Download Chapter 7 Cell Structure and Function Section: 7-1 Life

Chapter 7
Cell Structure and Function
Section: 7-1 Life Is Cellular
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7-1 Life Is Cellular
The Discovery of the Cell
Approximately how Many Cells are in the Human
Body?
100 trillion or 1 X 1014
Cell Size – How large are they?
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7-1 Life Is Cellular
The Discovery of the Cell
Early Microscopes
In 1665, Robert Hooke used an early compound
microscope to look at a thin slice of cork, a plant
material.
Cork looked like thousands of tiny, empty
chambers.
Hooke called these chambers “cells.”
Cells are the basic units of life.
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7-1 Life Is Cellular
The Discovery of the Cell
Hooke’s Drawing of Cork Cells
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7-1 Life Is Cellular
The Discovery of the Cell
What is the cell theory?
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7-1 Life Is Cellular
The Discovery of the Cell
The Cell Theory
In 1838, Matthias Schleiden concluded that all
plants were made of cells.
In 1839, Theodor Schwann stated that all animals
were made of cells.
In 1855, Rudolph Virchow concluded that new
cells were created only from division of existing
cells.
These discoveries led to the cell theory.
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7-1 Life Is Cellular
The Discovery of the Cell
The cell theory states:
• All living things are composed of cells.
• Cells are the basic units of structure and
function in living things.
• New cells are produced from existing cells.
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7-1 Life Is Cellular
Exploring the Cell
Electron Microscopes
Electron microscopes reveal details 1000 times
smaller than those visible in light microscopes.
Electron microscopy can be used to visualize only
nonliving, preserved cells and tissues.
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7-1 Life Is Cellular
Exploring the Cell
Transmission electron microscopes (TEMs)
• Used to study cell structures and large protein
molecules
• Specimens must be cut into ultra-thin slices
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7-1 Life Is Cellular
Exploring the Cell
Scanning electron microscopes (SEMs)
• Produce three-dimensional images of cells
• Specimens do not have to be cut into thin slices
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7-1 Life Is Cellular
Exploring the Cell
Scanning Electron Micrograph of Neurons
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Prokaryotes and Eukaryotes
Cells come in a variety of shapes and sizes.
All cells:
• are surrounded by a barrier called a cell
membrane (aka - plasma membrane)
• contain DNA.
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Cells are classified into two categories, depending on
whether they contain a nucleus.
The nucleus is a large membrane-enclosed structure
that contains the cell's genetic material in the form of
DNA.
The nucleus controls many of the cell's activities.
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Eukaryotes are cells that contain nuclei.
Prokaryotes are cells that do not contain nuclei.
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
What are the characteristics of
prokaryotes and eukaryotes?
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Prokaryotes
Prokaryotic cells have genetic material
that is not contained in a nucleus.
•Prokaryotes do not have membrane-bound
organelles.
•Prokaryotic cells are generally smaller and
simpler than eukaryotic cells.
•Bacteria are prokaryotes.
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Eukaryotes
Eukaryotic cells contain a nucleus in
which their genetic material is separated
from the rest of the cell.
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
• Eukaryotic cells are generally larger and more
complex than prokaryotic cells.
• Eukaryotic cells generally contain many
structures and internal membranes.
• Many eukaryotic cells are highly specialized.
• Plants, animals, fungi, and protists (algae,
protozoa, slime molds, amoeba, plankton) are
eukaryotes.
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The cell theory states that new cells are
produced from
a. nonliving material.
b. existing cells.
c. cytoplasm.
d. animals.
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7-1
The person who first used the term cell was
a. Matthias Schleiden.
b. Lynn Margulis.
c. Anton van Leeuwenhoek.
d. Robert Hooke.
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Which organism listed is a prokaryote?
a. protist
b. bacterium
c. fungus
d. plant
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One way prokaryotes differ from eukaryotes is
that they
a. contain DNA, which carries biological
information.
b. have a surrounding barrier called a cell
membrane.
c. do not have a membrane separating DNA
from the rest of the cell.
d. are usually larger and more complex.
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END OF SECTION
7-2 Eukaryotic Cell Structure
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7-2 Eukaryotic Cell Structure
Comparing the Cell to a Factory
The eukaryotic cell is much like a living version of a
modern factory.
The specialized machines and assembly lines of the
factory can be compared to the different organelles of
the cell.
Cells, like factories, follow instructions and produce
products.
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7-2 Eukaryotic Cell Structure
Eukaryotic Cell Structures
Eukaryotic Cell Structures
Structures within a eukaryotic cell that perform
important cellular functions are known as
organelles.
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.
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Eukaryotic Cell Structures
Plant Cell
Nucleolus
Nucleus
Smooth
endoplasmic
reticulum
Nuclear envelope
Ribosome (free)
Rough endoplasmic
reticulum
Ribosome
(attached)
Golgi
apparatus
Cell wall
Cell membrane
Chloroplast
Mitochondrion
Vacuole
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Eukaryotic Cell Structures
Animal Cell
Nucleolus
Smooth endoplasmic
reticulum
Nucleus
Ribosome (free)
Nuclear envelope
Cell membrane
Rough
endoplasmic
reticulum
Ribosome
(attached)
Centrioles
Golgi
apparatus
Mitochondrion
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7-2 Eukaryotic Cell Structure
Nucleus
What is the function of the nucleus?
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7-2 Eukaryotic Cell Structure
Nucleus
Nucleus
The nucleus is the control center of the cell.
The nucleus contains nearly all the cell's
DNA and with it the coded instructions for
making proteins and other important
molecules.
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7-2 Eukaryotic Cell Structure
Nucleus
The Nucleus
The nucleus is surrounded by a nuclear envelope composed of two
membranes and dotted with thousands of nuclear pores that allow
materials to move in and out of the nucleus.
Nuclear envelope
Nucleolus
Nuclear
pores
Most nuclei also contain a small, dense region known as the nucleolus.
The nucleolus is where the assembly of ribosomes begins.
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7-2 Eukaryotic Cell Structure
Ribosomes
What is the function of the ribosomes?
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7-2 Eukaryotic Cell Structure
Ribosomes
Ribosomes
One of the most important jobs carried out in
the cell is making proteins.
Proteins are assembled on ribosomes.
Instructions for protein production come from
DNA.
Ribosomes are small particles of RNA and
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protein found throughout the cytoplasm.
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7-2 Eukaryotic Cell Structure
Ribosomes
What is the function of the endoplasmic
reticulum?
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7-2 Eukaryotic Cell Structure
Endoplasmic Reticulum
There are two types of ER—rough and smooth.
Smooth ER – contains enzymes that help to cell membrane lipids and
also detoxify drugs. A lot of smooth ER is found in liver cells.
Ribosomes
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7-2 Eukaryotic Cell Structure
Endoplasmic Reticulum
Lipid portions of the cell membrane and proteins
are made by the endoplasmic reticulum.
New proteins leave the ribosomes on roughendoplasmic reticulum and may be chemically
altered in the ER.
Newly assembled proteins are carried from the
rough-ER to the Golgi apparatus in vesicles.
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7-2 Eukaryotic Cell Structure
Golgi Apparatus
What is the function of the Golgi apparatus?
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7-2 Eukaryotic Cell Structure
Golgi Apparatus
The Golgi apparatus appears as a stack of flattened membranes.
The Golgi apparatus modify, sort, and package proteins
received from the ER for shipment inside or outside of the cell
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7-2 Eukaryotic Cell Structure
Golgi Apparatus
What is the function of lysosomes?
Lysosomes breakdown and recycle old cell parts, and
also breakdown macromolecules such as lipids,
carbohydrates and proteins into smaller molecules.
Remove the “junk” that may accumulate and clutter up
the cell.
They are found in both animal and plant cells.
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7-2 Eukaryotic Cell Structure
Vacuoles
What is the function of vacuoles?
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7-2 Eukaryotic Cell Structure
Vacuoles
In many plant cells there
is a single, large central
vacuole filled with liquid
(water, salts, proteins and
carbohydrates).
Vacuole
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7-2 Eukaryotic Cell Structure
Vacuoles are also found
in some unicellular
organisms and in some
animals.
Vacuoles
Contractile vacuole
The paramecium contains
a contractile vacuole
that pumps excess water
out of the cell.
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7-2 Eukaryotic Cell Structure
Mitochondria and Chloroplasts
What is the function of the mitochondria?
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7-2 Eukaryotic Cell Structure
Mitochondria and Chloroplasts
Mitochondria
Nearly all eukaryotic
cells contain
mitochondria.
Mitochondria convert the
chemical energy stored
in food into compounds
that are more
convenient for the cell to
use.
Mitochondrion
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7-2 Eukaryotic Cell Structure
Mitochondria and Chloroplasts
What is the function of chloroplasts?
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7-2 Eukaryotic Cell Structure
Chloroplasts
Mitochondria and Chloroplasts
Chloroplast
Plants and some other
organisms contain
chloroplasts.
Chloroplasts capture
energy from sunlight
and convert it into
chemical energy in a
process called
photosynthesis.
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7-2 Eukaryotic Cell Structure
Cytoskeleton
What are the functions of the
cytoskeleton?
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7-2 Eukaryotic Cell Structure
Cytoskeleton
The cytoskeleton is a network of protein
filaments that helps the cell to maintain its
shape. The cytoskeleton is also involved in
movement.
The cytoskeleton is made up of:
• Microfilaments (made-up of the protein actin)
• Microtubules (made-up of tubulin) –
examples are centrioles, cilia and flagella
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7-2 Eukaryotic Cell Structure
Cytoskeleton
Cytoskeleton
Cell membrane
Endoplasmic
reticulum
Microtubule
Microfilament
Ribosomes
Mitochondrion
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7-2 Eukaryotic Cell Structure
Cytoskeleton
Centrioles are located near the nucleus and help to
organize cell division.
Cell Organelle Interactive
Plant and Animal Model Interactive
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7-2
In the nucleus of a cell, the DNA is usually visible
as
a. a dense region called the nucleolus.
b. the nuclear envelope.
c. granular material called chromatin.
d. condensed bodies called chloroplasts.
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7-2
Two functions of vacuoles are storing materials
and helping to
a. break down organelles.
b. assemble proteins.
c. maintain homeostasis.
d. make new organelles.
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Chloroplasts are found in the cells of
a. plants only.
b. plants and some other organisms.
c. all eukaryotes.
d. most prokaryotes.
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Which of the following is NOT a function of the
Golgi apparatus?
a. synthesize proteins.
b. modify proteins.
c. sort proteins.
d. package proteins.
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7-2
Which of the following is a function of the
cytoskeleton?
a. manufactures new cell organelles
b. assists in movement of some cells from one
place to another
c. releases energy in cells
d. modifies, sorts, and packages proteins
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END OF SECTION
Chapter 7
Cell Structure and Function
Section: 7-3 Cell Boundaries
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7-3 Cell Boundaries
7-3 Cell Boundaries
All cells are surrounded by a thin, flexible barrier
known as the cell membrane.
Many cells also produce a strong supporting layer
around the membrane known as a cell wall.
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7-3 Cell Boundaries
Cell Membrane
Cell Membrane
The cell membrane regulates what enters and
leaves the cell and also provides protection
and support.
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7-3 Cell Boundaries
Photograph of a Cell Membrane
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7-3 Cell Boundaries
Cell Membrane
Cell Membrane
Outside of
cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside of cell
(cytoplasm)
Protein
channel
Lipid bilayer
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Cell Membrane
(Plasma Membrane)
• Separates the cytoplasm of the cell from its
environment
• Protects the cell & controls what enters and
leaves
• Cell membranes are selectively permeable only
allowing certain materials to enter or leave. CO2,
O2, and H2O enter and leave easily.
• Maintains a balanced cell environment or
homeostasis
Selectively Permeable
Structure of the Cell Membrane
Composed of a lipid bi-layer (two layers) made up of
phospholipid molecules
Phospholipids
Make up 2
thefatty
cell
Contains
membrane
acid
chains that
are nonpolar
Head is polar &
contains a (PO4-)
phosphate group
Fluid Mosaic Model
Phospholipids move within the membrane like water molecules
within lake currents.
Proteins within the membrane move among the phospholipids like boats
within the lake – and create a mosaic (pattern) on the membrane surface.
Membrane Proteins
• A variety of protein molecules are attached and embedded in the
cell’s lipid bi-layer.
• “Transport proteins” help move materials into and out of the cell
(membrane).
– “Channel proteins” have holes or pores that enable certain
substances – like ions Na+, Ca+ and K+ to cross the cell membrane.
– “Carrier proteins” can change shape to move material from one side
of the membrane to the other
• Some embedded proteins have carbohydrate chains attached to
them to serve as chemical signals to help cells recognize each
other or for hormones or viruses to attach
• Cholesterol – also found in the cell membrane stabilizes the
phospholipids and prevents the fatty acid tails from sticking
together
Three Forms of Transport Across the Membrane
Passive Transport
Simple Diffusion
Doesn’t require energy
Moves high to low
concentration
Example: Oxygen or
water diffusing into
a cell and carbon
dioxide diffusing out.
Passive Transport
Facilitated Diffusion
Doesn’t require energy
Uses transport
proteins to move high
to low concentration
Examples: Glucose or
amino acids moving
from blood into a cell.
Types of Transport Proteins
• Channel proteins are embedded in
the cell membrane & have a pore
for materials to cross
• Carrier proteins can change shape
to move material from one side of
the membrane to the other
Facilitated Diffusion
Molecules will randomly move through
the pores in Channel Proteins.
Active Transport
• Some carrier
proteins do not
extend through
the membrane.
• They bond and
drag molecules
through the lipid
bi
bi--layer and
release them on
the opposite side.
Active Transport
Requires energy or
ATP
Moves materials
from LOW to HIGH
concentration
AGAINST
concentration gradient
Active transport
Example:
Pumping Na+ (sodium ions)
into a cell and K+ (potassium
ions) out of a cell against
strong concentration
gradients.
Called Na+ - K+ Pump
SodiumSodium
-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped out
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7-3 Cell Boundaries
Cell Walls
What is the main function of the cell wall?
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7-3 Cell Boundaries
Cell Walls
Cell Wall
Cell walls are found in plants, algae, fungi, and
many prokaryotes.
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
Measuring Concentration
A solution is a mixture of two or more
substances.
The substances dissolved in the solution are
called solutes.
The concentration of a solution is the mass of
solute in a given volume of solution, or
mass/volume.
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
What happens during diffusion?
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
Diffusion
Particles in a solution tend to move from an area
where they are more concentrated to an area
where they are less concentrated.
This process is called diffusion.
When the concentration of the solute is the same
throughout a system, the system has reached
equilibrium.
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
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Simple Diffusion
• Requires NO energy
• Molecules move
from area of HIGH to
LOW concentration
DIFFUSION
Diffusion is a
PASSIVE process
which means no
energy is used to
make the
molecules move,
they have a
natural KINETIC
ENERGY
Diffusion of Liquids
Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to
LOW)
7-3 Cell Boundaries
Osmosis
Osmosis
Osmosis is the diffusion of water through a
selectively permeable membrane.
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Osmosis
• Diffusion of water
across a membrane
• Moves from HIGH
water potential (low
solute) to LOW
water potential (high
solute)
Diffusion across a membrane
Semipermeable
membrane
Diffusion of H2O Across A
Membrane
High H2O potential
Low solute concentration
Low H2O potential
High solute concentration
7-3 Cell Boundaries
Osmosis
How Osmosis Works
Dilute sugar
solution
(Water more
concentrated)
Concentrated
sugar solution
(Water less
concentrated)
Sugar
molecules
Selectively
permeable
membrane
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Movement of
water
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7-3 Cell Boundaries
Osmosis
Water tends to diffuse from a highly concentrated
region to a less concentrated region.
If you compare two solutions, three terms can be
used to describe the concentrations:
hypertonic (“above strength”).
hypotonic (“below strength”).
isotonic (”same strength”)
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Cell in Isotonic Solution
10% NaCl
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
NO NET
MOVEMENT
What is the direction of water movement?
equilibrium
The cell is at _______________.
Cell in Hypotonic Solution
10% NaCl
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
Cell in Hypertonic Solution
15% NaCl
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
7-3 Cell Boundaries
Osmosis
Osmotic Pressure
Osmosis exerts a pressure known as osmotic
pressure on the hypertonic side of a selectively
permeable membrane.
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Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
Moving the “Big Stuff” Out
Exocytosis
- moving
things
out.
Molecules are moved out of the cell by vesicles that fuse
with the plasma membrane.
This is how various types of hormones are secreted.
secreted
Exocytosis
Exocytic
vesicle
immediately
after fusion
with plasma
membrane.
Moving the “Big Stuff” In
Large molecules move materials into the
cell by endocytosis
endocytosis.
Endocytosis and Exocytosis
What is the direction of water movement?
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7-3
Unlike a cell wall, a cell membrane
a. is composed of a lipid bilayer.
b. provides rigid support for the surrounding
cell.
c. allows most small molecules and ions to
pass through easily.
d. is found only in plants, fungi, algae, and
many prokaryotes.
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7-3
The concentration of a solution is defined as the
a. volume of solute in a given mass of solution.
b. mass of solute in a given volume of solution.
c. mass of solution in a given volume of solute.
d. volume of solution in a given mass of solute.
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7-3
If a substance is more highly concentrated
outside the cell than inside the cell and the
substance can move through the cell membrane,
the substance will
a. move by diffusion from inside the cell to
outside.
b. remain in high concentration outside the cell.
c. move by diffusion from outside to inside the
cell.
d. cause water to enter the cell by osmosis.
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7-3
The movement of materials in a cell against a
concentration difference is called
a. facilitated diffusion.
b. active transport.
c. osmosis.
d. diffusion.
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7-3
The process by which molecules diffuse across
a membrane through protein channels is called
a. active transport.
b. endocytosis.
c. facilitated diffusion.
d. osmosis.
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END OF CHAPTER
Chapter 7
Cell Structure and Function
Section: 7-4 Homeostasis and Cells
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7-3 Cell Boundaries
Osmosis
• The Cell as an Organism
• Single-celled organisms must be able to carry
out all the functions necessary for life.
• Unicellular organisms maintain homeostasis,
relatively constant internal conditions, by
growing, responding to the environment,
transforming energy, and reproducing.
• Unicellular organisms include both prokaryotes
and eukaryotes.
• Unicellular organisms play many important roles
in their environments.
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7-3 Cell Boundaries
Osmosis
• Multicellular Life
• Cells of multicellular organisms are interdependent and
specialized.
• The cells of multicellular organisms become specialized for
particular tasks and communicate with one another to
maintain homeostasis.
• Specialized cells in multicellular organisms are organized
into groups:
• A tissue is a group of similar cells that performs a particular
function.
• An organ is a group of tissues working together to perform
an essential task.
• An organ system is a group of organs that work together
to perform a specific function.
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7-3 Cell Boundaries
Osmosis
• The cells of multicellular organisms
communicate with one another by means of
chemical signals that are passed from one cell to
another.
• Certain cells form connections, or cellular
junctions, to neighboring cells. Some of these
junctions hold cells together firmly.
• Other cells allow small molecules carrying chemical
signals to pass directly from one cell to the next.
• To respond to a chemical signal, a cell must have a
receptor to which the signaling molecule can bind.
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