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

AQA A-Level Biology (new spec) Unit 1A - Biological Molecules Monomers Small basic molecular units Examples of monomers Polymers monosaccharides, amino acids and nucleotides 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? Structure of Alpha Glucose Structure of Beta Glucose Are the types of glucose isomers? What is a condensation reaction? Yes Alpha-glucose and beta-glucose 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? What is formed when 2 monosaccharides join together? Glycosidic 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? What is a hydrolysis reaction? Alpha glucose and galactose When 2 molecules are broken apart using a water molecule What is broken down by hydrolysis to form monosaccharides? Benedict's Test for Reducing Sugars I Carbohydrates Add Benedict's reagent to a sample and add it to a water bath which is boiling Benedict's Test for Reducing Sugars II it's negative, it'll stay blue If the test is positive, it will form a coloured precipitate, if 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 hydrogencarbonate Benedict's Test for Non-Reducing Sugars III Polysaccharide Neutralise the solution with sodium Carry out the Benedict's test as normal 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? What structure is glycogen similar to? Glycogen 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? Structure of cellulose Cellulose Long unbranched chains of beta glucose What is formed when beta glucose molecules bond? Advantage of cellulose chains Straight 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? What is a saturated fatty acid? Condensation A fatty acid with no double bonds between the carbon atoms What is an unsaturated fatty acid? atoms A fatty acid with at least one double bond between the carbon 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? Triglycerides are used as what? Hydrophilic Energy storage molecules What do the hydrocarbon tails of triglycerides contain which is useful for us? Lipids contain how much more energy than carbohydrates? Are triglycerides insoluble or soluble? Double Insoluble, don't affect water potential How do triglycerides act in cells? Chemical energy They clump together as insoluble droplets, the tails face inwards and the heads face out What do phospholipids do? enters and leaves the cell What do phospholipids form? Make up the bilayer of cell membranes, meaning they control what 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? How is a polypeptide formed? Amino acids Formed by more than 2 amino acids join together