hello and welcome this is a science break video for the unit called bioenergetics This is for unit four for AQA GCC combined Science Biology and triple Science Biology as well time stamps and more information in the description below like And subscribe if you can other than that let's begin we will start off with photosynthesis photosynthesis happens in Plants it also happens in algae as well we have carbon dioxide from the air which enters the leaves by diffusion we have water from the soil which enters the roots by osmosis we have sunlight absorbed by chlorophyll which is found in chloroplasts and then we have glucose that's made in the leaves we also have a waste product of oxygen which exits the leaves by diffusion these are the key components in the process of photosynthesis carbon dioxide plus water gives us glucose and oxygen this is a summary word equation we have energy from sunlight and we have that sunlight absorbed by chlorophyll which is found in the chloroplasts this is the formula equation we can balance this very easily we just put sixes in front of everything except the glucose you should be able to recognize and write this formula equation down we describe photosynthesis as an endothermic reaction this means energy is transferred from the surroundings to chloroplasts by light what happens to the glucose that's made these are the uses of the glucose it can be used in respiration to release energy for use by the plant it can be converted to insoluble starch for storage of the glucose it can be used to make fats or Oils for storage of energy as well it can be used to produce cellulose to strengthen cell walls and it can be combined with nitrates from the soil to make amino acids amino acids make proteins for growth we'll look at this in more detail in a moment limiting factors in photosynthesis there are conditions that affect the rate of photosynthesis these are light intensity carbon dioxide concentration temperature and the amount of chlorophyll present in leaves the effect of limiting factors in photosynthesis here are some axes for a graph light intensity along the bottom and along the y- AIS we have the rate of photosynthesis this graph looks a little something like this let's take a look at this part here region one we say light intensity is the limiting factor for that part of the graph this is because as light intensity increases so does the rate of photosynthesis for part two light intensity is no longer limiting light intensity increases but the rate of photosynthesis does not carbon dioxide concentration or temperature or both are limiting let's take a look at another graph with carbon dioxide concentration on the x-axis rate of photosynthesis on the y-axis the graph has a very similar shape for region one again that part of the graph we say carbon dioxide concentration is the limiting factor this is because as the concentration of CO2 increases so does the rate of photosynthesis for region two of the graph carbon dioxide concentration is no longer limiting it's no longer a limiting factor carbon dioxide concentration increases es but the rate does not that means light intensity or temperature is limiting the rate of photosynthesis for Region 2 if we look at the effect of temperature that's slightly different temperature along the x-axis and rate on the Y we can see the graph has a slightly different shape for region one temperature is the limiting factor as we raise the temperature the rate of photosynthesis increases and that's because the rate of action of enzymes increases for a warmer temperature as the temperature increases so does the rate for region two the rate decreases rapidly the rate of photosynthesis decreases rapidly this is because enzymes that control photosynthesis Den nature which means the active sites of those enzymes permanently lose shape which means they cannot work anymore photosynthesis rapidly stops the next part is for the higher tier this is both for Combined students and triple science student higher tier knowledge of limiting factors can help Growers to keep the best conditions in a greenhouse here is the idea of a greenhouse that Greenhouse diagram will disappear shortly so you have the notes in front of you again this knowledge helps to maximize photosynthesis but also to maintain profits let's take a look at a graph again we have light intensity on the x-axis and rate on the Y and here is a curve let's say that this is at 20° centigrade with a 0.0 4% carbon dioxide concentration we could change the condition slightly this one we have the same temperature but we have increased the concentration of carbon dioxide you can see the maximum rate of photosynthesis is a little higher we can also increase the temperature and increase the carbon dioxide concentration you can see here that the maximum rate of photosynthesis is at its highest we have conditions a b and c important to note that condition C may not be used even though it's got the highest rate of photosynthesis because energy costs may be too high also note that light intensity beyond that red line there's no point increasing light intensity Beyond this point because there is no increase in the rate of photosynthesis so you don't want to have the lights too bright using more energy and causing more cost let's put those notes back up there next we're looking at measuring the rate of photosynthesis there are various ways we can do this this is one way we could take a pondweed plant called lodia we can measure the number of bubbles it produces over a certain amount of time or count the number of bubbles so we would measure the rate as number of bubbles per minute for example 10 bubbles per minute we can have a slightly different setup in this case we are actually collecting the oxygen gas that's given off that's collected in the upside down measuring cylinder there and we can measure the volume of oxygen per minute not the number of bubbles but the volume for example 3 cm cubed per minute here is a slightly fancier piece of equipment again we collect the oxygen bubbles that are given off they collect at the top of the curved bit of the tube there the syringe can be used to draw the bubble next to the scale and we can measure the volume so this measures volume of oxygen per minute for example 2 cm cubed per minute or for example smaller units of 10 mm cubed per minute these are just example rates of photosynthesis the photosynthesis practical in this case I'm going to use the example of counting bubbles per minute which is something you might have done we have a ruler scale we have a lamp and we set up the apparatus as shown in the diagram we may add some sodium bicarbonate to the water there this is so carbon dioxide is added to the water to make sure it is in excess in other words it's more than we need it is not a limiting factor we would move the lamp to for example 10 cm switch it on and wait for a few minutes we wait so that the rate of photosynthesis stabilizes and then we count the number of bubbles produced in a minute we would change the distance to 20 cm and and then wait a little while and then count the number of bubbles produced again in 1 minute we would repeat this for about five different distances no less than four certainly five or six would be good the graph that we would get would look something like this number of bubbles per minute on the y- AIS to give us an indication of the rate and distance of the lamp on the x-axis the graph should curve downwards like this the number of bubbles per minute indicates the rate of photosynthesis in other words it tells you how quickly photosynthesis is happening the bigger the distance of the lamp the lower the light intensity so the number of bubbles per minute decreases this tells us that we have a lower rate of photosynthesis notice the line is not straight and it curves control variables for this experiment these are variables that we would keep the same we would have the same pondweed same length of pondweed same temperature and this can sometimes be achieved by using a water bath or a heat screen same carbon dioxide concentration or at least carbon dioxide in excess and we also repeat The Experiment three times for each distance to take a mean and this would give us a more accurate measurement we can do other experiments as well which have come up on papers before we could change the light intensity by changing the brightness of the bulb instead of moving the distance there's the lamp we would not move the distance of the lamp we would just increase the light intensity by for example increasing the potential difference for the bowl we can also change the color of the light that hits the pondweed we can do this by using filters color filters we could place the red one there first that would shine red light on the pondweed we could then change to various different colors measure the number of bubbles per minute and record the results for that which color light do you think has the lowest rate of photosyn is you might be surprised that it's green green is actually not absorbed very well by plants at all it's reflected that's why plants tend to look green now to the fun part the inverse Square law this is for higher tier students for both combined science and for triple science the inverse Square law looks like this light intensity is proportional to one / distance squared that Curly little symbol there means proportional we say this by saying light intensity is proportional to one/ distance squared I think it would be better if we thought about it as one over the increas in distance squared we can also say light intensity is inversely proportional to distance squared I think a better way to think about it is thinking of it as inversely proportional to the increase in distance squared what does this all mean let's take a look at some data here is the experiment we're going to look at an example set of results let's start off at 10 cm so the distance of the lamp is 10 cm away from the pondweed we're going to give example data of light intensity of 180 Lux that's a measure measurement unit for light intensity and we're going to give an example of the rate of photosynthesis as 60 bubbles per minute now if we increase the distance from 10 cm to 20 cm what have we done to the distance we have doubled the distance so we have gone from 10 to 20 that's times 2 if we then look at it from our inverse Square law this tells us that light intensity is 1/ 2^ 2 which is a quar that means the light intensity is also going to be a quarter of what it was that gives us a light intensity of 45 this tells us the rate of photosynthesis will also reduce and that will be a quarter of what it was before so in this case that's 15 bubbles per minute let's take a look at another example imagine we Chang the distance to 30 cm from my original 10 cm the distance is now three times more than it was so light intensity will be 1 over 3^2 which is 1 9 so if we look at the light intensity row 180 1 nth of that is 20 if we look at the rate of photosynthesis it will also be 1 nth of 60 which is 7 in fact if you put it into your calculator it will say 6.7 however we can't have 7 of a bubble we either we either have a bubble or we do not have a bubble so I've rounded that to seven bubbles per minute let's take a look at the rest of the data you can actually pause here and test for yourself for example if we went from 30 to 60 what have I done to the the distance well I've doubled the distance so from above we can see if I double the distance I quarter the light intensity so I've gone from 20 to 5 that is 1 qu and in fact the rate of photosynthesis has gone from 7 to 2 remember we can't have decimals for bubbles we only have whole numbers for bubbles so that's the inverse Square law let's take a look at respiration respiration provides energy for processes in all living things it's exothermic and it happens continuously in living cells it can be aerobic where it uses oxygen or it can be anerobic where it happens without oxygen let's take a look at aerobic respiration first here is a digestive system here is the lungs or here are the lungs and here are two cells very close to a blood capillary these are our working cells we have oxygen that's taken into the lungs glucose that's taken into the Dig digestive system in the small intestine and these are transported by the blood to our cells through the capillaries respiration happens and we have two waste products of carbon dioxide and water we also have the release of some energy energy released from this process is used for one chemical reactions that build large molecules for example proteins we have energy released for movement that's via muscle contraction we have energy release for keeping us warm and if you look up here we said respiration was an exothermic reaction that's the release of energy so that actually is used to help keep us warm also for active transport of molecules or mineral ions so let's take a look at aerobic respiration in animal cells plant cells and we're going to include yeast cells here as well the equation for this is glucose plus oxygen gives carbon dioxide side and water this is aerobic respiration in animal cells plant cells and yeast cells this is the formula equation we have sixes in front of everything except for the glucose let's take a look at anerobic respiration we're first going to take a look at the example of animal cells especially muscle cells here are two working cells glucose is converted to lactic acid and we have the release of energy we have less energy released than aerobic respiration in plants and yeast cells it's slightly different still anerobic respiration but slightly different here's a plant here is a single yeast cell we have glucose that is converted to ethanol and carbon dioxide in anerobic respiration we have much less energy released because the breakdown or the oxidation of glucose is incomplete we also need a little bit more information about anerobic respiration in yeast we call this ferment fation fermentation is important for making bread carbon dioxide released by yeast in bread dough makes it rise carbon dioxide if you look is in our equation there here is um some dough that's being used to make some bread if we add yeast to the dough it will cause it to rise because of the release of that carbon dioxide which makes carbon dioxide bubbles in the dough so there's the dough the dough Rises because of the yeast and then after that the dough is baked to make bread fermentation is also important in making alcoholic drinks ethanol from fermentation is the alcohol and if you look in our equation glucose goes to ethanol and carbon dioxide the ethanol is the alcohol the specification wants us to be able to make a comparison of aerobic and anerobic respiration in plants animals and yeast so we've got aerobic respiration in plants plants animals and yeast and we've got anerobic respiration in animals and in plants and yeast you might want to pause here and give this a go we use ticks and crosses in the boxes to see if the statement is correct or incorrect so I'll just go through these I won't say much I'll just put in the answers there you go a very important summary comparison of those processes next we're going to take a look at response to exercise and Metabolism response to exercise during exercise more energy is needed by the body to provide more energy the breathing rate of the lungs increases this means we have deep and faster breaths this is so more oxygen can be taken into the blood for aerobic respiration the heart rate increases this means more beats per minute this means more oxygenated blood and glucose is supplied to working muscle cells this means more aerobic respiration to release more energy for muscle contraction this is during exercise if there is not enough oxygen available anerobic respiration takes place this is when glucose if you remember is converted to lactic acid glucose is supplied to the cells there's our lactic acid this lactic acid causes something called an oxygen debt we'll describe what that means in a moment lactic acid builds up muscles become fatigued and tired and stop Contracting efficiently this can happen during long periods of heavy exercise the next part we're going to look at is again for the higher tier we have our muscle cells working there during anerobic respiration remember lactic acid can be formed there's that lactic acid this is part of the body that includes a liver there's the liver there we have blood that will come along and transport the lactic acid to the liver in the liver we have lactic acid which is converted into glucose this will remove it from the blood so lactic acid is converted to glucose in the liver the oxygen debt is the amount of extra oxygen needed after exercise to react with the lactic acid and remove it from cells it can actually also be converted to carbon dioxide and water and removed in that way let's now take a look at metabolism here are some examples simple sugars in the body can be converted to more complex carbohydrates and these complex carbohydrates can be converted into more simple carbohydrates the sugars we have amino acids these can be built up into proteins proteins can also be broken down into amino acids we have fatty acids and glycerol this can be made into lipids and lipids can also be broken down into fatty acids and glycerol metabolism is the sum of all the reactions in a cell or the body this includes both plants and animals let's take a look in slightly more detail metabolism examples this is in Plants only one example is the conversion of glucose to starch so here are our glucose molecules these can be converted to starch by made by being made into a long chain there's our starch so glucose into starch that's one example glucose can also be converted into cellulose so I've got a few more glucose molecules here and they can be converted into a substance called cellulose there's our cellulose glucose into cellulose next we have conversion of glucose to amino acids using nitrate ions so here are our glucose molecules here are some nitrate ions these will combine with the glucose and make amino acids so let's simplify that slightly here's our glucose here's our Nitro ions these join the glucose molecules and make amino acids nitrate ions combine with glucose to make amino acids this is in plants and in animals the formation of lipid molecules from glycerol and Three fatty acids here is a glycerol molecule here are three fatty acids these will join onto the glycerol and make lipid molecules so so let's summarize that here's our glycerol here's our Three fatty acid molecules they join together to make our lipid molecule next in animals only we have the breakdown of excess amino acids to form Ura for excretion excess amino acids are amino acids that are in the body that are not needed here are our excess amino acids these are broken down into Ura and Ura is moved or removed from the body so we can summarize that like this here's our excess amino acids broken down into Ura Ura is removed from the body we have a final example the conversion of glucose to a substance called glycogen which is used for storage in animals here's our glucose and similar to making starch is made into chains so glucose converted into glycogen that can be used used to store the glucose in muscles and in the liver so that's pretty much it the whole of unit 4 bioenergetics for AQA GS combined Science Biology and for triple Science Biology thank you for watching and I'll see you soon