Biozone+Answers

**__ Carbohydrates __** 1. Structural isomers have the same molecular formula but their atoms are linked in different sequences. Optical isomers are identical in every way except that they are mirror images of each other. 2. Isomers will have different bonding properties & will form different disaccharides and macromolecules depending on the isomer involved. 3. Compound sugars are formed and broken down by condensation and hydrolysis reactions. Condensation: join 2 CHO’s molecules by a glycosidic bond with the release of a water molecule. Hydrolysis: use water to split a CHO molecule (water molecule provides a hydrogen atom and a hydroxyl group) 4. Are all polymers of glucose, but differ in form and function because of the optical isomer involved, the length of the polymer and the degree of branching __Cellulose__: unbranched, long chain glucose polymer held together by B-1, 4 glycosidic bonds. The straight, tightly packed chains give cellulose high tensile strength and resistance to hydrolysis. __Starch__: mixture of 2 polysaccharides (amylase/unbranched and amylopectin/branched), the more branched nature of starch account for its properties; it is powdery and more easily hydrolysed. __Glycogen__: like starch is a branched polymer. More soluble and more easily hydrolysed than starch
 * __ Biozone Answers __**

**G****lycosidic bond** A type of [|covalent] chemical bond that joins two simple sugars, or [|monosaccharide’s], via an oxygen atom. If the bond is below the plane of the ring it is said to an alpha glycosidic bond; if it above the plane of the ring it is known as a beta glycosidic bond. The bond is normally formed between the carbon-1 on one sugar and the carbon-4 on the other (see illustration). An α-glycosidic bond is formed when the –OH group on carbon-1 is below the plane of the glucose ring and a β-glycosidic bond is formed when it is above the plane. [|Cellulose] is formed of glucose molecules linked by 1-4 β-glycosidic bonds, whereas starch is composed of 1-4 α-glycosidic bonds.

**__ Amino Acids __**
1. 20 different amino acids comprise the building blocks of constructing proteins (diverse structural & metabolic functions). The non-protein amino acids have specialised roles as intermediates in metabolic reactions

2. The side chains (R groups) differ in their chemical structure and therefore their chemical effect.

3. Translation of the genetic code. Genetic instructions from the chromosomes (genes on DNA) determine the order in which amino acids are joined together

4. The carboxyl group confers acidic properties to an amino acid and the R group can also effect the acidic or alkaline nature of the molecule. This means the Amino acid will act as a buffer by removing excess hydroxyl or hydrogen ions present in the surrounding solution. AA’s retain this capacity even when incorporated into proteins

5. Essential AA’s: Cannot be manufactured by the human body they must come be included in the food we eat. E.g. Isoleucine, Lysine, methionine, threonine

6. Condensation: involve joining 2 AA’s by a peptide bond with the release of a water molecule Hydrolysis: splitting of a dipeptide where a peptide bond is broken and a water molecule is used to provide a hydrogen atom and a hydroxyl group

**__Proteins__** 1. a) __Structural:__ proteins form an important component of connective tissues and epidermal structures e.g. Collagen and keratin (hair, horn). Proteins are also found scattered on, in and through cell membranes, but tend to have a regulatory role in this instance. Proteins are also important in maintaining a tightly coiled structure in a condensed chromosome

b) __Regulatory:__ Hormones e.g. Insulin (protein), adrenalin (modified AA), glucagon (peptide) are chemical messengers which trigger a response in target tissues. They help maintain homeostasis. Enzymes: regulate metabolic processes in cells

c) __Contractile:__ Actin and myosin are structural components of muscle fibres. Using a ratchet system these 2 proteins move past each other when energy is supplied.

d) __Immunological:__ Gamma globins are blood proteins that act as antibodies, targeting antigens (foreign substances and microbes) for immobilisation and destruction.

e) __Transport:__ Haemoglobin and myoglobin are proteins that act as carrier molecules for transporting oxygen in the bloodstream of vertebrates. Invertebrates using have some other type of oxygen carrying molecule in the blood.

f) __Catalyst:__ Enzymes (amylase, lipase, lactose, trypsin) are involved in the chemical digestion of food. A vast variety of other enzymes are involved in just about every metabolic process in organisms

2. Denaturation destroys protein function b/c it involves an irreversible change in the precise tertiary or quaternary structure that confers biological activity. E.g. a denatured enzyme protein may not have its reactive sites properly aligned and will be prevented from attracting the substrate molecule.

3. Fibrous proteins have a tertiary structure that produces long fibres or sheets, often with many cross-linkages. This makes them very tough physically and ideal as structural molecules e.g. Collogen

4. The tertiary structure of globular proteins produces a spherical shape which is critical to their interaction with other molecules. E.g. the active site in enzymes or the recognition sites in regulatory molecules like insulin