6. Plants Flashcards
What is the word equation for photosynthesis?
Carbon Dioxide + Water -> Glucose + Oxygen
What is the symbol equation for photosynthesis?
6CO2 + 6H2O -> C6H12O6 + 6O2
What does photosynthesis produce?
Glucose (and oxygen) for respiration
Where in the cell does photosynthesis happen?
Inside the chloroplasts.
In what organisms are chloroplasts found?
In some plant cells and in algae.
What substance do chloroplasts contain?
Chlorophyll, which is green.
What is chlorophyll used for?
It absorbs light energy from sunlight and uses it to convert CO2 and H2O into glucose and oxygen.
What is needed for photosynthesis to happen?
- Carbon dioxide
- Water
- Light energy
- Chlorophyll
In which part of the plant does photosynthesis happen?
In the leaves.
How is sunlight obtained for photosynthesis?
Light energy is absorbed by chlorophyll in chloroplasts.
How is water obtained for photosynthesis?
It is taken from the soil and reaches cells via the xylem.
How is carbon dioxide obtained for photosynthesis?
It diffuses into the leaf through stomata.
What is the structure of the leaf from top to bottom?
Cuticle, Upper Epidermis, Mesophyll = (Palisade, Spongy Layer), Lower Epidermis (+ Guard Cells), Cuticle (+ Stomata)
(Diagram Pg 58)
What factors affect the rate of photosynthesis?
• Light intensity • Carbon dioxide • Temperature (• Water) (• Chlorophyll)
Why is water usually not considered a rate limiting factor in photosynthesis?
By the time water becomes the rate limiting factor for photosynthesis, the plant is already mostly likely dying or in big trouble.
What does “rate limiting factor” mean in terms of photosynthesis?
The factor which is stopping photosynthesis from happening any faster.
How can the rate of photosynthesis be investigated?
- Get a water plant like Canadian Pondweed
- Measure the gas produced in a certain amount of time (e.g. number of bubbles, volume of gas, etc.)
- Repeat -> Each time change a factor, like light
- Plot a graph of results
How can light intensity be changed in an investigation on photosynthesis?
- Light intensity can be changed by moving a lamp closer or further from a plant
- Plot a graph of gas produced against light intensity (NOT distance from lamp)
How can CO2 be changed in an investigation on photosynthesis?
• Dissolve different amounts of sodium hydrogencarbonate, which gives off CO2.
How can temperature be changed in an investigation on photosynthesis?
• Put the flask with the plant in a water bath
What does a graph of rate of photosynthesis against light intensity look?
The rate increases until a certain point, after which it remains constant.
What does a graph of rate of photosynthesis against CO2 % look?
The rate increases until a certain point, after which it remains constant.
What does a graph of rate of photosynthesis against temperature look?
The rate slowly increases up to a point, after which it quickly decreases.
How does light affect the rate of photosynthesis and why?
As light intensity increases, so does the rate of photosynthesis at a constant rate. After a point, the rate of photosynthesis levels out because another factor becomes rate limiting.
How does CO2 concentration affect the rate of photosynthesis and why?
As CO2 concentration increases, so does the rate of photosynthesis at a constant rate. After a point, the rate of photosynthesis levels out because another factor becomes rate limiting.
How does temperature affect the rate of photosynthesis and why?
As temperature increases, so does the rate of photosynthesis because enzymes which catalyse photosynthesis work more efficiently. After a point, the rate decreases because the enzymes are denatured.
At which temperature are plant enzymes responsible for photosynthesis denatured?
About 45*C.
How can light, temperature and CO2 concentration be controlled in investigations into photosynthesis?
Light - Use a bench lamp
Temperature - Keep the flask in a water bath
CO2 - Not much can be done -> Just use a large flask to ensure there is more than enough CO2
What is the most common way to artificially create the ideal environment for plants to grow?
Grow them in a greenhouse.
How do greenhouses work?
- Trap sun’s heat, ensuring temperature doesn’t become rate limiting
- Ensure lots of light reaches plants
- Prevents pests and disease reaching plants
How do farmers help greenhouses maximise growth?
- In summer, use blinds to lower temperature -> In winter, use heaters to increase temperature
- Artificial light after dusk -> More photosynthesis time
- Paraffin heaters -> Increase heat and release CO2
- Fertiliser
Why is it important for farmers to provide just the right amount of heat, light, CO2, etc. for their plants?
They need to provide enough so that the plants grow well, but not too much so that money is wasted.
What are the ways in which plants use glucose?
1) Respiration
2) Making cell walls
3) Making proteins
4) Stored as fats or oils
5) Stored as starch
How is glucose used for respiration?
Respiration releases energy -> Energy allows plant to convert glucose into other useful substances-> Which can be used for building new cells and growth
How is glucose used for making cell walls?
Glucose is converted into cellulose for making cell walls.
How is glucose used for making proteins?
Glucose is combined with nitrate ions (from soil) to make amino acids, which then join to make proteins.
What are carnivorous plants adapted for?
Living in nutrient poor soil -> They get most of the nutrients they need (e.g. nitrates) from the animals they catch.
How is glucose used for storage as fats or oils and where is it stored?
Glucose is turned into lipids (fats and oils) for storing in seeds.
How is glucose used for storage as starch and where is it stored?
Glucose is turned into starch and stored in roots, stems and leaves.
Give an example of glucose being stored as fats or oils.
Sunflower seeds contain a lot of oil - we get cooking oil and margarine from them.
Give an example of glucose being stored as starch.
Potato and parsnip plants store starch underground over the winter so a new plant can grow form it the next spring.
Why is glucose stored as starch in plants?
So that it is ready for use when photosynthesis isn’t happening (e.g. winter).
Why is starch a suitable form of storing glucose?
It is insoluble, so water is not drawn into cells.
How does CO2 reach plant cells?
It diffuses into the leaf through stomata, then it diffuses into cells.
How are leaves adapted to take in CO2?
• Many stomata
• Flattened shape -> Increases SA:V ratio
• Air spaces inside leaf -> Increase SA:V ratio
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