Cell Theory 1.All living things are composed of cells. 2.Cells are the simplest form of life 3.All cells come from preexisting cells.

Compound Light Microscope

Different methods for seeing cell structures. TECHNIQUE RESULT Brightfield (unstained specimen). Passes light directly through specimen. Unless cell is naturally pigmented or artificially stained, image has little contrast. (a) Brightfield (stained specimen). Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved). (b) Phase-contrast. Enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells. (c) 50 µm

Scanning Electron Microscope …provides for detailed study of the surface of a specimen TECHNIQUE RESULTS Scanning electron microscopy. Micrographs taken with a scanning electron microscope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps move inhaled debris upward toward the throat. (a) Cilia 1 µm

Transmission Electron Microscope provides for detailed study of the internal structure of cells Longitudinal section of cilium Cross section of cilium 1 µm

All cells have several basic features in common. 1.bounded by a plasma membrane 2.contain a semi-fluid substance called the cytoplasm. 3.contain chromosomes 4.all have ribosomes

Prokaryote vs. Eukaryote Cells prokaryotic Do not contain a nucleus Have their DNA located in a region called the nucleoid eukaryotic Contain a true nucleus, bounded by a membranous nuclear envelope Have extensive and elaborately arranged internal membranes, which form organelles Are generally quite a bit bigger than prokaryotic cells

Animal Cell

Plant Cell

Plant Cell Structure Onion Cells Elodea with chloroplasts

Surface to Volume Ratio Smaller cells have a higher surface to volume ratio. This facilitates the exchange of materials into and out of the cell. Surface area increases while total volume remains constant 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)

Cell Membrane

Phospholipid Bilayer w/ Proteins

Plasma (cell) Membrane Functions as a selective barrier Allows sufficient passage of nutrients and waste Outside of cell Inside of cell Hydrophilic region Hydrophobic region Hydrophilic region (b) Structure of the plasma membrane Phospholipid Proteins TEM of a plasma membrane. The plasma membrane, here in a red blood cell, appears as a pair of dark bands separated by a light band. (a) 0.1 µm

Mitochondria

Chloroplasts

Ribosomes in the Endoplasmic Reticulum

Ribosomes

other miscellaneous structures/functions golgi apparatus- distributes molecules within the cell. lysosomes- digest/recycle obsolete cell organelles. Not found in plant cells. vacuoles- store materials in the cell. cytoskeleton- “cyte” = cell – support, protein fiber construction.

Cytoskeleton