hello everybody and welcome to bite size biology and today we are looking at food food is perhaps one of the most continuous chapters to come up in exam papers pretty much every year it comes up in either question one or question two i i actually cannot think of a year that has not come up in so it's definitely a chapter you do need to know you would know some of from junior cycle anyhow but there is extra detail in this chapter since then so the main questions to be able to describe carbohydrates and that means the monosaccharides the polysaccharides disaccharides the lipids and you know the components of lipid proteins and their chemical compositions meaning what elements are they made out of you are to be able to stay examples of both catabolic and that should be anabolic their um reactions and you are to be able to link it to the cell structure chapter food so it comes up quite often in the cell structure chapter like such as phospholipids and you've also got likes of keratin and so forth um and what else to space a reason for trace elements and to give examples of different ones state to functions for both food and water to be able to contrast water and a fat soluble vitamin to be able to name some minerals and their functions for both plants and animals and i advise you guys to learn off two fit two minerals for plants and two for animals and finally the food tests which you should be familiar with from junior cycle so let's start off give one example of a trace element into human diet iron is the easiest one to go to iron copper zinc and one of those um name three chemical elements found in all lipids so carbon hydrogen oxygen exact same as likes of carbohydrates except you have a different ratio named a basic unit that makes up lipids so lipids are composed of three fatty acids and glycerol respiration is example of a metabolic pathway what type of metabolic pathway is in question respiration is catabolic you are breaking down something large such as glucose into something smaller such as carbon dioxide and water vapor what is meant by the term polysaccharide polysaccharide is simply many monosaccharides and finally name a storage polysaccharide found in animals there's only one that we really discuss and that's glycogen it is found in the liver 2019 state two main reasons why food is required by all living organisms so this question has been asked a few times now so you need food for energy you need food for growth and repair of tissue what is the ratio of hydrogen atoms to oxygen atoms in a carbohydrates so that's two is to one always so there will always be twice as many hydrogen atoms as there is oxygen atoms give a structural role of lipids and cells be careful with this one this one caught a lot of students house a lot of students said for a structural role there they said insulation and they would have got no marks the reason being is for this question they specifically refer to cells in previous questions they just asked neymar's structural role so if it's asking for a structural role in a cell it has to be a cell membrane if it doesn't specify the cell you can say insulation or you can say cell membrane give a metabolic role of lipids and cells a lot of students got caught in that one too but it's the same thing as carbohydrates to provide energy give an example of a fat-soluble vitamin well you've only got two vitamins to learn off vitamin c and vitamin d i always think of vitamin c being sea so being water so therefore water is soluble and therefore vitamin d is fat soluble and in this order there is ricketts 2018 give two main reasons why we require food so we've seen that question before and the reason it was asked again was because it was so poorly answered it is energy growth and repair growth and repair are considered to be the same point by the way so i don't want to see writing down growth and repair as one and two energy always goes in there no matter what and what is the polysaccharide manual monosaccharides connected that's actually more a better answer a more appropriate answer than just saying manual manny monosaccharides because you're not saying that they're all connected even kind of obvious but remember you must treat the examiner as if he or she correcting us doesn't know anything about biology so really spell it out for them so really you should use the word connected name the main structural polysaccharide in plants salos is the main one and that's found in cell walls you didn't have to say where it was found but it has been asked before in the cell chapter structure chapter so i just put it in described composition of triglyceride molecule three fatty acids glycerol give a structural role of lipids in the human body now you see here says the human body not specifically cells so therefore you could say to cell membranes or you could say insulation and finally name a test or give the chemicals used to demonstrate presence of protein now the bioretest is what we would say and if you do if you don't want to do that you might want to write down the chemicals you must refer to both chemicals so that's um sodium hydroxide which is your base and your copper sulfase and the copper sulfate why the color is blue initially and it'll go virus if protein is present 2017 so you can see it comes up every single year near protein has vapor structure keratin whereas found hair and nails as a standard question given name a role of a named mineral other than calcium which is required by plants so to be careful with this okay because like i said you should know at least two and you weren't allowed to use calcium this time so you have to use magnesium magnesium is the mineral it is used in chlorophyll it is found in chlorophyll to help with photosynthesis now state of reason and two reasons for why water is acquired by living organisms again it's the same um question that's been asked time and time again so it's a solvent and it's used for transport and you can say minerals you can you can say it doesn't matter what you say for transport really as long as you weren't used or transported there's more than that just for water but there are two easy ones to remember off by heart named a metallic element present in hemoglobin so that's your iron and that helps you know with um has an affinity for oxygen so it helps transport oxygen and finally for f which type of fruit by a molecule may be identified by using the benefits of feeling solution so that's your reducing sugar okay 2016 for alm we're halfway there so identify a non-metallic element other than carbon hydrogen oxygen or nitrogen commonly found in proteins sulfur he learns off given metabolic role of proteins in the human body enzymes usually always comes down to enzymes all enzymes are proteins made up from proteins and give a structure a lot of proteins in the human body we've seen that already so that's keratin so we now have a metabolic role and we have a structural rule okay um two different biomedical biomolecular components of a lipid so that's again fatty acids and your glycogen that's glycogen that should be glycerol there someone just spelt it wrong where would you find expect to find phospholipids in human cells so the cell membrane again that question was poorly answered you see a lot of students writing down insulation or you see them writing down different parts of the body or whatever but specifically refer to human cells so it has to be a part of this so cell membrane give a role of a named mineral other than iron which is required by the human body so i was saying before you need to know at least two generally for for plants i learn enough magnesium and calcium and for animals calcium and iron calcium same function really is plants is to strengthen now for plants it strengthens the cell wall for humans it strengthens bones and teeth g was a bit of a controversial question when it came up um what is the approximate percentage of water by mass in a human cell now this can actually vary hugely um so if you look at mark's games it will accept a wide range of answers here but i just say 70 okay moving on um and i have two questions here marked because they were also slightly controversial in terms of not controversial but students just didn't read the question properly so typically by the way i don't know if you notice this but food questions you answer five of the following parts so five out of six but most students will answer all five or all six i should say so a what name is given to the simplest units of carbohydrates that's your monosaccharide fair enough name a catabolic process um that produces these simplest units loss of students wrote down respiration respiration doesn't produce monosaccharides in fact respiration helps to break down monosaccharides it is digestion that helps to produce these simplest units there are two catabolic processes that processes that you need to know digestion and respiration the general formula of carbohydrates is cxh2o brackets y was the most common value of y in carbohydrates used for energy by the human cells so glucose is the most one and that's c6h12o6 so therefore y has to be two and for that matter x um sorry y is not two i don't know why i have two there y is six and for that matter x is also six uh name up a structural polysaccharide found in plants uh cellulose and again they were looking for the word structural um if you had wrote down likes of starch that wouldn't have got you the marks because starch although it is a polysaccharide it's not a structural polysaccharide name polysaccharide other than the one um referred to above that's commonly found in plants so that's your starch finally what carbohydrates is always found in dna so that's your deoxyribose if you haven't done the dna and rna chapter yes he wouldn't have known that 2014 question two to following biochemical reactions took place in some living cells is this an example of anabolic or catabolic well a must have been a large molecule it's been broken down into three smaller molecules so therefore that reaction is catabolic identify x and y x has to be lipase a catalyst okay and because it's breaking down fast into fatty acids and glycerol how does a phospholipid differ from a fast well a phospholip phospholipid contains two fatty acids a phosphate and a glycerol whereas a fat consists as a triglyceride consists of three fatty acids and glycerol name of fat soluble vitamin vitamin d a disorder of rickets you've seen that before two functions and minerals now you didn't actually have to specify what the minerals were but like calcium strengthens bones and teeth uh iron has an affinity for oxygen and that's the ones i wrote down but you actually didn't need to mention the minerals at all which was a bit unusual 2013 i really liked this question because you had to really think about it and for all of these and it brings in multiple chapters too so starch glucose well starch is a polysaccharide glucose monosaccharide amino acid cell proteins well proteins are made of amino acids linked together and therefore amino acids must be the building blocks for a protein cellulose and keratin well cellulose is a carbohydrates and keratin is a protein um i specified um that it was a structural polysaccharide but you could have said a carbohydrate enzymes and hormones enzymes just state what they are they're biological catalysts hormones or chemical messengers both are actually very much protein based the biuret test into um the feelings or benedict's test so you just say what they're testing for so to put your head test is testing for proteins whereas um the bendix test is testing for reducing sugar fats and oils fats are solid at room temperature oils a liquid at room temperature you must use the word room temperature if you leave out room temperature dairy you do not get the marks okay so fats and oils you must refer to room temperature 2012 name a monosaccharide so that's your glucose uh you could say fructose too uh it's probably more than that but i suppose glucose is the more common one gives a form of a monosaccharide referred to so that's the one that you would have learned off so that's c6h12o6 that's the formula for glucose it's not the general formula for carbohydrates the general form of carbohydrates is cx brachus h2o bracket y that's the general formula a polysaccharide you can guess there is starch so you get lots of glucose molecules and joining together and you make starch give one way which amino acids differs from a monosaccharide in respect to chemical composition so whenever it goes back to chemical composition think of the elements and the easiest way to refer to us is amino acids they're essentially going to make up proteins and they contain nitrogen whereas carbon hydroxyl nitrogen whereas polysaccharides oh sorry in this case monosaccharides it doesn't matter monosaccharides contain only carbon hydrogen oxygen in other words no nitrogen moving on what do carbohydrates and fats have in common in respect to chemical composition well they have three things in common carbon hydrogen oxygen the difference between the two of them is the ratios of carbon hydrogen oxygen and how may one fat differ from another in terms of chemical composition well for triglycerides you have three fatty acids try meaning tree uh any glycerol but for a phosphate a phospholipid you have a phosphate replacing a fatty acids in other words you have two fatty acids a phosphate and a glycerol so how does it differ a phosphate replaces a fatty acid that's it okay second last question answer five the following but again you do all six just to be sure what test might be used um what type of food might be um found out by using brown paper so that's testing for fats lipids it's fine give one roll of a named mineral in plants so i said calcium and strengthens cell walls you could refer to magnesium helps with photosynthesis watercolor indicates a strong positive result for benedict's test for reducing sugar brick red color give a role of lipids and cells well they didn't specify whether it was a metabolic role which would be energy or a structural role which would be cell membranes so you could have said either give a role of water in the human body other than as a component of cytoplasm and body fluids i just said it was a solvent how many common amino acids have found in proteins so just about 20. finally in relation to human diet wasn't meant by a trace element trace element is something that's found in tiny amounts okay it's something that's only required by the body in tiny amounts i use the word tiny okay i don't want to see students writing down in small amounts because trace is actually smaller than that really um give an example of this so iron copper zinc and iron being the common one that i use state one way in which an oil differs from a fast well an oil is liquid at room temperature vitamins divide up into two groups so you've got fat soluble and you've got water soluble you didn't have to name the vitamins i did however just to um provide a little bit more information for you guys uh water is a treat triglyceride that's simply tree fatty acids and glycerol and give example of a catabolic reaction in a cell now if it's referring to in a cell digestion is no good in the body yeah fair enough digestion but refers to in a cell has to be respiration a lot of students would have got caught out on that one okay so just going back up to the top there you can see actually all the main questions are asked multiple times it's a very common chapter to come up and it's definitely a chapter that all students should be attempting to get full marks in