Topic 4: Bioenergetics Flashcards
What is the word equation for photosynthesis?
Carbon dioxide + water —> glucose + oxygen
What is the symbol equation for photosynthesis?
6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂
Why is photosynthesis an endothermic reaction?
Energy is transferred from the environment to the chloroplasts by light
What do plants use glucose for? [5]
- Respiration
- Making cellulose
- Making amino acids
- Stored as oil and fats
- Stored as starch
What are the 4 limiting factors of photosynthesis?
- Light
- Carbon dioxide conc.
- Temperature
- Amount of chlorophyll
How does increased light affect the rate of photosynthesis? [3]
- As the light level is increased, the rate of photosynthesis will increase up to a certain point
- Beyond that, increased light will no longer increase the rate
- This is because either CO₂ or the temperature is now the limiting factor, not light
How does increased CO₂ affect the rate of photosynthesis? [3]
- As the CO₂ level is increased, the rate of photosynthesis will increase up to a certain point
- Beyond that, increased CO₂ will no longer increase the rate
- This is because either light or temperature is now the limiting factor, not CO₂
Why does a too low temperature limit the rate of photosynthesis?
The enzymes needed for photosynthesis are working too slowly
What would farmers put plants in to create the ideal conditions for photosynthesis?
A greenhouse
How would a farmer keep the temperature of a greenhouse ideal? [2]
- Use a heater in the winter
- Use shade and ventilation in the summer
How would a farmer increase light to a greenhouse?
Use artificial light at night
How would farmers increase the amount of CO₂ in a greenhouse?
Use paraffin heaters, which make CO₂ as a by-product
What are some further advantages of keeping plants in a greenhouse? [2]
- Keep plants free from pests and diseases
- Fertilisers can be added to the soil, to provide all the minerals needed for healthy growth
What economic benefits does keeping plants in a greenhouse with ideal conditions have?
Plants will grow much faster and a decent crop could be harvested more often, which could then be sold
Why should a farmer not pump a greenhouse full of too much CO₂, light etc?
It wastes money
Define ‘respiration’
The process of transferring energy from glucose, which goes into every cell
Why is respiration said to be an exothermic reaction?
It transfers energy to the environment
What 3 things do organisms need the energy from respiration for?
- Chemical reactions to make larger molecules
- Movement
- Keeping warm
Define ‘metabolism’
All the chemical reactions in an organism
Describe 3 reactions in the metabolism (smaller molecules to larger ones)
- Glucose molecules joined together to form starch, glycogen and cellulose
- Lipid molecules made from 1 molecule of glycerol and 3 fatty acids
- Glucose combined with nitrate ions to make amino acids, which are then made into proteins
Describe 2 reactions in the metabolism (larger molecules to smaller ones)
- Glucose broken down in respiration
- Excess protein broken down to form urea for excretion
What is the word equation for respiration?
Glucose + oxygen —> carbon dioxide + water
What is the symbol equation for respiration?
C₆H₁₂O₆ + 6O₂ —> 6CO₂ + 6H₂O
Characteristics of aerobic respiration [3]
- Lots of oxygen present
- Releases lots of energy
- Produces CO₂ and water
