Topic 4- Bioenergetics Flashcards
(31 cards)
What type of reaction is photosynthesis?
Endothermic reaction as energy is transferred from the environment to chloroplasts by light
What happens in photosynthesis?
- Light energy is absorbed
- By chlorophyll in chloroplasts in plant/angal cells
- This energy is used to convert carbon dioxide and water into glucose and oxygen
State the word and symbol equation for photosynthesis.
carbon dioxide + H2O = Glucose + Oxygen
6CO2 + 6H20 = C61206 +602
What does a limiting factor do?
Restricts rate of photosynthesis if in low levels
Describe and explain how temperature affects rate of photosynthesis
- As temperature increases the rate of photosynthesis
- as enzyme controlling photosynthesis gain kinetic energy - Above an optimum temperature the rate decreases
- As the enzymes denature (active site changes shape)
Describe and explain how light intensity affects rate of photosynthesis
- As light intensity increases, rate increases
- as light provides energy needed for photosynthesis - Above a certain light intensity, rate stops increasing
- another factor is limiting
Describe and explain how CO2 concentration affects rate of photosynthesis
- As CO2 concentration increases, rate increases
- as CO2 is a reactant/raw material needed for photosynthesis - Above a certain CO2 concentration, rate stops increasing
- another factor is limiting e.g temperature or light intensity
Inverse square law
1/d2
How can farmers use their knowledge of limiting factors to increase their profits?
- remove limiting factors - gain maximum rate of photosynthesis- increase plant yield
- profit from extra yield must be greater than the costs of providing conditions
What factor is most likely to limit the rate of photosynthesis in plants in a greenhouse on a hot summers day. Explain why?
- carbon dioxide concentration
- as atmospheric carbon dioxide concentration is very low
-temperature is high - light intensity is high
A greenhouse owner wants to grow his lettuce as quickly and cheaply as possible in winter. At what temperature should he keep his greenhouse in order to do this?
- 21.5/22 degrees
- maximum rate of photosynthesis
- most economical/cheapest heating
Describe a method to investigate the effect of light intensity on rate of photosynthesis
- How to vary light intensity
- change distance of white light source from the pondweed, e.g 10, 20, 30, 40
- leave for 5 mins for pondweed to acclimatise to new light intensity - How to control other variables (to make experiment valid)
- pondweed- use same length of pondweed or same pondweed
- temperature- put tube in a thermostatically controlled water bath or put beaker of water between lamp/tupe to absorb heat produced by light
- C02 conc- use set conc of sodium hydrogen carbonate solution - How to measure photosynthesis rate
- count the number of bubbles of oxygen released or collect gas in a syringe
- in a set period of time e.g one minute
(divide volume by time to get rate)
-repeat 3x at each light intensity to identity anomalies and calc a mean
Investigate light intensity of photosynthesis.
What are the variables for this investigation?
independent- distance of pondweed from the light source
dependent- volume of O2 released/number of O2 bubbles produced per minute
control- temperature, co2 supply, pond weed (colour or type), colour of light
Why place pondweed in a solution of sodium hydrogen carbonate (1 mark)
- to provide carbon dioxide
- so that carbon dioxide is not a limiting factor
How could you test bubbles to show they contained oxygen (1 mark)
- add a burning splint
- it will burn more brightly
Why is counting bubbles not an accurate way of measuring volume of oxygen produced? (1 mark)
- bubbles are different sizes
- bubbles can be easy to miss
How could the method be improved to measure the rate of photosynthesis more accurately (2 marks)
- measure volume of O2 released in a gas syringe
- increase length of time
What is the advantage of using an LED light source? (2 marks)
- does not emit a lot of infrared radiation
- so temperature is controlled
- temperature affects rate of photosynthesis as photosynthesis is controlled by enzymes
How could you modify the experiment to investigate the effect of CO2/ temperature/wavelength of light and the rate of photosynthesis? (4 marks)
- carbon dioxide - use different concentrations of sodium hydrogencarbonate solution
- temperature- use different temp water baths
- wavelength- different coloured filters over bulb
- control distance from light source
- control type/length of pondweed
Describe the uses of glucose produced in photosynthesis
- Used for respiration- to release energy
- Converted into insoluble starch for storage
- Used to produce fat/oils (lipids) for energy storage
- Used to produce cellulose to strengthen cell wall
- Used to produce amino acids for protein synthesis
- combine with nitrate ions from the soil to form amino acids
Explain why a leaf left in the cupboard with no light fir 2 days did not contain glucose but did not contain starch?
- starch has not been converted to glucose
- so glucose can be used for respiration/to release energy
- as no light to make glucose for photosynthesis
TMV can cause plants to produce less chlorophyll. Explain why plants with TMV have stunted growth.
- lack of chlorophyll/ reduces photosynthesis
- so less glucose made
- glucose needed for respiration
- so less energy released for growth
- glucose needed for making amino acids/proteins/cellulose
- so less amino acids/proteins/cellulose for growth
What is cellular respiration?
- a series of chemical reactions that release/transfer energy from glucose
- occurs continuously in all living cells
- exothermic reaction
Describe how energy released in respiration is used
- chemical reactions to builder larger molecules
- keeping warm (birds and mammals)
- movement e.g muscle contraction in animals
