Photosynthesis (green) Flashcards
What are the reactants in photosynthesis?
Carbon dioxide and water
What are the products in photosynthesis?
Oxygen and glucose
What is the word equation for photosynthesis?
carbon dioxide + water → oxygen + glucose
What is the balanced symbol equation for photosynthesis?
6CO2 + 6H2O → 6O2 + C6H12O6
Is photosynthesis endothermic or exothermic?
Endothermic
What absorbs the light energy required for photosynthesis?
Chlorophyll (a green pigment in the chloroplasts)
In which layer in the leaf does most photosynthesis happen?
Palisade mesophyll
What is the main photosynthetic organ in plants?
Leaves
How do plants obtain the carbon dioxide they need for photosynthesis?
Carbon dioxide diffuses into the leaf from the air through the stomata
How do leaves obtain the water they need for photosynthesis?
- Enters the plant through the roots (by osmosis)
- Transported to the leaf through xylem
What are five ways that plants use the glucose they produce in photosynthesis?
For:
- Respiration (to release energy)
- Stored as starch
- To make cellulose
- To make amino acids / proteins
- To make lipids (fats and oils)
How do plants store the glucose they produce in photosynthesis?
As starch in their leaves
What is cellulose used for in plants?
To build cell walls
What are the three ways of measuring the rate of photosynthesis?
- The rate of oxygen output
- The rate of carbon dioxide uptake
- The rate of carbohydrate production
Why is measuring oxygen output or carbohydrate production not a perfect method of measuring the rate of photosynthesis?
Plants will respire, which uses oxygen and glucose
Why does rate of photosynthesis level off at high light intensities?
There is a limiting factor (something in short supply)
E.g. carbon dioxide, chlorophyll, temperature
Why does rate of photosynthesis level of at high concentrations of carbon dioxide?
There is a limiting factor (something in short supply)
E.g. light intensity, temperature, chlorophyll
Why is rate of photosynthesis low at low temperatures?
- Reactants have little energy, so move less quickly
- Enzymes and substrates collide less frequently
Why does rate of photosynthesis decrease at high temperatures?
Enzymes become denatured
Which parts of the electromagnetic spectrum are reflected or absorbed by chlorophyll?
- Absorbs the red and blue parts
- Reflects the green parts
You are investigating the effects of light intensity on the rate of photosynthesis in pondweed.
What is the independent variable in this investigation?
The light intensity (distance of LED bulb from pondweed)
You are investigating the effects of light intensity on the rate of photosynthesis in pondweed.
What is the dependent variable in this investigation?
The rate of photosynthesis (number of oxygen bubbles produced in 1 minute)
You are investigating the effects of light intensity on the rate of photosynthesis in pondweed.
What are the control variables in this investigation?
- Concentration of sodium hydrogencarbonate
- Temperature
- Using the same piece of pondweed each time
How could this investigation be improved so that the rate of photosynthesis is more accurate?
Measure the volume of oxygen produced by collecting the gas produced in a gas syringe.
Explain why only the green parts of a variegated leaf test positive for starch.
- Green parts contain chlorophyll
- Only green parts photosynthesise
- Produce glucose, which is stored as starch
When testing a variegated leaf for starch, why is it important to boil the leaf in water first?
This kills the leaf, so stops it photosynthesising
When testing a variegated leaf for starch, why it important to drop the leaf in boiling ethanol first?
This removes the chlorophyll
Why does light intensity decrease as distance form the light source increases?
Because photons of light get spread over a wider area
