Photosynthesis

Question 1

why are photosynthetic organisms producers of biomass

Answer 1

• glucose is made during photosynthesis
• some glucose is used to make more complex molecules that plants need to grow
• these make up the organisms biomass

Question 2

what is biomass

Answer 2

biomass the the mass of a living organism

Question 3

what do plants do in order to have energy when there is no sunlight

Answer 3

• they store glucose in insoluble forms like starch, fats and oils,
• so when there is no light to produce glucose they already have some to use

Question 4

what is glucose used for in a plant (3)

Answer 4

• respiration (its needed by cells)
• to produce cellulose which strengthens cell wall
• to produce proteins such as enzymes and chlorophyll

Question 5

what happens in photosynthesis

Answer 5

• light energy is absorbed by chlorophyll and so is water and carbon dioxide (the reactants)
• in order to carry out a chemical reaction which produces glucose
• oxygen is released as a by-product

Question 6

can photosynthesis happen without light and why

Answer 6

• no
• because the light energy is used to convert the CO2 and water into the sugar glucose
• it is the activation energy required

Question 7

word and symbol equation for photosynthesis

Answer 7

• carbon dioxide + water = glucose + oxygen

- 6CO2 + 6H2O = C6H12O6 + 6O2

Question 8

why is photosynthesis an endothermic reaction

Answer 8

• it is an endothermic reaction
• because the activation energy required is more than the energy released into its surroundings
• and it uses energy from its surroundings
• the energy level of the plant increases, as the product is stored, after the reaction

Question 9

how are leaves adapted for photosynthesis

Answer 9

• large surface area to absorb sunlight
• thin so the distance for CO2 to diffuse into leaf cells is short
• contains tightly packed cells full with chlorophyll to absorb more sunlight
• network of veins to support the leaf and transport water + carbs
• has stomata to allow CO2 to diffuse into the leaf

Question 10

how does energy stored in an organism’s biomass contribute to life on earth

Answer 10

• energy from biomass works its way through the food chain as animals eat them and each other
• so photosynthetic organisms are the main producers of food for nearly all life on earth

Question 11

in the investigation of light intensity on the rate of photosynthesis, what is canadian pondweed used for and why does it work

Answer 11

• it can be used to measure the effect of light intensity on the rate of photosynthesis
• because the rate at which the pondweed produces oxygen is correspondent to the rate at which its photosynthesising

Question 12

why would you add sodium hydrocarbonate to the water you put the pondweed in

Answer 12

• to make sure the plant has enough carbon dioxide

as it releases CO2 in a solution

Question 13

why would you attach a gas syringe to the conical flask that the pondweed is in

Answer 13

• the oxygen released will collect in the gas syringe

- this allows you to accurately measure the volume of gas produced in a given time

Question 14

which variables should be controlled in the investigation of phtotsynthesis

Answer 14

• temperature (which can be controlled by conical flask in a water bath)
• carbon dioxide concentration (which can be controlled by adding a set amount of sodium hydrocarbonate to a set volume of water

Question 15

what do you actually do in the experiment for investigating light intensity on the rate of photosythesis

Answer 15

• you repeat the experiment with the light source at different distances from the pondweed
• the rate of oxygen production a teach distance can then be calculated (volume produced / time taken)