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CHAPTER 7
CELL
STRUCTURE
AND FUNCTION
SECTION 1
Life Is Cellular
Key Concept Questions:
1. What is the cell theory?
2. What are the characteristics of
prokaryotes and eukaryotes?
• Since the 1600s, scientists have made
many discoveries that have showed how
important cells are in living things.
• The cell theory grew out of the work of
many scientists and improvements in the
microscope.
– Many scientists contributed to the cell
theory.
• 1600’s Anton van Leeuwenhoek was the
first person to see tiny living organisms in
a drop of water – he called them
“animalcules”
– 1665 Robert Hooke looked at slices of
cork and observed tiny chambers or
“cells”
• 1838 Matthias Schleiden concluded
plants are made of cells
• 1839 Theodor Schwann concluded
animals are made of cells
• In 1858, Rudolph Virchow, a German
physician, proposed that cells come
only from the division of existing
cells.
– More was learned about cells
as microscopes improved.
– The cell theory is a unifying
concept of biology.
• Early studies led to the development of
the cell theory.
– The Cell theory has three principles.
1. All organisms are made of cells.
2. All existing cells are produced by
other living cells.
3. The cell is the most basic unit of life.
• McDougall Littell video – Cell theory
• All cells share certain
characteristics.
• Cells tend to be
microscopic.
• All cells are enclosed
by a membrane.
• All cells are filled with
cytoplasm.
cell membrane
cytoplasm
Bacterium
(colored SEM; magnification 8800x)
• There are two cell
types: eukaryotic
cells and prokaryotic
cells.
nucleus
– Prokaryotic cells do
not have a nucleus.
– Prokaryotic cells do organelles
not have membranebound organelles. cell membrane
cytoplasm
• The root kary means “kernel,” which
describes the nucleus. Eu- means
“true,” so a eukaryotic cell has a true
nucleus. If pro- means “before,” what
does prokaryotic mean?
– Before a nucleus
Key Concept Questions:
1. What is the cell theory?
–
The cell theory states all living things are
composed of cells, cells are the basic units
of structure and function in living
organisms, new cells come from existing
cells.
2. What are the characteristics of prokaryotes
and eukaryotes?
–
Both have a cell membrane and DNA.
Prokaryotes do not have a nucleus but
eukaryotes do.
Section 2
Eukaryotic Cell
Structure
Key Concept Question
• What are the functions of the
major cell structures?
• Cell biologists divide the eukaryotic cell
into two major parts: the nucleus and the
cytoplasm.
• The cytoplasm is the portion of the cell
outside the nucleus.
• Eukaryotic cells contain structures known
as organelles. (The root word organ
means a group of parts that work together.
The suffix –elle means a small part.)
• The cell membrane controls what enters
and leaves the cell.
• Cells have an internal structure.
– The cytoskeleton has many
functions.
• supports and shapes cell
• helps position and transport
organelles
• provides strength
• assists in cell
division
• aids in cell
movement
• Several organelles are involved in making
and processing proteins.
– The nucleus stores genetic information.
– Contains instructions for all proteins
• Many processes occur in the
endoplasmic reticulum.
• There are two types of endoplasmic
reticulum.
• rough endoplasmic
reticulum
• smooth endoplasmic
reticulum
• Ribosomes link amino acids to form
proteins.
• Vesicles are membrane-bound sacs that
hold materials.
• The function of the Golgi apparatus is to
modify, sort, and package proteins and
other materials from the ER for storage in
the cell or secretion outside the cell.
• Other organelles have various functions.
– Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that store
food, water, and waste
• Lysosomes contain enzymes to digest
material.
• Centrioles are tubes found in the
centrosomes.
• Centrioles help divide
DNA.
• Centrioles form cilia and
flagella.
• Plant cells have cell walls and
chloroplasts.
– A cell wall provides rigid support.
• Chloroplasts convert solar energy to
chemical energy.
• McDougall Littell video Cell Structure 1
Smartboard Volunteer
• McDougall Littell Explore Cell Organelles –
animated biology
Key Concept Question
• What are the functions of the major cell
structures?
– Cell Membrane = controls what enters and
leaves the cell
– Cell Wall = Provides support and protection
to the cell
– Nucleus = control center
– Ribosomes = make proteins
– Smooth ER = makes lipids
– Rough ER = helps make proteins
– Golgi = modify, sort, package proteins
– Vacuoles = store food, water, waste
– Lysosome = break down and digest
materials
– Mitochondria = provides cell with energy
– Chloroplast = site of photosynthesis
– Cytoskeleton = structure, support and
movement
Section 3
Cell Boundaries
Key Concept Questions:
• What are the main functions of the
cell membrane and the cell wall?
• What happens during diffusion?
• What is osmosis?
• Cell membranes are composed of two
phospholipid layers.
– The cell membrane has two major functions.
• forms a boundary between inside and outside of
the cell
• controls passage of materials
cell membrane
inside cell
outside cell
• The cell membrane is made of a
phospholipid bilayer.
– There are other molecules embedded in the
membrane.
– The fluid mosaic model describes the
membrane.
cell membrane
carbohydrate
chain
cholesterol
protein
protein channel
protein
• The cell membrane is selectively
permeable.
Some molecules can cross the membrane while
others cannot.
• The cell membrane is selectively
permeable.
Some molecules can cross the membrane
while others cannot.
• Chemical signals are transmitted across
the cell membrane.
– Receptors bind with ligands and
change shape.
– There are two
types of receptors.
• intracellular
receptor
• Chemical signals are transmitted across
the cell membrane.
– Receptors bind with ligands and change
shape.
– There are two
types of receptors.
• intracellular
receptor
• membrane
receptor
•Materials move across membranes because
of concentration differences.
When the concentration of a solute is the
same throughout a solution, the solution has
reached equilibrium.
• Passive transport does not require
energy input from a cell.
• Molecules can move across the cell
membrane through passive transport.
• There are two types of passive transport.
– Diffusion
– Osmosis
Diffusion and osmosis are
types of passive transport.
• Molecules diffuse down a
concentration gradient.
• Diffusion is the movement of
molecules from area of high
cocentration to areas of low
concentration
• Osmosis is the diffusion of
water molecules across a
semipermeable membrane.
Let’s practice with diffusion. How
will the final picture look?
Let’s practice with osmosis. How
will the final picture look?
70% water
30% water
50% water
50% water
• There are three types of solutions.
• isotonic
• hypertonic
• hypotonic
freshwater
balanced
saltwater
Some molecules can only diffuse
through transport proteins.
• Some molecules cannot easily diffuse
across the cell membrane.
• Facilitated diffusion is diffusion through
transport proteins.
• Active Transport, Endocytosis, and
Exocytosis
• Cells use energy to transport materials
that cannot diffuse across a membrane.
• Active transport requires energy input from a
cell and enables a cell to move a substance
against its concentration gradient.
• Passive transport
requires no energy from
the cell.
• Active transport is
powered by chemical
energy (ATP).
• Active transport occurs
through transport protein
pumps.
• Cells use active transport
to maintain homeostasis.
• A cell can import and export large
materials or large amounts of material in
vesicles during the processes of
endocytosis and exocytosis.
• Cells use energy to transport material in
vesicles.
• Endocytosis is the process of taking material
into the cell.
• Phagocytosis is a type of endocytosis.
• Exocytosis is the process of expelling
material from the cell.
• Some unicellular eukaryotes have
contractile vacuoles, which collect
excess water inside the cell and force the
water out of the cell.
• http://www.linkpublishing.com/Videos/trans
port/para_osmotic.wmv
• McDougall Littell animated biology passive transport and plasma membrane
Smartboard Volunteer
• McDougall Littell animated biology – get
through a cell membrane
Key Concept Questions:
• What are the main functions of the cell
membrane and the cell wall?
• The cell membrane controls what enters
and leaves the cell. The cell wall
provides structure and support.
• What happens during diffusion?
• Molecules move from an area of high
concentration to an area of low
concentration
• What is osmosis?
• The diffusion of water molecules
Section 4 The
Diversity of
Cellular Life
Key Concept Questions:
• What is cell specialization?
• What are the four levels of
organization in multicellular
organisms?
• An organism that consists of a single cell is
called a unicellular organism.
• Unicellular organisms carry out all the
essential functions of life that larger
organisms do.
• Organisms that are made up of many cells
are called multicellular organisms.
• Cells throughout a multicellular organism can
develop in different ways to perform different
tasks.
• This process is called cell specialization or
differentiation.
• The levels of organization in a multicellular
organism are individual cells, tissues,
organs, and organ systems.
• Individual cells are the first level.
• Similar cells are grouped into units called
tissues.
• A tissue is a group of cells that perform a
particular function.
• Groups of tissues that work together form an
organ.
• A group of organs that work together to
perform a specific function is called an organ
system.
Key Concept Questions:
• What is cell specialization?
– Cells throughout a multicellular organism can
develop in different ways to perform different
tasks
• What are the four levels of organization
in multicellular organisms?
– Cells, tissues, organs, and organ systems