Chemistry Of Life Notes

3- THE CHEMISTRY OF LIFE:

Organic chemistry is the chemistry of carbon compounds. Biochemistry is the branch of organic chemistry which explains the chemistry in living organisms. The biochemistry from one type of organism to another is very similar.
Organic compounds are based on carbon and are found in living things. There are a number of exceptions: hydrogen carbonate (HCO3-), carbondioxide (CO2) and Carbon monoxide (CO).
Inorganic compounds are by default all the molecules other than those in the category above.
The majority of organic molecules can be classified into one of these four types:
- Carbohydrates.
- Lipids.
- Proteins.
- Nucleic acids.
CHEMICAL ELEMENTS AND WATER:
The most frequents chemical elements are: C, H, O and , and these elements areused in the molecular structure of Carbohydrates, Lipids, Proteins and Nucleic acids. Other elements include: S, Ca, P, Fe, Na; which are extremely important, but less common.
Sulphur which is an important element in some amino acids.
Calcium which is found in bones / Teeth
Iron which is to be found in haemoglobin (animal)
Sodium which is needed for a nerve impulse
Phosphorus found in cellmembrane structures

STRUCTURE OF WATER:
Water is not a biological molecule but it is essential to living things. Water is often called the universal solvent or solvent of life. Thus, all cells have water within them (cytoplasm), and in the surrounding environment (intercellular fluid…). Many of the properties of water depend on its structure:
This image of water show the covalent bonds betweenoxygen and two hydrogen atoms.
The nuclei of oxygen is significantly larger and greater charge than the hydrogen nuclei.
This creates a polar molecule in which the oxygen carries and additional small negative dipole and each hydrogen a small positive dipole.


[pic]


Due to the polarity of the water molecules, the small negative charge on each oxygen atoms is attracted the hydrogen atoms ofother water molecules. These attractions are called HYDROGEN BONDS. The hydrogen bond does not change the chemical properties of water but does accounts for physical properties. The three of the more important properties for biological systems include:
1. Cohesive properties.
2. Thermal properties.
3. Solvent properties.
cohesion
- hydrogen bonds between polar water molecules cause themto cohere allowing for transpiration in plants moving water against gravity
- surface tension between cohering water molecules allowing for animals such as water striders to walk over the surface of ponds even though they are denser than water
thermal properties
- hydrogen bonds between polar water molecules cause water to resist change
high specific heat (energy required to changewater temperature)
- high heat of vaporization (energy required to boil water)
- high heat of fusion (loss of energy required to freeze water)
thus, water produces a stable environment for aquatic organisms
solvent properties
- the polarity of water attracts, or dissolves, any other polar or charged particles by forming hydrogen bonds with them. Proteins, glucose, or ions, such assodium or calcium are all soluble
Relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium.
coolant
- hydrogen bonds between polar water molecules cause water to resist change
- high heat of vaporization (energy required to change liquid water to vapor) because hydrogen bonds must be broken
-thus, evaporation of water from plant leaves (transpiration) or from human skin (sweat) removes heat, acting as a coolant
medium for metabolic reactions
- cytoplasm is primarily water, providing a polar medium in which other polar or charged molecules dissolve
- many enzymes are globular proteins that are water soluble so they dissolve in cytoplasm where they control metabolic reactions...