Cells

Scientists Hooke-saw cork cells under a microscope Van Leeuweenhoek – saw living bacteria Pasteur – studied bacteria and developed the germ theory that said that ‘germs’ cause disease. He also developed the first vaccines. Koch – rules to test if a germ is the cause of a specific disease Margulis – tested DNA in mitochondria and found it was the same as bacteria DNA

Cell Theory All living organisms are composed of one or more living cells Cells are the basic units of life All cells come from preexisting cells

Microscopes Compound Light Microscope – series of glass lens that can be no better than 1000X, but can be used to view living cells Electron microscopes – aims a beam of electrons at thin slices of cells (dead) –Transmission electron microscope (TEM) –Scanning electron microscope (SEM)

Microscopes

Cell size As cell size increases, the surface area to volume ratio decreases Rates of chemical exchange may then be inadequate for cell size Cell size, therefore, remains small

Cell Size

Basic Cell Types Prokaryotes – cells without a nucleus or other membrane bound organelles –Example: most unicellular organisms, e.g., bacteria Eukaryotes – cells with a nucleus and other membrane bound organelles (ER, mitochondria, Golgi apparatus, chloroplast, lysosome)

Plasma Membrane

The Lipid Bilayer Lipids of the bilayer –fluid or liquid-crystalline state Proteins move within the membrane

Fig. 5-2b, p. 108 Integral (transmembrane) protein (b) Fluid mosaic model. According to this model, a cell membrane is a fluid lipid bilayer with a constantly changing “mosaic pattern“ of associated proteins. Phospholipid bilayer Peripheral protein Hydrophilic region of protein Hydrophobic region of protein

Cytoplasm Environment inside cell membrane Cytoskeleton – supporting network of long, protein fibers that form a network and anchor for the cell organelles

Membrane structure Phospholipids~ membrane fluidity Cholesterol~ membrane stabilization “Mosaic” Structure~ proteins Membrane carbohydrates ~ cell to cell recognition;

Nucleus Genetic material... chromatin chromosomes Nucleolus:; ribosome synthesis Double membrane envelope with pores Protein synthesis

Ribosomes Protein manufacture

Endomembrane system, I Endoplasmic reticulum (ER) Smooth ER no ribosomes; synthesis of lipids Rough ER with ribosomes; synthesis of proteins

Endomembrane system, II Golgi apparatus –ER products are modified, stored, and then shipped

Endomembrane system, III Lysosomes sac of hydrolytic enzymes; digestion of macromolecules Tay-Sachs disease~ lipid-digestion disorder

Other membranous organelles, I Mitochondria quantity in cell correlated with metabolic activity; cellular respiration contain own DNA

Other membranous organelles, II Chloroplast (doubled membranous plastid) photosynthesis own DNA

Peroxisomes Metabolism of fatty acids; detoxification of alcohol (liver)

Cellular Transport Passive Transport – does not require energy –Diffusion –Across a membrane Osmosis Facilitated diffusion Active Transport – requires energy –Sodium/Potassium pump –Transport of Large Particles Endocytosis Exocytosis

Diffusion

Osmosis

Water balance Osmoregulation~ control of water balance Hypertonic~ higher concentration of solutes Hypotonic~ lower concentration of solutes Isotonic~ equal concentrations of solutes Cells with Walls: Turgid (very firm) Flaccid (limp) Plasmolysis~ plasma membrane pulls away from cell wall

Turgor and Plasmolysis

Facilitated Diffusion

Types of Active Transport Sodium-potassium pump Exocytosis~ secretion of macromolecules by the fusion of vesicles with the plasma membrane Endocytosis~ import of macromolecules by forming new vesicles with the plasma membrane phagocytosis pinocytosis

Fig. 5-17b, p Three Na+ bind to transport protein. 2. Phosphate group is transferred from ATP to transport protein. 3. Phosphorylation causes carrier protein to change shape, releasing 3 Na+ outside cell. 4. Two K+ bind to transport protein. 5. Phosphate is released. 6. Phosphate release causes carrier protein to return to its original shape. Two K+ ions are released inside cell.

Phagocytosis Large particles enter cell