Photosynthesis and plants Flashcards
What is photosynthesis?
A chemical reaction used to make food from light energy, CO2 and H2O.
Plants only and O2 is a waste product from this reaction.
What is the word equation for photosynthesis?
Carbon + Water —> Glucose + Oxygen
Where does photosynthesis take place?
In the chloroplasts of leaf cells
What does chlorophyll do?
Absorb light energy
What controls the chemical reactions of photosynthesis?
Enzymes
Whats glucose used for?
Respiration
What does glucose transform into?
- Starch for storage
- Cellulose to make new cell walls
- Protein for growth
- Oils for storage
How do you test a leaf for starch?
- Place the leaf in boiling water for a minute - Breakdown all walls
- Boil the leaf in ethanol (alcohol) - Remove chlorophyll
- Rinse the leaf in hot water - To soften the leaf to spread on the tile
- Spread the leaf on a white tile and blot dry - As it allows us to save a colour change better
- Add a few drops of iodine solution - Added as an indicator test for starch (stored sugar)
- If leaf turns black, starch is present - chaka chaka
Is carbon dioxide needed for photosynthesis?
Yes as it is one of the conditions for it to proceed
Which cell layer does most photosynthesis take place?
Palisade layer, has chloroplasts and is near the top
What are the three main factors of photosynthesis?
Light Intensity, CO2 concentration, and Temperature.
Why does photosynthesis have an optimum temperature?
Photosynthesis is controlled by enzymes which work slowly when too cold and denature when too hot
What happens to rate of photosynthesis when you increase light/carbon dioxide concentration?
The rate increases
At night what would most likely be the limiting factor for photosynthesis?
Light Intensity
Which side of a leaf has stomata?
The underside (the bottom)
How does air enter a leaf?
Through the stomata
What is the name of the loss of water through stomata?
Transpiration
Where does water enter the plant?
Roots, specifically root hairs
What is water needed for in plants?
Photosynthesis, carrying minerals, keeping cells turgid (rigid and preventing wilting)
What are root hairs?
They increase the surface area that can absorb water or minerals
How does water move into the roots?
By osmosis
How do minerals enter the roots?
By active transport
What do the xylem and phloem transport?
Xylem: Water (one way)
Phloem: Sucrose/sugar (up and down)
How is water pulled up the xylem?
After diffusion of water vapour through the stomata, more water is pulled up as a column because the molecules stick together
How would wind increase the rate of transpiration?
water molecules blown away, steepening concentration gradient
What does the phloem look like?
Living tissue made from columns of interconnecting cells
What does the xylem look like?
Tissue made of elongated tubes called xylem vessels
What are limiting factors?
The factor that stops the rate of photosynthesis increasing e.g. if there’s too little light, photosynthesis is slow even if CO2 concentration is plentiful therefore, light intensity is the limiting factor.
What is transpiration?
The loss of water vapour from a plant by diffusion from the stomata of leaves. Also makes more water being drawn up the plant through the xylem vessels
Loss of water vapour through the leaf
What are chloroplasts?
Contains the green pigment, chlorophyll and where photosynthesis takes place
What is humidity?
A measure of how much water is in the atmosphere
What are mineral salts?
Simple chemicals found in the soil containing elements such as nitrogen, phosphorus and potassium
What is the stomata (or a stoma)
Gaps in the epidermis (outer layer) of a leaf that allow gases to diffuse in and out of leaf. It can also open and close
What are guard cells?
Cells located around the stomata that open the stomata by pulling apart/coming together if they want to close
Why is the waxy cuticle and the upper epidermis transparent?
To allow sunlight to get in
How does water enter the plant?
They go through their root hairs. The soil water is more dilute (higher water concentration) therefore osmosis takes place when going inside the root hair cell.
What is meant by turgid?
Swollen cells. If the plant has plenty of water its cytoplasm + vacuole have plenty of water
Why do plants need a variety of minerals?
For healthy growth
What do farmers add to soil if it has mineral deficiencies?
NPK
Nitrogen - nitrates - less chlorophyll, yellow leaves
Phosphorus - phosphates - discoloured purple leaves, poor root growth
Potassium - potassium nitrate - poor growth of flowers and fruit
If its a hot day, the stomata closes to reduce transpiration and prevent wilting. What is the disadvantage of it closing?
Gas exchange cannot occur. No CO2 = no photosynthesis :(
