Bioenergetics Flashcards
what is the definition of photosynthesis?
the process by which plants and some other organisms uses light energy to change carbon dioxide and water into glucose and oxygen
what is the word and symbol equation for photosynthesis?
word equation :
carbon dioxide + water → glucose + oxygen
symbol equation :
6CO2 + 6H2O → C6H12O6 + 6O2
where does photosynthesis take place?
in the chloroplasts, which contain pigment like chlorophyll that absorbs light
what type of reaction is photosynthesis?
its endothermic, meaning energy is transferred from the environment in the process
what do plants use glucose for?
respiration - this transfers energy from glucose allowing the rest of the glucose to be converted into other useful substances
making cellulose - its converted into cellulose to make strong plant cell walls
stored as starch - stored in the roots, stems, leaves, ready for when photosynthesis isn’t happening e.g. in winter
making amino acids - glucose is combined with nitrate ions to make amino acids which then make proteins
stored as oils or fats - for storing in seeds
why is starch better for storing glucose?
because its insoluble (a cell with lots of glucose would draw in water and swell up)
what are the limiting factors that affect the rate of photosynthesis?
- intensity of light
- concentration of CO₂
- temperature
- (chlorophyll)
limiting factor means it stops photosynthesis from happening as fast
what environmental conditions affect these limiting factors?
- at night light is the limiting factor
- in winter temperature is the limiting factor
- if its warm enough or bright enough its temperature
what is the amount of chlorophyll affected by?
- disease (e.g. tobacco mosaic virus) or environmental stress such as lack of nutrients
- these factors can cause chloroplasts to become damaged or to not make enough chlorophyll, meaning photosynthesis is reduced because they cant absorb as much light
describe the experiment of how oxygen production shows the rate of photosynthesis
- a source of white light 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 the capillary tube
- the syringe is used to draw the gas bubble in the capillary tube up alongside a ruler and the length of the gas bubble is measured, this is proportional to the volume of oxygen produced
- any variables that could affect the results should be controlled e.g. temperature and time the pondweed is left to photosynthesise for a
- the experiment is repeated twice with the light source at the same distance and the meab volume of oxygen produced is calculated
- then the experiment is repeated with the light source at different distances from the pondweed
how can the pondweed experiment be changed to measure the affect of temp or carbon dioxide on photosynthesis?
- the test tube of pondweed can be put in a water bath at a set temperature, or a measured amount of sodium hydrogencarbonate can be dissolved in the water which gives off CO2
- experiment can be repeated with different water temps or concentrations of sodium hydrogencarbonate
what is the equation for the inverse square law?
light intensity = 1/distance²
- when the lamp is moves away from the pondweed the amount of light that reaches it decreases
- as distance increases, the light intensity decreases, so distance and light intensity are inversely proportional to each other
how are greenhouses used to create an ideal environment?
- to artificially create the ideal environment for plants is to grow them in a greenhouse
- greenhouses help trap the suns heat and make sure that the temperature doesn’t become limiting
- in winter a farmer might use a heater as well to keep the temperature at the ideal level
- in summer it could get too hot so they might use shades or ventilation
How do farmers supply light in a greenhouse?
light is always needed for photosynthesis so farmers often supply artificial light after the sun goes down to give their plants more photosynthesis time
how do farmers supply more carbon dioxide in a greenhouse?
farmers and gardeners can increase the level of carbon dioxide in the greenhouse by using a paraffin heater to heat the greenhouse. as the paraffin burns, it makes carbon dioxide as a by-product
how can pests and diseases be reduced from a greenhouse? How can fertilisers be used?
- keeping plants enclosed in the greenhouse makes it easier to keep them free from pests and diseases
- the farmer can also add fertilisers to the soil, to provide all the minerals needed for healthy growth
what are the advantages and disadvantages of a greenhouse?
- sorting all this out costs money but if the farmers keeps the conditions just right the plants will grow much faster and a decent crop can we harvested much more often, which can then be sold
- it’s important that the farmer supplies the right amount but not more than the plants need as this would be wasting money
what is respiration?
the process of transferring energy from glucose which goes on in every cell
what type of reaction is respiration?
it’s exothermic
how do organisms use the energy transferred by respiration?
- to build up larger molecules from smaller ones (like proteins from amino acids)
- in animals it’s used to allow the muscles to contract so they can move
- in mammals and birds the energy is used to keep their body temperature steady in colder surroundings
what is metabolism?
the sum of all the reactions that happen in a cell or the body
what are chemical reactions controlled by?
enzymes
what are examples of reactions of larger molecules being made from smaller ones?
- lots of small glucose 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 proteins
what are examples of reactions of larger molecules being broken down into smaller ones?
- glucose is broken down in respiration. respiration transfers energy to power all 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
