Topic 4 - Bioenergetics Flashcards
what is photosynthesis?
it uses energy to change carbon dioxide and water into glucose and oxygen.
where does photosynthesis happen?
it takes place in chloroplasts in green plant cells - they contain pigments like chlorophyll that absorb light. energy is transferred to the chloroplasts from the environment by light
what kind of reaction is photosynthesis?
endothermic, this means energy is transferred from the environment into the place of reaction in the process
what is the word equation for photosynthesis?
carbon dioxide + water —-light—-> glucose + oxygen
what is the symbol equation for photosynthesis?
6CO₂ + 6H₂O ———light———-> C6H12O6 + 6O₂
what do plants make glucose for?
for respiration making cellulose making amino acids stored as oils or fats stored as starch
what happens when plants use glucose for respiration?
this transfers energy from glucose which enables the plants to convert the rest of the glucose into various other useful substances
why do plants use glucose for making cellulose?
glucose is converted into cellulose for making strong plant cell walls
how do plants use glucose for making amino acids?
glucose is combined with nitrate ions (absorbed from the soil) to make amino acids, which are then made into proteins
how do plants use glucose for storing as oils or fats?
glucose is turned into lipids (fats and oils) for storing in seeds
how do plants use glucose for storing 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 loads of glucose would draw in lots of water and swell up
what affects the rate of photosynthesis?
intensity of light, concentration of CO2 and temperature. they all have a combined affect on the rate of photosynthesis but any of these could be a limiting factor
whats a limiting factor?
this means that the factor is stopping photosynthesis from happening any faster
the factor of photosynthesis that is limiting at one time depends on:
the environmental conditions: at night, light is the limiting factor in winter, it's the temperature if its warm and bright enough, CO2 is usually limiting chlorophyll can also be limiting
how can chlorophyll be a limiting factor of photosynthesis?
the amount of chlorophyll in a plant can be affected by disease or environmental stress (lack of nutrients). these factors can cause chloroplasts to become damaged or to not make enough chlorophyll. so rate of photosynthesis is reduced because they can’t absorb as much light
what are the 3 important graphs for rate of photosynthesis?
not enough light slows down rate of photosynthesis
too little carbon dioxide also slows it down
the temperature has to be just right
what does the graph for rate of photosynthesis when light intensity increases look like?
light provides energy for photosynthesis, as light level increases, rate of photosynthesis increases, to a point. beyond that light intensity won’t increase rate of photosynthesis, this is because CO2 or temperature will be a limiting factor.
how can an experiment for lights affect on photosynthesis be conducted?
in a lab you can change light intensity by moving a lamp closer or further from a plant, but if you plot the rate of photosynthesis against the distance of the lamp from plant the shape of the graph will be weird, instead a light meter should be used
what does the graph for rate of photosynthesis when light intensity increases look like?
the amount of CO2 will only increase the rate of photosynthesis until it is no longer a limiting factor, then the graph will flatten out.
what does it mean when temperature is the limiting factor?
usually its because its too low, the enzymes needed for photosynthesis work more slowly at low temperatures, but if its too hot the enzymes will become damaged (this is usually 45*C
how can a graph show more than 1 limiting factor?
a graph for light intensity against rate of reaction can be used except the temperatures are labelled on each line, so that both lines increase are directly proportional until the one for the lowest temperature levels off and the higher temperature can level off later
what can be used to measure the effect of light intensity on rate of photosynthesis?
Canadian pond weed. the rate at which the pond weed produces oxygen corresponds to the rate at which its photosynthesising, the faster the rate of oxygen production the faster the rate of photosynthesis
how can an experiment be carried out using a lamp to increase photosynthesis in a plant?
a source of white light is placed a specific distance from the pond weed, it is left to photosynthesise and as it does the oxygen released is collected in the capillary tube. at the end of the experiment a syringe is used to draw the bubble along the tube up to a ruler. the length of the bubble is measured and it is proportional to the oxygen produced by the plant.
repeat the experiment with the lamp at different distances
what are the control variables for measuring photosynthesis with a lamp experiment?
any variables that could affect the results should be controlled e.g. the temperature and the time that the pond weed is left to photosynthesise
what should be done to increase accuracy for the measuring photosynthesis with a lamp experiment?
the experiment is repeated twice with the lamp at the same distance and the mean volume of O2 produced is calculated
what experiments can be used to show how temperature or CO2 affects photosynthesis?
the test tube of pond weed can be put in water baths at different set temperatures, or a different measured amounts of sodium hydrocarbonate(which releases CO2) can be dissolved in the water
how are light intensity and distance related?
in the experiment the further away the lamp was from the pant the lower the light intensity, so light and distance are inversely proportional, but with the inverse square law
what is the inverse square law of light intensity and distance?
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light intensity ∝ distance (d²)
what does the inverse square law of light intensity and distance mean?
if you halve the distance, the light intensity will be 4 times greater, if you third the distance the light intensity is 9 times greater. double the distance, light intensity will be 4 times smaller
what can be used as a measure of light intensity?
1/d²
whats the most common way to artificially create the ideal environment for plants?
a greenhouse
how can greenhouses control heat for plants?
they help trap the sun’s heat and make sure that temperature doesn’t become limiting. but in winter a farmer may use a heater to keep temperature at the ideal level and shades or ventilation in summer
how can greenhouses control light for plants?
its always needed for photosynthesis so some farmers supply artificial light after the sun goes down so that plants can photosynthesise for longer
how can greenhouses control CO2 for plants?
a paraffin burner could be used for heating and it produces CO2 as a by-product
how else do greenhouses help plants?
they will be safer from pests and disease. fertilisers can be used to provide all the minerals needed fro healthy growth
how can farmers manage money?
creating the right conditions for their crops will cost money but they will grow faster and better crop will be harvested more often, but farmers shouldn’t give plants more than they need because this can waste money
what does respiration involve?
respiration transfers the energy that the cell needs, to do almost everything - this energy is used for all living processes
respiration is not:
it’s not breathing in and out.
where does respiration happen?
other than in animals, it can happen in plants too, all living things respire. its how they transfer energy from their food to their cells
what is respiration?
the process of transferring energy from glucose which goes on in every cell
what kind of reaction is respiration?
it’s exothermic - it transfers energy to the environment
what are 3 examples of how organisms use the energy transferred by respiration?
to build up larger molecules from smaller ones (like proteins from amino acids
in animals its used to allow muscles to contract
in mammals and birds the energy is used to keep their body temperature steady in colder surroundings
what is happening in cells all the time?
there are lots of chemical reactions happening all the time, which are controlled by enzymes. many of these reactions are linked together to form bigger reactions
what are enzymes?
biological catalysts
what happens in the reactions that take place continuously within cells?
larger molecules are made from smaller ones
larger molecules are broken down into smaller ones
example of larger molecules being 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 1 molecule of glycerol and 3 fatty acids
glucose is combined with nitrate ions to make amino acids, which are then made into proteins
example 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 excreted in urine
what is metabolism?
the sum of all reactions that happen in a cell or the body
what are the 2 types of respiration?
aerobic respiration
anaerobic respiration
what is aerobic respiration?
respiration using oxygen, its the most efficient way to transfer energy from glucose
where does aerobic respiration take place?
it goes on all the time in plants and animals. most of the reactions in aerobic respiration happen inside mitochondria
what is the word equation for aerobic respiration?
glucose + oxygen —————–> carbon dioxide + water
what is the symbol equation for aerobic respiration?
C6H12O6 + 6O₂ —————–> CO₂ + 6H₂O
when do you do anaerobic respiration?
when you do vigorous exercise and your body can’t supply enough oxygen to your muscles, they start doing anaerobic respiration as well as anaerobic respiration
what is anaerobic respiration?
anaerobic means without oxygen. its the incomplete breakdown of glucose, making lactic acid
what is the word equation for anaerobic respiration?
glucose ——–> lactic acid
why is anaerobic respiration only for emergencies?
it doesn’t transfer nearly as much energy as aerobic respiration, because glucose isn’t fully oxidised. so its only used for emergencies like when you need to keep using your muscles a bit longer
what else can perform anaerobic respiration?
plants and yeast cells, but they produce ethanol and carbon dioxide instead of lactic acid.
what is the word equation for anaerobic respiration in plants and yeast cells?
glucose ————-> ethanol + carbon dioxide
what is anaerobic respiration in yeast cells called?
fermentation
why is fermentation valuable?
in food and drinks industry, fermentation by yeast is of great value because its used to make bread and alcoholic drinks. in bread-making its carbon dioxide from fermentation that makes bread rise. in beer and wine- making fermentation makes alcohol
why do muscles need energy?
to contract, when you exercise some of your muscles contract more frequently than normal so you need more energy. this energy comes from increased respiration
what happens when you exercise?
increased respiration in your cells means you get more oxygen into them. your breathing rate and breath volume increases to get more oxygen in the blood, and heart rate increases to get this oxygenated blood around the body faster. this removes CO2 more quickly at the same time
what happens when you do really vigorous exercise?
your body can’t supply oxygen to your muscles quickly enough so they respire anaerobically. this is not the best way to transfer energy from glucose, because lactic acid builds, which is painful. long periods of exercise also cause muscle fatigue - the muscles get tired and the stop contracting efficiently
what happens after you stop exercising after respiring anaerobically?
you get an oxygen debt
whats an oxygen debt?
the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells. oxygen reacts with water to form harmless CO2 and water. so you have to repay the oxygen that you didn’t get to your muscles in time
what happens as a result of oxygen debt?
you have to keep breathing hard for a while after you stop to get more oxygen into your blood which is transported to the muscle cells. pulse and breathing rate stay high whilst there are high levels of lactic acid and CO2
how else can our body handle lactic acid?
the blood that enters your muscles transports the lactic acid to the liver. in the liver it’s converted back to glucose
how can you measure breathing rate?
counting breaths
how can you measure heart rate?
by taking the pulse. e.g. you can take your pulse after sitting for 5 mins gentle walking for 5 mins slow jogging for 5 mins running for 5 mins and plotting your results in a bar chart
what will a bar chart about heart rate show?
your pulse rate will increase the more intense the exercise is because your body needs to get more oxygen to the muscles and take more CO2 away from the muscles
how can random errors be reduced in making a bar chart about heart rate?
doing it as a group and plot the average pulse rate for each exercise
