BS 161 1st Edition Lecture 10Outline of Last Lecture I. Lipids and membranesOutline of Current Lecture II. A tour of the cellCurrent Lecture-Fundamental units of life: -all organisms are made of cells-the cell is the simplest collection of matter that can live-cell structure is correlated to cellular function-all cells arise from pre existing cells-Prokaryotic: cells that don’t have a nucleus (bacteria)-archaea: lumped together with prokaryotes, bacteria, example: organisms that live in extreme envionments-Eukaryotic: cells with a nucleus-protists: single celled eukaryotes-Composition of a cell: -Wet weight: 70% water, 25% macromolecules, 5% ions and small molecules-Dry weight: 60% proteins, 25% nucleic acids, 10% carbohydrates, 5% lipids-majority of nucleic acids in a cell are RNA-The logistics of carrying out cellular metabolism sets limits on the size of cells-The surface area to volume ratio is critical-as the surface area increase by a factor of n2, the volume increases by a factor of n3-Basic features of all cells:1. small (want a high surface area to volume ratio)2. obtain energy from environment-autotrophs: self feeders, plants, convert light into chemical energy-heterotrophs: feed on other things, everything other than plants3. selective in what comes in/goes out (membrane allows passage of certain materials, selective permeability)4. use genetic material to reproduce (DNA)-The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients and waste to service the volume of every cell-Hydrophobic molecules (ex. Hydrocarbons) can dissolve in the lipid bilayer and pass through the membrane rapidly-Polar molecules (ex sugars) do not cross the membrane easily-If a molecule cannot easily pass through but is needed, transport proteins are used to convey itthrough a space within a dedicated transmembrane protein-Five types of transport across membranes:1. Passive transport: movement of a permeable molecule across the membrane in unaided diffusion2. Osmosis: the passive diffusion of water across a membrane which has impermeable molecules3. Facilitated transport: net diffusion movement of an impermeable molecule across the membrane using a transporter4. Active transport: movement of an impermeable molecule from low to high concentration sides using energy5. Bulk transport: carrying the impermeable molecule across in a vesicle;
View Full Document
Unlocking...