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Cells
I. Cells are the basic units of life and fall under 2 categories.
A. Prokaryotic cells have a nucleoid (area where DNA is
concentrated) instead of a nucleus and do not have
membrane-bound organelles. They are also
generally smaller and simpler. An example is bacteria.
B. Eukaryotic cells have a nucleus and other membranebound organelles and are generally larger and more
complex. Examples include animals, plants, and fungi.
1. Although they are different in many ways, both types
of cells have a cell membrane, cytoplasm, DNA, and
ribosomes.
Cells
(basic unit of life)
Eukaryotic
Prokaryotic
DNA, ribosomes,
Cell membrane,
cytoplasm
Bacteria
Characteristics
(4)
Simpler
Smaller
Nucleoid
No MembraneBound organelles
Animal, Plant,
Fungi
Characteristics
(4)
Larger
Complex
Nucleus
MembraneBound organelles
II. Eukaryotic cells have membrane-bound organelles (“little
organs”) that are mainly in the cytoplasm (area outside of the
nucleus).
A. The nucleus is the “brain” of the cell because it contains
most of the cell’s DNA which directs the making of proteins.
1. The nucleus is surrounded by the nuclear envelope that
is double-membraned perforated by nuclear pores that
allows certain things in and out of the nucleus.
2. Within the nucleus is the DNA found as chromatin (thin
thread-like DNA wrapped around proteins) sectioned
into chromosomes that condense during cell division.
a. The nucleolus/nucleoli is the area within the nucleus
where there is a dense collection of chromatin making
ribosomal parts.
Cell Organelles
Nucleus
(Brain, contains DNA)
Nuclear Envelope
(double-membraned)
Nuclear Pores
(Allows things in/out)
Chromatin/Chromosomes
(DNA + Proteins)
Nucleolus/Nucleoli
(makes ribosomes)
B. Ribosomes are the “protein factories” of the cell and
make proteins from the directions of mRNA (messenger)
produced in the nucleus.
1. Ribosome parts are made in the nucleolus, shipped out
through the pores, and assembled in the cytoplasm and
are made out of rRNA (ribosomal) and proteins.
2. Ribosomes can be found “free” floating in the cytoplasm
or “bound” on the surface of the endoplasmic reticulum
and the nuclear envelope.
Cell Organelles
Ribosomes
(Protein Factories, reads mRNA)
Made of rRNA
and proteins
Types
Free
(cytoplasm)
Bound
(On ER and
nuclear envelope)
C. The endoplasmic reticulum is a membrane system consisting
of sacs and tubules and is connected to the nuclear envelope.
It is divided into two main types:
1. The rough ER has ribosomes giving it a rough look
and makes secretory proteins that are released from the
cell, membrane-bound proteins and also produces
membranes.
a. Its products are shipped in vesicles, which are
membranous sacs made by the ER itself, and moved
to destinations by motor proteins.
2. The smooth ER does not have ribosomes making it smooth.
Its function is to make lipids (all three types) and
detoxify drugs.
Cell Organelles
Endoplasmic Reticulum
(membrane system connected
To nuclear envelope)
Rough ER
(with ribosomes)
Smooth ER
(without ribosomes)
Makes Membrane- Makes Makes Secretory
Bound Proteins Membrane
Proteins
Vesicle
(membranous sacs)
Motor Proteins
(moves vesicles)
Makes Lipids
(3 types)
Detoxify
drugs
D. The Golgi apparatus is like the “post office” of the cell
and is located near the ER. It is a stack of membranous sacs.
1. The Golgi apparatus receives proteins in vesicles made by
the ER, sorts and modifies these proteins before they
ship the modified proteins to where they need to go
also using vesicles.
Cell Organelles
Golgi Apparatus
(post office)
Receives, sorts, modifies,
and ships proteins in vesicles
E. Lysosomes are the cell’s “chop shop” and “recycling” crew
and are vesicles with enzymes that break things down inside.
They are made by the RER and then modified by the G.A.
1. Lysosomes break down macromolecules into small pieces
for the cell to use in a process called phagocytosis (“cell
eating”) after they fuse with vesicles containing food.
2. Lysosomes also recycle damaged organelles to reuse their
parts in a process called autophagy when they fuse with
vesicles containing the damaged organelles.
Cell Organelles
Lysosomes
(chop shop, recycling vesicles
with enzymes)
Phagocytosis
(cell eating food)
Autophagy
(recycle damaged
organelles)
F. Vacuoles are the cell’s “storage warehouse” and are large
membranous sacs that can be filled with water and
macromolecules.
1. The central vacuole in a plant cell holds a lot of the plant
cell’s water, makes the cell grow, and helps give the plant
cell its shape.
2. A contractile vacuole, found in certain organisms, pumps
water out to prevent the organism from bursting.
G. Mitochondria are the cell’s “power plants” and their job is
to turn food into energy for the cell.
1. Mitochondria have two membranes, the outer membrane
and the inner membrane which is very folded up.
2. Between the two membranes is an intermembrane space
and within the inner membrane is the fluid called the
mitochondrial matrix.
a. The matrix has its own DNA, ribosomes, and proteins
unique from the rest of the cell.
H. Plant cells have chloroplasts which make food using
energy from the sun in a process called photosynthesis.
1. Chloroplast also have an inner and outer membrane
with an intermembrane space and the area within the
inner membrane filled with fluid is called the stroma.
2. In the stroma are membranous sacs called thylakoids
that are stacked into granum/grana.
a.The stroma also has its own DNA, ribosomes and
proteins separate from the rest of the cell.
III. The cytoskeleton is used for maintaining the shape of
the cell and various other functions and contain 3 main
components.
A. Microfilaments are thin rods made out of proteins called
actin. They can be made and broken down quickly and
are used to change a cell’s shape.
1. Microfilaments create extensions called microvilli
to increase surface area to help cells increase
absorption.
B. Microtubules are hollow tubes made of tubulin and
they are used as highways for motor proteins to move
things around in the cell and can also be made and
broken down quickly.
1. Microtubules come out of the centrosome which is
also known as the “microtubule organizing center”.
a. The centrosome in animal cells have two centrioles
that help in dividing chromosomes during mitosis.
2. Microtubules are used to make cilia and flagella
that help cells move fluids or through liquid.
a. Cilia are usually shorter and occur in large
numbers.
b. Flagella usually are longer and occur in small
numbers.
C. Intermediate filaments are a more permanent component
of the cytoskeleton and are made out of keratins, a family
of proteins that make up hair, nails, and horns.
1. Intermediate filaments are used to keep organelles
that are stationary, like the nucleus, in place.