7-2 : Plasma Membrane and
Cell Structures
Plasma
Membrane of
aveolar sac
But first...
Let’s Review
What is cell theory?
Light microscopes vs. electron
microscopes
Prokaryotic vs. eukaryotic
Basic Cell Structures
Cell Membrane
Cell Wall
Nucleus
Cytoplasm
VOCABULARY
Chromatin
Chromosome
Nucleolus
Nuclear envelope
Cytoskeleton
Microtubule
Microfilament
Endoplasmic Reticulum
Golgi Apparatus
Lysosome
Vacuole
Chloroplast
Mitochondrion
Ribosome
Plasma Membrane
Boundary between
cell and
environment
Allows for nutrients
to enter and exit
cell
Maintains cell’s
homeostasis
Nerve cell plasma membrane
How does plasma membrane
maintain homeostasis?
Selective permeability
– Allows certain molecules in while keeping
others out
– Water usually enters/exits cells freely
– Ion (e.g. Ca and Na) allowed in at certain
times
Structure of PM
Composed of 2
layers of
phospholipids (oh
no…not again!)
Phospholipids
– Hydrophilic head (outside of cell)
– Hydrophobic tail (inside of cell)
– These form a barrier and do not allow waterwatersoluble molecules to pass through
Fluid mosaic
Thin flexible layer
What else is in the plasma
membrane?
Cholesterol
– Aids in phospholipid stability by preventing
them to stick together
Proteins
– Transport proteins
Help with allowing nutrients come in and wastes
exit cell
– Cell identification
– Cell structure and support
Cytoplasm
Material inside the
cell membrane but
not including the
nucleus
Cytoplasm
Cell Wall
in some cells, including plants,
algae, fungi, and nearly all prokaryotes (NOT
animal cells)
Found
Surrounds
the cell
membrane (allows water
and gases to pass
through)
Provides support and
protection for the cell
Nucleus
Nucleus (pl. Nuclei)
– Large structure that
contains the genetic
information (DNA) and
controls the cell’s
activities
DNA contains the instructions for
making proteins
*the nucleus is important because making
proteins is one of the main functions of
cells
Way
to go
DNA!
CHROMATIN &
CHROMOSOMES:
Chromatin: DNA chain wound
around a protein visible DNA
(looks granular—is spread
throughout the nucleus)
Chromosomes: when a cell
divides, chromatin continues to
condense into these structures
these are distinct
structures
NUCLEOLUS:
•Dense region inside most nuclei
(looks darker)
•Ribosome assembly begins here
NUCLEAR ENVELOPE:
•Double-membrane layer which surrounds
nucleus
•Thousands of pores allow material into and out of
the nucleus
Nucleus
Cytoskeleton
Network of protein filaments that helps the
cell maintain shape & move around
Help in cell division!!!
Ribosomes
Ribosomes are made
of RNA & protein
Proteins are
assembled (made)
here
Proteins are produced
following the specific
code in DNA
ENDOPLASMIC RETICULUM (ER):
•Some proteins are modified
•Components of the cell membrane are assembled
ROUGH ER: ribosomes on the ER make
proteins & these new proteins move into the
ER where they may be chemically modified
SMOOTH ER: no ribosomes; contains
specialized enzymes that perform specific
tasks (ex: make lipids)
What’s
missing??
Real Picture…
“Fake” Picture
GOLGI APPARATUS:
• Proteins produced by Rough ER
ribosomes move into these sac-like
structures
• Enzymes attach carbohydrates & lipids
to the proteins
• These proteins are then sent to their
final destination
Lysosomes
Filled with
digestive
enzymes: break
down carbo’s,
lipids, & proteins
for use by cell
Break down old
cells
Vacuoles
Store materials
like water, salts,
proteins, &
carbo’s for the
cell
Large central
vacuole in plants
is the reason
plants are rigid!
•PLANTS ONLY!
•Use energy from sun to make
glucose (photosynthesis)
•Visible stacks of membranes
Mitochondria
• Release energy from
food—cell uses that
food—
energy to power
growth, movement,
etc.
Cilia and Flagella
Aid in locomotion or
feeding