light slows down the rate of photosynthesis

- Too little carbon dioxide also slows it down

- The temperature has to be just right - too high = enzymes denatured

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What is respiration?

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

- breakdown of glucose

- Respiration is exothermic - energy going to the environment

examples: to build larger molecules from smaller ones, allows muscles to contract and to keep the body temperature of birds and mammals steady

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What is metabolism?

- all the chemical reactions in an organism controlled by enzymes

reactant ---> product ---> product ---> product --->

- larger molecules are made into smaller ones

glucose --> starch, glucose and cellulos

- larger molecules are broken down into smaller ones

glucose --> respiration

- excess protein - urea

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What is aerobic respiration?

- Respiration using oxygen - most efficient way to transfer energy from glucose

- most reactions happen inside mitochondria

glucose + oxygen ---> carbon dioxide + water

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What is anaerobic respiration?

'Anaerobic' - 'without oxygen'

Incomplete breakdown of glucose, making lactic acid

glucose ---> latic acid

does not transfer nearly as much energy - glucose isn't fully oxidised

used in emergencies

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How is anaerobic respiration in plants/yeast diffe

Plants produce ethanol and carbon dioxide instead of lactic acid

glucose ---> ethanol + carbon dioxide

anaerobic respiration in yeast cells - fermentation (food and drink)

bread-making = carbon dioxide ----> bread rise

beer and wine making - fermentation produces alcohol

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Why do you respire more during exercise?

- During exercise, muscles contract more - needing more energy - from increased respiration 

- Increase in respiration - needs more oxygen

- Breathing rate and breath volume increase - heart rate increases to get oxygenated blood around the body

- vigorous exercise - muscles start to respire anaerobically

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How does anaerobic respiration lead to an oxygen d

- After resorting to anaerobic respiration, an 'oxygen debt' will occur (amount of oxygen needed to remove lactic acid)

- Pulse and breathing rate stay high - high levels of lactic acid and carbon dioxide

- Lactic acid is converted back to glucose in the liver

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