The Nucleus

--nuclear envelope contains pores for some things to enter and exit
-- chromatin is DNA and proteins, when the cell begins to divide, chromatin condenses and forms chromosomes
--DNA remains in the nucleus, it sends instructions to the cytoplasm via messenger RNA
--RNA directs the synthesis of proteins on ribosomes in the cytoplasm
--Nucleolus assembles ribosomes within the nuclues, ribosomes contain the "tools" to construct proteins

Endoplasmic Reticulum -- Transport System
(endoplasm means "within cytoplasm", reticulum means "little net"

--divides cell into compartments
--channels molecules through the cell's interior, like a little highway

Rough ER

--has ribosomes which give it its "rough" appearance
--functions in protein synthesis
--ER transports newly assembled proteins to the Golgi Apparatus

Smooth ER

--mostly contains enzymes that unction in lipid synthesis (such as hormones like estrogen and testosterone)

Golgi Apparatus -- Delivery System

--flattened stacks of membranes
--functions in collection, packaging and distribution of molecules made in the cell and used elsewhere
-- front end (cis) faces the ER, and the back end (trans) faces the cell membrane
--unprocessed proteins enter the Golgi apparatus, are processed and exit near the cell membrane for export
--the folded stacks are called cisternae

Jobs of the Golgi Apparatus (aka Golgi Complex)

1. separates proteins according to their destinations
2. modifies proteins (adds sugar and makes glycoproteins)
3. packages materials into vesicles which are exported outside the cell

Lysosomes - Intracellular Digestion Centers

--vesicles that are used to digest
--contain high levels of degrading enzymes (to "lyse" means to dissolve)
--recycle old and worn out cell parts
--"suicide sac"
--digest other particles taken in by phagocytosis
--this "food" is stored in food vacuoles, the lysosomes fuse with the vacuoles and release digestive enzymes
--found in animal cells

Ribosomes - Sites of Protein Synthesis

--each is compused of two subunits, one large and one small
--mRNA is "read" by the ribosomes and amino acids are assembled into proteins
--ribosomes are manufactured by the nuceolus inside the nucleus

--contains its own DNA, support for Endosymbiosis Theory
--singular is "mitochondrion"
--2 membranes, one smooth outer membrane, and an inner membrane folded into layers called cristae
--Cristae has two compartments: the matrix and the intermembrane space
--mitochondria divide before cell division, they are not synthesized like other cell parts
--function to store energy for cell use. Energy is stored in the form of ATP - adenosine triphosphate

Chloroplasts - Where Photosynthesis Takes Place (page 94)

--only found in plant cells
--has its own DNA, like mitochondrion
--functions to convert light energy to ATP
--consists of grana, closed compartments that are stacked
--thylakoids are the individual disk shaped compartments that make up the grana
--stroma is the fluid surrounded the thylakoids

Cytoskeleton - Support System (page 97)

Cell is not "just a bag in a bubble". Lots of internal fibers = internal "skeleton". Not rigid like bone; capable of being assembled, broken down in minutes. Allows cell movement, cell division, internal motion of compartments.

Composed of Microtubes & Microfilaments

Centrioles - Microtubule Assembly Centers

--usually occur in pairs arranged at right angles
--assemble microtubules which influence the cell shape and movement - part of the cytoskeleton
--also function in cell divisioin, mitosis
--only found in animal cells

Cilia & Flagella

--function in movement
-- 9+ 2 Arrangement of microbtubules

Vacuoles - Storage Areas

--in plants the vacuoles are large and centralized, storage of water makes the cell turgid
--in animals, they store food, water and other substances