Carbohydrates, lipids and proteins 3. 2. 1 Distinguish between organic and inorganic compounds (2). Distinguish means to give the differences between two or more different items. ?Organic compounds are based on carbon and are found in living things. There are a number of exceptions including hydrogen carbonate (HCO3- ), carbon dioxide (CO2 )and Carbon monoxide (CO). ?Inorganic compounds are by default all the molecules other than those in the category above. Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure(2).
Identify means to find an answer from a given number of possibilities. The following are examples of the most common organic molecules in living things: Monosaccharide sugars. These are the monomers from which larger polymer molecules are constructed. Molecules like glucose and fructose are metabolically active molecules usually stored in an inactive, insoluble polysaccharide form. ?Glucose: C6H12O6 this is a hexose sugar (six carbons) most commonly found in this ring structure. ?Glucose will be known to most students as a product of photosynthesis or the substrate molecule for respiration. Glucose is also found in a polymer as starch, glycogen or cellulose. ?All bonds are covalent. ?Glucose is a reducing sugar and will give positive (Brick red) precipitate in a Benedicts test. ?Glucose is metabolically active compound Glucose is soluble and has osmotic effects when in solution This is an alternative diagram of glucose where the carbons are assumed to be at each of the corners or ends of the lines (bonds). In this image the carbons are numbered so you can compare to the diagram above. Normally such numbers would be omitted form a diagram.
These shorthand diagrams allow organic molecules to be drawn faster. There are examples further down the page of this type of diagram. ?Ribose: Pentose (5 carbon sugar). ?Ribose is part of one the important organic molecules in photosynthesis, ribulose bisphosphate. (RUBP) ? A modified version of ribose, deoxyribose is perhaps best known for its role in Deoxyribonucleic acid or DNA where it forms part of the sugar phosphate backbone. The chemical properties of deoxyribose are very different from the properties of ribulose ?
Both Ribose and Glucose will attract water molecules (hydrogen bonding ) to form solutions. Amino Acids: There are 20 common amino acids found in the protein structures of living things. Amino acids are monomers which combine to form the larger polypeptides. In turn polypeptides combine to form proteins. Proteins molecules are the basis of enzymes and many cellular and extra cellular components. ? This model shows the structure of the general amino acid. If you build one in a molecular kit you will appreciate better the 3D structure. Each of the common amino acids has the same structure as the one shown except that the R group is different. ?Amino acids are soluble ? This is an alternative way to draw the general amino acid structure. ?This diagram illustrates the ‘amino’ group which is -NH2 ? There is also the acidic group -COOH which ionizes in solution to form an -COO-and H+groups ? This acid group is known as a carboxylic acid group. ? This is an illustration of the smallest of the amino acids, Glycine. ?Notice that Glycine has an amino group, carboxylic acid group and a R group = H ?
A common source of glycine is sugar cane. This image shows a common amino acids, Alanine ?Note the similarity in structure with glycine but this time the R group is -CH3 ? Students are not required to know the structure of all 20 common amino acids Fatty Acids: These molecules are the basis of triglycerides and many other types of lipid. These molecules are also the basis of the phospholipid molecules that form the bilayer of the cell membrane. ? The image shows a basic saturated (no double bonds) fatty acid. ?There is a methyl group (-CH3) at one end of the chain. Chain is the formed from a series of covalently bonded carbons saturated with hydrogens. ?The chain is non-polar and hydrophobic ?The carbonyl group is polar making this ends of the molecule hydrophilic. ? The complex diagram of the fatty acid can be abbreviated to this simpler diagram. ? This image show the unsaturated double bond which is characteristic of animal fats. ?If there are many double bonds the fatty acid is known as polyunsaturated. Micelle ?In water fatty acid molecules arrange themselves into spheres called micelles. The polar carbonyl groups on the outside in contact with water molecules. ?The non-polar tail sections are in the centre away from water. ?This is an important aspect of fat digestion and membrane structure. List three examples each of monosaccharide, disaccharides and polysaccharides (1) List means to Give a sequence of names or other brief answers with no explanation. State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants(1) State means to give a specific name, value or other brief answer without explanation or calculation.
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