Transcript Chapter 7 A View of the Cell

Chapter 7 Cellular Structure
and Function
7.1 Cell Discovery and Theory
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The History of the Cell Theory
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Cells are the basic units of living
things
Before microscopes people believed
diseases were caused by curses and
supernatural spirits (wrath of God)
The idea that a living thing like a
bacteria could cause disease or
infection never occurred. Why?
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Development of the Light Microscope
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Today's
microscope is a
compound
microscope with
two lenses
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Eyepiece lens
Objective lens
Can magnify 1500
times
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Simple Light Microscope
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Developed by
Anton van
Leeuwenhoek in
the mid 1600
One lens
Much like a
magnifying glass
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The Cell Theory
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Robert Hook
First to use the
term “cell”
Looked a cork
under a
microscope, saw
the cell walls
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Robert Hook
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Contemporary of
Anton van
Leeuwenhoek
English
Published and
encouraged others
to use
microscopes
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Matthias Schleiden
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1838
German botanists
Examined plants
of all types
All plants are
made of cells
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Theodore Schwann
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1839
German zoologist
Contemporary of
Schleidens
Examined animal
tissues of many
types
All animals are
made of cells
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Rudolph Virchow
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1855
German physician
All cells come from
preexisting cells
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The Cell Theory
1.
All organisms are composed of one
or more cells
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2.
The cell is the basic unit of
organization of all organisms
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3.
Unicellular or multicellular
Structure
Function
All cells come from preexisting
cells
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Technology Since the 1800’s
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Compound light microscopes
continued to improve so that
bacteria were able to be classified
Most magnification possible with
light microscopes cannot see inner
cell parts
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Electron Microscopes
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Developed in the 1940’s
Uses magnets to focus a beam of
electrons (in place of light)
Can magnify 500,000X
Several types
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Scanning: looks at surface; get 3-D
Transmission: looks at interior
Scanning-Tunneling: atoms on surface
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Microscope Aids
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Both light and electron microscopes
use dyes and stains which helps to
contrast cell and parts
Most dyes and stains kill the cells
Most specimens of electron
microscopes need to be in a
vacuum and/or coated with gold
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Two Basic Cell Types
Prokaryote
 Have plasma
membrane
 No internal membrane
bound structures
 Unicellular
 Smaller in size
 No specialization
 Example: bacteria
Eukaryote
 Have plasma
membrane
 Internal membrane
bound structures
 Unicellular and
multicellular
 Larger size
 Much specialization
 Example: animal
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Two Basic Cell Types
Prokaryote
Eukaryote
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Two Basic Cell Types
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Chapter 7 Cellular Structure
and Function
7.2 The Plasma Membrane
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Plasma Membrane Diagram
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Plasma Membrane Micrograph
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Plasma Membrane Structure
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Made of
phospholipid
bilayer
Polar ends are
hydrophilic
Nonpolar ends are
hydrophobic
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Plasma Membrane Function
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Job of plasma membrane is homeostasismaintain balance
For cells to survive they must keep the
inside in and the outside out, yet allow
some materials to move into and out of
the cell
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Structure Fits Function
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The structure of the plasma
membrane (how it is put together)
allows the plasma membrane its
function or job, selective
permeability
Selective permeability: the ability to
allow some materials into or out of
the cell but not other materials
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Selective Permeability
Out side
of cell is
different
from
inside of
cell
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Structure Fits Function
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Both the inside of the
cell and the outside
are water
environment so the
hydrophilic ends face
in and out
The hydrophobic fatty
tails are in the middle
so that materials can’t
pass through easily
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Structure Fits Function
Role of proteins in plasma membrane
 Channels or tunnels for substances
to pass through with specific fit
 Identification of organism and
tissue type
 Signal sending proteins
 Provide support for the
phospholipids
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Plasma Membrane Proteins
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Plasma Membrane
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Cholesterol stabilizes the plasma
membrane in animal cells
Animal cells have no cell wall as do
plant cell
High blood cholesterol is a risk
factor for heart disease and stroke
Animals (including us) produce
cholesterol for the stabilization of
the cell membrane
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Fluid Mosaic Model
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Fluid Mosaic Model
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FLUID: Plasma membrane in
constant motion with the
phospholipids of one layer moving
one direction and the phospholipids
of the other layer moving in the
opposite direction
MOSAIC: something consisting of a
number of different things of
different types
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Chapter 7 Cellular Structure
and Function
7.3 Structures and Organelles
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Cellular Boundaries
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Plant Cell outer
most part is the
cell wall; plasma
membrane is
inside of the cell
wall
Also fungi, algae
and other
Kingdom Protista
organisms
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Animal Cell outer
most part is the
plasma membrane
Also protozoans
(Kingdom Protista)
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Cell Wall
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Functions to protect and support
NOT selectively permeable
Porous: let anything in
Plant cell wall made of cellulose
(wood)
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Plant Cell Wall
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Nucleus
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Controls all cell
activities
Contains
information to
make proteins; all
parts of the cell
depend on
proteins to do its
job
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Nucleus
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Contains DNA in
strands known as
chromatin
(chromosomes are
chromatin that is
condensed and
visible during cell
reproduction)
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Nucleolus
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Found in the
nucleus
Organelle that
makes ribosomes
Ribosomes are
sites where
proteins are
manufactured
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Ribosomes
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Ribosomes are
unique because
they do not have a
membrane around
them
Found in
prokaryotes and
eukaryotes
Look like pepper
on the ER
(spaghetti)
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Nuclear Membrane
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Also called Nuclear
Envelope
Surrounds the
nucleus
Same composition
as the plasma
membrane
Contains pores to
allow large
materials to pass
out (ribosomes
and RNA)
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Cytoplasm
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All the gelatinous
material with the
organelles inside
the cell between
the nucleus and
the cell membrane
Cytosol is that part
of the cytoplasm
that is liquid
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Organelles for Assembly, Transport
and Storage
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Endoplasmic Reticulum (ER)
Golgi Apparatus
Vacuoles
Lysosomes
All have phospholipid bilayer
membrane structure
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Endoplasmic Reticulum (ER)
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Folded membrane like
an accordion for
workspace
Rough ER contains
ribosomes for protein
production
Smooth ER (No
ribosomes) for lipid
production
Tube-like for transport
of materials
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Golgi Apparatus
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Takes protein from
the ER and makes
it ready to be
transported
Like UPS,
packages it and
gives it a
destination
address
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Vacuoles
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Large central
vacuole in plant
cells to store water
Smaller vacuoles
for storage of
food, waste,
water, enzymes
and other
substances in both
plant and animal
cells
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Lysosomes
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Double membrane
bound sac
containing
digestive enzymes
Digests food
particles, engulfed
viruses and
bacteria, and worn
out cell parts
Can fuse with
vacuole to digest
contents of
vacuole
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Energy Transformers
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Chloroplasts
Mitochondria
Both have phospholipid bilayer
membrane structure
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Chloroplasts
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Capture light
energy and
produce food to be
used later
Pigment
chlorophyll give
plants their green
color
Other plastids
store starch, lipids
and other
pigments
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Chloroplasts
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Double membrane
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Clear outer
Folded inner:
thylakoid
Stacks of
membranes sacs
grana and liquid
stroma
Site of
photosynthesis
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Mitochondria
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Break down food
to release energy
Found in
eukaryotes
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Mitochondria
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Double membrane
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Outer
Folded Inner to
increase membrane
space
Some cells need much
energy and have
hundreds of
mitochondria; other
cell have few
mitochondria because
these cells use little
energy
Site of cellular
respiration
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Structures for Support and Locomotion
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Cytoskeleton
Cilia
Flagella
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Cytoskeleton
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Internal framework in
the cell to keep the
organelles in place
Maintains the cell’s
shape
Made of microtubules
(hollow) and
microfilaments (solid)
protein fibers
Shown in green
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Centrioles
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Made of groups of
microtubules
Function in cell
division (Ch. 9)
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Cilia and Flagella
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Enclosed by
plasma membrane
Used for
locomotion and
feeding
Made of pair of
microtubules
surrounded by 9
additional pairs
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Cilia
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Short numerous
hair like
projections
Beat like oars on a
boat
Line our
respiratory system
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Flagella
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Tail like structure
that is whip like
May have one
flagella or several
Mostly used for
locomotion
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Chapter 7 Cellular Structure
and Function
7.4 Cellular Transport
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Passive Transport
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NO energy
expended by cell
Diffusion
Facilitated
diffusion
Osmosis
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Diffusion
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All molecules are in constant motion;
called Brownian Motion
The high the temperature the faster the
motion because they have more energy
Diffusion is the net movement of
particles from higher concentration to
lower concentration because of this
movement of particles
Diffusion is slow because it is a random
process
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Rates of Diffusion
Concentration of substances involved
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More concentrated substances speed up rate
of diffusion
Energy by temperature or agitation
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Increased temperature speeds up rate of
diffusion
Agitation or stirring speeds up rate of
diffusion
Pressure
3.
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Increased pressure speeds up diffusion
because pressure increases molecular
movement
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Dynamic Equilibrium
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Equilibrium is
reached when
there is no net
concentration
change
Dynamic because
Brownian motion
continues
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Diffusion in Living Systems
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In living things
materials must diffuse
into and out of cells all
the time
Concentration
gradient exists so that
substances will move
into the cell until there
is the same number
on each side
Liquids, solids and
gasses can diffuse into
and out of a cell
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Facilitated Diffusion
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Diffusion of
materials through
proteins in cell
membranes
NO energy
required
Common for
sugars and amino
acids
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Osmosis
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Diffusion of water through a cell
membrane
Cell membranes are selectively
permeable
NO energy expended by the cell
Moves water from high
concentration to low concentration
Must occur for homeostasis to occur
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Control of Osmosis
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Unequal distribution
of particles on either
side of a selectively
permeable
membrane
Water moves
through the
membrane until
equilibrium is
reached (no net
change)
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Cells in Solutions
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Isotonic Solution = same solutes
Hypotonic Solution = lower solutes
Hypertonic Solution = higher solutes
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Cells in Isotonic Solutions
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Isotonic solutions have the same
solute concentration as the cell, so
water moves in and out at the same
rate; no osmosis; no net change
Dissolved substances outside the
cell equals dissolved substances
inside the cell
Examples: Normal saline IV solution
(0.9% salt) and tap water in most
areas
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Cells in Hypotonic Solutions
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Dissolve substances lower outside
the cell than inside the cell
Water moves into the cell; cell
swells
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Animal cell bursts
Plant cell becomes more firm (higher
turgor pressure); reason why plants
are sprayed at grocery store
Example: Distilled water
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Cells in Hypotonic Solutions
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Cells in Hypertonic Solutions
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Dissolved substances higher outside
the cell than inside the cell
Water leaves the cell; cell shrinks
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Animal cell wrinkled (reason why meat
is salted after cooking)
Plant cell plasmolyzed; cell membrane
moves away from cell wall
Example: salt water, syrup
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Cells in Hypertonic Solutions
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Cells in Solutions
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Comparing Plant and Animal Cells
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Active Transport
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ENERGY used by the cell
Carrier proteins with a SPECIFIC FIT
with a specific molecule
Bringing substances into the cell
against the concentration gradient
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Active Transport
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When molecule fits with carrier protein the
carrier protein molecule changes shape to allow
the molecule to move into or out of the cell
When movement complete, the carrier protein
changes back to original shape for another
molecule
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Active Transport
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Also used to rid the
cell of materials
against the
concentration gradient
Takes energy to use a
pump
Much of your cell’s
energy is expended in
the sodium-potassium
pump
(2 K+ in 3 Na+ out)
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Large Materials Into Cells
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Endocytosis,
getting large
materials INTO the
cell
Cell expends
energy
Engulfs and forms
a vacuole
Example: white
blood cells
engulfing a
bacteria
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Large Materials Out of Cells
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Exocytosis: large
materials out of a
cell
Cell expends
energy
Example:
secretions or
hormones
Example: waste
products
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Pseudopodia
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Structure of
locomotion
Used for capture
of food
Extensions of the
cell contents
within the cell
membrane
Example: Amoeba
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