Transcript Chapter 7 Cellular Structure & Function

Chapter 7
Cellular Structure & Function
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7.1 Cell Discovery & Theory
7.2 Plasma Membrane
7.4 Cellular Transport
7.3 Structures & Organelles
7.1 Cellular Discovery & Theory
• Main idea-The invention of the microscope led to
the discovery of cells
• Objectives
– Relate advances in microscope technology to
discoveries about cells
– Compare compound light microscopes with electron
microscopes
– Summarize the principles of the cell theory
– Differentiate between a prokaryotic cell and a
eukaryotic cell.
• Review Vocabulary
– Organization: the orderly structure of cells in an
organism
History of the Cell Theory
• 1665, Robert Hooke made a simple
microscope
• Cell-the basic structural and functional unit
of all living organisms
• Late 1600’s Anton Van Leeuwenhoek
designed his own microscope
The Cell Theory
• Fundamental idea of modern biology that includes
these three principles:
– All living organisms are composed of one or more cells
– Cells are the basic unit of structure and organization of
all living organisms
– Cells arise only from previously existing cells, with
cells passing copies of their genetic material on to their
daughter cells
Microscope Technology
• Compound Light
Microscope
• Utilizes a series of glass
lenses and visible light to
produce a magnified
image
• Maximum magnification
is around 1000X.
Microscope Technology
• Electron Microscope
• Utilizes magnets to
aim a beam of
electrons at a cell to
produce images
• Specimens must be
nonliving
• Magnifies images up
to 500,000X
Basic Cell Types
• Cells exists in various shapes and sizes
• Cells differ based on their function they
perform for the organism
• All cells have at least one physical trait in
common - the plasma membrane
Two Categories of Cells
• Prokaryotic Cells
– Cells without
specialized internal
structures
– Unicellular
– Similar to the first
organisms on Earth
Two Categories of Cells
• Eukaryotic Cells
– More complex than prokaryotic cells
– Contain a structure called a nucleus (a distinct central
organelle that contains the cell’s genetic material in the
form of DNA) and other organelles (specialized
structures that carry out specific cell functions)
– Generally one to one hundred times larger than
prokaryotic cells
Origin of Cell Diversity
• Why two basic cell types?
– Eukaryotic cells derived from prokaryotic cells?
• Endosymbiont Theory
– A symbiotic mutual relationship involved one
prokaryotic cell living inside the plasma membrane of
another
• Because eukaryotic cells are larger and have
distinct organelles, these cells have developed
specific functions.
• Specific functions has led to cell diversity, and
thus more diverse organisms that can adapt better
to their environment.
7.2 The Plasma Membrane
• Main idea: The plasma membrane help’s to
maintain a cell’s homeostasis
• Objectives:
– Describe how a cell’s plasma membrane
functions
– Identify the roles of proteins, carbohydrates,
and cholesterol in the plasma membrane
• Review Vocabulary
– Ion: an atom or group of atoms with a positive
or negative electric charge
Plasma Membrane
• Primarily responsible for homeostasis in the
cell
• A thin, flexible boundary between a cell and
its environment that allows nutrients into
the cell and allows waste and other products
to leave the cell
Selective Permeability
• A key property of the
plasma membrane
which allows some
substances to pass
through while keeping
others out
• Controls the
substances in and out
of the cell
Plasma Membrane Structure
• The plasma membrane is composed of the
phospholipid bilayer.
• Phospholipid is a molecule that has a
glycerol backbone, two fatty acid chains,
and a phosphate-containing group
• Phospholipid bilayer is two layers of
phospholipids arranged tail to tail
Plasma Membrane Structure
Plasma Membrane Structure
• Phosphate group makes the head polar and are
hydrophillic
• The two fatty acid tails are non-polar and
hydrophobic
• The phospholipids are arranged in such a way that
the polar heads can be closest to the water
molecules and the non-polar tails can be farthest
away from the water molecules
Other Components of the
Plasma Membrane
• Proteins
– Transmit signals inside the cells (receptor
proteins)
– Acts as a support structure to give the cell its
shape
– Provide pathways for substances to enter and
leave the cell (transport proteins)
Proteins
Cholesterol
• Prevents fatty
acid tails of the
phospholipid
bilayer from
sticking together
• Helps maintain
cell homeostasis
Carbohydrates
• Help cells identify chemical signals
Fluid Mosaic Model
• The components of the plasma membrane are in constant motion
(fluid)
• The different substances in the plasma membrane creates a pattern
(mosaic) on the surface
7.4 Cellular Transport
• Main idea – Cellular transport moves substances
within the cell and moves substances into and out
of the cell
• Objectives
– Explain the processes of diffusion, facilitated diffusion,
and active transport.
– Predict the effect of a hypotonic, hypertonic, or
isotonic solution on a cell
– Discuss how large particles enter and exits cells.
• Review Vocabulary
– Homeostasis: regulation of the internal environment of
a cell or organism to maintain conditions suitable for
life.
Passive Transport
• Movement of particles across the cell
membrane without using energy is passive
transport
– Diffusion
– Facilitated Diffusion
– Osmosis
Diffusion
• Movement of particles
from an area of high
concentration to an
area of lower
concentration
• Diffusion Rate Factors
– Concentration
– Temperature
– Pressure
Dynamic equilibrium
• Reached when
diffusion of material
into the cell equals
diffusion of material
out of the cell
• Molecules continue to
move, but the overall
concentration remains
the same.
Diffusion in a cell
Facilitated Diffusion
• Movement of materials across the plasma
membrane using transport proteins
– Channel proteins-water filled transport protein
that opens and closes to allow the substance to
diffuse through the plasma membrane
– Carrier proteins – change shape to move
particles through the membrane
Channel Proteins
Carrier Proteins
Osmosis
• Diffusion of water across a selectively
permeable membrane
• Three types of solutions
– Isotonic – the cell is at equilibrium
– Hypotonic – lower concentration of solute
– Hypertonic – higher concentration of solute
Isotonic Solution
• Water and dissolved substances diffuse into and
out of the cell at the same rate.
Hypotonic Solution
• Solute concentration is higher inside the cell
• Water diffuses into the cell
• Cell swells and may burst
Hypertonic Solution
• Solute concentration is higher outside the cell
• Water diffuses out of the cell
• Cell wilts or shrinks
Active Transport
• Requires energy to move substances against a
concentration gradient or from low to high
concentration
• Active transport using carrier proteins or pumps
to maintain cell homeostasis. Ex. Na+/K+ ATPase
Pumps – moving 3 Na+ ions out of the cell and 2
K+ ions into the cell
Transport of Large Substances
• Endocytosis - Process
by which the cell
surrounds and takes
particles into the cell
• Exocytosis - Secretion
of material out of the
plasma membrane
7.3 Structures & Organelles
• Main idea: Eukaryotic cells contain organelles that
allow the specialization and the separation of
functions within the cell.
• Objectives
– Identify the structure and function of the parts of a
typical eukaryotic cell
– Compare and contrast structures of plant and animal
cells
• Review vocabulary
– Enzymes: a protein that speeds up the rate of a chemical
reaction.
Cytoplasm and Cytoskeleton
• Cytoplasm - a semi-fluid material that
constitutes the environment inside the
plasma membrane (Plant & Animal Cells)
• Cytoskeleton - a supporting network of
long, thin protein fibers that form a
framework for the cell and provide an
anchor for the organelles inside the cell
(Plant & Animal Cells)
Cytoskeleton
• A framework for the cell within the
cytoplasm that rapidly assemble and
disassemble and slide past one another. This
allows cells and organelles to move.
– Microtubules-long, hollow protein cylinders
that form a rigid skeleton for the cell and assist
in moving substances within the cell
– Microfilaments-thin protein threads that help
give the cell shape and enable the entire cell or
parts of the cell to move
Cytoskeleton
Cell Structures
• Nucleus - brain of the cell; directs the cell
processes (Plant & Animal Cells)
– Contains most of the cell’s DNA, which stores
information used to make proteins for cell growth,
function, and reproduction
– Nuclear envelope - double membrane with nuclear
pores that surrounds the nucleus
– Nuclear pores - allow larger-sized substances to move
in and out of the nucleus
– Nucleolus – site of ribosome production
– Chromatin – the complex DNA attached to protein;
spread throughout the nucleus
Nucleus
Ribosomes
• Ribosomes are the most numerous of the cell’s
organelles (Plant & Animal Cells)
• The ribosome is the site of protein synthesis.
(Protein factories)
• Composed of RNA & protein
• The concentration or distribution of ribosomes in
the cells depends on how the proteins they
produce will be used.
• Proteins used by the cells are made by free
floating ribosomes.
• Exported proteins are made by ribosomes that are
attached to the ER.
Ribosomes
Endoplasmic Reticulum (ER)
• The “ER” is a membrane system of folded
sacs and tunnels (Plant & Animal Cells)
• Rough ER are covered with ribosomes
• Smooth ER have little or no ribosomes and
function primarily as an intercellular
highway, a path which molecules can move
from one part of the cell to another
– Also the site of carbohydrate and lipid synthesis
ER
Golgi Apparatus
• The processing, packaging and secreting
organelle of the cell (Plant & Animal Cells)
• Notice that the Golgi Apparatus consists of
a stack of membranes.
• It operates like a production line in a
factory, where a product is assembled at one
end, then packaged, and finally shipped out.
• The protein vesicle is modified as it passes
from sac to sac. Finally it is released to be
sent out of the cell.
Golgi Apparatus
Vacuole
• A membranebound vessicle
for the
temporary
storage of
materials
• Plant cells-one
large; Animal
cells-a few small
Lysosomes
• Lysosomes are organelles that contain
powerful digestive (Animal Cells Only)
• They destroy foreign bodies that get into the
cell
• They also digest food vacuoles to help feed
the cell
• They destroy the cell when it is too old or
damaged. This is why they are sometimes
called the “suicide sacs of the cell”
Lysosomes
Centrioles
• Centrioles are tiny
t-shaped structures
in the cell that
function in helping
the cell when it
divides to form two
new cells (Animal
Cells and most
Protists)
Mitochondria
• The Mitochondria are the respiration centers
of the cell (Plant and Animal Cells)
• They are called the “powerhouse of the
cell”
• They provide energy for the cell.
• Mitochondria have their own DNA.
• The number of mitochondria in a cell
depends on the needs of the cell.
Mitochondria
Chloroplasts
• The Chloroplast is an
organelle that is
responsible for making
food (Plants Cells Only)
• This process is called
photosynthesis.
• They use sunlight + Water
+ Carbon dioxide and
make glucose (sugar).
• The waste product of this
is oxygen and water vapor.
Cell Wall
• A Cell Wall is the rigid
covering of a plant cell
that provides shape and
protection (Plant Cell
Only)
• It is made primarily of
cellulose (carbohydrate)
• Pores in the cell wall
allow ions and
molecules to pass to and
from the cell
membrane.
Cellular Projections
• The Cilia is a hair-like
cellular projection that
functions in movement both
of an organisms and of
moving particles. Like in the
illustration to the right (Some
Animal Cells).
• The Flagella is a whip-like
tail cellular projection that is
long and help movement in
unicellular organisms and
some individual cells such as
the sperm on the right (Some
Animal Cells)
Animal Cell
Plant Cell