Cell Structure and Function
Chapter 3
AKS STANDARDS
8a - state the cell theory
The size range of cells.
The History of the Microscope
Early studies led to the development of the
cell theory.
Cells – The Basic Unit of Life

The accumulated research of Schleiden, Schwann,
and Virchow can be summarized in the cell
theory, one of the first unifying concepts in the
field of biology:

All organisms are made of cells.

All existing cells are produced by other living
cells.

The cell is the most basic unit of life.
Prokaryotic cells lack a nucleus and most internal
structures of eukaryotic cells.

Prokaryotes:
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
NO NUCLEUS, but do have nucleoid
region with DNA present
Small and Simple – do not contain
membrane-bound organelles
Have cell membranes and cytoplasm
All are single-celled

Ex. Bacteria & Archaea
Eukaryotes:

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Contain nucleus that house genetic
information
Contains organelles that perform
specialized functions
Can be unicellular or multicellular

Ex. Protists, fungi, plants, and
animals
Prokaryotic Cell v. Eukaryotic Cell
Diversity of Cellular Life

Unicellular organisms are made of
a single cell.


This grouping includes all prokaryotes
(i.e. bacteria & archaea) and some
eukaryotes (such as algae and yeasts).
Multicellular organisms are made of
many cells.

These organisms are always
Eukaryotic (i.e. many protistans, most
fungi, all plants and animals).
Cell Specialization

Cell specialization describes an event where a cell
becomes specialized to perform a specific function
for an organism.
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Muscle cells
Skin cells
Leaf cells
Nerve Cells
Etc.
Levels of Cellular Organization

In multicellular organisms:
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Individual cells – basic unit of life
Tissues – groups of similar cells working together
for a similar function
Organs – groups of tissues working together
Organ systems – groups of organs working
together
A Comparison of Cells
Prokaryotic Cell (Bacterium)
Not in Prokaryotic Cells:
-nucleus
-membrane bound organelles
Practice, Application & Critical Thinking

The following virtual textbook activities are
highly recommended:



Section 3.1 Assessment Questions (Textbook pp.
72)
Classzone.com: Animated Biology – Cell
Structures
Interactive Review: Concepts Maps – Section 1
AKS STANDARDS
8c - identify common cell organelles and
describe the function of each (e.g. diagrams
and microscopic examinations),
8d - explain the role of cell organelles
(including the cell membrane) in maintaining
homeostasis and cell reproduction for both
prokaryotic and eukaryotic cells (GPS),
Cells have an internal structure.

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On a small scale, your cells carry out a
necessary division of labor.
They contain specialized structures that work
together to respond to stimuli and efficiently
carry out other necessary processes.
Cell organelles and molecules are anchored to
specific sites, which vary by cell type.
The division of labor provided by membranebound organelles works to increase the overall
efficiency of cellular processes.
Animal Cell
Plant Cell
Cytoskeleton


Each eukaryotic cell has a cytoskeleton, a network
of proteins that is constantly changing to meet the
needs of the cell.
The cytoskeleton provides structural support, and
aids in cell motility and cell regulation.
Organelles
http://bcs.whfreeman.com/thelifewire/content/chp04/0402001.html

Organelles that function in control:
*Nucleus
*Centrosome
(plant and animal)
(plant and animal)

Organelles that function in assembly, transport, and storage:
*Endoplasmic reticulum
(plant and animal)
*Ribosomes
(plant and animal)
*Golgi apparatus
(plant and animal)
*Vacuoles
(plant has 1 large and animals have many)
*Lysosomes
(animal)

Organelles that function in energy transformations:
*Chloroplasts
*Mitochondria
(plant only)
(plant and animal)
The Nucleus, Nucleolus, and Nuclear Envelop
Ribosomes
Endomembrane System


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Many of the different membranes of the eukaryotic cell
are part of an ENDOMEMBRANE SYSTEM.
Membranes within cell are not identical in structure or
function (modifications are present according to job).
Includes:
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nuclear envelope
endoplasmic riticulum (smooth and rough)
Golgi apparatus,
lysosomes
vacuoles
plasma membrane
Relationships Among Organelles of the Endomembrane System
Endoplasmic Reticulum


The ER is a membranous system of
channels and flattened sacs that
traverse the cytoplasm.
Exists in 2 varieties:
 Rough ER: the site of protein
synthesis resulting from the
attached ribosomes
 Smooth ER: assists in the
synthesis of steroid hormones and
other lipids


Also connects rough ER to the Golgi
apparatus and carries out various
detoxification processes in liver
Smooth and rough E.R. are actually
connected, not distinct, separate
sections
The Golgi Apparatus
Vesicles

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Cells need to separate
reactants for various chemical
reactions until it is time to be
used.
Vesicles are a general name
used to describe small
membrane-bound sacs that
divide some materials from the
rest of the cytoplasm.
They transport these materials
from place to place within the
cell.
Vesicles are generally shortlived and are formed and
recycled when needed.
Vacuoles



A vacuole is a fluid-filled sac
used for the storage of
materials needed by the cell.
Most animal cells contain many
small vacuoles.
A large central vacuole, as
shown in the diagram to the
right, is a prominent structure
unique to plant cells.


It is filled mostly with a watery fluid
that strengthens the cell and helps
to support the entire plant.
When a plant wilts, its leaves
shrivel because there is not
enough water in each cell’s central
vacuole to support the leaf’s
normal structure.
Lysosomes


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Lysosomes are membrane-bound
sacs of hydrolytic enzymes…they are
the principle site of intracellular
digestion.
Different lysosomes break down
each of the major classes of
macromolecules – proteins,
polysaccharides, fats, and nucleic
acids.
Lysosomes defend a cell from
invading bacteria and viruses and are
also used in autophagy – the
recycling of the cell’s own organic
material for use.
The Formation and Functions of Lysosomes (Layer 1)
The Formation and Functions of Lysosomes (Layer 2)
The Formation and Functions of Lysosomes (Layer 3)
Centrosomes & Centrioles
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The centrosome is a small region of
the cytoplasm that produces
microtubules.
In animal cells, it contains two small
structures called centrioles.
Centrioles are cylinder-shaped
organelles arranged in a circle.
Before an animal cell divides, the
centrosome, including the centrioles,
doubles and the two new
centrosomes move to opposite ends
of the cell.
Microtubules grow from each
centrosome forming spindle fibers
that attach to the chromosomes and
aid during cell division.
Peroxisomes
Mitochondria
Chloroplasts
Endosymbiosis and the First Eukaryotes
http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.html


The hypothesis of endosymbiosis proposes
that mitochondria and chloroplasts were
formerly small prokaryotes living within larger
host cells.
An endosymbiont is a cell that lives within a
host cell.
Theory of Endosymbiosis
Evidence Supporting the Endosymbiotic Theory

Evidence for this hypothesis includes:

Both organelles have enzymes and transport systems
homologous to those found in the plasma membranes of
living prokaryotes.

Both replicate by a splitting process similar to prokaryotes.

Both contain a single, circular DNA molecule, not
associated with histone proteins.

Both have their own ribosomes which translate their DNA
into proteins.
Cilia and Flagella
Cell Walls

In plants, algae, fungi, and most bacteria,
the cell membrane is surrounded by a
strong cell wall.

This rigid layer provides protection,
support, and shape to the cell.

The cell walls of multiple cells can
adhere to each other and help support
the entire organism.

Cell wall composition varies and is
related to the different needs of each
type of organism:

Plants & Algae: cellulose

Fungi: chitin

Bacteria: peptidoglycan
Practice, Application & Critical Thinking

The following virtual textbook activities are
highly recommended:





Section 3.2 Assessment Questions (Textbook pp.
79)
Classzone.com: Animated Biology – Cell
Structures
Interactive Review: Concepts Maps – Section 2
Classzone.com: WebQuests: Organelle
Dysfunction
Data Analysis (Textbook pp. 80) – Defining
Variables
AKS STANDARDS
8d - explain the role of cell organelles
(including the cell membrane) in
maintaining homeostasis and cell
reproduction for both prokaryotic and
eukaryotic cells
Cell Membrane


The cell membrane, or
plasma membrane, forms a
boundary between a cell
and the outside environment
and controls the passage of
materials into and out of a
cell.
The cell membrane consists
of a double layer of
phospholipids interspersed
with a variety of other
molecules.


The phospholipid “heads” are polar
and are directed toward the
outside of the membrane.
The phospholipid “tails” are
nonpolar and are directed toward
the inside of the membrane.
Structure & Function of Cell Membrane
Some Functions of Membrane Proteins
Fluid Mosaic Model of the Cell Membrane
Selective Permeability



The cell membrane has the
property of selective
permeability, which means
it allows some, but not all,
materials to cross.
Selective permeability
enables a cell to maintain
homeostasis in spite of
unpredictable, changing
conditions outside the cell.
How a particular molecule
crosses the membrane
depends on the molecule’s
size, polarity, and
concentration inside versus
outside the cell.
Selective Permeability
Practice, Application & Critical Thinking

The following virtual textbook activities are
highly recommended:


Section 3.3 Assessment Questions (Textbook pp.
84)
Interactive Review: Concepts Maps – Section 3
AKS STANDARDS
8g - describe processes whereby substances enter
and leave the cell (passive and active transport
mechanisms),
8h - investigate factors that affect the rate of cellular
transport (e.g., molecule size, charge,
concentration, temperature),
8i - compare the reaction of plant and animal cells
in solutions of different solute concentrations (e.g.,
isotonic, hypotonic, hypertonic solutions),
Passive Transport

Cells almost continuously import and export substances.
Passive transport is the movement of molecules across
a membrane without energy input from the cell.
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Diffusion is the movement of molecules in a fluid or gas from a
region of higher concentration to a region of lower concentration.
A concentration gradient is the difference in the concentration of
a substance from one location to another.
Molecules generally diffuse down their gradient, from a region of
high concentration to a region of low concentration.
Diffusion exists in TWO forms:
1.
2.
Dialysis: the PASSIVE movement of particles across a semipermeable membrane from an area of high particle concentration to an
area of low particle concentration (no energy).
Osmosis: the PASSIVE movement of water molecules across a semipermeable membrane from an area of high water concentration to an
area of low water concentration (no energy).
Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Net diffusion
Equilibrium
(a) Diffusion of one solute
Net diffusion
Net diffusion
(b) Diffusion of two solutes
Net diffusion
Net diffusion
Equilibrium
Equilibrium
Types of Solutions

All of the components of a solution are evenly distributed throughout
the solution:

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The substance that is dissolved is the solute.
The substance in which the solute is dissolved is the solvent.
Example: salt/water mixture – salt is the solute and water is the solvent.
A solution may be :

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Hypertonic: more solutes than liquid.
Hypotonic: less solutes than liquid.
Isotonic: equal amount of solute and liquid.
Water Balance of Cells WITHOUT Walls
Water Balance of Cells WITH Walls
Hypotonic solution
H2O
Isotonic solution
H2O
H2O
Hypertonic solution
H2O
(a) Animal
cell
Lysed
H2O
Normal
H2O
Shriveled
H2O
H2O
(b) Plant
cell
Turgid (normal)
Flaccid
Plasmolyzed
Facilitated Diffusion
 In
facilitated diffusion, transport proteins speed the passive
movement of molecules across the plasma membrane from
high to low concentration – NO ENERGY REQUIRED!
 Channel proteins provide corridors that allow a specific
molecule or ion to cross the membrane
 Channel proteins include:
Aquaporins, for facilitated diffusion of water.
 Ion channels that open or close in response to a stimulus (gated
channels).

 USEFUL

ANIMATION:
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter3/animation__h
ow_facilitated_diffusion_works.html
EXTRACELLULAR
FLUID
Channel protein
Solute
CYTOPLASM
(a) A channel protein
Carrier protein
(b) A carrier protein
Solute
Practice, Application & Critical Thinking

The following virtual textbook activities are
highly recommended:



Section 3.4 Assessment Questions (Textbook pp.
87)
Classzone.com: Animated Biology – Getting
Through a Cell Membrane
Interactive Review: Concepts Maps – Section 4
AKS STANDARDS
8g - describe processes whereby substances
enter and leave the cell (passive and active
transport mechanisms),
Active Transport



Active Transport uses energy
to move molecules AGAINST
their concentration gradients or
in large quantity (bulk).
Active transport is performed
by specific proteins embedded
in the cell membranes.
Active transport allows cells to
maintain concentration
gradients that differ from their
surroundings.
http://www.wiley.com/college/pratt/0471393878/student/animations/membrane_tr
ansport/index.html
Bulk Transport Across the Cell Membrane
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Small molecules and water enter or leave the
cell through the lipid bilayer or by transport
proteins.
Large molecules, such as polysaccharides
and proteins, cross the membrane in bulk via
vesicles.
Bulk transport requires energy (ACTIVE).
There are two types of bulk transport in cells:


Endocytosis
Exocytosis
Endocytosis
http://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf

In endocytosis, the cell takes in liquids or fairly
large molecules by engulfing them in a
membrane.
Exocytosis
http://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf

Exocytosis is the opposite of endocytosis, it
releases substances out of the cell by the
fusion of vesicles with the membrane.
Practice, Application & Critical Thinking

The following virtual textbook activities are
highly recommended:








Section 3.4 Assessment Questions (Textbook pp. 91)
Classzone.com: Animated Biology – Getting Through
a Cell Membrane
Interactive Review: Concepts Maps – Section 5
Reviewing Vocabulary (Textbook p. 95)
Reviewing Main Ideas (Textbook pp. 95)
Critical Thinking (Textbook pp. 96)
Analyzing Data (Textbook pp. 96)
Connecting Concepts (Textbook pp. 96)