Cellular Structure
SOL BIO 4.a-c
1
Cell Theory

The cell theory is the unifying theme in biology
because it emphasizes the similarity of all living
things.
 All organisms are composed of one or more
cells.
 Cells are the smallest living units of all living
organisms.
 Cells arise only by division of a previously
existing cell.
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Cell Characteristics

Cells contain specialized structures to
perform functions necessary for life.

Cellular activities necessary for life include
chemical reactions that facilitate:
 acquiring energy
 reproduction
 adaptation
 maintaining homeostasis
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Cell Characteristics
The basic processes necessary for living things to
survive are the same for a single cell as they are for
a more complex organism.
 A single-celled organism has to conduct all life
processes by itself.
 A multi-cellular organism has groups of cells that
specialize to perform specific functions.

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Cell Characteristics
All cells contain:
 Genetic material





single circular molecule of DNA in prokaryotes
double helix located in nucleus in eukaryotes
Cytoplasm jelly-like substance that fills the
cells interior
Phospholipids
Plasma membrane encloses the cell
 – phospholipid bilayer
Membrane
proteins
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Cell Types

Cell structure is one of the ways
in which organisms differ from
each other.
 2 Types of Cells
•Prokaryote
•Eukaryote
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Prokaryotic Cells

Earth’s first cells were prokaryotes.

The simplest life forms are the prokaryotes.

Prokaryotic cells exist in two major forms:
eubacteria and archaebacteria.
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Prokaryotic Cells

Prokaryotes are the Earth’s most abundant
inhabitants. They can survive in a wide range of
environments and obtain energy in a variety of
ways.
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Prokaryotic Cells
Prokaryotes are cells that
lack a nucleus and
membrane bound
organelles.

Bacteria and related
microorganisms are
prokaryotes
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Prokaryotic Cells
Some use flagellum for locomotion
 ALL are UNICELLULAR

Bacterial cell wall
Rotary
motor
Flagellum
Sheath
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Generalized Prokaryotic Cell
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Eukaryote
• Eukaryotes arose from
prokaryotes and
developed into larger
more complex organisms.
• Eukaryotes are cells that
contain a nucleus and
organelles surrounded by
a membrane, such as
mitochondria and
chloroplasts.
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Eukaryote
• Can be both
unicellular or
multi-cellular
• Examples of
eukaryotes are:
• All fungus,
plant, and
animal cells
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Generalized Eukaryotic Cell
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Cell Size

Most cells are relatively small because
as size increases, volume increases
much more rapidly.
 longer diffusion time
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Visualizing Cells
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Nucleus
Stores genetic material
 Contains DNA
 site where RNA is made
 Nucleolus: Chromatin and ribosomal subunits


Nuclear envelope:

Double membrane with pores
Largest organelle
 BRAIN of the cell – controls protein synthesis

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Nucleus
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Nucleus
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Nucleus
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Ribosomes

Ribosomes are RNA-protein complexes composed
of two subunits that join and attach to messenger
RNA.
 site of protein synthesis
 assembled in nucleolus
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Ribosomes
They can be found alone in
the cytoplasm or attached
to the endoplasmic
reticulum.
 Alone in cytoplasmmakes proteins for use
within the cell
 Attached to RER- makes
proteins for export out of
the cell
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Ribosomes
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Endoplasmic reticulum
 transports
materials through the cell
•Rough ER - studded with ribosomes
•Attached to nuclear membrane
•site of protein synthesis and processing
•Smooth ER - lacks ribosomes
•site of synthesis of phospholipids and
the packaging of proteins into vesicles
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Endoplasmic reticulum
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Endoplasmic reticulum
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Golgi apparatus
 collection
of Golgi
bodies
•Stacked flattened
sacks
•Site where cell
products are
packaged for export
• Proteins are
modified by being
combined with fats
or carbohydrates
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Golgi apparatus
 Vesicles
then pinch
off from the Golgi
body to be secreted
(outside the cell)
 Involved in the
production of
lysosomes
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Golgi apparatus
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Golgi apparatus
Proteins
Transport
vesicle
Golgi
apparatus
Protein
Ribosome
Migrating
Vesicle
transport Fusion
budding
from rough vesicle of vesicle
with Golgi
endoplasmic
apparatus
reticulum
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Lysosomes

vesicles produced by the
Golgi apparatus.

Lysosomes contain
digestive enzymes and
are involved in
intracellular digestion of
food particles, disease
causing bacteria and
worn out cell parts
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Cytoplasm
Endoplasmic
reticulum
Food
vesicle
Golgi
apparatus
Lysosomes
Plasma
membrane
Extracellular
fluid
Digestion of
food particles
or cells
Transport
vesicle
Old or damaged
organelle
Breakdown
of old
organelle
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Vacuoles
Found in PLANT and ANMAL cells
 The vacuole acts a container, storing water and
dissolved particles
 Plants have a large central vacuole for water
storage
 Unicellular animals can use contractile vacuoles
for movement

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Organelles With DNA

Mitochondria


site of cell respiration
Chloroplasts

site of photosynthesis
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Mitochondria
"Powerhouse of the cell" - cellular metabolism
 Structure- outer and inner membranes, cristae
 Found in both plant and animal cells
 Very active cells have more mitochondria

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Chloroplasts
•Chloroplasts are larger and more complex than
mitochondria
•Contain green pigment called chlorophyll that
absorbs sunlight in the first step of photosynthesis
•Found ONLY in PLANTS
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Cell Membrane
•controls what enters
and leaves the cell
•Found in ALL cells
•Phospholipid bilayer
with transport
proteins, and
cholesterol (for
flexibility)
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Cell Wall
•provides support
•Found in PLANT
and BACTERIA cells
•Made from cellulose
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Cytoskeleton

Long slender protein tubes and fibers that extend
from the nucleus to the plasma membrane.

The cytoskeleton contains three types of elements
responsible for cell shape, movement within the
cell, and movement of the cell:
 Actin filaments
 Microtubules
 Intermediate filaments
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Cytoskeleton

The cytoskeleton
contains three types
of elements :
 Actin filaments
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Cytoskeleton
The cytoskeleton
contains three
types of elements:
 Microtubules
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Cytoskeleton
The cytoskeleton
contains three types
of elements:
 Intermediate
filaments
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Cytoskeleton
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Centrioles
•Cylindrical structures found near the nucleus
•Made of hollow, tubular structures arranged in
bundles
•Important in cell division
•Found ONLY in ANIMAL cells
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Plant vs. Animal Cells
PLANT
CELL
HAVE:
Cell Wall
LARGE vacuoles
Chloroplasts
DO NOT HAVE:
Centrioles
ANIMAL
CELL
Cell membrane
Mitochondria
HAVE:
Golgi apparatus
Centrioles
Nucleus
Cytoskeleton
DO NOT HAVE:
Ribosomes
Cell Wall
Endoplasmic
LARGE vacuoles
reticulum
Chloroplasts
Lysosomes
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Plant Cell
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Endosymbiosis

Endosymbiosis theory suggests that
eukaryotes arose from a symbiotic relationship
between various prokaryotes.

Heterotrophic bacteria became mitochondria.

Cyanobacteria became chloroplasts.

Host cell was a large eukaryotic cell.
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Endosymbiosis
Prokaryotic
cell is
engulfed
Eukaryotic cell
Symbiosis
Prokaryotic
cell
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ta_03_14 Evolution of the eukaryotic cell
Slide number: 2
plasma membrane
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ta_03_14 Evolution of the eukaryotic cell
Slide number: 3
plasma membrane
endoplasmic
reticulum
nucleus
nuclear
envelope
Cell has a nucleus
and other organelles.
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ta_03_14 Evolution of the eukaryotic cell
Slide number: 4
aerobic
bacterium
plasma membrane
endoplasmic
reticulum
nucleus
nuclear
envelope
Cell has a nucleus
and other organelles.
Cell has mitochondria.
59
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ta_03_14 Evolution of the eukaryotic cell
Slide number: 5
aerobic
bacterium
plasma membrane
spirochete
Animal cell has a flagellum.
endoplasmic
reticulum
nucleus
nuclear
envelope
Cell has a nucleus
and other organelles.
Cell has mitochondria.
60
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ta_03_14 Evolution of the eukaryotic cell
Slide number: 6
aerobic
bacterium
plasma membrane
spirochete
Animal cell has a flagellum.
endoplasmic
reticulum
nucleus
nuclear
envelope
cyanobacterium
Cell has a nucleus
and other organelles.
Cell has mitochondria.
Plant cell has chloroplasts.
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Cell Differentiation
Cell specialization occurs during the development
of a multi-cellular organism.
 The genetic information necessary for all cellular
functions remains in each cell but may not be
used.

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