Fundamentals of Biology

     Most organic molecules belong to one of these four groups: CARBOHYDRATES, PROTEINS, LIPIDS, and NUCLEIC ACIDS.  Carbohydrates are simple single-monomer sugars (monosaccharides), two-monomer sugars (disaccharides), and other multiunit sugars (polysaccharides).  Carhobydrates are simple sugars like glucose in sodas and more complex like starch in potatoes.  Proteins are functional biological molecules consisting of one or more polypeptides folded into a specific three-dimensional structure.  Different protien monomers connect to create different polymers.  Polymer strands go through a dehydration reaction to create long strands.  Long polymers go through enzymes to enter a cell and throught hydrolysis the polymer gets broken down to speed chemical reactions in a cell.  Lipids are organic compounds made of carbon and hydrogen atoms connected by nonpolar covalent bonds.  These compounds are mostly hydrophobic (not soluble in water).  This is why fat or oil sits on top of water.  Nucleic acids are a polymer made of many nucleotide monomers; these are blueprints for proteins, and through the actions of proteins; for all cellular structures and activities.  They are DNA and RNA. 

     The molecules that make up living things interact in many complex chemical systems.  Most importantly, organisms have to capture, store and use energy.  The two main ways to process energy are PHOTOSYNTHESIS and RESPIRATION. 
     Most organisms ultimately get their energy from the sun.  In photosynthesis, algae, plants and other photosynthetic organisms capture the sun's energy and use it to make glucose, a simple sugar, which is stored, utilized, and/or converted into other organic compounds.  Such organisms are called autotrophs.  Solar energy is captured by pigments such as chlorophyll and is converted into chemical energy which is then used to make glucose out of CO2 and H2O; releasing O2 as a by-product. 
     Organisms that cannot photosynthesize and produce their own food are called heterotrophs.  Heterotrophs must obtain energy from organic matter that was produced by autotrophs.  Both autotrophs and heterotrophs perform respiration to utilize the energy stored in organic compounds by photosythesis.  In respiration sugars are broken down using oxygen, giving off CO2 and water as a result.