in this video we are going to be looking at topic four of biology paper 1 and that is bioenergetics here are the main subtopics we're going to be looking at throughout this video in more depth and as always all of these pages are available on the Etsy in the description thank you very much for watching and I hope you enjoy first of all we have arguably the most important thing in the whole of biology paper 1 photosynthesis we have the word equation here word equation is carbon dioxide plus water uses light to convert into glucose and oxygen please please please remember that equation we also have the balanced symbol equation which is also very important to remember 6 CO2 6 H2O uses the light to convert into glucose which is C6 h126 and 602 now as you can see through this word equation and the symbol equation the plants use photosynthesis to create their own glucose another thing you could be asked is how do they use it so they use it for respiration to make energy we're going to get onto the respiration equation in a minute and you'll see it is the photosynthesis equation but flipped around making cellulose for those cell walls which you should know in the plant cells making amino acids which they convert to proteins storing as oils and fats and storing as starch for the winter when they need to convert that back into glucose for photosynthesis when there's not as much sun those last three are probably a bit more higher based um so Foundation don't worry too much about those two but definitely the first two will be useful the rate of photosynthesis we talk about something called limiting factors here so that is factors that could limit the rate of photosynthesis so light temperature and carbon dioxide now on this graph in the bottom left you can see we've got rate on the Y AIS and percent CO2 on the X AIS so you can see as the percentage of CO2 gets higher and higher the rate of photosynthesis does hit a point where it begins to Plateau or level off and the reason for this is because at the start where it's really steep you might have enough light and temperature but if one of those factors drops off say the sun doesn't quite come out as much as it should or the temperature gets a bit colder the plant doesn't have all three of the things it needs to photosynthesize as effectively as it could so this becomes a limiting factor these graphs are really important that you are able to analyze them so please spend your time wisely to learn about these controlling conditions so a lot of industrial farming nowadays we use green houses to control the carbon dioxide and temperature by building the green houses we trap the sun's Heating and we can use artificial lights to maintain those sunlight levels in the night and the winter something called paraffin heaters produce carbon dioxide as a byproduct again that last point is probably edging a bit more on the higher side of things just one last point about those graphs on the bottom if you can see that bottom bullet point on the right hand side if the temperature becomes too high enzymes Den nature so photosynthesis cannot happen so if we were to repeat this graph and instead of percent CO2 on the x-axis we had temperature you might not see the same kind of trend because if the temperature gets too high the enzymes will start to denat and the rate will drop off completely next we have respiration again a very very important part of paper 1 biology so how organisms use energy from the respiration they build up larger molecules so proteins from those amino acids this would also be carbohydrates from simple sugars and stuff like that it allows the muscles to contract in animals and it allows them to maintain a constant body temperature the word equation as I said before it is photosynthesis but flipped around this time we're using glucose and oxygen and converting it into carbon dioxide and water and again the balance symbol equation exactly the same as photosynthesis again with the symbols C 6 h126 that is quite a difficult one to remember but just spend a bit of time learning that one and it will pay off in the long run plus 62 makes 6 CO2 and 6 H2O again just two things you got to learn very common exam question could just be fill them in fill in the blanks balance out this equation so it's just a six on everything that isn't the glucose so again a good one to remember metabolism next so metabolism a very common definition that comes up all the chemical reactions in an organism that is it so if someone says they have a slow or fast metabolism it just means that their body takes a little bit longer or a little bit quicker to complete all those chemical reactions that happen in an organism so your digestive system for example might be a bit slower because all the chemical reactions that happen just take that little bit longer the chemical reactions this is definitely more of a higher thing they consist of a synthesis reaction and a decomposition reaction now synthesis just means making or building and decomposition is like the breakdown of stuff by creation of as I mentioned before that is starch from glucose proteins from amino acids and lipids from glycerol and fatty acids and the breakdown of glucose for respiration and protein to Ura again bit of a higher thing so Foundation don't worry too much at all next we have aerobic versus anerobic aerobic respiration just means it uses oxygen and it is the same equation that we see for General respiration and this is the most common kind anerobic respiration just means it doesn't use oxygen this purely takes your glucose because there's no Oxygen input and converts it into lactic acid so when we Sprint or do some high intensity activity this is what happens oxygen de so after anerobic respiration the body is in what we call an oxygen deficit or oxygen debt effectively and it means that we just need to repay our body of that oxygen which is why we breathe really heavily after we do this exercise when we're breathing in all this extra oxygen after what we're mainly trying to do is flush out that lactic acid and return the oxygen to the tissues where it is absent and then once it's repaid your body just returns to a normal breathing rate and that is the end of all the paper one topics that you need so our next topic will be the start of paper 2 chapter homeostasis and response thank you very much for watching and I hope you found that useful