Bioenergetics Flashcards
What is the word equation for photosynthesis?
carbon dioxide + water (light)→
glucose + oxygen
What is the symbol equation for photosynthesis?
6CO₂+6H₂O→C₆H₁₂O₆+
6O₂
What is photosynthesis?
An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.
Where does photosynthesis take place?
In chloroplasts in green plant cells (containing green pigments like chlorophyll which absorb light).
What do plants use the glucose produced in photosynthesis for?
- used for respiration
- converted into insoluble starch for storage
- used to produce fat or oil for storage
- used to produce cellulose, which strengthens the cell wall
- used to produce amino acids for protein synthesis
Why do plants use glucose for respiration?
Energy is transferred from glucose which enables the plants to convert the rest of the glucose into various other useful substances.
How do plant use glucose from photosynthesis to make proteins?
Glucose is combined with nitrate ions absorbed from the soil to make amino acids, which are then made into proteins.
How do plants convert glucose for storage?
-Glucose is converted into lipids (oils and fats) for storing in seeds
-Glucose is converted into insoluble starch and stored in roots, stems, and leaves ready for when photosynthesis isn’t happening, like in the winter
Why is starch better for storing energy than glucose?
It is insoluble but glucose isn’t. A cell with lots of glucose in would draw in loads of water via osmosis and swell up.
What are the (limiting) factors that affect the rate of photosynthesis?
-Light intensity
-Carbon dioxide concentration
-Temperature
-(Chlorophyll)
How does temperature affect the rate of photosynthesis?
-Usually, if the temp is the limiting factor its because it’s too low.
-As temperature increases, the rate of photosynthesis also increases - initially
-After optimum temperature is reached, the rate of photosynthesis decreases
What is a limiting factor?
A factor which prevents the rate of photosynthesis increasing any further.
How does Carbon Dioxide concentration affect the rate of photosynthesis?
-Increasing the levels of carbon dioxide increases the rate of photosynthesis because it is one of the reactants.
-But only up to a point where the graph will plateau (as CO2 increases, the rate of photosynthesis no longer increases)
-This shows CO2 is no longer the limiting factor
Why might a too low temperature be limiting?
The enzymes needed for photosynthesis work more slowly at low temperatures.
Why can’t we measure the rate of growth to measure the rate of photosynthesis?
Glucose is used for a variety of things other than growth.
Why might a too high temperature be limiting?
The enzymes that catalyse the photosynthesis reaction (and the plant’s other reactions) will denature so will be unable to carry out their function.
This happens at around 45°C and causes the rate of photosynthesis to drop sharply until it stops altogether
How does light intensity affect the rate of photosynthesis?
-Light provides the energy needed for photosynthesis
-As light levels increase, so does the rate of photosynthesis, but only up to a point (the graph will plateau)
-Then light is no longer the limiting factor (it will be CO2 conc. or temp.)
How does levels of chlorophyll affect the rate of photosynthesis?
-The amount of chlorophyll in a plant can be affected by disease (e.g. TMV) or environmental stress, such as a lack of nutrients.
-These factors can cause chloroplasts to become damaged or to not make enough chlorophyll
-This reduces the rate of photosynthesis because they can’t absorb as much light.
When looking at graphs of photosynthesis rates…
-If a line levels of it is no longer the limiting factor
-If there are two lines and one is at a lower temp/conc. then at that line, temp/conc. must be the limiting factor
If factors are high, then…
…another factor must be limiting.
How are leaves adapted for photosynthesis?
-Wide to increase surface area
-Flat to provide a short diffusion path for Carbon dioxide
-Mesophyll cells have lots of chloroplasts (maximum absorption of light)
-Xylem to transport water (and minerals)
-Phloem to transport glucose produced to rest of plant
-Lower epidermis has spores called stomata (CO2 can diffuse into leaf, O2 can diffuse out).
How can farmers manipulate the rate of photosynthesis?
-Artificial lights
-Use heaters
-Increase CO₂ concentration
-Ensure plants have enough minerals and nitrates
-Greenhouses
How do greenhouses increase the rate of photosynthesis?
Trap the sun’s heat to make sure temperature doesn’t become limiting.
How do heaters/ventilation increase the rate of photosynthesis?
In winter a farmer might use a heater to keep temp. at the right level
In summer, they might use shades/ventilation to cool things down when they get too hot
How does using artificial lights increase the rate of photosynthesis?
Gives plants more quality photosynthesis time.
How do farmers increase the rate of photosynthesis by manipulating levels of carbon dioxide?
By using a paraffin heater to heat the greenhouse. As the paraffin burns, it makes CO2 as a by-product.
Pros of farmers using light and heaters to increase the rate of photosynthesis in crop farming.
Gas heaters will warm up the greenhouse and give off carbon dioxide, increasing the rate of photosynthesis.
Artificial lights means plants can be lit during the night, increasing the rate of photosynthesis particularly within the winter months.
Cons of farmers using light and heaters to increase the rate of photosynthesis in crop farming.
Gas used in gas heaters is a fossil fuel, adding additional CO2 to the atmosphere, contributing to the enhanced greenhouse effect.
Artificial lights run on mains electricity which can be expensive.
Limiting factors are important in the economics of …
… enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit.
What does the inverse square law state?
Light intensity decreases in proportion to the square of the distance.
Inverse square law formula:
light intensity ∝ 1/d²
The inverse square law means that if you halve the distance, the light intensity will be…
four times greater
The inverse square law means that if you double the distance, the light intensity will be…
four times smaller
What is a measure of light intensity?
1/d²