B4-Bioenergetics Flashcards
What is photosynthesis?
The biochemical reaction that fixes light energy into organic compounds. It is an endothermic reaction as energy is taken in.
What are the reactants and products in photosynthesis?
Reactants: Carbon Dioxide and Water
Products: Glucose and Oxygen
What is the relationship between light intensity and the rate of photosynthesis?
As light intensity increases, the rate of photosynthesis increases until different limiting factors come into play
What could the limiting factors be other than light intensity for rate of photosynthesis?
- carbon dioxide
- temperature
- amount of chlorophyll
Describe the method for the required practical which investigates the relationship of light intensity and the rate of photosynthesis:
1) Collect boiling tube of bicarbonate solution and elodea
2) Fix boiling tube into clamp stand, low down
3) Set up lamp 5cm from the tube and switch on
4) Wait 3 minutes
5) Count the number of bubbles being produced from the elodea in 3 one minute intervals
6) Repeat measurements with lamp at different distances
How could the validity of the light intensity and rate of photosynthesis required practical be improved?
- Reduce other light sources, so lamp is only one
- Add more bicarb to the tube for each test so there is an excess of carbon dioxide
- Use an LED bulb or heat sink so the heat emitted from the bulb doesn’t affect the results
- Measure volume of oxygen produced as bubbles could be different sizes
How is carbon dioxide a limiting factor in photosynthesis?
If there is no carbon dioxide available, there is a lack of the reactants carbon and oxygen to reactant with the hydrogen and oxygen from water so no more glucose will be produced. Therefore, photosynthesis doesn’t take place
How is temperature a limiting factor in photosynthesis?
If the temperature is low, the rate of photosynthesis is low since the enzymes controlling the reactions are below their optimum temperature and there is a low thermal energy transfer to kinetic energy stores of the reactants. If the temperature is too high, the enzymes denature.
How is light intensity a limiting factor in photosynthesis?
In the absence of light, there is not enough energy to allow for the activation energy to be reached to initiate the reaction between carbon dioxide and water
What are the main ways in which living organisms use energy from respiration?
- Movement (muscle contraction)
- Keeping warm (homeostasis)
- Synthesis
- Active transport
- Nerve impulses
What is metabolism?
The sum of all the chemical reactions that occur inside a cell or an organism
What is an anabolic reaction?
A reaction which joins (makes) stuff
What is a catabolic reaction?
A reaction which breaks stuff
What are the six main ways in which plants use glucose?
- Respiration: transferring energy from glucose
- Making cellulose: glucose is converted into cellulose
- Making amino acids: Glucose is combined with nitrate ions to make amino acids which are then made into proteins
- Stored as oils or fats: glucose turned into lipids for storing in seeds
- Stored as starch: glucose turned into starch, ready to use when photosynthesis isn’t happening because starch is insoluble(stores better as it doesn’t effect osmosis)
- Making fructose: attract animals to eat their fruit
Why can chlorophyll be a limiting factor in photosynthesis?
The amount of chlorophyll in a plant can be affected by disease or environmental stress. This can lead to chloroplast damage or lack of chlorophyll production in them. Therefore, not as much light can be absorbed for photosynthesis
Define respiration:
The process of transferring/releasing energy from glucose, which goes on in every cell. It is an exothermic reaction.
What is the relationship between light intensity and distance?
the light intensity decreases in proportion to the square of the distance. light intensity ∝ 1/distance^2
Describe some anabolic reactions:
- Glucose molecules are joined together to form starch, cellulose and glycogen
- A lipid molecule can be 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 proteins
Describe some catabolic reactions:
- Glucose is broken down in respiration. (Respiration transfers energy to power all reactions in body which make molecules)
- Excess protein/ amino acids are broken down to produce urea which is excreted as urine
What is aerobic respiration?
Respiration which utilises oxygen- it is the most efficient way to transfer energy from glucose. It happens all the time in plants and animals (particularly in mitochondria)
What are the reactants and products in aerobic respiration?
Reactants: -Glucose -Oxygen Products: -Carbon dioxide -Water