B2 - Photosynthesis Flashcards
Which parts of the plant have chloroplasts in their cells?
Leaves and stem
Where does photosynthesis take place?
Chloroplasts in plant cells
Why is the large surface area of leaves useful for photosynthesis?
Absorb as much light as possible
What do chloroplasts contain?
The green pigment chlorophyll
Why is light needed for photosynthesis?
To break apart the bonds in carbon dioxide and water
How do plants get carbon dioxide?
From the air
Enters the leaves through stomata
What are stomata?
Tiny holes in the bottom of leaves that carbon dioxide passes through to get to the inside of the leaf
How does the water enter the plant?
From the ground and up the roots
It then travels to the leaves and stem through the pipe-like xylem
Describe what happens inside the chloroplasts
The light breaks apart the bonds in the carbon dioxide and water so that they form glucose and oxygen
Why do plants need glucose?
As energy for growth and repair
What happens to the glucose and oxygen after photosynthesis?
Glucose is either used for the energy immediately or stored
Oxygen is released through the stomata
How is the stored glucose used for energy? Give the chemical reaction
Glucose + Oxygen –> Carbon dioxide + Water (+ Energy)
How is glucose stored?
Long strands of glucose called starch
Give 2 reasons that some parts may not have been photosynthesising
Kept in darkness
No chlorophyll
Give 4 parts of a plant which store glucose?
Fruits
Seeds
Roots
Tubers
How do plants get protein?
The glucose combines with nitrate ions in soil to form amino acids
Amino acids form strands which are proteins
What is photosynthesis?
The process that gives plants and some bacteria food
Describe all parts of the leaf and what they do
The upper epidermis is a transparent surface that protects the inside that light passes through
The palisade layer which is where photosynthesis takes place because of the chloroplasts in the cells
The second mesophyll layer is where the carbon dioxide waits to be used in photosynthesis and where the oxygen waits to pass out of the leaf
The lower epidermis acts as protection as has stomata that gases and air can flow through
How can you measure the rate of photosynthesis?
Amount of oxygen or glucose is produced in a certain amount of time
What is a limiting factor?
A factor that, if too low, will affect the process regardless of other limiting factors
What are the 3 limiting factors of photosynthesis?
Carbon dioxide
Temperature
Light intensity
Why does temperature affect the rate of photosynthesis?
Because the enzymes work at different rates depending on the temperature
What are palisade leaf cells?
The cells that contain many chloroplasts so that photosynthesis can take place
How are palisade cells adapted?
The tall shape means that a lot of surface area is exposed down the side for absorbing carbon dioxide from the air in the leaf
The thin shape means that you can pack loads of them in at the top of the leaf
Describe what guard cells do
They open and close the stomata in a leaf
When the plant has lots of water, the guard cells fill with it and become plump which opens the stomata and allows gases to be exchanged for photosynthesis
When the plant is short of water, the guard cells lose water making the stomata close which stops water vapour escaping
Thin outer walls and thicker inner walls make the opening and closing work
They are also sensitive to light and close at night to save water without losing out on photosynthesis
What are the 3 main tissues in plants?
Mesophyll tissue (photosynthesis occurs here)
Xylem and phloem (transports water, minerals, sugars around plant)
Epidermal tissue (covers and protects plant)
How would you measure the effect of a limiting factor?
Let a plant photosynthesise in a flask and use a gas syringe to collect the oxygen given off so that the rate of photosynthesis can be measured
Do the whole thing again but change the factor you are testing inside the flask and measure the rate of photosynthesis again to see the difference
Describe a graph showing the rate of photosynthesis against the level of carbon dioxide
They increase together until you reach a specific point where the rate of photosynthesis stays the same
This is because a different limiting factor is stopping the rate from increasing
Describe the graph showing rate of photosynthesis against light
Same as carbon dioxide graph
Describe the graph showing rate of photosynthesis against temperature
They would increase together until 37 to 40C is reached where the rate of photosynthesis would rapidly decrease because the enzymes become denatured (about 45C)
Describe how greenhouses work
They trap the Sun’s heat meaning that temperature is never really a problem that limits the rate of photosynthesis
In winter, a heater could be used to keep the temperature up
The plants are exposed to sunlight in the day and artificial lighting is used at night
Paraffin burners are often put in a greenhouse because they release carbon dioxide as a by-product (they can be also used to keep temperature up)
Keeping plants in a greenhouse also makes it easier to keep them free from pests and diseases
Describe the 5 ways that plants use glucose
For respiration (glucose can be used to release energy so that the rest of the glucose can be used for other reasons)
Making cell walls (can be converted to cellulose)
Making proteins (combined with nitrate ions in the soil to make amino acids that can be made into proteins)
Stored in seeds (glucose turned into fats for storing in seeds)
Stored as starch (glucose turned into starch and stored in roots, stems, leaves and seeds)
Why is glucose turned into starch to be stored?
It is insoluble which means that water isn’t drawn into cells so that they don’t dwell up
