Ch+7+and+8

Test date: Thursday, October 15, 2009 (He said he might change it to 10/16)toc =Chapter 7= A Tour of the Cell Overview: What is inside a cell?

Microscopes
//Resolving power//: How clear the image is. Minimum distance two points can be and still be distinguished. //Magnification//: How much bigger a thing is than it REALLY is. Light Microscopes (LM)
 * Works by passing visible light through a specimen
 * Techniques used to improve visibility
 * Fluorescence, phase-contrast, confocal microscopy
 * Resolving power is really bad since it only uses visible light (10^3 micrometers)

Electron Microscopes (EM) TEM SEM
 * Uses electron beam that focuses through specimen
 * Short wavelength = more resolution power = 2 nanometers
 * Transmission Electron Microscope
 * Electron beam passes through thin section of specimen
 * Stain with //heavy metals// to increase contrast
 * Scanning Electron Microscope
 * Electron beam scans the surface coated with thin gold film
 * This excites electrons and collects+focuses them onto screen

Cell Fractionation

 * Take cell apart and seperate organelles in order to learn about their individual functions

Centrifuge
 * Machine that spins test tubes at different speeds (merry-go-round)
 * Ultracentrifuge: Very powerful centrifuge that goes at 80,000 rpm with 500,000g force
 * Homogenization: Disruption of cells
 * How a Centrifuge works
 * Seperates the cell parts by spinning homogenate into //pellet// and //supernatant//.
 * Pellet: Larger structures near bottom of test tube
 * Supernatant: Smaller parts suspended in liquid of test tube
 * The above is repeated again with more speed using the supernatant.



P and E cells
Area grows squarely and volume grows cubily -> a big cell will have a huge volume -> needs to be enough area [for exchange of oxygen, nutrients, wastes] to the volume of cell
 * Prokaryotic cells
 * Cells with no nucleus or membrane-enclosed organelles
 * Nucleoid holds the DNA of prokaryotic cells
 * They have...
 * Ribosomes, plasma membrane, cell wall, capsule, flagella, pili, Cytoplasm, cytosol, DNA, nucleoid
 * Size: range from 1-10 micrometers


 * Eukaryotic cells
 * Have nucleus enclosed in nuclear membrane
 * Organelles suspended in cytosol (which is a semifluid medium)
 * Size: ranges from 10-100 micrometers
 * They have...
 * Plasma membranes, organelles, nucleus, cytoskeleton
 * Cell size
 * There was an essay done about this so refer back to that. "Cell Size Essay"

Compartments
Compartamental Organization
 * Eukaryotic cells compartmentalize through its membrane
 * The membranes divide the cell and provide different environments for certain metabolic functions
 * Membrane made of double layer of phospholipids (is amphipathic) embedded with diverse proteins

Nucleus

 * //Nuclear Envelope//: A double membrane with pores that surrounds the nucleus.
 * regulates the movement of large macromolecules
 * //Nuclear Lamina//: Inner membrane of nucleus that maintains shape of nucleus.
 * //Nuclear Matrix//: Framework of fibers throughout the nucleus (not proven? someone help)
 * Nucleolus: Dense visible structure in nucleus that synthesizes ribosomal RNA and combines it with protein to make ribosomal subunits
 * Chromatin: Mass of DNA with proteins in the nucleus
 * Chromosomes: Strand of DNA combined with protein

Ribosomes

 * Ribosomes: Sites where cells assemble proteins
 * Free Ribosomes: Ribosomes that are suspended in the cytosol
 * proteins made here function in the cytosol
 * Bound Ribosomes: Ribosomes that are attached to outside of the Endoplasmic Reticulum
 * proteins made here usually are included into membranes or exporting

Endomembrane System

 * Different membranes of the eukaryotic cell
 * Connected to each other in someway or another (//**transport vesicle**//, direct contact)
 * Is made of
 * Nuclear Envelope, Endoplasmic Reticulum, Golgi apparatus, Lysosomes, Vacuoles, Plasma membrane

Endoplasmic Reticulum (ER)

 * Consists of network of //cistaernae// (membranous tubules/sacs)
 * Extensive membranous labyrinth that continues off of the nuclear envelope

Smooth ER
 * Lacks ribosomes
 * Functions
 * Detoxifies drugs and poisons
 * Phospholipid, steroid and sex hormone synthesis
 * Carbohydrate metabolism
 * Storaes and releases calcium ions during muscle contraction

Rough ER
 * Ribosomes are attached to the surface of it
 * Secretory proteins transported from rough ER by transport vesicles
 * Ribosomes make proteins that are meant for secretion and send them to the rough ER
 * Glycoproteins: many proteins are bonded (covalently) to small carbohydrates
 * Manufactures membranes by using the formed proteins made by the attached ribosomes
 * Makes membrane phospholipids assembled with help from built-in enzymes
 * Then transferred to other part of endomembrane system by transport vesicles



Golgi (googli) Apparatus

 * Stack of flattened membranous sacs
 * As shown in the image above, vesicles from the ER fuse with the golgi (at the cis face)
 * Golgi apparatus modifies/refines/adds phosphate
 * Can manufacture polyaccharides (?)
 * Transports finished products through the use of vesicles pinching off the golgi (trans face)



Lysosomes

 * Membrane-enclosed sacs of //hydrolytic enzymes//
 * Function: Digest macromolecules
 * Environment inside is acidic due to the enzymes
 * Cell can recycle its own macromolecules by autophagy
 * Can destroy parts during development (example: tadpole -> frog, the lysosome eats away the tadpole tail)
 * Protists/Macrophages have lysosomes that use phagocytosis to digest ingested material.



Vacuoles

 * Enclosed membrane sacs that are bigger than vesicles
 * Types
 * Contractile Vacuoles: pump excess water in protists
 * Food vacuoles: Result of phagocytosis
 * Central Vacuole: Vacuole that is in mature plant cells. It is surrounded by the tonoplast (membrane) and it stores poisons, organic compounds and inorganic ions
 * Plants can increase in size through vacuole absorbing water and expanding



Other organelles
Mitochondria
 * Composed of two phospholipid bilayers with embedded proteins
 * Has inter-membrane space
 * Cristae: Inner membrane folds
 * Mitochondrial matrix: The stuff in the cristae
 * Houses enzymes, mitochondrial DNA, ribosomes and other



Chloroplasts

Peroxisomes

Cytoskeleton