A. The cell is the basic unit of life

B. Cell Theory

1. All organisms are made of cells
2. All cells are made from other cells

C. Some organisms are unicellular; some are multicellular

D. Cells are small

1. some exceptions - bird eggs, some neurons, some species of algae
2. cells must exchange materials with their environment
3. for this exchange to work well, cells require a large surface area relative to their volume.

E. Cells are either prokaryotic or eukaryotic

1. prokaryotes are organisms with prokaryotic cells.
2. eukaryotes are organisms with eukaryotic cells

F. Prokaryotes

1. Domain Bacteria
a. Kingdom Eubacteria
2. Domain Archea
a. Kingdom Archebacteria
3. All prokaryotes are unicellular, but many form chains, filaments, colonies, etc.

G. Eukaryotes

1. Domain Eukarya
a. Kingdom Protista
b. Kingdom Plantae
c. Kingdom Fungi
d. Kingdom Animalia
2. Some eukaryotes are unicellular; some are multicellular

H. Some characteristics common to all cells

1. DNA and ribosomes
2. cytosol and cytoplasm
3. plasma membrane

I. Charactaristics of prokaryotic cells

1. true nucleus absent
2. nucleoid present
3. no separate, membrane-bound organelles
4. usually smaller than eukaryotic cells

J. Characteristics present in many (but not all) prokaryotic cells

1. cell wall
2. outer membrane
3. capsule
4. photosynthetic membranes
5. mesosomes
6. flagella
7. pili

K. Characteristics of eukaryotic cells

1. true nucleus present
2. nucleoid absent
3. many separate, membrane-bound organelles present
4. usually larger than prokaryotic cells
5. cytoskeleton present

L. endosymbiont hypothesis

1. Lynn Margulis - U. Mass., Amherst
2. mitochondria and chloroplasts have
a. double membranes
b. their own DNA
c. their own ribosomes, which are similar to prokaryote ribosomes
3. some modern cells contain smaller endosymbiotic cells

M. Organelles are structures inside cells that have specific shapes and functions

1. many, but not all, organelles are enclosed by membranes
2. organelles are found in both prokaryotic and eukaryotic cells

N. Selected differences between plant and animal cells

1. cell wall - present around plant cells; absent from animal cells
2. chloroplasts - present in some plant cells; absent from animal cells
3. centrioles - present in animal cells; absent from plant cells

O. The endomembrane system of eukaryotic cells

1. mainly includes these organelles
a. endoplasmic reticulum
b. golgi apparatus
c. lysosomes
d. vacuoles
2. endoplasmic reticulum (ER)
a. lumen - space inside ER
b. rough ER has ribosomes on outer surface of membrane
c. smooth ER lacks ribosomes on surface
3. functions of rough ER
a. transporting proteins produced by ribosomes on surface of rough ER
b. here proteins fold into tertiary structure
4. functions of smooth ER
a. protein transport and modification
b. synthesis of phospholipids, steroids, fatty acids
c. detoxification of harmful substances
5. golgi apparatus
a. cisternae - the flattened sacs
b. lumen - space inside cisternae
c. cis side - near rough ER (or sometimes near nucleus)
d. trans side - near plasma membrane of entire cell
e. vesicles - transport rough ER products to golgi; transport golgi products to other parts of cell or outside cell
6. functions of golgi apparatus
a. protein storage
b. protein modification
c. protein packaging
7. lysosomes
a. originally formed as vesicles from golgi apparatus
b. contain digestive enzymes that help break down organic molecules
8. functions of lysosomes
a. digesting food molecules
b. recycling damaged organelles
c. destroying harmful bacteria
d. apotosis
9. vacuoles
a. can be large or small
b. filled with aqueous solutions
c. formed by vesicles from rough ER and golgi apparatus
d. note that our text excludes them from endomembrane
10. functions of vacuoles
a. some are contractile
b. some contain pigments
c. some contain cellular waste products and toxins

P. Cytoskeleton

1. microfilaments
2. intermediate filaments
3. microtubules
4. all cytoskeletal elements are made of proteins
a. microfilaments - actin (G actin)
b. intermediate filaments - fibrous proteins like keratin
c. microtubules - tubulin
5. functions
a. microfilaments
- cytoplasmic streaming (cyclosis)
- cytokinesis in animal cells
- muscle contraction
- cell movement
b. intermediate filaments
- mostly structural support
c. microtubules
- mitosis and meiosis
- found in cilia, flagella, basal bodies and cenrioles

Q. Other important organelles

1. nucleus
2. mitochondrion
3. chloroplast
4. peroxisome
5. glyoxisome

R. Plasmodesmata are channels that extend through the cell walls to plants to connect adjacent cells

S. Animals have extra cellular matrix

1. the composition and extent of this matrix varies in different regions of the body
2. example: bone is composed mostly of extracellular matrix that includes collagen fibers and calcium phosphate