Bioenergetics Flashcards
Word equation for photosynthesis
Carbon dioxide + water —-light—-> glucose + oxygen
Symbol equation for photosynthesis
6CO2 + 6H2O —— C6H12O6 + 6O2
What is photosynthesis
- uses energy to change carbon dioxide and water into glucose and oxygen
- takes place in chloroplasts in green plant cells- they continue pigments like chlorophyll that absorb light
- energy is transferred to the chloroplast from environment by light
- endothermic: this means energy is transferred from the environment in th process
5 ways in which plants use glucose
- for respiration
- making cellulose
- making amino acids
- stored as oils or fats
- stored as starch
Plants using glucose for respiration
This transfer energy from glucose which enables the plans to convert the rest of the glucose into various other useful substances
Plants using glucose to make cellulose
Glucose is converted into cellulose for making strong plant cell walls
Plants using glucose to make amino acids
Glucose is combined with nitrate ions (absorbed) to make amino acids, which are then made into proteins
Plants using glucose to store as oils or fats
Glucose is turned into lipids (fats or oils) for storing in seeds
Plants using glucose o store as starch
Glucose is turned into starch and stored in roots, stems and leaves, ready for use when photosynthesis isn’t happening, like in winter. Starch is insoluble, which makes it much better for storing than glucose, a cell with lot of glucose in would draw in loads of water and swell up
Limiting factors that affect the rate of photosynthesis
- light
- concentration of CO2
- temperature
Limiting factors that affect photosynthesis depending on environmental conditions
- at night, light is the Iimiting factor
- in winter its often the temperature
- if its warm enough and bright enough, the amount of CO2 is usual limiting
Chlorophyll as a limiting factor o photosynthesis
- the amount of chlorophyll in a plant can be affected by disease or environmental stress such as lack of nutrients
- these factors can cause chloroplasts to become damaged or to not make nough chlorophyll.
- this means the rate of photosynthesis is reduced because they cant absorb as much light
Light as a limiting factor
- light provides the energy needed for photosynthesis
- as the light level is raised the rate of photosynthesis increases steadily but only up to a certain point
- be on that, the light can still increase but rate will no longer increase because either temperature or carbon dioxide level is now the limiting factor
(On graph, light intensity increases then go flat, flat line is when light is no longer the limiting factor)
Carbon dioxide as a limiting factor
(On graph, increasing line, co2 being increased as its a limiting factor, flat line means co is no longer limiting factor and light or temp need to be raised)
- co2 is one of the raw materials needed for photosynthesis
- as with light intensity, the amount of co2 will only increase the rate of photosynthesis up to a point, after this co2 is no longer the limiting factor
Temperature as a limiting factor of photosynthesis
- if temperature is the limiting factor its usually because its too low, the enzymes needed for photosynthesis work more slowly at low temperatures
- but if the last gets to hot, the enzymes it needs for photosynthesis and its other reactions will be damaged
- this happens at about 45 degrees celcius
Pondweed experiment
- A source of white ight is placed at a specific distance from the pondweed
- The pondweed is left to photosynthesise for a set amount of time
- As it photosynthesises, the oxygen released will collect in a capillary tube
- At the end, the syringe is used to draw the gas bubble in the tube up alongside a ruler and the length of the gas bubble is measured. This is proportional to the volume of O2 produced
- Experiment is repeated multiple times, with the light source at different distances from the pondweed weed
Light intensity equation
Light intensity = 1/distance^2
What is respiration
The process of transferring energy from glucose which goes on in every cell
3 examples of how organisms use the energy transferred by respiration
- To build up larger molecules from smaller ones
- In animals its used to allow the muscles to contract
- In mammals and birds the energy is used to to keep their body temperature steady in colder surroundings
Large molecules that 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 3 fatty acids
- glucose is combined with nitrate ions to make amino acids, which are then made into proteins
Large molecules that are broken down into smaller ones
- glucose is broken down in respiration. Respiration transfers energy to power al the reactions in the body that make molecules
- excess protein is broken down in a reaction to produce urea. Urea is then excreted in urine
What is metabolism
The sum of al reactions that happen in a cell or the body
What is aerobic respiration
- respiration using oxygen
- most efficient way to transfer energy from glucose
- goes on all the time in pants and animals
- most reactions in aerobic respiration happens inside mitochondria
Word equation for aerobic respiration
Glucose + oxygen —- carbon dioxide + water
