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CELLS AND
CELL
THEORY
CELL SCIENTISTS
Robert Hooke-1665, observed
small cavities in cork which
he called cells.
Anton van
Leeuwenhoeklate 1600’s,
refined the
microscope; saw
single-celled
organisms which
he called
“animalcules”
Rene Dutrochet-1824,
discovered osmosis; concluded
that plants and animals are
both made of cells.
Robert Brown-1831, First
to see and name the
nucleus
Felix Dujardin-1835, first to
notice cytoplasm
Matthias Schleiden-1839,
wrote a paper stating all
plants are made of cells
Theodor Schwann-1839,
wrote a paper stating all
animals are made of cells.
Rudolf Virchow-1855, first
to see cell division
CELL THEORY:
•All living things are made
of cells
•Cells are structurally and
functionally similar
•Cells come from other
cells
WHAT IS A CELL?
The smallest unit that
can perform all life
processes.
What is an
Organelle?
•one of several
specialized structures,
suspended in the
cytoplasm of a
eukaryotic cell.
Prokaryotic Cells:
1. No nucleus
2. No membrane-bound
organelles
3. Very small
4. DNA in one loop
5. Only bacteria
Eukaryotic Cells:
1. DNA in long strands
(chromatin) in nucleus
2. Large in comparison to
bacteria (prokaryotes)
3. Many membrane-bound
organelles
4. All other organisms, except
bacteria
EUKARYOTIC
CELL STRUCTURE:
CELL MEMBRANEEncloses all parts of the
cell;
Controls what
goes in and out
Cell Membrane Structure:
•Phospholipid bilayer
•Embedded with proteins:
(Marker, Channel, Receptor)
•Glycolipids
•Glycoproteins
•Fluid Mosaic Model
Cell Wall:
•Found in plants
•Made of cellulose
•Surrounds cell membrane
•Provides rigidity for plant
CELL
WALL
Cytoplasm:
•Jelly-like substance in a
cell
•Surrounds other cell parts
•Composed of water, salt,
& other organic molecules
cytoplasm
Nucleus:
•Directs & stores
instructions for cell
functions
•Encloses
DNA
(chromatin)
Nuclear Membrane
• Double membrane that
isolates the interior of the
nucleus from the cytoplasm
• Has pores to allow things to
be transported into and out
of the nucleus.
• 4 phospholipid layers
Nucleolus:
•Inside of nucleus
•Assembles ribosomes
•May be 1 or more than 1
nucleolus
Chromatin:
•Long strands of a DNAprotein complex found in
nucleus
chromatin
Nucleoplasm:
•A viscous fluid in the
nucleus in which the
chromatin &
nucleolus are
suspended.
Ribosomes:
•Protein factories of cell
•Line up amino acids in
correct order ribosomes
Mitochondria:
•“Powerhouses” of cell
•Make ATP
•Complete breaking down
of glucose molecules
Golgi Apparatus:
•Packages & distributes
organic molecules that
leave the cell
•Surround molecules with
membrane
Lysosomes:
Bags of enzymes that:
•Digest macromolecules
•Digest worn out cell parts
•Destroy invading bacteria
Endoplasmic Reticulum (ER):
•Membrane system of
folded sacs & tunnels
•Helps maintain
homeostasis
•Endoplasmic Reticulum (ER):
•Rough ER has ribosomes
& transports proteins
•Smooth ER has no
ribosomes & transports
lipid & carbs.
•Attached to nucleus
Centrioles & Centrosomes:
•Organizing centers for cell
division
•Found only in animal cells
centrioles
centrosome
PLASTIDS:
A class of organelles found
only in plants and in some
protists.
Chloroplasts:
•Site where glucose is made
•Contain chlorophyll
Leucoplasts:
•Change glucose to starch
•Look like grains of rice
•Starch is stored here
leucoplast
•Manufacture & store plant
pigments
•Red, orange, purple, yellow
•Found in fruit, flowers &
colorful leaves
Vacuoles:
•Fluid filled sacs
•Store enzymes, water, and
waste products
•Large, central vacuole in
plants
•Many small vacuoles in
other cells (or none at all)
CYTOSKELETON:
•Helps cell hold its shape
•Made of microtubules and
microfilaments
•Animal cell rely on this for
maintaining cell structure
Microtubules:
•Hollow rods of protein
•Some extend from the
cytoplasm to make up cilia
and flagella
Microfilaments:
•Threadlike fibers found
below the cell membrane
•Produce flowing motion in
cytoplasm
•Help circulate organelles;
improve cell efficiency
Comparison of Plant Cells to
Animal Cells:
PLANT
Cell Wall
Plastids
Large Vacuole
Rely on cell wall
for structure
No centrioles
ANIMAL
No Cell Wall
No Plastids
Small vacuoles
or none
Rely on
cytoskeleton
Centrioles