Molecular Biology

central idea of molecular biology

DNA stores information → RNA copies it → Proteins are made

Carbohydrates

are made of carbon, hydrogen and oxygen → quick energy and energy storage

Monosaccharide

one sugar → glucose, fructose, ribose

Disaccharide

two sugars → maltose, sucrose

Polysaccharide

many sugars → starch, glycogen, cellulose

Lipids

insoluble in water: fatty acids, triglycerides, phospholipids, steroids

Triglycerides

1 glycerol + 3 fatty acids → long-term energy storage, insulation, membrane structure

Fatty acids

saturated = no double bonds, unsaturated = one or more double bonds

Phospholipids

hydrophilic phosphate head, two hydrophobic fatty acid tails → phospholipid bilayer (cell membrane)

Proteins

made of amino acids (join by condensation reactions → form peptide bond)

functions of proteins

enzymes, antibodies, transport proteins, hormones, receptors, muscle contraction, structural support → protein shape determines protein function

Enzymes

biological catalysts → speed up reactions, are not used up, lower activation energy, have an active site and are substrate specific

factors affecting enzymes

temperature and pH (can cause denaturation → changes active site, substrate no longer fits), substrate concentration

DNA Replication

happens before cell division, semi-conservative: each new DNA molecule contains one old and one new strand

important enzymes for DNA replication

Helicase, DNA polymerase

Genetic code

tells a cell how the sequence of bases in mRNA is converted into amino acids to make proteins, read in groups of three bases called codons

codons

each codon = 3 bases, each codon codes for one amino acid, bases are read once only, degenerate because several codons can code for the same amino acid

Gene expression

using the information in a gene to produce a functional product → usually a protein or sometimes functional RNA, basically transcription and translation

gene expression controls

cell specialization, growth, development, metabolism, response to environment