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Topic 1(A) by Mind Map: Topic 1(A)

1. Sugars

1.1. Carbs contain the elements C, H and O, the monomers are monosaccharides (glucose, fructose and galactose). Glucose has two types (alpha and beta), they are isomers.

1.2. Disaccharides are formed when two monosaccharides join together via a condensation reaction, forming a glycosidic bond between them.

1.2.1. Glucose and fructose = sucrose, glucose and galactose = lactose.

2. Monomers and polymers

2.1. Carbs, proteins and nucleic acids are usually polymers, made up of monomer chains. Condensation reactions occur between monomers, releasing a water molecule and forming polymers. the reverse of this reaction is hydrolysis which uses a water molecule.

3. Polysaccharides

3.1. Polysaccharides are formed when more than two monosaccharides join together.

3.1.1. Starch is a storage molecule used by plants to store glucose. starch is made up of two poly saccharides of alpha-glucose-amylose and amylopectin Amylose a long unbranched a-glucose chain. The angles of the bonds give a coiled structure, making it compact. Amylopectin a long branched a-glucose chain. the side branches allow the enzyme to reach the glycosidic bonds and break them down.

3.1.2. Glycogen is a glucose storage molecule for animals. a similar structure to amylopectin, with side branches, this means quick energy release, also compact.

3.1.3. Cellulose long, unbranched b-glucose chains, bonds form straight chains linked by hydrogen bonds. Forms strong fibres (microfibrils). good for structural support.

4. Lipids

4.1. Made from proteins and carbs, all contain hydrocarbons. components they're made up of determine their function.

4.1.1. Triglycerides have one glycerol to three fatty acids, the. Fatty acids have long, hydrocarbon, hydrophobic tails. these make lipids insoluble in water. the fatty acids bond with the glycerol via an ester bond.

4.1.2. Phospholipids make up cell membranes, they only have two fatty acids, as well as a phosphate group. the phosphate group is hydrophilic. Form a bilayer with the hydrophobic tails facing in away from any water, this makes the centre hydrophobic, water-soluble substances can't pass easily through it, membrane acts as a barrier to these substances.

5. Protein

5.1. Proteins are made up of the monomers amino acids. A dipeptide is formed by two amino acids join and a polypeptide is more than two amino acids. Proteins are made up of one or more polypeptides.

5.2. Amino acids have a general structure - a carboxyl group, an amino or amino group, and an R group attached to a carbon group. All living things share a bank of only 20 amino acids.

5.3. Dipeptides and polypeptides join via condensation reactions and peptide bonds form between the amino acids.

5.4. Protein structure starts with the primary structure which is the sequence of amino acids in the polypeptide chain. The secondary structure is when the hydrogen bonds form causing an alpha helix or a beta pleated sheet. after this the tertiary structure produces more bonds including hydrogen and ionic bonds, causing further coiling and folding. Disulfide bridges also form. The final structure (only in proteins with multiple polypeptide chains) is the quartenary structure where the multiple polypeptide chains join together.

6. Enzymes

6.1. Enzymes speed up chemical reactions by acting as biological catalysts, catalysing metabolic reactions. Enzymes are proteins

6.2. Enzymes have a unique active site which is where the substrates will bind. The tertiary structure makes enzymes very specific

6.3. A certain amount of energy is supplied before the reaction starts, activation energy, which is often provided by heat. Enzymes lower the amount of activation energy needed by producing an enzyme-substrate complex.

6.3.1. The enzyme-substrate complex lowers the required activation needed because it holds the two substrates closer together so, reduces any repulsion splitting them apart, it also, puts a strain on the bonds in the substrate in breakdown reactions.

6.4. Factors affecting enzyme activity

6.4.1. Temperature - more heat means more energy making substrate molecules more likely to collide with the active site. However, past a certain optimum heat the enzyme will begin to denature causing the active site to change shape meaning that no reaction can take place within it.

6.4.2. pH - All enzymes have an optimum pH, either side of this the H+ and OH- ions found in acids and alkalis can disturb the hydrogen and ionic bonds that hold the tertiary structure causing the enzyme to denature.

6.4.3. Substrate concentration - more substrate molecules mean that collisions with active sites are more likely, speeding up the reactions. however, once past the saturation point enzymes have as much as they can deal with and adding more will have little affect as the majority of active sites are full.

6.4.4. Enzyme concentration - similarly the more enzymes there are the more likely it is to collide with substrate molecules therefore, speeding up reactions. But, if the number of substrates is limited there will reach a point where there's more than enough enzymes to deal with the substrates so, there's no further increase.

6.5. Enzyme inhibitors can prevent enzyme activity by binding to the enzyme they inhibit.

6.5.1. Competitive inhibitors - similar shape to the substrates so, they compete to bind to the active site. If an inhibitor binds to an active site no reaction will take place. In this case adding more substrate will lower the chances of inhibitors binding to active sites and, will speed up the rate of reaction.

6.5.2. Non competitive - these bind to the enzyme away from the active site. This causes the active site to change shape meaning that the substrate can no longer bind to it. Increasing substrate concentration will have no effect the rate of reaction will stay the same.