Topic 4 - Bioenergetics Flashcards
photosynthesis Equation
Carbon dioxide + water ———> glucose + oxygen
sunlight
Where does photosynthesis take place
In the chloroplasts which contains pigments like chlorophyll that absorb light
What type of reaction is photosynthesis
Endothermic as energy is transferred from the environment into the chloroplasts
Symbol equation for photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2
What do plants use glucose for respiration
This transfers energy from glucose enabling the plant to convert the rest of the glucose into various other useful substances
Why is glucose used for making cellulose
Glucose is converted into cellulose for making strong plant cell walls
How is glucose used for making amino acids
Glucose is combined with nitrate ions to make amino acids which are then made into proteins
Why is glucose stored as oils or fats
Glucose is turned into lipids for storing in seeds
Why is glucose stored as starch
-Stored into starch and stored in roots, stems and leaves for use when photosynthesis isn’t happening like in winter.
-Starch is insoluble so it is better for storing than glucose - a cell with lots of glucose in would draw in loads of water and swell up
What cour things can affect the rate of photosynthesis
The intensity of light, concentration of CO2 and temperature
What is the limiting factor
It stops photosynthesis from happening ang faster
Which factor limits photosynthesis at different times depending on the environmental conditions
-At night light is the limiting factor
-During winter it’s usually temperature
-If it’s warm and bright enough the limiting factor is usually the amount of CO2
How is chlorophyll a limiting factor for photosynthesis
-The amount of chlorophyll in a plant can be affected by disease or environmental stress (e.g. lack of nutrients)
-These can cause chloroplasts to become damaged or not to make enough chlorophyll so photosynthesis is reduced as they can’t absorb as much light
Practical for oxygen production showing the rate of photosynthesis
- A source of white light is placed at a specific distance from the pondweed
- It is left to photosynthesise for a set amount of time and as it photosynthesises the oxygen released will collect in the capillary tube
- At the end the syringe will be used to draw the gas bubble in the tube alongside a ruler and the length will be measured
- Any variables affecting the results should be controlled, like the temperature and time the pondweed is left to photosynthesise
- Repeat twice with the light source at the same distance and mean volume of O2 produced calculated
- Then the whole experiment is repeated with different light sources at different distances
What happens in the pondweed experiment when the distance of the light increases
The lightly intensity decreases
The light intensity decreases in proportion to the square of the distance
What is the inverse square law for the pondweed experiment
light intensity = 1 / distance (d)^2
How do greenhouses artificially create the ideal conditions for farming
Greenhouses trap the suns heat and make sure that temperature doesn’t become limiting so in Winter a farmer or gardener might use a heather to keep temperature at ideal level. In summer it could get too hot so they might use shades and ventilation
How do farmers artificially create the ideal light conditions for farming
Supply artificial light for plants after the sun goes down to give their plants more quality photosynthesis time
How do farmers artificially create the ideal carbon dioxide conditions for farming
By using a paraffin heater to heat the greenhouse as the paraffin burns it makes carbon dioxide as a by-product
How does keeping plants enclosed in a greenhouse artificially create the ideal conditions for farming due to pests
Keeps them free from pests and disease and the farmers can add fertilisers to the soil to provide minerals needed for healthy growth
How is light a limiting factor for photosynthesis
-Light provides energy needed for photosynthesis
-As the light level is raised, the rate of photosynthesis increases steadily- but only up to a certain point
-Beyond that it won’t make any difference - as light intensity increases, the rate will no longer increase. This is because it’ll be either be the temperature or the CO2 level which is now the limiting factor, not light.
How is CO2 a limiting factor for photosynthesis
-CO2 is one of the raw materials needed for photosynthesis
-The amount of CO2 will only increase the rate of photosynthesis up to a certain point. After this the rate no longer increases showing that CO2 is no longer the limiting factor
-As long as light and CO2 are in plentiful supply then the factor limiting photosynthesis must be temperature
How is temperature a limiting factor for photosynthesis
-Usually if the temperature is the limiting factor it’s because it’s too low and enzymes needed for photosynthesis work more slowly at low temperature
-If the plant gets too hot the enzymes it needs for photosynthesis will be denatured
-This happens at about 45°C
What is respiration
The process of transferring energy from the breakdown glucose and it goes on in every cell in your body continuously
What kind of reaction is respiration
Exothermic - it transfers energy to the environemtn
How do organisms use the energy transferred by respiration
-To build up larger molecules from smaller ones
-In animals it’s use to allow the muscles to contract
-In mammals and birds the energy is used to keep their body temperature steady in colder surroundings
What is metabolism
The sum of all reactions that happen in a cell or the body
Outline reactions where larger molecules are made from smaller ones
-Lots of small glucose molecules are joined together in reactions to form starch, glycogen and cellulose
-Lipid molecules are each made from one molecule of glycerol and three fatty acids
-Glucose is combined with nitrate ions to make amino acids, which are then made into
Outline reactions where larger molecules are broken into smaller molecules
-Glucose is broken down in respirations which transfers energy to power all the reactions in the body that make molecules
-Excess protein is broken down in a reaction to produce urea which is then excreted in urine
