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INTRODUCTION TO THE
CELL
EARLY CONTRIBUTIONS
• Robert Hooke - First person to see cells, he was
looking at cork and noted that he saw "a great many
boxes. (1665)
• Anton van Leeuwenhoek - Observed living cells in
pond water, which he called "animalcules" (1673)
• Theodore Schwann - zoologist who observed tissues of
animals had cells (1839)
• Mattias Schleiden - botanist, observed tissues of plants
contained cells ( 1845)
• Rudolf Virchow - also reported that every living thing is
made of up vital units, known as cells. He predicted that
cells come from other cells. (1850 )
THE CELL THEORY
• 1. Every living
organism is made of
one or more cells.
• 2. The cell is the basic
unit of structure and
function. It is the
smallest unit that can
perform life functions.
• 3. All cells arise from
pre-existing cells.
*Why is the Cell Theory
called a Theory and not a
Fact?
CELLS ARE ALWAYS SMALL, HOW SMALL DEPENDS ON THE TYPE OF
CELL
CELLS CAN COME IN A VARIETY OF SHAPES
FIGURE 4.3
Single Cheek Cell - at different illuminations
CELL TYPES
•
•
•
There are 2 main categories of cells:
Prokaryotes - Bacteria
Eukaryotes – Plants, Animals
THE DIFFERENCES
Prokaryotes
• No Nuclei
• DNA not wrapped
around histones
• Small ribosomes
• Lack membrane
bound organelles
• Structural differences
in cell wall structure
•
•
•
•
Eukaryotes
Contain Nuclei
DNA wrapped around
histones
Larger Ribosomes
Contain Organelles
PROKARYOTES
•
•
Baceria, Cyanobacteria, Archeabacteria
DNA is not found in a nucleus, and there
are no histones
o
•
•
DNA is often found as a Plasmid (a circle of
DNA) (nucleoid region)
Prokaryotes lack organelles (do contain
ribosomes)
Prokaryotes are generally much smaller
STUDYING CELLS
•
•
Scientists use microscopes to study cells
2 General Types of microscopes:
o
o
Light Microscopes
Electron Microscopes
CELL MEMBRANE STRUCTURE
CELL MEMBRANE
•
•
•
All cells are surrounded by a
PHOSPHOLIPID BILAYER
This surrounding is selectively permeable
(O2, H20, CO2)
The phospholipid bilayer contains various
proteins that have specific jobs
CELL MEMBRANE
•
•
•
Diffusion – The random movement of
molecules moving from an area of high
concentration to low concentration
Since cell membranes are selectively
permeable, cells use osmosis to reach
equilibrium in their fluid environments
Osmosis – The diffusion of water through
a selectively permeable membrane
OSMOSIS
When talking about Osmosis, there are
three types of environments:
• Isotonic – Concentration of solutes is the
same inside and outside of the cell
• Hypotonic – Solution has a lower solute
concentration than inside the cell
• Hypertonic – Solution has a higher solute
concentration than inside of the cell
ENVIRONMENTS
Hypotonic
Isotonic
Hypertonic
Cell Membrane is made of:
a) Phospholipid Bilayer (double layer)
b) Proteins
c) Carbohydrates
PROTEINS
•
•
Integral Proteins – proteins that go into the
hydrophobic region of the bilayer
Peripheral Proteins – Proteins bound to the
surface of the cell
CHANNEL PROTEINS
•
Channel Proteins – Provide open
passageways for large, hydrophilic
molecules to pass through
ION CHANNELS
•
Ion Channels – Allow ions to pass across
the membrane
PORINS AND AQUAPORINS
•
•
Porins – Allow polar molecules into the
cell
Aquaporins – Allows large amounts of
water into the cell
CARRIER PROTEINS
•
Carrier Proteins – Bind to a molecule, and
while it is binded, take it across the cell
membrane
o
This is how glucose enters the cell
TRANSPORT PROTEINS
•
•
•
Transport Proteins – Use ATP to transport
materials across the membrane
Active Transport – When energy is used
to bring molecules across the cell
membrane
Ex: Sodium Potassium Pump
MOLECULAR TRANSPORT
RECOGNITION PROTEINS
•
•
Recognition Proteins – Glycoproteins that
allow other cells to identify it
Glycoprotiens have a polysacharide chain
attached to it
ADHESION PROTEINS
•
Adhesion Proteins – Attach cells to one
another, or provide anchors for the
cytoskeleton
RECEPTOR PROTEINS
•
Receptor Proteins – Provide binding sites
for hormones or other molecules
CHOLESTEROL
•
•
Lipid-like waxy alcohol found in cell
membrane of ANIMALS ONLY
Adds rigidity to cell membrane
ENDOCYTOSIS
•
Endocytosis – Process by which a cell
takes in material by folding the cell
membrane
o
o
Phagocytosis
Pinocytosis
PHAGOCYTOSIS
•
Phagocytosis – Process in which extensions of
cytoplasm surround and engulf large particles
PINOCYTOSIS
•
Pinocytosis – Process by which a cell
takes in liquid from the surrounding
environment
EXOCYTOSIS
•
Exocytosis – Process by which a cell
releases materials
VESICLE
•
Vesicle – Structure that moves materials
between organelles and/or the plasma
membrane
o
Pino and phagocytosis produce vesicles
ORGANELLES
•
•
Organelle – a specialized structure that
performs a certain function within a cell
The following organelles are found in
Eukaryotoic cells
CYTOPLASM/CYTOSOL
•
•
•
All organelles within the cell lie within the
CYTOSOL/CYTOPLASM
Cytosol – The semi-fluid substance within
the cell where the organelles are found
Cytoplasm – The entire region between
the nucleus and the cell membrane
NUCLEUS
•
•
Nucleus – structure that contains genetic
material, and controls cellular activity
The nucleus is surrounded by a 2
membrane NUCLEAR ENVELOPE, with
tiny holes in it called NUCLEAR PORES
THINGS FOUND IN THE
NUCLEUS:
•
•
•
Chromatin – Granular material of DNA
coiled around protein
Chromosomes – Tightly wound, threadlike
DNA
Nucleolus – Small dense region full of
ribosome's
o
The nucleolus aides in ribosome synthesis
RIBOSOMES
•
Ribosomes – Tiny spheres of rRNA and
protein that put together protein
molecules
ENDOPLASMIC RETICULUM
•
Endoplasmic
Reticulum –
Internal
membrane
system that
makes lipids
and modifies
proteins
ER
•
The ER and nuclear envelope is
continuous
SMOOTH AND ROUGH
Smooth ER
• Lacks bound
ribosomes
• Makes lipids
• Breaks down carbs
• Produces some
hormones
• Aid in detoxification of
drugs
Rough ER
• Has bound ribosomes
• Produces proteins,
glycoproteins
• Produces membranes
(puts lipids and proteins
together)
GOLGI APPARATUS
•
Golgi Apparatus – The organelle that sorts
and packages proteins from the ER
The cis face acts as the receiving center of the organelle
Fuse
Break
Off
The trans face acts as the shipping center of the organelle
LYSOSOMES
•
Lysosome – Cell organelle filled with
enzymes needed to break down certain
materials in the cell
VACUOLES
•
Vacuole – Cell organelle that stores
materials such as water, salts,
proteins, and carbs
o Food Vacuoles – Form via Phagocytosis
o Contractile Vacuoles – Remove excess
H20
o Plants have 1 CENTRAL VACUOLE
Plant Cell
Animal Cell
Food Vacuole
Central Vacuole
MITOCHONDRIA
•
Mitochondria – Converts macromolecules
into energy for the cell to use
2
Membranes
MITOCHONDRIA
•
•
Mitochondria are the sites of cellular
respiration (form ATP’s)
We will look at Cellular Respiration in the
next few weeks
CHLOROPLASTS
•
Chloroplasts – Capture light energy and
converts it into chemical energy
CHLOROPLAST STRUCTURE
•
Thylakoids – Membrane sacs
•
Granum – Stacks of thylakoids
•
Stroma – The fluid outside of the
thylakoids
PEROXISOME
•
•
•
An organelle that contains enzymes and
attaches hydrogens to oxygens to
produce hydrogen peroxide as a
byproduct
Peroxisomes break down lipids
H2O2 is then broken down into water
CYTOSKELETON
•
Cytoskeleton – Network of protein
filaments within some cells that helps the
cell maintain its shape and is involved in
many forms of cell movements
Microfilaments – Protein threads that give cell
support
o Microtubules – Protein tubes that give cell
support
o
Microfilaments
Microtubules
FLAGELLA/CILIA
•
Flagella – Long whip-like structure that
aid in cell locomotion
o
•
Few in number, move in snake-like motion
Cilia – Short, hair like structures that aide
in locomotion, and in transportation of
material
o
Numerous, move in back in forth motion
FLAGELLUM/CILIA STRUCTURE
CENTRIOLES AND BASAL
BODIES
•
•
•
Both microtubule organizing centers
(MTOC’s)
Centrioles – Give rise to spindle and aide
in cellular division
Basal Bodies – At base of flagella and
cilia for support and developmental
purposes
EXTRACELLULAR REGION
•
•
The extracellular region is everywhere
outside of the plasma membrane
The following are structures found in the
extracellular region
CELL WALLS
•
Cell Wall – Strong supporting layer
offering support to the cell
Found in plants, fungi, some protists, and
some bacteria
o Made of cellulose or chitin
o
Cell Membrane
Cell Wall
EXTRACELLULAR MATRIX
•
•
•
This is found in animals
Composed of structural proteins, and sugars
for mechanical support between adjacent cells
Collagen is a common protein found in the
ECM
CELL JUNCTIONS
•
•
•
Anchor cells to one another, and allow
cells to exchange various materials:
Anchor Junctions – Proteins that bind
adjacent animal cells together
Tight Junctions – Tightly ‘stitched’ seams
between animal cells (impenetrable)
COMMUNICATING JUNCTIONS
•
Gap Junctions – Narrow tunnels between
animal cells made of proteins called
‘connexins’
o
•
Allow ions to pass through, but does not permit
cytoplasm to mix
Plasmodesmata – Channels between
plant cells that allow materials to pass
o
Narrow tube of ER passes through