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The Cellular Basis of Life Historical contributions Modern Cell Theory Types of Microscopes Micrographs Cell membranes Membrane transport Nucleus Organelles

Contributors to Our Knowledge of Cells Anton von Leeuwenhoek Assembled the first microscope Robert Hooke Observed and named “cells” Robert Brown Discovered the nucleus. Schleiden and Schwann Determined that all plants and animals are made of cells. Rudolf VirchowCells come only from pre-existing cells.

Modern Cell Theory 1.All living things are made of cells. 2.Cells are the basic structural unit (ie, building blocks) of life (plant, animal, bacterial, etc.) 3.All cells come from other (pre-existing) cells. 4.The way a cell is made is determined by its function (ie, what it has to do) = principle of complementarity

Visualizing Cells Done using microscopes. Different types –Compound light microscope –Compound light microscope: most common. Passes beam of light through specimen. Contains more than one lens and magnifies up to 1000 times. Can be used to view living organisms.

EYEPIECE OCULAR LENS (inside) REVOLVING NOSEPIECE COARSE ADJUSTMENT KNOB FINE ADJUSTMENT KNOB STAGE DIAPHRAGM LIGHT SOURCE

“Compound” lenses… COMPOUND MAGNIFICATION!! Which combination would show the largest AREA? Which combination would you use to examine details? Eyepiece Lens Objective Lens Total Magnification 15x 10x 20x40x

Compound Micrographs

Electron Microscopes TRANSMITTING = TEM Specimen is thinly sliced. Electrons pass through and image forms on fluorescent screen. SCANNING = SEM Specimen is coated with metal (Os,Pb,Au) Electrons bounce off surface to form image. Concentrates a beam of electrons within a vacuum; magnifies up to 1,000,000 times. Used to view much smaller organisms.

Sample Electron Micrographs

Types of Cells PROKARYOTE Smaller, more primitive Bacteria Fewer organelles No nucleus; instead has nucleoid region EUKARYOTE Larger (~10 x) Complex inner membrane system More organelles Contains a true nucleus

*Nucleus *Endomembrane system *Mitochondria *Chloroplasts Key features of Eukaryotic Cells:

What molecule is this?

The Fluid Mosaic Model of the Cell Membrane. AMPHIPATHIC: having both hydrophilic and hydrophobic areas

Cell Wall Found outside the cell membrane in PLANTS, FUNGI, and BACTERIA. Plants use pressure against the cell wall (called turgor pressure) to help support it.

The Nucleus “Control center” of the cell Contains DNA which determines cell activity through the manufacture of proteins

The rest of the cell … Cytoplasm - semi-liquid material which fills the space between the membrane and the nucleus. Contains structural fibers called microfilaments. Contains “little organs” (organelles) which each have a specific job to do.

Organelles RibosomesNot bound by a membrane Assemble proteins Endoplasmic reticulum May be rough or smooth Process and transport proteins Golgi apparatusModify proteins and ship to new site Contain special enzymes to attach carbohydrates or lipids to proteins delivered by the ER VacuolesSites for storage of materials Animals store proteins, fats or carbohydrates; plants store water or salts.

Organelles, continued Lysosomes Sacs filled with chemicals and enzymes. Attach target, release enzymes which recycles components. Mitochondria Powerhouse of the cell; double membrane allows maximum surface area. Produces energy (ATP) for cellular activities using a carbohydrate source. Nucleolus Dark area found inside the nucleus of eukaryotic cells. Produces ribosomes. PlastidsStorage sacs.Contain starch, pigments, ChloroplastsContain chlorophyll Important in photosynthesis. Found only in plants, algae.

Cell Permeability

Membrane Transport Mechanisms PASSIVE TRANSPORT Powered by the concentration gradient Must move down the gradient from [high] to [low] Examples: diffusion At equilibrium, concentration is equal on both sides. Osmosis = diffusion of water Facilitated diffusion = uses carrier molecule (ex: membrane protein) ACTIVE TRANSPORT Requires the use of ATP Can move up the gradient Examples: ion pumping Bulk transport –EXOcytosis moves material OUT of the cell –ENDOcytosis moves material INTO the cell »Water in = pinocytosis »Food in = phagocytosis

Vesicle-Mediated Transport

What process is this?

Tonicity Solution is HYPOTONIC Solution is HYPERTONIC

Complexity of Organisms Single-celled organisms are unicellular. Other organisms are multicellular. In order to maintain complexity, there must be a hierarchy of structure. Cells form tissues which form organs; Organs are arranged into organ systems which all combine to form the organism.