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NOTES: 7.2 (Cell Structures & Functions)
Comparing the cell to a factory:
● each cell part (“organelle”) can be compared to a specialized machine in a factory;
● each part
towards the functioning of the cell as a whole…
Cell Organization:
● each eukaryotic cell can be divided into 2 major parts:
1)
;
2)
CYTOPLASM:
● CYTOPLASM: the portion of the cell outside the nucleus;
organelles suspended in cytoplasm
; all other
NUCLEUS:
● NUCLEUS:
(the coded instructions for making all of
the cell’s proteins);
● considered the
;
● nucleus is surrounded by a nuclear envelope
NUCLEAR ENVELOPE
● double membrane which encloses the nucleus;
● includes many nuclear pores (holes) which
CHROMATIN
● threadlike complex of DNA bound to proteins which
in eukaryotic cells
CHROMOSOMES
●
;
●human cells have
NUCLEOLUS
● spherical region in the nucleus
-
Organelles that Store, Clean Up, and Support:
● vacuoles & vesicles
● lysosomes
● cytoskeleton
VACUOLE:
●
(of water, salts, proteins, carbs);
● in animal cells, vacuoles are smaller than in plant cells
PLANT VACUOLES…
● may contain soluble pigments in some cells (red and blue pigments in flowers);
● help protect from predators by storing waste products that may also be poisonous compounds
● contractile vacuole: specialized vacuole that pumps excess water out of cell.
VESICLES:
● VESICLES: small, membrane-enclosed structures that
, or to and from cell surface
LYSOSOMES:
● the cell’s “clean-up crew”!
●
that break down macromolecules into smaller subunits;
●
;
● can destroy cells by breaking open all at once and digesting the cell from within
CYTOSKELETON:
● CYTOSKELETON:
; also involved in transport of
materials within the cell, as well as whole-cell movement
● includes protein filaments:
-microfilaments
-microtubules
MICROTUBULES & MICROFILAMENTS
●
● structural support to cell; maintain shape
●
Microfilaments:
● threadlike structures;
● made up of protein:
●
● microfilament assembly & disassembly allow amoebas & other cells to “crawl” along surfaces
Microtubules:
● thin, hollow cylinders made of protein:
●
;
● can serve as “tracks” to guide organelle movement;
● involved in
in cell division; make up
SPINDLE FIBERS / CENTRIOLES (in animal cells)
● responsible for movement of flagella & cilia
FLAGELLA and CILIA:
● FLAGELLA: longer usually single extensions;
● CILIA:
; wavelike motion used to sweep extracellular
material over/away from cell
Organelles that Build, Modify, and Transport Proteins:
● ribosomes
● endoplasmic reticulum
● Golgi Apparatus
RIBOSOMES:
●
-small particles of RNA & protein
-follow coded instructions from DNA
-made in the nucleolus
-cells especially active in protein synthesis often contain large #s of ribosomes
-may be free (in cytoplasm) or attached to the ER
ENDOPLASMIC RETICULUM (ER):
● extensive network of internal membranes
● used to
● can be
(ribosomes) or
(no ribosomes)
Rough ER:
● rough appearance due to ribosomes on outer surface;
● newly made proteins leave the ribosomes and are
●
;
;
Smooth ER:
● synthesizes lipids, phospholipids, steroids
● detoxifies drugs and poisons
GOLGI APPARATUS:
● stacked, flattened membranes
● finishes, sorts, packages and ships many cell products (a.k.a.
)
Organelles that Capture and Releas Energy:
● chloroplasts
● mitochondria
CHLOROPLASTS: (a.k.a. “the organelles that feed the world”)
●
;
●
(convert light energy into “food”, or chemical
energy)
MITOCHONDRIA:
●
● convert the
into usable energy packets for the cell
● the # in cells varies and is related to the cell’s metabolic activity (i.e. if a cell uses more energy, it will have more
mitochondria!)
Cellular Boundaries:
● cell wall
● cell membrane
● CELL WALL:
- semi-rigid structure outside of cell membrane of
;
(CELL WALL, cont.)
- in plants, consists of CELLULOSE fibers;
- provides support, limits cell’s volume, and protects against fungi and/or microorganism infection.
- most cell walls are porous enough to allow water, oxygen, carbon dioxide, etc. to pass through
CELL MEMBRANE:
What must a membrane do?
● let some things leave / enter cell
●
● be flexible as cell changes shape
● cell membranes form a LIPID BILAYER that is
&
;
● The cell membrane is composed of molecules called
.
-one end is strongly nonpolar (
);
-one end is extremely polar (
)
● the nonpolar lipid “tails” are repelled by polar water molecules; the polar “heads” of the molecules form hydrogen
bonds with water molecules.
● So, every phospholipid molecule orients so that its polar “head” faces water and its nonpolar “tails” face away...
two layers are formed with the tails facing each other...the result is called a
.
● Lipid bilayer membranes are:
● PERMEABLE to:
-nonpolar molecules:
-small polar molecules:
● IMPERMEABLE to:
-ions (
)
-large polar molecules:
3 Main Types of Membrane PROTEINS…
1.
2.
3.
1. Channels:
● a channel will transport only certain kinds of molecules...which gives the cell membrane its
nature
2. Receptor proteins:
●
from the cell’s environment
3. Cell surface markers:
● identify your body‘s cells as belonging to you (
)