biology unit 1

• the entire set of proteins expressed by a genome proteome
• more than one protein can be produced from a single gene because of alternative RNA splicing
• genes that dont code for proteins are called  non coding RNA genes
• examples of non coding genes tRNA, mRNA, rRNA
• Factors affecting the set of proteins expressed by a cell type  metabolic activity, cellular stress, response to signalling molecules, diseased vs healthy cells
• Because of their size, eukaryotes have a small  surface area to volume ratio
• The endoplasmic reticulum forms a network of  membrane tubules continuous with the nuclear membrane
• The Golgi apparatus is a series of flattened membrane discs
• Lysosomes are membrane bound organelles containing a variety of hydrolases
• Hydrolases in lysosomes can digest proteins, lipids, nucleic acids and carbohydrates
• Vesicles transport materials between membrane compartments
• Lipids and proteins are synthesized in  the endoplasmic reticulum
• Lipids and synthesized in the  smooth ER
• Rough ER has - on its cytosolic face ribosomes
• Smooth ER - ribosomes  doesnt have
• the synthesis of all proteins begins in  cytosolic ribosomes
• Transmembrane proteins carry a signal sequence, which halts translation and directs ribosome synthesising proteins to dock w ER forming RER
• what is a signal sequence  a short stretch of amino acids at one end of the polypeptide
• the signal sequence determines  the eventual location of a protein in the cell
• Once proteins are in the ER, they are transported by vesicles
• as proteins move through the Golgi apparatus they undergo  post translational modification
• The major post transitional modification is the addition of carbohydrates
• vesicles that leave the Golgi apparatus take proteins to  the plasma membrane and lysosomes
• Vesicles move along microtubules
• Examples of secreted proteins peptide hormones and digestive enzymes
• - are translated in ribosomes on the RER and enter its lumen secreted proteins
• Proteolytic cleaveage is a type of post translational modification
• Example of secreted proteins that require proteolytic cleaveage to become active digestive enzymes
• many secreted proteins are synthesized as inactive precursors
• Polymers of amino acid monomers  proteins
• Amino acids are linked by - to form polypeptides peptide bonds
• Amino acids have the same basic structure, differing only in  the R group
• R groups of amino acids vary in size, shape, charge, H bonding capacity and chemical reactivity
• Basic amino acids are  + charged
• Acidic amino acids are  - charged
• 4 types of amino acids R groups basic, acidic, polar, non-polar
• hydrophillic molecules are polar
• hydrophobic molecules are  non polar
• wide range of functions carried out by proteins results from diversity of R groups
• The primary structure is the sequence in which the amino acids are synthesized into the polypeptide