2.1 Molecules to Metabolism

Metabolism

Sum of all reactions that occur in an organism. Metabolism consists of pathways by which one type of molecule is transformed into another, in a series of small steps. These pathways are mostly chains of reactions but there are also some cycles.

Four main classes of carbon compound

Living organisms use four main classes of carbon compound. They have different properties and so can be used for different purposes. Life is based on carbon compounds including: Carbohydrates Lipids Proteins Nucleic Acids

Draw

1) D-ribose (5C's) 2) alpha-D-glucose 3) beta-D-glucose 4) a saturated fatty acid 5) generalised amino acid structure

Identifying Molecules

1) sugars based on their ring structures (ribose vs. glucose) 2) triglycerides 3) phospholipids 4) steroids 5) proteins or parts of polypeptides from diagrams showing peptide bonds Proteins contain C, H, O and N/Carbohydrates and lipids contain C, H and O, but not N Many proteins contain sulphur (S) but carbohydrates and lipids do not. Carbohydrates contain hydrogen and oxygen atoms in a ratio of 2:1 Lipids contain relatively less oxygen than carbohydrates

Anabolism, Energy?, Example

Anabolism is reactions that build up larger molecules from smaller ones. Anabolic reactions require energy, which is usually supplied in the form of ATP. Ex: condensation of macromolecules from monomers Anabolism includes these processes: - Protein synthesis using ribosomes - DNA synthesis during replication - Photosynthesis, including production of glucose from carbon dioxide and water - Synthesis of complex carbohydrates including starch, cellulose and glycogen

Properties of carbon

Carbon atoms form covalent bonds with other atoms. Covalent bonds are bonds where two adjacent atoms share a pair of elections, with one electron contributed by each atom. Covalent bonds are the strongest bond between atoms, therefore compounds created by carbon are very stable. Molecules containing carbon can have complex structures because each carbon atom can form up to four covalent bonds. Carbon atoms can bond with just one other element, such as hydrogen in methane, or they can bond to more than one other element as in ethanol (alcohol found in beer and wine). The four bonds can all be single covalent bonds or there can be two single and one double covalent bond, for example the carboxyl group of ethanoic acid (the acid in vinegar)

Carbon

Carbon is only the 15th most abundant element on Earth, but it can be used to make a huge range of different molecules, giving living organisms almost limitless possibilities for the chemical composition and activities of their cells. The diversity of carbon compounds is explained by the properties of carbon.

Catabolism, Energy?, Example

Catabolism is the part of metabolism in which larger molecules are broken down into smaller ones. Catabolic reactions release energy and in some cases this energy is captured in the form of ATP, which can then be used in the cell. Ex: hydrolysis of macromolecules into monomers Catabolism includes these processes: - Digestion of food in the mouth, stomach and small intestine - Cell respiration in which glucose or lipids are oxidized to carbon dioxide and water - Digestion of complex carbon compounds in dead organic matter by decomposers

Nucleic Acids

Chains of subunits called nucleotides, which contain carbon, hydrogen, oxygen, nitrogen and phosphorus. There are two types of nucleic acid: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

Carbohydrates

Characterized by their composition. They are composed of carbon, hydrogen and oxygen, with hydrogen and oxygen in the ratio of two hydrogen atoms to one oxygen, hence the name carbohydrate.

Proteins

Composed of one or more chains of amino acids. All of the amino acids in these chains contain the elements carbon, hydrogen, oxygen and nitrogen, but two of the twenty amino acids also contain sulphur.

Lipids

A broad class of molecules that are insoluble in water. (including steroids, waxes, fatty acids and triglycerides. In common language, triglycerides are fats if they are solid at room temperature or oils if they are liquid at room temperature.)

Explain how urea is an example of a compound that is produced by living organisms but can also be artificially synthesized

First organic compound produced from an inorganic compound Urea is a nitrogen-containing compound with a relatively simple molecular structure. It is a component of urine. It is produced when there is an excess of amino acids in the body, as a means of excreting the nitrogen from the amino acids. A cycle of reactions, catalysed by enzymes, is used to produce it. This happens in the liver. Urea is then transported by the blood stream to the kidneys where it is filtered out and passes out of the body in the urine. Urea can also be synthesized artificially. The chemical reactions used are different from those in the liver and enzymes are not involved, but the urea that is produced is identical. ammonia + carbon dioxide -> ammonium carbamate -> urea + water About 100 million tonnes are produced annually. Most of this is used as a nitrogen fertilizer on crops.

(How did urea falsify vitalism?)

In the 1720s, it was widely believed that organic compounds in plants and animals could only be made with the help of a "vital principle". This was part of the vitalism - the theory that the origin and phenomena of life are due to a vital principle, which is different from purely chemical or physical forces. Aristotle used the word "psyche" - a Greek word meaning breath, life or soul. When Friedrich Wöhler synthesized urea artificially in 1828, the theory was falsified as no vital principle had been involved in the synthesis. It was deducted that if urea had been synthesized without a vital principle, other organic compounds could be as well.