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1. All cells
are microscopic
2. Human
cells vary widely in size (rbc = 7.5 um, ovum = slightly less than 1 mm.
3. Differ in
shape: flat, cuboidal, rectangular, round, disk shaped, thread-like, spindle,
etc.
B. Composition
1. Cytoplasm
with organelles surrounded by a plasma membrane
2. Three main
parts are:
a. Plasma
membrane – surrounds entire cell
b. Cytoplasm
– all “living matter” inside the cell except the nucleus; cell water +
organelles
c. Nucleus-
membrane bound, contains genetic information
C. Relationship
of cell structure and function
1. Every cell
does certain things to maintain it’s own survival
2. Every cell
does things to insure survival of the body, but these functions differ from
cell type to cell type:
3. Relationship
of structure to function apparent in number and type of organelles seen in
different cells
b. Sperm
cells - flagella
II. Structural
parts
A. Plasma
membrane
1. Double-layered
membrane of phospholipids containing proteins and cholesterol, 7-8 nm in diameter
2. Integral
and peripheral proteins
3. Receptors
and signals, tissue antigens
4. Selectively
permeable
1. Nuclear
envelope
a. Double
membrane, surrounds nucleoplasm
2. Nucleoplasm
like cytoplasm, contains:
a. Nucleolus
(1) Programs
formation of ribosomes in nucleus
(2) Ribosomes
then migrate through nuclear envelope to cytoplasm
b. Chromatin
granules
(1) DNA
(2) Chromosomes
– tightly coiled DNA
(3) Histones –
proteins that DNA is wrapped around
C. Cytoplasm
2. Organelles
a. Ribosomes
(1) May attach
to rough ER or lie free in cytoplasm
(2) Manufacture
proteins
(3) Often
called protein factories
b. Endoplasmic
reticulum
(1) Network of
connecting sacs and canals, from nucleus almost to cell membrane
(2) Rough and
smooth
(3) RER
collects and transports proteins made by ribosomes
(4) SER has
enzymes associated to make lipids; cholesterol, lipoproteins, phospholipids
(5) Vesicles
bud off and transport products to Golgi for processing and packaging
c. Peroxisomes
(1) Enzymes to
breakdown hydrogen peroxide, alcohol, formaldehyde
d. Golgi
apparatus
(1) Stacks of
flattened sacs near the nucleus
(2) Transport
vesicles from ER fuse with cis face
(3) Products
are modified and concentrated as they move from “plate” to “plate”
(4) Vesicles
bud off trans face and move to plasma membrane; fuse and are relased to outside
of cell
e. Mitochondria
(1) Powerhouse
of the cell – ATP from cellular respiration
(2) Double
membrane, inner highly convoluted
(3) Folds
contain enzymes for cellular respiration
f. Lysosomes
(1) Digestive
bags – stomachs of the cell
(2) Membranous
sacs with hydrolytic enzymes
(3) Digest
worn out cell proteins, phagocytized material
(4) If
membrane ruptures contents digest cell – sucide bags
g. Centrioles
(1) Paired
(2) Lie at
right angles to each other
(3) Composed
of tubules, rod or barrel shaped
(4) Function
in cellular reproduction
(5) Found near
the nucleus in the MOC
h. Cilia
(1) Fine
hairlike extensions on surface of some cells
(2) Move in
wave like fashion to move substances over the surface fo the cell
i. Flagella
(1) Single
projection extends from surface of cell
(2) Much
larger than cilia
(3) Moves in
whiplike fashion to propel cell
(4) In humans
only sperm have flagella (tail)
A. Passive
transport process
1. Diffusion
– movement from an area of high to low concentration
3. Dialysis –
solutes across the selectively permeable membrane
4. Filtration
– hydrostatic pressure
B. Active
transport process
1. Require
energy (ATP) – push against a
concentration gradient
2. Ion pumps
a. Move specific ions across the cell membrane
against their concentration gradient
b. May be
coupled to other ion pumps; sodium/potassium pump
c. May also
be coupled to transport proteins that act as carriers to get large
lipid-insoluble substances into the cell
a. Cell
eating and drinking
b. Engulf
particles; phagocytosis for large insoluble particles, pinocytosis for small
dissolved substances
4. Exocytosis
– extrude substances to exterior, secretion