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Cell Structure and Function
Cell
Structure
Cell
membrane
(Plasma
membrane)
Location-Structure
Forms outer boundary of
cell;
Forms membrane-bound
organelles
Function
Semi-permeable (restricts the
access of certain compounds
and ions)
Prokaryote/
Eukaryote
Both
Aids in maintaining the complex
internal organization of a cell
Cytoplasm
Everything between the
nuclear envelope (nucleoid
region in prokaryotes) and
the cell boundary
Cytosol
The semi-fluid portion of the
cytoplasm
Nucleus
10% of the volume of the cell
Mission control—manages
protein synthesis
Eukaryotes
only
Nucleolus
Small dense spheres within
the nucleus (often 2-3
visible)—tightly coiled
regions of the DNA
Genes for ribosomal RNA
(building block of ribosomes)
Eukaryotes
only
Nuclear
envelope
Porous double-membrane
organelle;
Protects the DNA
Eukaryotes
only
Forms outer boundary of
nucleus
Bound
ribosomes
Small dense granules (each
has a large and a small
subunit) made of proteins
and rRNA;
Site of most chemical reactions
of life
Both
Both
mRNA exits the nucleus
through pores after
transcription
Site of protein synthesis
Eukaryotes
only
Ribosomes build proteins
Attached to endoplasmic
reticulum;
Can become free;
Part of the endomembrane
system
Free
ribosomes
Small dense granules (each
has a large and a small
subunit) made of proteins
and rRNA;
Suspended in cytosol;
Can become bound
Site of protein synthesis
Ribosomes build proteins
Both
Rough
endoplasmic
reticulum
Network of membranous
tubes dotted with bound
ribosomes;
Loosely surrounds the
nucleus;
Part of the endomembrane
system
Smooth
endoplasmic
reticulum
Network of membranous
tubes;
Loosely surrounds the
nucleus;
Modify proteins
Eukaryotes
only
Many proteins are modified
here by cleaving the
polypeptide, forming quaternary
structures, removing amino
acids or adding non-protein
substances (e.g. enzymes
often require a metallic ion to
work)
Makes carbohydrates and lipids
Eukaryotes
only
(e.g. the SER of liver cells
convert glucose to glycogen,
and make triglycerides and
cholesterol)
Part of the endomembrane
system
Transport
vesicle
Membrane-bound bubble;
Buds off both RER and
SER;
Moves modified proteins, lipids,
and carbohydrates to cis face
of Golgi apparatus
Eukaryotes
only
Receives compounds from ER;
Eukaryotes
only
Part of endomembrane
system
Golgi apparatus
Network of membranous
tubes;
Located closer to cell
boundary than ER;
Attaches a chemical “address
label” for compounds destined
for export
Cis face toward nucleus;
Trans face toward cell
membrane;
Part of the endomembrane
system
Secretory
vesicle
Membrane-bound bubble;
Buds off trans face of Golgi
apparatus;
Part of endomembrane
system
Moves finished compounds to
cell membrane for export
Eukaryotes
only
Lysosome
Membrane-bound bubble
containing hydrolytic
enzymes;
Cell’s stomach;
Eukaryotes
only
Merges with food vacuole and
digests organic compounds;
Buds off Golgi apparatus
Autophagy (recycles old and
damaged organelles and
cytosol);
Apoptosis (programmed cell
death/self-destruction)
Food vacuole
Membrane-bound bubble;
Buds off cell membrane
Transports food particles and
captured microbes from outside
the cell into cytoplasm;
N/A
Fuses with lysosome
Mitochondrion
Double membrane bound
organelle;
Inner membrane called
cristae;
Aerobic cellular respiration;
Eukaryotes
only
Harvests chemical energy from
organic monomers and stores
the energy in ATP
Semi-fluid interior called
matrix;
Has own DNA and proteinmaking machinery
Descendent of free-living
prokaryote
Chloroplast
Double membrane bound
organelle;
Inner membrane discs
called thylakoids;
semi-fluid space
surrounding thylakoids
called stroma;
Has own DNA and proteinmaking machinery
Descendent of free-living
prokaryote
Photosynthesis;
Harnesses light energy and
uses it to build sugar
Eukaryotes
only
(Plants and
Photosynthes
izing Protists)
Cytoskeleton
All through cytoplasm
Three filament types (Listed
below)
Gives shape to cell; Supports
organelles;
Aids in motion and cell division;
Moves material (organelles)
through cytoplasm
Actin Filaments
One kind of cytoskeletal
element;
Most often located just
below cell membrane;
Movement (e.g. Amoeba
pseudopods, cytoplasmic
streaming, formation of
cleavage furrow, microvilli
extension and retraction)
Eukaryotes
only
Internal monorail system for
moving organelles through
cytoplasm;
Eukaryotes
only
Twisting strand of globular
actin subunits
Microtubules
One kind of cytoskeletal
element;
Spread through out
cytoplasm;
Small hollow tube built of
tubulin dimers
Intermediate
filaments
components of centrosome,
centrioles, cilia, and flagella;
Microtubules are the spindle
fibers that move the
chromosomes in cell division
One kind of cytoskeletal
element;
Scaffolding that supports
organelles;
Spread through out
cytoplasm;
Gives shape to cells
Eukaryotes
only
Anchored to cell membrane
and organelles
Centrosome
(Microtubule
Organizing
Center
[MTOC])
Within cytoplasm;
Centriole
Small pair of hollow tubes;
In animal cells the location
is covered by a pair of
centrioles
Built of microtubules
Organized into a 9+0
arrangement
Covers centrosome in
animal cells
Region of the cytoplasm that
makes spindle fibers for cell
division
Associated with cell division but
not necessary
Eukaryotes
Eukaryotes
(Animal cells)
Cilia
Small oar-like structure
projecting outside the cell
membrane;
Built of microtubules (9+2
arrangement);
Synchronized rhythmic rowing;
Eukaryotes
Movement for single-celled
microbes;
Ciliary escalator in trachea
Basal body has 9+0
arrangement like centriole
Flagella
Long whip-like tail
projecting outside the cell
membrane;
Wiggles back and forth moving
cell through liquid;
Sperm cells have a flagellum
Both
(prokaryotic
flagella are
different in
structure and
motion
[rotary])
Large membranous sac in
plant cells;
Maintains structural integrity of
plant cells (turgidity);
Eukaryotes
(Plants only)
Takes up most of the space
in cytoplasm
Water storage;
Built of microtubules (9+2
arrangement);
Basal body has 9+0
arrangement like centriole
Central
Vacuole
Alkaloid storage;
Pigment storage
Perioxisome
Small membrane bound
organelle in aerobic
eukaryotes
PLASMA MEMBRANE
Catalase enzymes in organelle
convert hydrogen peroxide
(slightly toxic intermediate
metabolite of superoxide free
radical breakdown) to water
and oxygen gas
Eukaryotes
NUCLEUS, NUCLEAR ENVELOPE, NUCLEAR PORES
GENERALIZED ANIMAL CELL
GENERALIZED PLANT CELL
BOUND AND FREE RIBOSOMES
RER AND SER
GOLGI APPARATUS
LYSOSOME
MITOCHONDRION
CHLOROPLAST
PEROXISOME
CENTRIOLES
FLAGELLA AND CILIA
MICROTUBULES
ACTIN FILAMENT
INTERMEDIATE FILAMENT
Trace the path of the production of a protein from the DNA in the nucleus to its
secretion outside the cell. (endomembrane system). Explain the function of each
member.
Proteins are synthesized by the bound ribosome. The resulting protein is modified
(glycoprotein is attached, plus any other modifications) by the rough endoplasmic
reticulum. A small section of the RER containing the protein pinches off the end
enclosing the protein inside a transport vesicle. The transport vesicle moves to the
Golgi apparatus where it fuses with the cis face of the Golgi apparatus. The protein
receives a chemical address label (glycoprotein is modified) as it is moved through
the layers of membranous sacs of the Golgi apparatus. On the trans face of the Golgi
apparatus the finished protein is enclosed inside a secretory vesicle that moves to
the cell membrane and dumps the protein out of the cell.
Secretory vesicle
Lipids or carbohydrates are synthesized by the smooth endoplasmic reticulum. A
small section of the SER containing the compound pinches off the end enclosing the
protein inside a transport vesicle. The transport vesicle moves to the Golgi apparatus
where it fuses with the cis face of the Golgi apparatus. The compound receives a
chemical address label (glycoprotein is modified) as it is moved through the layers of
membranous sacs of the Golgi apparatus. On the trans face of the Golgi apparatus
the finished compound is enclosed inside a secretory vesicle that moves to the cell
membrane and dumps the compound out of the cell.
Explain the endosymbiosis theory.
Mitochondria and chloroplasts have many characteristics that make them look like
prokaryotic cells (see table below). Lynn Margulis hypothesized that these two
energy-producing organelles were once free-living prokaryotes with a special talent
that were engulfed but not digested by a larger prokaryote. A mutalistic relationship
developed. The smaller aerobic cellular respiring bacterium was protected and in
return the larger symbiont was supplied with energy. In plants and photosynthesizing
protists, symbiotic cyanobacteria were added to the mix making the larger symbionts
autotrophic.
Contrast plant and animal cells. See comparison below.