Cell TheoryRobert Hooke: saw “little rooms” when examining cork with his self-made microscope.

- cells

Four main principles:1. all organisms consist of one or more cells2. cells are the smallest living things3. today’s life is a continuous line of descent4. all cells come from cells

Cells are limited in size- surface-to-volume ratio important

- surface area

A cell is a sack of rich broth containing salts, minerals, and organic compounds.

1. Is filled with cytoplasm2. Contains many substructures

A cell is a sack of rich broth containing salts, minerals, and organic compounds

1. Is filled with cytoplasm2. Contains many substructures

Cells are active and vital

Main components of the cell1. Cell membrane (plasma membrane)

Regulates movement of substances into and out of cellSome molecules may pass freely acrossSome molecules may not pass freely acrossSelective permeability

2. CytoplasmColorless liquid that fills cellOrganelles found within - each with a specific functionOrganelles surrounded by membranes

Cell Membrane• Composition

a. Lipids, proteins, carbohydrates

b. Primary component = phospholipids

c. Embedded proteins

2. lipid bilayera. phospholipidsb. nonpolar fatty acids turn away from H2Oc. polar heads turn toward H2O

3. Embedded membrane proteinsa. most are transmembrane

3. Embedded membrane proteinsa. most are transmembraneb. selective transportc. some are enzymes

i.e., for neurotransmitters and hormonesd. some are receptors for signal transduction

• Fluid Mosaic Model1. Plasma membrane is not a “solid” structure.

2. Individual lipid and protein molecules are not covalently bonded together.

3. The lipid bilayer acts like a 2-D fluid.4. Some of the proteins are “floating” and can move about.

Cell TypesProkaryotes (bacteria)

1. simple2. have no organelles3. have some substructures

Cell TypesEukaryotes

1. have membrane-bound organelles2. DNA is found inside a nucleus3. are larger

Cytoskeletonmade up of protein fibers

Functions of Cytoskeletona. Support the cell like a “skeleton”b. Maintains cell shapec. Movementd. Connects organelles

Microtubules1. Hollow cylindrical structures

- made up of individual subunits (tubulins)

Microtubules1. Hollow cylindrical structures

- tubulins

2. Support

“scaffolding”all cells would otherwise form a sphere

Microtubules1. Hollow cylindrical structures

- tubulins

2. Support

“scaffolding”all cells would otherwise form a sphere

3. Provide the “machinery” for cellular movement- cilia and flagella made of microtubules- also used to move organelles and chromosomes within cells

Microfilaments1. Solid rods of protein

- actin is the primary one

2. Responsible for contraction in muscle cells

3. Found in virtually all cells

Motility• Cilia

hair-like projections on surface of cell

found on cells lining certain body passages

used by some single-celled organisms to “swim”

tracheaoviduct

Motility• Flagellum

long whip-like “tail”propulsion through liquid

Motility• Cilia

• Flagellum

hair-like projections on apical surface of cellfound on cells lining certain passages

tracheaoviduct

long whip-like “tail”sperm propulsion

• Similar composition9 + 2 arrangement of microtubulesaxoneme