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Chapter 7
Cell Structure & Function
7-1: Life is Cellular
»OBJECTIVES:
• What is the cell theory?
• What are the characteristics of prokaryotes
and eukaryotes?
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• There is a common structure that makes up
every living thing - the cell
The Discovery of the Cell
• In 1665, Robert Hooke used a microscope and
saw chamber in cork that he called cells
• Anton van Leeuwenhoek also observed tiny
organisms in water
• Contributions to the cell theory:
– Schleiden - all plants are made of cells
– Schwann - all animals are made of cells
– Virchow - new cells could only come from the
division of existing cells
• The Cell Theory:
– All living things are composed of cells
– Cells are the basic units of structure & function
– New cells are produced from existing cells
CORK CELLS
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• Who was the first scientists to see
living cells?
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• Which scientist determined that all
animals are made of cells?
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• The cell theory says:
– All living things are composed of cells
– New cells are produced from existing
cells
– Cells are the basic units of _____?_____
Exploring the Cell
• Light microscopes are limited in detail
(resolution) because light is easily scattered as it
passes through air
• Electron microscopes (TEM’s and SEM’s) can
view things 1000x smaller than light microscopes
• Scanning probe microscopes can operate in
ordinary air and can even show samples in
solution (DNA, protein, and other biomolecules)
SEM
IMAGES
Prokaryotes and Eukaryotes
• All cells have two things in common
– Surrounded by a barrier (membrane)
– Contain DNA
• The nucleus is a membrane-enclosed structure
that contains the cell’s genetic material in the
form of DNA
• Prokaryotic cells have no nucleus
• Eukaryotic cells have a nucleus
Prokaryotes and Eukaryotes
Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
Nucleus
NO
YES
Size
Generally
Smaller
Not
Usually
Unicellular
Generally
Larger
YES
Specialized
Structures
Number of
Cells
Unicellular or
Multicellular
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• What two features do all cells
share?
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• Which type of organism has cells
that contain a nucleus?
PROKARYOTIC or EUKARYOTIC
7-1 Section Assessment
1. What three statements describe the cell theory?
2. What are the differences between prokaryotic
cells and eukaryotic cells?
3. Compare the processes used to create a TEM
and an SEM.
4. What structures do all cells have?
5. How did the invention of the microscope help
the cell theory?
7-2: Eukaryotic Cell Structure
• What are the functions of the major cell
structures?
Comparing the Cell to a Factory
• At first, cells look impossibly complex, but
patterns eventually emerge
• Many structures are common to eukaryotic
cells
• These structures act as specialized organs and
are called organelles
• Eukaryotic cells are divided into two parts:
The nucleus and the cytoplasm
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• Eukaryotic cells are divided into
two parts: the ________ and the
________.
Nucleus
• The nucleus is the control center
• The nucleus contains nearly all the cell’s DNA:
Coded instructions for making proteins and other
molecules
• It is surrounded by a nuclear envelope which has
pores to let materials in and out
• Chromatin is granular material in the nucleus
which is made of DNA bound to protein
• Chromatin condenses to form chromosomes when
the cell divides
• The dark region in the nucleus is the nucleolus:
The location of ribosome construction
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• ________ is made of DNA bound
to protein.
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• When a cell divides, chromatin
condenses to form ________.
Ribosomes
• Proteins are assembled on ribosomes
• Ribosomes are small particles of RNA and
protein and are found throughout the
cytoplasm
• They produce proteins by following coded
instructions that come from the nucleus
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• Where do the instructions for
making proteins come from?
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• Proteins can be found throughout
the ________ and are sometimes
attached to the ________.
Endoplasmic Reticulum
• The endoplasmic reticulum (ER) is the site
where lipid components of the cell membrane
are assembled, along with proteins and other
materials that are exported from the cell
• Rough ER is covered with ribosomes and is
involved in the synthesis of proteins
• Smooth ER does not contain ribosomes and
contains collections of enzymes that perform
specialized tasks (synthesis of lipids,
detoxification, etc.)
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• Rough ER is involved with the
synthesis of ________.
Golgi Apparatus
• 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
• The golgi ships proteins to their final
destinations throughout the cell or outside
of the cell
Lysosomes
• Lysosomes are small organelles filled with
enzymes
• Lysosomes digest (break down) lipids,
carbohydrates, and proteins into small
molecules that can be used by the rest of the cell
• Lysosomes also break down unuseful organelles
and other “junk” in the cell
Vacuoles
• Vacuoles are saclike structures used for
storage of materials such as water, salts,
proteins, and carbohydrates
• Plant cells have a large central vacuole used
for support
• Vacuoles can also be found in some singlecelled organisms and some animals
Mitochondria & Chloroplasts
• Mitochondria are organelles that convert the chemical
energy stored in food into compounds that are more
convenient for the cell to use
• Nearly all mitochondria in humans come from the
cytoplasm of the mother’s egg cell
• Chloroplasts are organelles that capture energy from
sunlight and convert it into chemical energy in a
process called photosynthesis
• Chloroplasts and mitochondria contain their own
DNA
• Lyn Margulis developed the endosymbiotic theory:
Prokaryotic ancestors of mitochondria and
chloroplasts developed symbiotic relationships with
early eukaryotes
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• Organelles that capture energy from
sunlight and convert it to chemical
energy are called ________.
Cytoskeleton
• The cytoskeleton is a network of protein filaments
that help the cell to maintain its shape
• The cytoskeleton is also involved in movement
• Microfilaments are threadlike structures made of
actin that:
– Support the cell
– Assist with movement
• Microtubules are hollow structures made of
proteins called tubulins that:
– Maintain shape
– Form centrioles during cell division (Animal cells only)
– Form cilia and flagella
7-2 Section Assessment
1. Describe the functions of the endoplasmic
reticulum, Golgi apparatus, chloroplast, and
mitochondrion.
2. Describe the role of the nucleus in the cell.
3. What are two functions of the cytoskeleton?
4. How is a cell like a factory?
5. You examine an unknown cell under the
microscope and discover the cell contains
chloroplasts. What type of organism could you
infer that the cell came from?
7-3: Cell Boundaries
• Cell membrane: thin, flexible barrier
• Cell Wall: Strong supporting layer around the
membrane of some cells
• What are the main functions of the cell
membrane and the cell wall?
• What happens during diffusion?
• What is osmosis?
Cell Membrane
• The cell membrane regulates what enters and
leaves the cell and also provides protection and
support
• Composed of a lipid bilayer with embedded
protein molecules and carbohydrates attached to
some of the proteins
• Often described as a mosaic
• The proteins form channels and pumps to move
materials
• The carbohydrates act like chemical identification
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• The cell membrane is composed of
a ________ ________ with
embedded protein molecules and
carbohydrates attached to some of
the proteins.
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• What is the role of the protein in the
cell membrane?
Cell Walls
• Plants, algae, fungi, and many prokaryotes
have cell walls
• The main function of the cell wall is to
provide support and protection for the cell
• Made from fibers of carbohydrate and
protein
• Plant cell walls are made of cellulose: the
principal component of wood and paper
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• What types of organisms have cell
walls?
Diffusion Through Cell Boundaries
• The concentration of a solution is the mass of
solute in a given volume of a solution
(mass/volume)
• Particles in a solution are in constant motion
• The particles tend to spread out from areas of
higher concentration to areas of lower
concentration: diffusion
• Diffusion occurs until equilibrium is reached
• Diffusion does not require the cell to use energy
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• ___________ is when particles
spread out from areas of high
concentration to areas of low
concentration.
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• Diffusion occurs until _______ is
reached.
Osmosis
•
•
•
•
Permeable: substances can pass through
Impermeable: substances cannot pass through
Selectively Permeable: Some can, some can’t
Osmosis is the diffusion of water through a
selectively permeable membrane
• Isotonic = same strength, Hypertonic = above
strength, Hypotonic = below strength
• Osmosis exerts a pressure known as osmotic
pressure on the hypertonic side of a selectively
permeable membrane
• Cells do not fill with water and burst because they
are surrounded by isotonic fluids or a cell wall
Diffusion & Osmosis
Diffusion & Osmosis
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• The diffusion of water through a
selectively permeable membrane is
called ________.
Facilitated Diffusion
• Cell membranes have protein channels that make
it easy for some molecules to cross
– Example: red blood cells have a channel that allows
only glucose to cross
• These cell membrane proteins are said to
facilitate, or help, diffusion: known as
facilitated diffusion
• Facilitated diffusion depends on concentrations
for movement and does not require use of the
cell’s energy
Active Transport
• Active transport moves materials against the
concentration difference and requires energy
• Carried out by transport proteins: “pumps,” or by
endocytosis or exocytosis (for large molecules)
• Active transport can concentrate materials even
when diffusion tries to move them apart
• Endocytosis takes materials into the cell with
infoldings, or “pockets”
• Exocytosis is the process of releasing large
amounts of material from the cell
Endocytosis
Exocytosis
Active Transport
Active Transport
7-3 Section Assessment
1. Describe the functions of the cell membrane
and cell wall.
2. What happens during diffusion?
3. Describe how water moves during osmosis.
4. What is the basic structure of a cell
membrane?
5. What is the difference between phagocytosis
and pinocytosis?
6. What id the main way that active transport
differs from diffusion?
7-4:Diversity of Cellular Life
• All living things are:
–
–
–
–
Composed of cells
Use the same basic chemistry
Follow the same genetic code
Contain the same kinds of organelles
• What is cell specialization?
• What are the four levels of organization in
multicellular organisms?
Unicellular Organisms
• A single-celled organism is also called a
unicellular organism
• Unicellular organisms do everything you
would expect any cell to do:
– Grow, respond, use energy, reproduce, etc.
• In terms of their numbers, unicellular
organisms dominate life on earth
Multicellular Organisms
• Cells can develop in different ways to perform
different tasks: Cell Specialization
• Specialized animal cells:
– Red blood cells transport oxygen
– Pancreas cells produce protein for digestion
– Muscle cells use actin and myosin for movement
• Specialized plant cells:
– Stomata are holes in the underside of leaves use for
gas exchange – surrounded by guard cells
Red Blood Cells
Muscle Cells
Pancreas Cells
Stomata &
Guard Cells
Levels of Organization
• Levels of organization in a multicellular
organism are: individual cells, tissues, organs,
and organ systems
• TISSUE: Group of similar cells that perform a
particular function
– Muscle, epithelial, nervous, connective
• ORGAN: Groups of tissues working together
• ORGAN SYSTEM: A group of organs that work
together
7-4 Section Assessment
1. In what kinds of organisms is cell
specialization a characteristic?
2. List the levels of biological organization in
multicellular organisms from most simple to
most complex.
3. How are unicellular organisms similar to
multicellular organisms?
4. Using what you know about the ways muscles
move, predict which organelles would be
most common in muscle cells.
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