Biology

• What are monomers? Small units which are the components of larger molecules (polymers).
• Give 3 examples of monomers. Monosaccharides (such as glucose), amino acids and nucleotides.
• What is a condensation reaction? A reaction which joins monomers by chemical bonds and it involves the elimination of water.
• What is hydrolysis? The opposite of condensation, it's when water is added to break a chemical bond between two molecules.
• What are carbohydrates? Molecules which consist of only carbon, hydrogen and oxygen and they are long chains of sugar units called saccharides.
• What are the three types of saccharides? Monosaccharides, disaccharides and polysaccharides.
• What can monosaccharides form when they are joined together? Disaccharides and polysaccharides by glycosidic bonds which are formed in condensation reactions.
• What is glucose? A monosaccharide containing six carbon atoms in each molecule. It is the main substrate for respiration. It has two isomers - alpha and beta glucose.
• What is maltose? A disaccharide formed by condensation of two glucose molecules.
• What is sucrose? A disaccharide formed by condensation of glucose and fructose.
• What is lactose? A disaccharide formed by condensation of glucose and galactose.
• What is glycogen? It is the main energy storage molecule in animals and it's formed from many molecules of alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds. It has a large number of side branches meaning that glucose (and therefore energy) can be released quickly. It is a relatively large but compact molecule thus maximising the amount of energy it can store.
• What is amylose? Amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, as a result of that amylose is coiled and so it is a very compact molecule meaning it can store a lot of energy.
• What two polysaccharides is starch a mixture of? Amylose and amylopectin.
• What is amylopectin? A component of starch. Amylopectin is branched and is made up og glucode molecules joined by 1, 4 and 1, 6 glycosidic bonds, due to the presence of many side branches it is rapidly digested by enzymes therefore energy is released quickly.
• What is cellulose? A component of cells wells in plants. It is composed of long, unbranched chains of beta glucose which are joined by glycosidic bonds.
• What are microfibrils? Strong threads which are made of long cellulose chains joined together by hydrogen bonds, they provide structural support in plants cells.
• What are lipids? Lipids = fats and oils. Lipids are a group of substances that - like carbohydrates - are made up of carbon, hydrogen and oxygen, although in a different ratio.They are insoluble in water because they are not polar, but do dissolve in alcohol.Examples include triglycerides, phospholipids and steroids.They are not polymers but are macromolecules
• What are the two types of lipids? Saturated lipids such as those found in animal fats - saturated lipids dont contain any carbon-carbon bonds.Unsaturated lipids which can be found in plants - unsaturated lipids contain carbon-carbon double bonds and melt at lower temperatures than saturated fats.
• What are triglycerides? Lipids made of one molecule of glycerol and three fatty acids joined by ester bonds formed in condensation reactions. Triglycerides are used as energy reserves in plant and animal cells.
• What are amino acids? Amino acids are the monomers from which proteins are made. Amino acids contain an amino group - NH2, carboxylic acid group and a variable R group which is a carbon containing chain.
• What are amino acids joined by? Peptide bonds formed in condensation reactions.
• How many amino acids do dipeptides and polypeptides contain? Dipeptides = 2 amino acids Polypeptides = 3 or more amino acids
• What is the general structure of amino acids?
• What is the structure of a protein determined by? The order and number of amino acids, bonding present and the shape of the protein.
• What is the primary structure of a protein? The order and number of amino acids in a protein.
• What is the secondary structure of proteins? The shape that the amino acids takes - either alpha helix or beta bleated sheet. The shape is determined by the hydrogen bonding.
• What is the tertiary structure of proteins? The 3D shape of the protein. It can be globular or fibrous (globular proteins such as enzymes are compact whereas fibrous proteins such as keratin are long and thus can be used to form fibres).
• What is the test for proteins? Biuret test
• What is the test for lipids? The emulsion test
• What is the test for reducing and non-reducing sugars? Benedict's test
• Describe how Benedict's test is carried out. An alkaline solution of blue copper (II) sulphate is added to the sugar and subsequently heated, in the presence of reducing sugar, a red precipitate of copper (I) oxide is formed. In the absence of reducing sugar, the Benedict’s reagent does not change colour.
• Describe how the biuret test is carried out. A sample of the solution is placed in a test tube and an equal amount of NaOH is added. Afterwards, a few drops of dilute copper (II) sulfate solution is added and gently mixed. In the presence of a protein, the solution turns lilac as an indicator of peptide bonds. In the absence of protein, the solution remains blue.
• Describe how the emulsion test is carried out. 2ml of the sample is added to 5ml of ethanol. They are then mixed thoroughly by shaking to ensure that the lipids are dissolved. 5ml of water is added and mixed. The solution turns cloudy indicating the presence of lipid due to the formation of an emulsion.
• How is starch tested for? Using iodine - in the presence of starch, the colour of potassium iodide solution from yellow to black/blue.
• What is the nucleus surrounded by? A double membrane called the nuclear envelope containing pores which enable molecules to enter and leave the nucleus. The nucleus also contains chromatin and a nucleolus which is the site of ribosome production.
• What is the structure of the rough endoplasmic reticulum? It is a system of membranes containing fluid-filled cavitiess (cisternae) that are continuous with the nuclear membrance. It is coated with ribosomes.
• What is the structure of smooth endoplasmic reticulum? A system of membrane bound sacs. There are no ribosomes on its surface level.
• What is the golgi apparatus? A series of fluid filled, flattened and curved sacs with vesicles surrounding the edges. Golgi apparatus processes and packages proteins and lipids. It also produced lysosomes.
• What is the mitochondria? They are usually oval shaped, bound by a double membrane called the envelope. The inner membrane is folded to form projections called cristae with matrix on the inside containing all the enzymes needed for respiration.