Download The Cell

The Cell
Microscopes, History & the Cell
Theory
The Microscope
► Originally
created for trade purposes
► Merchants needed a way of examining types
of fibers more closely (i.e., silk, wool, etc)
to ensure quality of the product
Anton van Leeunwenhoek
► Dutch
biologist
► Generally credited w/developing
first microscope (early to mid
1600’s)
► Studied never-before-seen living
organisms in pond water, blood
cells and bacteria
► Called what he saw “animalcules”
and “beasties”
Robert Hooke
► English
scientist
► Examined cork slices and
other plant tissues under a
microscope
►What
he saw were the remnants
of dead cells
► He
saw box-like structures he
called ‘cells’
►Named
them after the rooms in a
monastery lived in
The Happenin’ 1800’s
► 1824-French
scientist Henry Dutrochet says
all living things are made of cells
► 1831-Scottish
scientist Robert Brown calls
the dense round body in the middle of a cell
the “nucleus”
►Didn’t
know the function of the nucleus
The Happenin’ 1800’s:
The Big Three
► 1838-German
botanist Matthias Schleiden
says all plants are made of cells
► 1839-Zoologist Theodor Schwann says all
animals are made of cells
► 1855-German Physician Rudolf Virchow
says that all cells arise from pre-existing
cells
► These guys helped to form the “Cell
Theory”
The Cell Theory: The modern
Version
► 1.
All organisms are made up of cells.
► 2.
New cells are always produced from preexisting cells.
► 3.
The cell is a structural and functional unit of all
living things.
► 4.
The cell contains hereditary information
which is passed on from cell to cell during
cell division.
► 5.
All cells are basically the same in chemical
composition and metabolic activities
The Cell Structure
Types of Cells, Examples and
Organelles
Cell Size Limitations: Think “The
Roman Empire”
► Cell
size is limited by the:
►The
flow of information and materials
through the cell
►
The cell on the right takes 5
times as long to get info from
nucleus to membrane!
Two Types of Cells
► Two
major categories of cells based upon nuclei
 Eukaryotic Cells (Eukaryotes)
►Have a nucleus and membrane-bound
organelles
 Prokaryotic Cells (Prokaryotes)
►Do NOT have a nucleus
►No internal membrane-bound organelles
Eukaryotic and Prokaryotic Cells
Eukaryotic Organisms Comprise 4 of
the 5 Kingdoms
► Single-Celled
Eukaryotes
 Kingdom Protista: Protists including Algae
 Kingdom Fungi: Yeasts
► Multi-celled
Eukaryotes
 Kingdom Fungi: Molds, Mushrooms
 Kingdom Plante: Plants
 Kingdom Animalia: Animals
Prokaryotic Organisms Comprise the
Kingdom Monera
► Monera
► The
include all of the bacteria
simple structure of bacteria, and
prokaryotic cells in general, make them the
most numerous of all the kingdoms
Basic Cell Structure
► Three
common organelles (little organs)
to all Plant and Animal cells:
► Cell
Membrane
► Nucleus
► Cytoplasm
Cell Membrane
► Present
in all cells
► The outer boundary of the cell
► Regulates what enters and exits the cell
► Provides protection and support
► REAL WORLD EXAMPLE: A chain link
fence around a city
Cell Membrane Structure
► Lipid
Bilayer (Composed of Phospholipidsa type of fat)
► Proteins imbedded in the bilayer provide:
►Support
►Channels
for molecular transit
►Pumping action for transit
► Carbohydrates
on cell surface act as
chemical identification for the body
Diagram of Cell Membrane
Cell Membrane Junctions
► Gap
Junctions
 Communication
► Tight
Junctions
 Impermeable
► Desmosomes
 Anchoring
Nucleus
► The
control center of the cell
► Not all cells have nuclei “true” nuclei
(think of prokaryotes-i.e., bacteria!)
► The most important part of the nucleus is
the DNA inside of it  The genetic
blueprint of life
Nucleus Structure
► The
Nuclear Envelope (also nuclear
membrane)
►Two membranes closely held
together
► Nuclear pores allow transit in and out of
the envelope
► Real world example: Security checkpoints
at City Hall
Nucleus Structure
► Nucleolus
 Consists of the Ribonucleic Acid (RNA) and
protein
 Ribosomes are made here
► Chromosomes
 Elaborate protein “frame” that holds and
protects DNA
Nucleus Diagram
Cytoplasm
► Gel/water-like
material between the
nucleus and the cell membrane
► Holds all the organelles in place
► Provides a place for chemical reactions to
take place
Cell Wall
► Found
in plants, algae and some bacteria
► Lies outside the cell membrane
► Provides protection and incredible
support
► Very porous (lots of holes!) for important
molecules to pass through
► Made of multiple layers of different
types of carbohydrates including
Cellulose-otherwise known as fiber
Cell Wall Structure
Mitochondria
► Power
station (animal cell)
► Takes chemical energy stored in food and
converts it to a form the body can use-ATP
► Contains two membranes:
►Outer
membrane surrounds and
protects
►Inner membrane folds to increase
surface area
 energy conversion happens here
Chloroplasts
► Power
station (plant and algae cell)
► Captures light energy from the sun (using
chlorophyll) and converts it into chemical
energy
►The innermost membrane captures
the light energy from the sun
Chloroplast Structure
Plastids
► Plant
organelles w/many forms
►Chloroplasts are one form
► Stores food and pigments
►Leukoplasts  Store food
►Chromoplasts  Store pigments
(coloration)
Ribosomes
► Makes
proteins from amino acids
► Cells that need more protein will have
significantly more ribosomes (e.g., muscle
cells will have more than skin cells)
► Composed of RNA and proteins
► Membrane-bound or free-floating
► Among the smallest of the organelles
Endoplasmic Reticulum (ER)
► Complex
network of channels throughout
a cell
► Acts as an superhighway within the cell
for transport of materials
► Two types of Endoplasmic Reticulum
►Smooth
►Rough
Smooth Endoplasmic Reticulum
► Have
a smooth appearance (do not have
ribosomes attached to them)
► Some cells’ ER hold special enzymes and
chemicals for various functions
Rough Endoplasmic Reticulum
► Rough
due to ribosomes being stuck to
the outside
► Involved in making proteins
► New proteins are inserted into Rough ER
for transport through the cell
Golgi Apparatus
► Discovered
by Italian scientist Camillo Golgi
► Resembles a flattened stack of membranes on
top of one another
►Located
► Assists
by the cell membrane
in the collection, modification,
packaging and distribution of proteins and other
molecules throughout the cell
► The UPS-United Parcel Service of the cell
Lysosomes
► The
“Cleanup Crew” of the cell
► Small, they contain chemicals and enzymes for
digestion
► Involved in cleaning up cell parts, molecules,
etc. that have died or outlived their usefulness
► Formed by the Golgi Apparatus
► Also called the “Suicide Sac”
Lysosomes
► Conducts
the process of endocytosis
► Engulfing of large particles too big to fit
through a cell membrane
Vacuoles
► Saclike
structure that:
 Stores water, salts, proteins and
carbohydrates
► Found
in plant and animal cells
► Vacuole is much larger in plants due to
enormous amounts of water being
stored
► Builds up water pressure and makes
plants sturdy
Cytoskeleton
► Cell
framework
► Composed of filaments and fibers that
help maintain shape, aide in transport,
etc.
► Composed of two parts:
►Microtubles
►Mictrofilaments
Microtubles
► Hollow
tubes made from protein
► Provide support & organelle transport
► Aide in cell division by forming centrioles
(animal cells only)
► Support Cilia and Flagella
►Finger-like or whip-like structures that
help with:
►Cell
movement
►Movement along the cell surface
Microfilaments
► Long,
thin fibers made of proteins
► Provide:
►Support
and movement of cell
►Movement of the cytoplasm (called
cytoplasmic streaming)
Cytoskeleton Diagram
Maintaining a Constant
Cell Environment
Osmosis & Diffusion
Diffusion
 The process by which
molecules of a
substance move from
areas of higher
concentration of that
substance to areas of
lower concentration
Diffusion
► In




the fluid and gaseous state of matter:
Molecules are constantly in motion; colliding
with one another and spreading out randomly
This random motion has a general pattern
Molecules move from an area where there are
more molecules to where there are less
molecules
In other words, they move from an area of
higher concentration to an area of lesser
concentration.
Equilibrium
► The
point at which the distribution of
molecules and materials are evenly spaced
out in any given area.
Osmosis
►
The diffusion of water across
a selectively permeable
membrane.
►
Some membranes are
selectively permeable so some
substances cannot pass
through or across them
(Those substances that “don’t
mix well” with the fat in the
membrane).
►
Water is the exception:
 Water doesn’t mix with
lipids however its
molecules pass very rapidly
through the membrane.
Osmotic Pressure
► The
force exerted by osmosis.
► Tends to move water across a membrane from a
dilute solution to a more concentrated solution.
► When solutions are of equal concentration (the
desired state) then you have equilibrium and
NO movement of water across the membrane.
Solution Types
Relative to a cell, there are three
solution types
Hypertonic
► When
the solution outside of a cell is of
higher concentration than the solution
inside of a cell.
► Water will leave the cell in order to dilute
the solution outside of the cell.
Hypotonic
► When
the solution outside of a cell is of
lesser concentration than the solution
inside of a cell.
► Water will enter the cell in order to
dilute the solution inside of the cell.
Isotonic
► When
the solution outside of a cell is of
the same concentration of the solution
inside of a cell.
► Water will neither enter nor leave the
cell.
► There will be no net movement of water.
Solution Pictures
Transport
Active v. Passive Transport
Passive Transport
► Transport
of water from areas of higher
concentration to areas of lower
concentration (either across a membrane or
not) that requires NO energy.
Facilitated Diffusion
►
Deals with the movement of molecules across a membrane
that cannot cross a membrane by themselves.
►
The channel proteins that facilitate the passage of these
molecules are typically specific to that particular
substance.
 In other words, the proteins have an affinity for whatever
substance is dissolved in the solution and will attract it.
►
Movement of the substance is reliant upon difference in
charge of the molecules and the proteins.
►
This process DOES NOT require energy and so is
diffusion driven.
►
Therefore, there must be a difference in concentration on
either side of the cell membrane.
Active Transport
► Energy
requiring process that moves
molecules across a membrane and AGAINST
a concentration gradient (from an area of
lower concentration to an area of higher
concentration).
Types of Active Transport
► Pumping
action:
 “Pumps” move individual molecules across the membrane and
against the concentration gradient.
 Chemical energy is required to power the pumping action of the
protein channel.
 Calcium, potassium and sodium are among those substances
transported across the membrane.
► Called
a “Sodium Potassium Pump”
Types of Active Transport
►
Endocytosis
 Particles “push” against the outside of the cell membrane causing a
pocket to form.
 This pocket breaks loose on the inside of the cell forming an
individual vacuole, or storage structure.
 Large molecules, clumps of food and other cells can be taken into
the cytoplasm this way.
► Phagocytosis:
 A form or Endocytosis where large, solid particles are taken in.
 Amebas feed this way.
► Pinocytosis:
 When liquid forms pockets along the cell membrane, forms a vacuole and
is taken into the cell cytoplasm.
►
Exocytosis
 When large particles push against the cell membrane from the
inside and the membrane surrounds it as it leaves the cell.