Download Notes-Organelles - Svetz-wiki

The Parts of the Cell
The Nucleus
--nuclear envelope contains nuclear pores for some things to enter
and exit (nucleoplasm within)
-- 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 nucleus, 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
--the folded stacks are called cisternae
--unprocessed proteins enter the Golgi apparatus from ER
proteins are packaged and exported near membrane
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 - secretion
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" - apoptosis
--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 composed 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 nucleolus inside the nucleus
--polyribosomes – strings of ribosomes in the cytoplasm that work
to make a protein
Other Organelles
-- Peroxisomes – result in hydrogen peroxide, broken down by
catalase
-- Vacuole -- mainly storage or specific functions (contractile
vacuole)
-- Plant cells have a CENTRAL VACUOLE - used for storage and
help to maintain hydrostatic pressure
ENERGY RELATED ORGANELLES
Mitochondria - The Cell's Chemical Furnaces
--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
TAY-SACHS disease – missing an
enzyme of the lysosomes that breaks
down a fatty substance. Over time this
fat builds up in the brain and nervous
tissue, smothering the cells. Results in
degeneration and death.
Chloroplasts - Where Photosynthesis Takes Place
--only found in plant cells
--has its own DNA, like mitochondrion
--functions to convert light energy to carbohydrates
--carbohydrates then broken down in mitochondria to produce
ATP
--consists of grana, closed compartments that are stacked
--thylakoids are the individual disk shaped compartments that
make up the grana (stack of thylakoids)
--stroma is the fluid surrounded the thylakoids
*Chloroplasts are a type of plastid
Chromoplasts – red, yellow and orange pigment
Leucoplasts – colorless (potatoes)
Cytoskeleton - Support System
Microfilaments (now called actin filaments) – occur in bundles,
form tracks within the cell for the movement of organelles, used to
form pseudopods (ameba)
Intermediate filaments - support membrane, cell to cell junctions
Microtubules - (little pipe) – regulated by the MTOC (microtubule
organizing center), radiate from the centrosome - form the spindle
during cell division
Centrioles – used during cell division to move and separate
chromosomes, only found in animal cell
Related to Movement
Pseudopod – extensions of the cell that allow for movement
(ameba), depend on actin filaments
Cilia (hair) & Flagella (whip)
--function in movement
-- 9+ 2 Arrangement of microtubules