AP Biology
Buckley
Name:_________________________________
Cell Review
Date:______
Cell Structure and Function
Robert Hooke-First person to see cells, he coined the term "cell" for the great many “boxes” he saw
under the microscope
The Cell Theory
(Shleiden, Virchow, Schwann – know these!)
1. Every living organism is made of one or more cells
2. Cells are the functional unit of multicellular
organisms
3. Cells arise from pre-existing cells
Endosymbiosis theory: All organelles seem to
share many properties with bacteria. Lynn
Margulis proposed endosymbiont hypothesis:
that organelles derived from ancient
colonization of large bacteria (became the
eucaryotic cell) by smaller bacteria (became
the mitochondria, chloroplast, etc.) Symbiosis
= "living together".
Cell Size
atoms --> DNA --> virus --> bacteria -->mitochondria--> Eukaryotic cells
Cells must remain small in size due to the ratio of surface area and volume
As the cell increases in size, its surface area becomes too small to support its internal structures.
Oxygen and other important substances cannot diffuse fast enough. Cells that get too large, may
divide.
All Cells Have Three Basic Features: Cell Membrane, Genetic Material,
Cytoplasm
Plasma Membrane (aka Cell Membrane)
1. Isolates cytoplasm from external environment
2. regulates flow or material into and out of the cell
3. allows interaction with other cells
Each type has unique
combo of
phospholipids and
proteins for function.
Genetic Material
1. provides cellular "blueprint" that controls the functions of the cell
2. In the form of DNA (Deoxyribonucleic acid)
3. DNA is universal for all cells, an all living things - evidence of common ancestry
4. Chromatin is the complex of proteins and DNA, it condenses into chromosomes before cell division
Cytoplasm (aka cytosol)
1. inside plasma membrane
2. contains water, salts, and other chemicals
3. organelles float within this jelly-like substance
Cytoplasm = area
Cytosol = semifluid substance in
cytoplasm
AP Biology
Buckley
Name:_________________________________
Cell Review
Date:______
Prokaryote vs. Eukaryote Cells
Prokaryotes




no membrane bound
nucleus, chromosomes
grouped together in an
area called the "nucleoid"
no membrane bound
organelles
smaller than eukaryotes
consist of bacteria and
archaebacteria
Eukaryotes




has a membrane bound nucleus
has membrane bound organelles in cytoplasm
much larger than prokaryotes
animals, plants, fungi, protists
Organelles
The Nucleus
--nuclear envelope contains pores for some things to enter and exit
-- chromatin is DNA and proteins, when the cell begins to divide, chromatin condenses and forms
chromosomes
--DNA remains in the nucleus, it sends instructions to the cytoplasm via messenger RNA
--RNA directs the synthesis of proteins on ribosomes in the cytoplasm
--Nucleolus assembles ribosomes within the nucleus, ribosomes contain the "tools" to construct
proteins
rER – membrane factory
Endoplasmic Reticulum -- Transport System
(endoplasm means "within cytoplasm",
reticulum means "little net"
--divides cell into compartments
--channels molecules through the cell's
interior, like a little highway
Rough ER
Proteins made on ribosomes
thread into ER lumen & fold into
conformation
--has ribosomes which give it its "rough"
appearance
--functions in protein synthesis
--ER transports newly assembled proteins to
the Golgi Apparatus
Thru vesicles

Grows in place by adding membrane
proteins & phospholipids
ER: ½ total membrane in cell
 Continuous w/ nuclear membrane (space
b/t continuous)
 Space inside = cisternal space or ER
lumen
 Cisternae = folded stacks
Endomembrane System: membranes related thru
direct physical continuity or by transfer of vesicles
(membrane segments)
AP Biology
Buckley
Name:_________________________________
Cell Review
Smooth ER
Date:______
Has enzymes detoxify drugs/poisons (higher in liver) – add –OH to make more soluble
--mostly contains enzymes that function in lipid
synthesis
Steroids (sex hormones), phospholipids, stores Ca++ in muscle
Golgi Apparatus -- Delivery System
--flattened stacks of membranes
--functions in collection, packaging and
distribution of molecules made in the cell and
used elsewhere
-- front end (cis) faces the ER, and the back
end (trans) faces the cell membrane
--unprocessed proteins enter the Golgi
apparatus, are processed and exit near the
cell membrane for export
--the folded stacks are called cisternae
Jobs of the Golgi Apparatus (aka Golgi
Complex) PO4 groups act as zip codes
1. separates proteins according to their
destinations
2. modifies proteins (adds sugar and makes
glycoproteins)
3. packages materials into vesicles which are
exported outside the cell
Cis face: receives vesciles from ER
Trans face: forms vesicles which leave golgi
Lysosomes - Intracellular Digestion Centers
Hydrolytic enzymes (made from rER)
--vesicles that are used to digest
--contain high levels of degrading enzymes (to
"lyse" means to dissolve)
--recycle old and worn out cell parts
Damaged parts surrounded by membrane, lysosome fuses w/ &
--digest other particles taken in by
dismantle w/ enzymes; monomers returned to cytosol
phagocytosis
--this "food" is stored in food vacuoles, the
lysosomes fuse with the vacuoles and release
digestive enzymes
--found in animal cells
Acidic environment (enzymes work best); if leak/break, not active b/c cytosol pH neutral
 If excessive leakage  autodigestion of cell
AP Biology
Buckley
Name:_________________________________
Cell Review
Date:______
Ribosomes - Sites of Protein Synthesis
--each is composed of two subunits, one large
and one small
--mRNA is "read" by the ribosomes and amino
acids are assembled into proteins
--ribosomes are manufactured by the
nucleolus inside the nucleus
Mitochondria - The Cell's Chemical Furnaces
--contains its own DNA, support for
Endosymbiosis Theory
--singular is "mitochondrion"
--2 membranes, one smooth outer membrane,
and an inner membrane folded into layers
called cristae
Increase surface area
--Cristae has two compartments: the matrix
and the intermembrane space
--mitochondria divide before cell division, they
are not synthesized like other cell parts
--function to store energy for cell use. Energy is
stored in the form of ATP - adenosine
triphosphate


Not part of endomembrane system even though
enclosed by membrane!
100s – 1000s; # correlates w/ cell’s level of
metabolic activity
Matrix contains enzymes, mito DNA & ribosomes
Chloroplasts - Where Photosynthesis Takes
Place
--only found in plant cells
--has its own DNA, like mitochondrion
--functions to convert light energy to ATP
--consists of grana, closed compartments that
are stacked (singular is “granum”)
--thylakoids are the individual disk shaped
compartments that make up the grana
--stroma is the fluid surrounded the thylakoids
Not part of endomembrane system
Not static; move around cell (same w/ mito)
AP Biology
Buckley
Name:_________________________________
Cell Review
Date:______
Cytoskeleton - Support
System
Cell is not "just a bag in a
bubble". Lots of internal fibers
= internal "skeleton". Not rigid
like bone; capable of being
assembled, broken down in
minutes. Allows cell movement, cell division,
internal motion of compartments.
Composed of Microtubules & Microfilaments
Centrioles - Microtubule Assembly Centers
--usually occur in pairs arranged at right
angles
--assemble microtubules which influence the
cell shape and movement - part of the
cytoskeleton
--also function in cell division (mitosis)
--only found in animal cells
Function:
 Support & shape
 Anchorage for many organelles
 Cell motility (cilia & flagella)
o Vesicles travel along
“monorail” of fibers
Microtubules: thickest; wall of tube made from globular protein (called tubulin)
Microfilaments: protein called actin; function in motility (muscle cells, pseudopodia/
cytoplasmic streaming)
Cilia: move substances; propel unicellular organisms
Cilia & Flagella
Flagella: propel with undulating motion
--function in movement
-- 9+ 2 Arrangement of microbtubules
9 doublets of microtubules in ring w/ 2 single microtubules in
center
 Proteins connect (wagon wheel); outer doublets have
motor proteins attached (bending movements)
Vacuoles - Storage Areas
--in plants the vacuoles are large and
centralized, storage of water makes the cell
turgid
--in animals, they store food, water and other
substances
Store: proteins, pigments, cmpds poisonous to animals
Can be disposal site for by-products
Food vacuoles: phagocytosis
Contractile vacuole: pump excess water out of cell (maintain
salt [ ])
Central vacuole: enclosed by membrane (tonoplast) in plants
Peroxisomes:
 Single membrane (not part of endomembrane sys)
 Contain enzymes that transfer H+  O forming H2O2 (toxic – why compartments critical)
o Break down fatty acids, detox alcohol/toxins