• WW0171MWW01771M292
The Cellular Basis of Life
• Historical
contributions
•Cell membranes
• Modern Cell Theory
• Membrane transport
• Types of Microscopes
• Nucleus
• Micrographs
•Organelles
Contributors to Our
Knowledge of Cells
Anton
Assembled the first microscope
von Leeuwenhoek
Robert Hooke
Observed and named “cells”
Robert Brown
Discovered the nucleus.
Schleiden and
Schwann
Rudolf Virchow
Determined that all plants and
animals are made of cells.
Cells come only from pre-existing
cells.
Modern Cell Theory
1. All living things are made of cells.
2. Cells are the basic structural unit (ie,
building blocks) of life (plant, animal,
bacterial, etc.)
3. All cells come from other (pre-existing)
cells.
4. The way a cell is made is determined by its
function (ie, what it has to do) = principle of
complementarity
Visualizing Cells
• Done using microscopes.
• Different types
– Compound light microscope: most common.
Passes beam of light through specimen.
Contains more than one lens and magnifies up
to 1000 times. Can be used to view living
organisms.
EYEPIECE
OCULAR LENS
(inside)
COARSE
ADJUSTMENT KNOB
FINE ADJUSTMENT KNOB
REVOLVING NOSEPIECE
STAGE
LIGHT SOURCE
“Compound” lenses…
• COMPOUND MAGNIFICATION!!
15x
Objective
Lens
15x
10x
10x
20x
40x
Eyepiece Lens
Total
Magnification
• Which combination would show the largest AREA?
• Which combination would you use to examine details?
Compound Micrographs
Electron Microscopes
Concentrates a beam of electrons within a vacuum; magnifies up
to 1,000,000 times. Used to view much smaller organisms.
• TRANSMITTING = TEM
• Specimen is thinly sliced.
• Electrons pass through and
image forms on fluorescent
screen.
• SCANNING = SEM
• Specimen is coated
with metal (Os,Pb,Au)
• Electrons bounce off
surface to form image.
Sample Electron Micrographs
Types of Cells
• PROKARYOTE
• Smaller, more
primitive
• Bacteria
• Fewer organelles
• No nucleus; instead
has nucleoid region
• EUKARYOTE
• Larger (~10 x)
• Complex inner
membrane system
• More organelles
• Contains a true
nucleus
Key features of Eukaryotic Cells:
*Nucleus
*Endomembrane
system
*Mitochondria
*Chloroplasts
What molecule is this?
The Fluid Mosaic Model of the
Cell Membrane
.
AMPHIPATHIC:
having both
hydrophilic
and
hydrophobic
areas
Cell Wall
• Found outside the cell
membrane in PLANTS,
FUNGI, and
BACTERIA.
• Plants use pressure
against the cell wall
(called turgor pressure)
to help support it.
The Nucleus
• “Control center”
of the cell
• Contains DNA
which
determines cell
activity through
the manufacture
of proteins
The rest of the cell …
• Cytoplasm - semi-liquid material which fills
the space between the membrane and the
nucleus.
• Contains structural fibers called
microfilaments.
• Contains “little organs” (organelles) which
each have a specific job to do.
Organelles
Ribosomes
Not bound by a
membrane
Assemble proteins
Endoplasmic
reticulum
May be rough or
smooth
Process and
transport proteins
Golgi apparatus
Modify proteins
and ship to new
site
Sites for storage of
materials
Contain special enzymes
to attach carbohydrates
or lipids to proteins
delivered by the ER
Vacuoles
Animals store proteins,
fats or carbohydrates;
plants store water or
salts.
Organelles, continued
Lysosomes
Sacs filled with chemicals
and enzymes.
Attach target, release
enzymes which recycles
components.
Mitochondria
Powerhouse of the cell;
double membrane allows
maximum surface area.
Produces energy (ATP)
for cellular activities using
a carbohydrate source.
Nucleolus
Dark area found inside
the nucleus of eukaryotic
cells.
Produces
ribosomes.
Plastids
Storage sacs.
Contain starch,
pigments,
Chloroplasts
Contain chlorophyll
Important in
photosynthesis. Found
only in plants, algae.
Cell Permeability
Membrane Transport Mechanisms
• PASSIVE TRANSPORT
• Powered by the concentration
gradient
• Must move down the gradient
from [high] to [low]
• Examples: diffusion
• At equilibrium, concentration is
equal on both sides.
• Osmosis = diffusion of water
• Facilitated diffusion = uses
carrier molecule (ex: membrane
protein)
•
•
•
•
•
ACTIVE TRANSPORT
Requires the use of ATP
Can move up the gradient
Examples: ion pumping
Bulk transport
– EXOcytosis moves
material OUT of the cell
– ENDOcytosis moves
material INTO the cell
» Water in =
pinocytosis
» Food in =
phagocytosis
Vesicle-Mediated Transport
What process is this?
Tonicity
Solution is
HYPOTONIC
Solution is
HYPERTONIC
Complexity of Organisms
• Single-celled organisms are unicellular.
• Other organisms are multicellular.
• In order to maintain complexity, there must
be a hierarchy of structure.
• Cells form tissues which form organs;
• Organs are arranged into organ systems
which all combine to form the organism.