Chapter 4 Cells 1 Overview Basic functional unit

Chapter 4 Cells

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 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 3 D image Transmission Electron Microscope – TEM Cell ultrastructure – organelles and internal parts

10 m 1 m Light Length of some nerve and muscle cells 0. 1 m Chicken egg Unaided eye Human height 1 cm Frog egg 10 µm Most plant and animal cells nucleus Most bacteria 1 µm 100 nm Mitochondrion Smallest bacteria Viruses Ribosomes 10 nm Proteins Lipids Transmission Scanning 1 nm 0. 1 nm Small molecules Atoms Electron microscope 100 µm Light microscope 1 mm

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 • Simple • Smaller – ~1 -10 micrometers • Nucleiod – no nucleus – Plasmid – circular chromosome • No membrane bound organelles – Has ribosomes – not membrane bound • Cell wall: peptidoglycan Eukaryotes – true nucleus • 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 • 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 Surface area increases while total volume remains constant 5 1 1 Total surface area (height width number of sides number of boxes) 6 150 750 Total volume (height width length number of boxes) 1 125 Surface-to-volume ratio (surface area volume) 6 12 6

SA to Volume • Calculate the surface area and volume of a cube that is 3 cm x 3 cm. • Now give the SA to volume ratio – SA: 6(3 cm x 3 cm) = 54 cm 2 – V: 3 cm x 3 cm = 27 cm 3 – 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 (r. RNA) • Ribosomes – r. RNA & 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 • Mitochondria – Energy conversion – Cristae ( surface area) – Matrix • Enzymes & DNA • Chloroplasts – Photosynthetic production of sugar – Thylakoids, granum, stroma – Enzymes & DNA • Peroxisome – Single membrane – Transfer H to O 2

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 – Structural role in cells

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