AQA A-Level Biology (new spec) Unit 1A - Biological Molecules 100% Correct

AQA A-Level Biology (new spec) Unit 1A - Biological Molecules 100% Correct Monomers Small basic molecular units Examples of monomers monosaccharides, amino acids and nucleotides Polymers Large complex molecules composed of long chains of monomers joined together Examples of polymers Carbohydrates, proteins and nucleic acids What type of sugar is glucose? Hexose How many types of glucose are there? 2 What are the names of the types of glucose? Alpha-glucose and beta-glucose Structure of Alpha Glucose Structure of Beta Glucose Are the types of glucose isomers? Yes What is a condensation reaction? When 2 molecules join together with the formation of a new chemical bond, releasing a water molecule Condensation reactions join which molecules? Monosaccharides What type of chemical bond forms between 2 monosaccharides? Glycosidic What is formed when 2 monosaccharides join together? Disaccharide Which 2 molecules make maltose? Alpha glucose and alpha glucose What is sucrose made from? Alpha glucose and fructose Which 2 molecules make lactose? Alpha glucose and galactose What is a hydrolysis reaction? When 2 molecules are broken apart using a water molecule What is broken down by hydrolysis to form monosaccharides? Carbohydrates Benedict's Test for Reducing Sugars I Add Benedict's reagent to a sample and add it to a water bath which is boiling Benedict's Test for Reducing Sugars II If the test is positive, it will form a coloured precipitate, if it's negative, it'll stay blue Benedict's Test for Non-Reducing Sugars I Get a new sample of the test solution, add DILUTE HCl and heat it in a water bath that has been brought to the boil Benedict's Test for Non-Reducing Sugars II Neutralise the solution with sodium hydrogencarbonate Benedict's Test for Non-Reducing Sugars III Carry out the Benedict's test as normal Polysaccharide Formed when more than 2 monosaccharides are joined together by condensation reactions Function of Starch Energy store What makes up starch? Amylose and amylopectin Structure of amylose Long, unbranched chain of alpha-glucose; has a coiled structure, making it compact and good for storage Structure of amylopectin Long, branched chain of alpha-glucose, side branches allow the enzymes that break the molecule down to access the bonds easily, meaning glucose can be released quickly Features of starch Insoluble in water, doesn't affect water potential so water doesn't enter the cell, which would make them swell The iodine test Add iodine dissolved in potassium iodide solution to the test sample. If starch is present, sample turns from brown/orange to dark blue/black colour What do animals store glucose as? Glycogen What structure is glycogen similar to? Amylopectin, except it has more side branches, meaning stored glucose can released quickly, very compact What is a major component of cell walls in plants? Cellulose Structure of cellulose Long unbranched chains of beta glucose What is formed when beta glucose molecules bond? Straight cellulose chains Advantage of cellulose chains They're linked together by hydrogen bonds to form microfibrils, providing structural support for cells Structure of a triglyceride What are triglyceride tails made of? Hydrocarbons Are the triglyceride tails hydrophobic or hydrophilic? Hydrophobic Are lipids soluble or insoluble in water? Insoluble What's the basic structure of a fatty acid? Triglycerides are formed by what type of reaction? Condensation What is a saturated fatty acid? A fatty acid with no double bonds between the carbon atoms What is an unsaturated fatty acid? A fatty acid with at least one double bond between the carbon atoms What's the difference between a triglyceride and a phospholipid? A triglyceride has 3 fatty acid tails. A phospholipid has 2 fatty acid tails and a phosphate group attached to the glycerol Is the phosphate group hydrophilic or hydrophobic? Hydrophilic Triglycerides are used as what? Energy storage molecules What do the hydrocarbon tails of triglycerides contain which is useful for us? Chemical energy Lipids contain how much more energy than carbohydrates? Double Are triglycerides insoluble or soluble? Insoluble, don't affect water potential How do triglycerides act in cells? They clump together as insoluble droplets, the tails face inwards and the heads face out What do phospholipids do? Make up the bilayer of cell membranes, meaning they control what enters and leaves the cell What do phospholipids form? A double layer, heads outside and tails inside, forming a barrier against water soluble substances How do you do the emulsion test? Shake the test substance with ethanol for a minute so it dissolves and pour the solution in water. Any lipid will show as a milky emulsion What are the monomers of protein? Amino acids How is a polypeptide formed? Formed by more than 2 amino acids join together How are proteins made up? Made up of one or more polypeptides Structure of amino acids How many amino acids do all living things have? 20 What is the name of the bonds formed between 2 amino acids? Peptide bond Protein Structure: Primary Structure Sequence of amino acids in the polypeptide chain Protein Structure: Secondary Structure Hydrogen bonds form between the amino acids in the chain, making it coil into an alpha helix or a beta pleated sheet Protein Structure: Tertiary Structure The coiled or folded chain is coiled further, more hydrogen and ionic bonds form. When do disulfide bridges form? Whenever 2 molecules of cysteine come close together Protein Structure: Quaternary Structure Made of several different polypeptide chains, held together by different bonds How do you do the biuret test? Make the solution alkaline by adding sodium hydroxide solution Add copper(II) sulfate solution If protein is present, the solution turns purple If protein isn't present, the solution stays blue What are enzymes? Biological catalysts What do enzymes do? They catalyse metabolic reactions at both a cellular level and across the whole organism What can enzymes affect? Structures in an organism (such as collagen production) and functions (such as respiration) What makes each enzyme different? Their active site, which has a specific shape How are enzymes specific? Their tertiary structure Do enzymes slow down or speed up a reaction? Speed up How do enzymes speed up a reaction? If the substrate is being joined, the substrates being attached to the enzyme brings them closer together, reducing any repulsion significantly If the enzyme is catalyzing a breakdown reaction, fitting into the active site puts strain on the bonds in the substrate, allowing the molecule to break up more easily What is the lock and key model? Where the substrate fits exactly into the enzyme What is the induced fit model? Where the substrate fits into the enzyme, then the enzyme changes it's shape slightly to lock the substrate even tighter to itself What is it called when an enzyme and a substrate are joined together? Enzyme-substrate complex What happens if the tertiary structure of an enzyme is altered? The shape of the active site will change, meaning the substrate won't be able to fit, meaning the enzyme is unable to carry out its function of catalyzing the substrate What determines the primary structure of a protein? A gene Why does temperature have such a large impact on enzyme activity? Because each enzyme has its own optimum temp, anything before that will decrease the rate of reaction and anything above that will result in bonds breaking and the enzyme becoming denatured How does pH affect enzyme activity? All enzymes have an optimum pH (usually 7), Above and below the optimum temperature messes up the ionic and hydrogen bonds that hold the tertiary structure in place, denaturing the enzymes How does enzyme concentration affect enzyme activity? The more enzyme molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes How does substrate concentration affect enzyme activity? The more substrate molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes How can enzyme activity be inhibited by competitive inhibitors? Competitive inhibitor molecules have a similar shape to substrate molecules, so will compete with the substrate to bind with the enzyme and block the active site. The higher the competitive inhibitor concentration, the more active sites are filled and less enzyme-substrate complexes are formed How can enzyme activity be inhibited by non competitive inhibitors? Non-competitive inhibitors bind to the enzyme away from its active site, causing the active site to change shape so substrate molecules can't bind to the enzyme