Chapter4Cells

1. Overview Basic functional unit for life All living things are made of cells Life cannot exist below this level of organization Unicellular or multicellular Prokaryotic or eukaryotic (archea is more closely related to eukarya) Structure relates to function

2. Microscopy Identifies cells, but not most organelles Used to study cells Light Microscope – LM – Identifies cells, but not most organelles Magnification – ratio of the objects image to the real size Max ~ 1000 x the images actual size 200 nanometers – smallest (bacteria) Resolution – image clarity increase magnification = decrease in resolution Electron Microscope –EM – preparation kills the cell 0.002 nanometers Scanning Electron Microscope – SEM Used to study the surface of specimens gives 3D image Transmission Electron Microscope – TEM Cell ultrastructure – organelles and internal parts

Light Transmission Scanning 10 m Human height 1 m Length of some nerve and muscle cells Light 0.1 m Unaided eye Chicken egg 1 cm Frog egg 1 mm 100 µm Most plant and animal cells Light microscope 10 µm nucleus Most bacteria Mitochondrion 1 µm Electron microscope Smallest bacteria 100 nm Viruses Ribosomes 10 nm Proteins Lipids 1 nm Transmission Scanning Small molecules 0.1 nm Atoms

3. Cell Fractionation Separates major organelles to study their individual functions Uses density to separate cell parts

Cell Fractionation Cells are blended to disrupt the cell – homogenate Homogenate is centrifuged to separate out pellets containing organelles Pellets are separated by speed and duration Higher speed for longer duration = smaller organelles Important concept in Biotechnology http://www.accessexcellence.org/RC/VL/GG/images/biotechnology.gif

Characteristics of ALL cells Plasma membrane – phospholipid bilayer: selective Contain cytosol (jelly like fluid) – cytoplasm (space inside of cell) Chromosomes – DNA Ribosomes: make proteins ( not membrane bound)

5. Prokaryotes vs. Eukaryotes

5. Prokaryotes vs. Eukaryotes Prokaryotes – before nucleus Eukaryotes – true nucleus Simple Smaller – ~1-10 micrometers Nucleiod – no nucleus Plasmid – circular chromosome No membrane bound organelles Has ribosomes – not membrane bound Cell wall: peptidoglycan Complex Larger - ~10-100 micrometers Nucleus Linear chromosome w/ histone proteins Membrane bound organelles and ribosomes No cell wall in Animal cells Cellulose – plants Chitin – fungi

Genetic Recombination in Prokaryotes Binary Fission: asexual, rapid division (20 min. ish), faster evolutionary process Transduction: phages (viruses that infect bacteria) transfer genetic material from one bacterial cell to another Conjugation: Exchange genetic material in “good environmental conditions” Use sex pili to pull together, 1 way exchange F plasmid: allow mating bridge, fertility R plasmid: Allow antibiotic resistance

Cellular Structure of Bacteria and Archeae DNA (nucleoid region) & Ribosome in cytoplasm Cell wall in most, capsule in some Archea: * no nucleus * no membrane bound organelles * Sometimes introns (pieces of DNA that are cut out) * no histones (proteins that help coil DNA) * circular chromosomes

6. Surface Area and Volume Surface area increases while total volume remains constant 5 1 Total surface area (height  width  number of sides  number of boxes) Total volume (height  width  length  number of boxes) Surface-to-volume ratio (surface area  volume) 6 150 125 12 750 Smaller cells have a larger surface to volume ratio and therefore transport materials more efficiently through the cell Larger organisms have more cells NOT larger cells because of surface to volume ratio

SA to Volume Calculate the surface area and volume of a cube that is 3cm x 3cm x 3cm. Now give the SA to volume ratio SA: 6(3cm x3cm) = 54 cm2 V: 3cm x 3cm x 3cm = 27 cm3 SA : V = 2:1 Describe what happens if the cube increases in size. The SA : V ratio decreased b/c the V increases at a rate faster than the SA

Cellular Genetic Instructions Nucleus Nuclear Envelope Nuclear lamina Chromosomes Chromatin Neuleolus (rRNA) Ribosomes rRNA & Proteins Protein synthesis

Endomembrane system Endoplasmic Reticulum RER: has ribosomes, protein production SER: lipid synthesis, poison detox, carb metabolism Golgi Apparatus Modification of proteins & shipping Lysosomes (animal cells only) Hydrolytic enzymes in animal cells Vacuoles Food Central Contractile

Mitochondria & Chloroplasts Energy conversion Cristae ( surface area) Matrix Enzymes & DNA Chloroplasts Photosynthetic production of sugar Thylakoids, granum, stroma Peroxisome Single membrane Transfer H to O2

Cytoskeleton: Support, Motility & Regulation Motor Proteins Use ATP, movement of entire cell or cellular components Microtubules Shape, support, and a “track” for movement Centrosomes & Centrioles Microtubule organizing center 9 sets of triplet microtubules Cilia & Flagella Oars vs. undulating motion 9+ 2 microtubule arrangement Microfilaments (Actin) Structural role in cells Movement such as in muscle cells Intermediate Filaments

Extracellular Components & Cellular Connections Cell Wall Protection & support Primary: flexible Middle Lamella, glues cells together Secondary: strong & durable (wood) ECM Glycoproteins Integrins (cell signaling) Animal Tight Junctions cells pressed tightly Desmosomes cells held together Gap Junctions: cytoplasmic channels Plant Plasmodesmata Channel between cells, exchange of chemical environment