B4 - Bioenergetics Flashcards
How does photosynthesis produce glucose?
By using light
Give the word equation for photosynthesis
carbon dioxide + water –light –> glucose + oxygen
Where does photosynthesis occur?
In the chloroplasts in green plant cells
Chlorophyll is a green pigment, but how does it help photosynthesis?
It absorbs light
Photosynthesis is exothermic. True or false?
False - it is endothermic, so energy is transferred from the environment
Give the symbol equation for photosynthesis
6 CO2 + 6 H2O –light–> C6H12O6 + 6 O2
WHat are the 5 main ways that plants use glucose?
1) For respiration - transfers energy from glucose, enabling the plant to convert the rest of the glucose into otehr useful substances
2) Making cellulose - for making strong cell walls
3) Making amino acids - glucose combined with nitrate ions in soil, then the amino acids create proteins
4) Stored as oils or fats - lipids for storing in seeds
5) Stored as starch - Stored in roots, stems & leaves, ready to use when photosynthesis isn’t happening (like in winter)
Why do plants store glucose as starch instead?
Because starch is insoluble - a cell with lots of stored glucose in would draw in lots of water and swell up
What are the limiting factors of photosynthesis?
Light
Temperature
CO2 concentration
(Amount of chlorophyll)
What affect would these environmental conditions have on the rate of photosynthesis?
a) If its night
b) If its very warm
c) If there isn’t much CO2
a) Slower rate of photosynthesis
b) Faster rate of photosynthesis
c) Slower rate of photosynthesis
What can affect the amount of chlorophyll in a plant?
Disease (e.g. tobacco mosaic virus)
Environmental stress (e.g. lack of nutrients)
These can cause chloroplasts to get damaged or not make enough chlorophyll, so less absorbtion of light so reduced rate of photosynthesis
Fill the graph ^Rate of photosynthesis | | | | | | | |\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_>Light intensity
^Rate of photosynthesis | | | | r------------------------------------------------ | / | / | / |/\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_>Light intensity
It always levels out eventually because then the CO2 or the temperature is the limiting factor, not light
Fill the graph ^Rate of photosynthesis | | | | | | | |\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_>% Level CO2
^Rate of photosynthesis
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|
|
| r————————————————
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|/_____________________________>% Level CO2
When it levels out, this means that the level of CO2 is no longer the limiting factor
Fill the graph ^Rate of photosynthesis | | | | | | | |\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_>Temperature
^Rate of photosynthesis | | | r-----\ | / \ | / \ | / \ | / \ |/\_\_\_\_\_\_\_\_\_\_\_\_\_\\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_>Temperature There are enzymes needed for photosynthesis, so at around 45 degrees the graph is y=0, as the enzymes needed for photosynthesis and its other reactants will be damaged
Can one graph show the effect of more than one limiting factor of photosynthesis?
Yes - plotted rate of photosynthesis = y, light intensity=x, then there are 2 lines labelled with different temperatures and/or CO2%. the lowest line shows a limiting factor
What practical can be used t show the rate of photosynthesis?
Counting the bubbles produced off a plant, as oxygen production shows the rate of photosynthesis
Reorder these instructions of the practical used to show how the distance of light affects the rate of photosynthesis:
1) The whole experiment is repeated with the light source at different distances
2) The pond weed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen released will collect in the capillary tube
3) For this experiment, any variables need to be controlled - temperature, time, colour and distance of light
4) A source of white light is placed at a specific distance from the (Canadian) pond weed
5) At the end of the experiment, the syringe at the end of the capillary tube is used to draw the gas bubble alongside a ruler, and the length of the bubble is measured. This is proportional to the volume of oxygen produced
6) The experiment is repeated more times with everything the same, then a mean is calculated
4) A source of white light is placed at a specific distance from the (Canadian) pond weed
2) The pond weed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen released will collect in the capillary tube
5) At the end of the experiment, the syringe at the end of the capillary tube is used to draw the gas bubble alongside a ruler, and the length of the bubble is measured. This is proportional to the volume of oxygen produced
3) For this experiment, any variables need to be controlled - temperature, time, colour and distance of light
6) The experiment is repeated more times with everything the same, then a mean is calculated
1) The whole experiment is repeated with the light source at different distances
How can the practical used to see how the distance of light affects the rate of photosynthesis be used to measure the affect of temperature or CO2 on photosynthesis?
E.g. The test tube of the pond weed can be put into a water bath at a set temperature
Or a measured amount of sodium hydrogencarbonate can be dissolved in the water (which gives off CO2).
The experiment can then be repeated with different temperatures/ concentrations if sodium hydrogencarbonate
Light intensity is directly proportional to the distance of the light in photosynthesis. True or false?
False - light is inversely proportional to the square of distance - this is the inverse square law
What does the inverse square law mean? (use the photosynthesis example of light is inversely proportional to the square of the distance of the light)
If you halve the distance, the light intensity will be 4x greater.
If you third the distance, the light intensity will be 9x greater.
If you double the distance, the light intensity will be 4x smaller
If you treble the distance, the light intensity will be 9x smaller
How do greenhouses help artificially create ideal conditions for farming?
Greenhouses help to trap the sun’s heat, and make sure that temperature isn’t a limiting factor.
However, this can be damaging to the plants enzymes in summer, so shades and ventilation may be used to cool it down.
But in winter, heaters can also be used in the greenhouse