The Chemistry of Life

               The most frequently occurring chemical elements in living things are carbon, hydrogen, nitrogen and ozygen. A variety of other elements are needed by living organisms including nitrogen, calcium, phosphorus, iron, sodium and sulfur.

               State one role for each of the elements mentioned before

1.      Nitrogen : required by proteins. Nitrogen is included in the amino acid structure. Contains enzymes essential for plant function.

2.                                   Calcium : the mineral that strengthens bone and teeth uses calcium. Also important in nerve synaptic transmission of nerve impulses and muscle contraction. Regulates the cell wall construction in plants.

3.      Phosphorus : part of the phosphate groups in ATP and DNA molecules in plant. It is needed for

cell reproduction and division. It is part of the cell membrane.

4.      Iron : found in the structure of haemoglobin and essential for the production of red blood cells. It is involved in the light energy transferring compounds involved in photosynthesis in plants.

5.      Sodium :  major ion associated with propagation of  a nerve impulse. Can replace potassium in some plants.

6.      Sulfur : it is a component of amino acids.

          Outline the properties of water that are significant to living organisms, including transparency, cohesion, solvent propertiesand thermal properties.

            If water had a low heat capacity aquatic organisms candie and the water in organisms will heat quickly and can results in the destruction of the cell. If water had a low heat of vapourization, liquid water will be able to evaporate when absorbing a relatively low amount of energy. Imagine on a hot day, the water in the lakes would evaporate quite easily.

            Organic compounds are defined as compounds containing carbon that are found in living organisms. Compounds are considered inorganic when the contain carbon but are widely found in the environment.

            In a condensation reaction, two molecules work together and form one big molecule along with water, because water is released during this reaction. So, two amino acids could join together and form a dipepide and this would be a condensation reaction. Same applies for monosaccharides becoming disaccharides, you get the drift.

            Now in hydrolysis reaction, water molecules are used up to make a large molecule into a small molecule. Think about it “hydro” means water and “lysis” means splitting. So, water is used up to split a disaccharide into a monosaccharide.

            List two examples for each of monosaccharides, disaccharides and polysaccharide. Monosaccharide like glucose, fructose and ribose ; disaccharide like maltose (glucose + glucose) and sucrose (glucose + fructose) ; polysaccharide like starch (made of glucose subunits, but linked differently from starch). Plant use mostly starch, humans use mostly glycogen.

            Enzymes is globular proteins used to catalyse chemical reaction. The active site for an enzyme is very specific in shape, with very precise chemical properties. Active sites match the shape of their substrates. Other molecules do not fit or do not have the same chemical properties. The enzyme is therefore substrate specific. This enzyme is a look and the substrate is the key which can open it.

            Temperature, pH and substrate consentration all affect the rate at which enzymes catalyse chemical reactions. Enzyme activity increases as temperature increase, often doubling with each 10 C. This is because collision between substrate and active site happen more frequently at higher temperature, due to fast molecular movement. However at high temperatures enzymes are denatured and stop working. This is because heat causes vibrations inside the enzymes, which break bonds needed to maintain the structure.

            Denaturation is a structural change in a protein that results in a loss of its biological properties. This can be caused by pH or by temperature.

            A DNA is composed of a deoxyribose, a phosphate group and a nitrogen base ( adenine, cytosine, thymine and guanine). The phosphate group is covalently borded to carbon of the deoxyribose and then nitrogenous base is attached to the deoxyribose.

            DNA molecules consist of two strands of nucleotides which are then wound together to form a double heliz. These are formed between the bases of two strands. However, it is formed by complementary base pairing because adenine only forms hydrogen bonds with guanine.