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cells
Little Bit of Science
History
Hooke (1665) - used a
primitive microscope
observing cells for the
first time and naming
them “cells”
Early compound microscope (2 lenses)
Hooke’s drawing of cork cells
More History
Van Leeuwenhoek - 1674
first to use a microscope to
look at living cells in pond water
and just about anywhere else even
the plaque on his teeth!
Spirogyra
Vorticella
And Yet More History
Schleiden and Schwann - 1839
Schleiden stated that all plants are made up of cells.
Schwann stated that all animals are made up of
cells.
Virchow - 1857
States that “every cell
stems
from another cell.”
All of that History Gave
Rise to the Cell Theory
• All living things are made up of cells
• All cells come from preexisting cells
• Cells are the basic unit of structure and
function in living things (take away the
order of a cell and the organism will not
survive)
Types of Cells
Eukaryote
Prokaryote
Prokaryotes
‘Before the Nucleus’
• Archaebacteria and Eubacteria
• No nucleus, but all living things have
DNA?
• Smallest type of cell (0.5-1.5 microns)
• No membrane bound organelles
• Unicellular / Simpler
Prokaryotes don’t have a
nucleus !
DNA loosely organized close
to the cell membrane
Prokaryotes don’t have
organelles
Organelle - specialized
structures within a cell
with a specific function,
separated by a
membrane.
But they do have ribosomes,
protein factories.
Eukaryotes
True Nucleus
• Have a nucleus where DNA is protected
away from the rest of the cell
• Have membrane-bound organelles
• Larger / more complex
• Found in plants, animals, fungi and
protists
• Most multicellular but some uni- and
others are colonial
Modern History
The Endosymbiotic Theory
Lynn Margulis
Explanation as to how
eukaryotic cells evolved.
Margulis' original hypothesis proposed that aerobic
bacteria (that require oxygen) were ingested by
anaerobic bacteria (poisoned by oxygen), and may
each have had a survival advantage as long as they
continued their partnership.
Cell Parts and
Functions
Remember this?
Cell Membrane
All cells have a cell membrane
Boundary that allows
selected materials to pass
through
Cell-to-cell recognition
receptors made of
glycoproteins
Gatekeeper/Bouncer
Phospholipid Bilayer
Cell Wall
• Found in plants, fungi, protists and
bacteria
• Protective support for the organism
• Plants made up of CELLULOSE
• Porous allows H O, CO , and O
2
through
2
2
Nucleus
Directs all cell activities
Contains and protects
the DNA
Includes:
Nuclear Envelope
Nuclear Pores
Nucleolus
Chromosomes/
Chromatin
Nuclear Envelope
Lipid bilayer that protects
the DNA from the
cytoplasm
Nuclear pores allow proteins and
RNA
to travel into the cytoplasm but
prevent
DNA
from
leaving
Nuclear envelope is
continuous
with the endoplasmic
reticulum
Nucleolus
Nucleolus
Nucleus
Made up of
protein and RNA
Site of ribosome synthesis
Cytoplasm (Cytosol)
Jelly-like material that surrounds
and encases the organelles
Many chemical reactions occur
in the cytoplasm
Mostly made-up of water
and enzymes
Plastids (plants only)
Chloroplast
Leucoplast
Photosynthetic
factory of the cell
Storage of starch
(polysaccharide)
Production of glucose
using the energy of
sunlight
Cells of the potato are
filled with leucoplasts
Chromoplast
Contain pigments
such as
carotenoids
Gives tomatoes their color
Ribosomes
• Mammalian cell can synthesize 20,000
ribosome subunits per minute
• Tiny protein factories, made in the
nucleolus then moved into the
cytoplasm or attached to the
endoplasmic reticulum
• Made up of 2 subunits
Endoplasmic
Reticulum
2 Types: Rough and Smooth
Rough - ribosomes attached
important in protein synthesis,
packages new proteins and sends them to the
Golgi apparatus
Smooth - no ribosomes
contains many enzymes that serve different functions;
liver cells detoxifies drugs and breaks down glycogen,
muscle cells involved in calcium release needed for mus
contraction
Mitochondria
Powerhouse of the cell
Contain DNA can replicate
independent of the cell
Site of cellular respiration
Convert chemical energy in food
into usable cell energy (ATP)
Golgi Apparatus
Modifies, collects, packages
and distributes molecules
Attaches carbohydrates
and lipids to proteins
Flattened stack of pancakes
Lysosomes
• Primarily found in animal cells
• Small bubble-like
• Filled with enzymes necessary for
digestion of unneeded cell parts
• Recycling center of the cell
Vacuoles / Vesicles
Vacuole is very large, stores
water and sugars for the plant
Vesicles are small storage
structures
that can fuse with membranes to
release materials
Cytoskeleton
2 Types:
Microtubules
Microfilaments
Microtubules - hollow tubes, support,
movement of organelles
Framework made of proteins
Microfilaments - long, thin fibers, support and
movement of cytoplasm
Desmosomes
Cell snaps - connect cells together
and create cell junctions for materials
to pass through
Centrosomes /
Centrioles
Centrosomes - area of the cell close to
the nucleus where the centrioles are
found
Centrioles only found in animal cells,
used to separate the chromosomes during cell
division
Chromosomes
DNA
Tightly coiled chromatin
(DNA when the cell is at rest)
DNA takes the shape of a chromosome
only during cell division