TOPIC+3+THE+CHEMISTRY+OF+LIFE

= = =**__ TOPIC 3 The Chemistry of life __**= For extra detail on key Chemistry principals needed for Biology have a look here: http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect02.htm

Below is a brief summary of key points covered by the IB specification, I will add useful links as and when I find them, similarly if you find any links then send an email and I will add them:

The most frequently occurring chemical elements in living things are **__c__**arbon, **__h__**ydrogen, **__o__**xygen and **__n__**itrogen. A variety of other elements are needed by living organisms, including **sulfur** (di-sulphide bridges), **calcium** (bones), **phosphorus** (ATP), **iron** (haemaglobin) and **sodium** (sodium potassium pump & co-transport). __ WATER __ The structure of water molecules showing polarity and hydrogen bond formation.
 * __ 3.1 Chemical elements and water __**


 * Thermal: ** High SHC – regulating temperature & high heat of Vaporisation - cooling
 * Cohesive: ** attraction of water molecules to each other – used in transport in xylem vessels
 * Solvent: ** Water is polar and will dissolve many polar solutes – medium for metabolic reactions & transport

Compounds containing carbon that are found in living organisms (except hydrogen carbonates, carbonates and oxides of carbon) are regarded as **ORGANIC**.
 * __ 3.2 Carbohydrates, lipids and proteins __**
 * Monosaccharide ** : glucose, galactose and fructose (for respiration)
 * Disaccharides ** : maltose, lactose and sucrose (function – sucrose in plant transport
 * Polysaccharides ** : starch, glycogen and cellulose. ** (function – cell wall) **
 * __ Condensation and hydrolysis __**

Adenine, Cytosine, Thymine, Guanine – A with T, C with G DNA double helix is formed using complementary base pairing and hydrogen bonds.
 * __ 3.3 DNA structure __**
 * DNA nucleotide ** : sugar (deoxyribose), base and phosphate.

Unwinding the double helix and separation of the strands by **__helicase__**, followed by formation of the new complementary strands by **__DNA polymerase__**. Complementary base pairing ensures the conservation of the base sequence of DNA. DNA replication is semi- conservative. 3.3 - 3.5 (7.1-7.4) DNA
 * __ 3.4 DNA replication __**

Compare the structure of RNA and DNA (see sugars above, RNA single stranded, RNA U not T) Each codon on the mRNA is a triplet of bases that will code for one amino acid. Originally, it was assumed that one gene would invariably code for one polypeptide, but many exceptions have been discovered.
 * __ 3.5 Transcription and translation __**
 * __ In transcription __** a complimentary RNA strand is formed by **RNA polymerase.**
 * __ Translation __** leads to polypeptide formation: Messenger RNA (mRNA) attaches to a ribosome, transfer RNA (tRNA) with anticodon and specific amino acid binds to ribosome and mRNA complex.

3.6 (7.5) Biological Chemicals and enzymes
 * __ 3.6 Enzymes __**
 * enzyme: ** a globular protein molecule that accelerates a specific chemical reaction.
 * active site: ** the region of an enzyme’s surface that binds the substrate (reacting substance) during the reaction catalysed by the enzyme.
 * enzyme–substrate specificity & ** the effects of temperature, pH and substrate concentration on enzyme activity.
 * Denaturation ** : a structural change in a protein that results in the loss (usually permanent) of its biological properties. Refer only to heat and pH as agents.
 * Lactase: ** in the production of lactose-free milk. By attaching the enzyme **lactase** to a large molecule and then bringing it into contact with milk. Any lactose present will be broken down into **glucose** and **galactose** by the lactase.

Cell respiration is the controlled release of energy from organic compounds in cells to form ATP. In cell respiration, glucose in the cytoplasm is broken down by **glycolysis** into **pyruvate**, with a small yield of ATP. During **anaerobic cell respiration**, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. Ethanol and carbon dioxide are produced in yeast, whereas lactate is produced in humans. During **aerobic cell respiration**, pyruvate can be broken down in the **__mitochondrion__** into carbon dioxide and water with a large yield of ATP. 3.7 (8.1) Respiration
 * __ 3.7 Cell respiration __**

Photosynthesis involves the conversion of light energy into chemical energy. Light from the Sun is composed of a __range of wavelengths__ **chlorophyll** is the main photosynthetic pigment. Pigments absorb certain colours of light. The remaining colours of light are reflected. Light energy is used to produce ATP, and to split water molecules **(photolysis**) to form oxygen and hydrogen. ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules. The rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase in biomass. The effects of **temperature**, **light intensity** and **carbon dioxide** concentration on the __rate of photosynthesis__ -the shape of the graphs is required.
 * __ 3.8 Photosynthesis __**