Cell Theory

1) Cells are the fundamental units of life.

2) All organisms are composed of cells.

3) All cells come from preexisting cells

What are the three reasons why the cell theory is so important?

1) Studying cell biology is in some sense the same as studying life.

2) Life is continuous.

3) The origin of life was marked by the origin of the first cells.

Surface area-to-volume ratio

Determines cell size

--As an object increases in volume, its surface area also increases, but not to the same extent

--It is an advantage for small cells

Light Microscope

--uses glass lenses and visible light to form a magnified image of an object

         - cell sizes

         - cell shapes

         - internal structures

Electron microscope

--uses electromagnets to focus an electron beam on an object

       - can see subcellular structure

prokaryotic cells

Nucleoid

contains the hereditary material (DNA) of the cell

prokaryotic cell

cytosol

consists mostly of water that contains dissolved ions, small molecules, and soluble macromolecules such as proteins

prokaryotic

Ribosomes

complexes of RNA and proteins; are the sites of protein synthesis

prokaryotes (most)

Cell Wall

supports the cell and determines its shape

prokaryotes (some)

Internal Membranes

folds into the cytoplasm to form an internal membrane system that contains compound needed for photosynthesis

prokaryotes (some)

Flagella

used for motio and is attached to plasma membrane

prokaryotes (some)

Pili

short harlike projections that are used for attaching to other bacteria

prokaryotes (some)

Cytoskeleton

-- maintains cell shape

--filaments similar to thos made of actin (eukaryotes)

Eukaryotes

Nucleus

contains most of the cell's genetic material (DNA)

Eukaryotes

Mitochondria

 "a power plant and industrial park", where energy stored in the bonds of carbs and fatty acids is converted into aform more useful to the cell (ATP)

eukaryotes

Endoplasmic Reticulum (ER) & Golgi Apparatus

compartments in which some proteins synthesized by the ribosomes are packaged and sent to appropriate locations in the cell

eukaryotes

Lysosomes & Vacuoles

cellular digestive systems in which large molecules are hydrolyzed into usable monomers

eukaryotes (some)

Chloroplasts

perform photosynthesis

eukaryotes

Cytoskeleton components

1) Microfilaments - help cell/parts move, give cell shape; made of actin; extend pseudopodia

2) Intermediate filaments - composed of keratin; stabilize cell structure, resist tension

3) Microtubules - (long hollow cylinders) form rigid internal skeleton, framework for motor proteins; made of tubulin; 13 dimers surround inside of microtubule

Plant cell wall  vs. extracellular matrix

cell wall (plants)

--provides structure and support; barrier to infection; grows as plant cells expand

extracellular matrix (animals)

--holds cells together; contributes to physical properties of cartilage, skin, other tissues; helps filter materials; orients cell movements; plays a role in chemical signaling from one plant to another

Endosymbiosis theory

The theory that the eukaryotic cell evolved by the engulfing of one prokaryotic cell by another

Simalarities of prokaryotes and eukaryotes

Both:

- use nucleic acids as their genetic material

- use the same 20 amino acids in their proteins

- use D sugars and L amino acids