What is photosynthesis?
- a chemical reaction which takes place in plants where glucose is made using energy from the sun
Where in the plant does it take place?
- in chlorophyll (a chemical found in chloroplasts)
What type of reaction is photosynthesis?
- endothermic
Write the word equation for photosynthesis
- carbon dioxide + water → glucose + oxygen
Write the chemical symbols for the reactants of photosynthesis
- CO2 = carbon dioxide and H2O = water
Write the chemical symbols for the products of photosynthesis
- C6 H12 O6 = glucose and O2 = oxygen
What are the uses of the glucose which the plant makes in photosynthesis
- for respiration
- stored as fats or oils
- to make cell walls
- to make amino acids
- to store as insoluble starch granules
What are the 4 main limiting factors affecting the rate of photosynthesis?
- the light intensity
- the concentration of CO2
- the temperature
- the amount of chlorophyll a plant has
What is a limiting factor?
- is something which can stop photosynthesis happening any faster
Explain the graph when light intensity is the limiting factor
- at first, as you increase the light intensity , the rate of photosynthesis increases . Light is the limiting factor
- at a certain point, the graph goes flat and no matter how bright the light is, photosynthesis will not go any faster
- this is because light intensity is no longer the limiting factor. The concentration of CO2 or the temperature is now the limiting factor
Explain the graph when CO2 concentration is the limiting factor
- at first, as you increase the CO2 concentration, the rate of photosynthesis increases. CO2 concentration is the limiting factor
- at a certain point, the graph goes flat and no matter how much CO2 there is, photosynthesis will not go any faster
- this is because concentration of CO2 is no longer the limiting factor. The light intensity or the temperature is now the limiting factor
Explain the graph when temperature is the limiting factor
- at first, as you increase the temperature, the rate of photosynthesis increases. Temperature is the limiting factor
- the enzymes needed for photosynthesis work best at the temperature shown by the peak of the graph
- after this point, the rate of photosynthesis will slow down as the temperature is too high and the enzymes will start to denature
What is respiration?
- a chemical reaction which releases energy from glucose in all cells
What type of reaction is respiration?
- exothermic
Where does respiration take place?
- in the mitochondria of cells
Give 3 ways the organisms use the energy transferred by respiration
- to build large molecules from smaller ones
- to move
- to keep warm
What is metabolism?
- the total of all the reactions taking place in a cell or body
What controls the rate of chemical reactions in the body?
- enzymes
Give examples of 5 large molecules which are made in the body (say what each is made from)
- starch = made from glucose
- glycogen = made from glucose
- cellulose = made from glucose
- lipids (fats) = made from glycerol and 3 fatty acids
- proteins = made from amino acids
Give 2 examples of reactions in the body where large molecules are broken down into smaller ones
- respiration = the breakdown of glucose
- excess protein = broken down to make urea
What are the 3 type of respiration?
- aerobic respiration
- anaerobic respiration in muscle cells
- anaerobic respiration in plant and yeast cells
When does anaerobic respiration take place in muscle cells?
- when not enough oxygen is available
What is the word equation for anaerobic respiration in muscle cells?
- glucose → lactic acid
Compare the amount of energy released by this type of respiration with aerobic respiration
- much less energy is released in anaerobic respiration
