Parts of the Cell
I.
II.
Cell Membrane: controls substances that pass in and out of the cell.
a. Selectively permeable: membrane that keeps out some materials
but allows others to pass.
b. All membranes are made of lipids and proteins
i. Phospholipid bilayer: hydrophilic heads point outward
while hydrophobic tails are pointed inward.
ii. Proteins: Integral and peripheral proteins. Play a role in
transporting substances through the membrane.
iii. Fluid Mosaic Model: Lipid bilayers behaves more like a
fluid than a solid.
Organelles: internal structures that form special functions for the
cell.
a. Cytoplasm: material between cell membrane and nucleus that
contains the organelles.
b. Mitochondria: “Powerhouse” of the cell. Produce ATP which
provides energy for the cell.
i. Cristae: inner membrane of the mitochondria which
provides more space for chemical reactions.
c. Ribosomes: Most numerous organelle in the cell. Not
surrounded by a membrane. Some are free floating and others
are attached to ER. They make proteins.
d. Endoplasmic reticulum: Functions as intracellular highway.
Molecules move along ER from one part of the cell to another.
i. Rough ER: ribosomes attached
ii. Smooth ER: no ribosomes attached
e. Golgi Apparatus: processing, packaging and secreting organelle
of the cell. Looks like flattened sacs. Modifies proteins for
export by the cell.
f. Lysosomes: Small organelles that contain enzymes which
digest proteins, carbs, lipids, DNA and RNA. Also digests
virus and bacteria that have been ingested by the cell.
g. Cytoskeleton: “Skeleton” of the cell; maintains shape and size.
i. Microfilaments: made up of actin and contribute to cell
movement.
ii. Microtubules: function in cell division.
h. Cilia and Flagella: hair-like organelles that assist in movement.
When hair-like structures are short and numerous, they are cilia.
When they are long and less numerous, they are flagella.
III.
i. Nucleus: control center of the cell. Stores hereditary
information and is the site where RNA is copied from DNA.
i. Nuclear envelope: Double membrane around nucleus.
ii. Chromatin: fine strands of DNA and protein.
iii. Chromosomes: densely packed and coiled chromatin.
iv. Nuclear pores: RNA passes out into cell through these
openings.
v. Nucleolus: Site where ribosomes are made and partially
assembled.
Plant Cells
a. Cell Wall: Rigid wall that is outside the cell membrane. Gives
support and protects the plant.
b. Vacuoles: fluid-filled organelles that store enzymes and
metabolic waste. Usually large.
c. Plastids: Surrounded by 2 membranes and contain DNA. Some
store starch while others absorb light.
i. Chloroplast: where photosynthesis occurs. Process takes
place in thylakoids. Contains large amounts of green
pigment.