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Cell Structure and Function
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Slide # 3
Prokaryotic Cells
1. Prokaryotes: Do not have nucleus
but they DO have DNA
DNA
a. Smallest and simplest cells
b. DNA located in cytoplasm
(nucleoid region)
flagellum
c. Have cell walls
d. Have ribosomes
e. Many have flagella for
movement
f. NEVER multicellular
2. Bacteria have prokaryotic cells
Cytoplasm
Cell wall
Cell
membrane
ribosomes
Bacteria are the only
organisms that have
prokaryotic cells.
Slide # 3
Eukaryotic Cells
1.Eukaryotic: cells that have
nucleus
2. Have specialized structures
a.Larger & more complex
than prokaryotic cells
3. Unicellular & multicellular
organisms have eukaryotic
cells
mitochondria
nucleus
chloroplast
nucleolus
vacuole
Cell membrane
Cell wall
Cellular Structures
Structure and Functions of the Nucleus
1. Nuclear membrane is a
double membrane (each is a
lipid bi-layer) pourous (controls
what enters / exits nucleus
2. Nucleolus produces ribosomes
3. DNA is organized into distinct
units called chromosomes that
carries the genetic material
Nucleus controls cell’s activities
because it contains the cell’s DNA
Endoplasmic Reticulum (ER)
1. A network of membranous
tubules and sacs (cisternae)
2. ER membrane is continuous
with the nuclear membrane
3. Transports substances
throughout the cell
Smooth ER
* no ribosomes
4. Rough ER
* makes lipids & steroid
* has ribosomes
hormones
* produces proteins (pancreas
* breaks down toxins in
produces insulin)
liver cells
*makes membrane proteins
* controls release of
calcium in muscle cells
Golgi Apparatus (Body) (Complex)
1. Single membrane
2. Membrane covered sacs (5-8 layers)
3. Receives products from ER
4. Modifies products from ER
5. Packages products into vesicles
6. Sorts and targets products to
different parts of the cell or to be
exported from the cell
Hydrolytic enzymes & lysosomal membranes that
are made by the rough ER are packaged into
lysosomes by the Golgi
Ribosomes (Free & Attached)
1. NOT membrane bound
* found in prokaryotes &
eukaryotes
2. Proteins are synthesized
(made) here
3. Free Ribosomes:
* found throughout the
cytoplasm
* make proteins that function
in the cytoplasm
4. Attached ribosomes (on
ER) make proteins
that
are:
* destined for insertion
into membranes
* put into lysosomes
* many are exported
from the cell
Lysosomes
1. Single membrane
2. Contain hydrolytic enzymes that
break down cell waste & “junk”
from outside the cell into simple
compounds
* simple compounds transferred to
cytoplasm as new cell building
materials
3. Lysosomes originate in the Golgi
but enzymes are made in rough ER
4. Most numerous in disease fighting
cells (white blood cells) that engulf
bacteria by phagocytosis
Tay Sachs is a genetic
disorder that prevents the
formation of the enzyme that
breaks down ganglioside (a
lipid). Result is damage to
nervous system, mental
retardation, and death in
early childhood.
Mitochondria
1. Found in cytoplasm of ALL eukaryotic cells
* number of mitochondria in the celldepends on the cell & its
function
2. convert oxygen and nutrients into ATP (adenosine
triphosphate) through aerobic respiration (metabolism)
* ATP is the energy that cells use
3. Has its own DNA
4. Can reproduce independently of the cell
Cytoskeleton
1. Made up almost entirely of protein filaments
2. Functions:
* give cell shape
* provides mechanical strength
* aids in locomotion (especially in Amoeba
and white blood cells -- pseudopods)
* helps in separating chromosomes during
mitosis
* anchors organelles in cytoplasm
Vacuoles
1. Both plant and animal cells have
vacuoles
* Temporary structure in animal cells
* Large, permanent structure in plant
cells
2. Function: Stores water
3. When filled with water:
* helps cell maintain shape by
exerting pressure on cell membrane
& thus cell wall
* When plants wilt, they have lost
water from vacuole
Large, central vacuole
Plastids
1. Found in plant cells
2. Have a double membrane
3. Many different types
* chromoplasts
-- found in brightly colored flowers &
fruits & leaves
-- have accessory pigments involved in
photosynthesis
* amyloplasts
-- found in root cells; store starch
* leukoplasts (colorless)
-- contain oils and lipids
Chromoplasts
Amyloplasts
1. Double membrane
2. Plastids that convert light energy into
chemical energy (photosynthesis)
* found in leaves & green stems
3. Addition membrane system inside
the chloroplast
* Thylakoids; flattened sacs
* Grana; stacks of thylakoids
* thylakoids are surrounded by fluid
called stroma
4. Stroma contains circular DNA,
ribosomes, and enzymes
5. Can replicate on own by binary
fission
Chloroplasts
Chlorophyll is found
inside the thylakoids
Plasma (Cell) Membrane
The Boundary
1. Described as a lipid bi-layer
fluid mosaic model
2. Fatty acid tails face each other
(hydrophobic)
3. Phosphate heads (hydrophilic)
are on the inside and outside of
the membrane
4. Lipid portion: isolates hydrophilic
substances from entering /
exiting the cell
5. Protein portion: allows
hydrophilic molecules and ions
(charged) in / out of cell &
communicates with other cells
Phosphate head
hydrophilic
Fatty Acid tails
hydrophobic
proteins
Membrane Structures / Functions
hydrophilic
Changes
shape
1. Transport: provides a hydrophilic channel across the
membrane that is selective to a particular particle (salt,
sugars, water, etc)
2. Some transport proteins change their shape to move
substances from one side to another
Cell Wall
1. Found in plant cells (NOT
animals)
2. Protects cell, maintains cell
shape, & prevents excessive
uptake of water
3. Cellulose in cell wall – cross
linked structure (like a chain
linked fence) – makes cell
wall very strong
Theory of Endosymbiosis
1. Theory that Eukaryotes arose from
symbiotic relationship between
prokaryotes and aerobic bacteria that
they took in
2. 2 organelles involved: mitochondria
& chloroplasts
3. Evidence that supports theory:
* bacteria, mitochondria, & chloroplasts
all have circular DNA
* bacteria, mitochondria, & chloroplasts
all about the same size
* bacteria, mitochondria, & chloroplasts
can self replicate by binary fission
Prokaryote takes in aerobic
bacterium
Prokaryote takes in cyano
bacterium (capable of
photosynthesis)
Contractile Vacuoles
1. Found in animal-like PROTISTS,
not plants or animals
2. Pump excess water out of cell;
keeps them from bursting open
Diffusion through phospholipid bilayer
What molecules can get
through directly?
– fats & other lipids
inside cell
NH3
outside cell
lipid
salt
sugar aa
H 2O
What molecules can NOT get
through directly?
– polar molecules
• H2O
– ions (charged)
• salts, ammonia
– large molecules
• starches, proteins
Slide # 10
Structures in Animal verses Plant Cells
Animal Cells
Several
small
vacuoles
scattered
throughout
the cell
Go to
Section:
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Vacuoles
Mitochondria
Plant Cells
Cell Wall
Chloroplast
1 Large central vacuole