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Cell Theory & Cell Parts
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Proposed after hundreds of years of
microscopy
◦ In 1665 Robert Hooke discovered cells in Cork
(wood). Saw “little boxes” (cell walls). Coined the term “Cell”.
 Used a crude compound microscope
◦ In late 1680’s, Anton van Leeuwenhoek observed
microorganisms in water from ponds and rainwater
 Lead to idea of single celled organisms
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1831, Robert Brown discovered & named the
nucleus of the cell.
MJ. Schleiden- Plants are made of cells which
are made up of nuclei and cell fluid.
1839-Theodore Schwann- Animals made up
of small units.
In 1858, Rudolph Virchow suggested
◦ “All cells come from cells”
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Cell Theory- cells are the basic unit of
structure in every living thing. Either
unicellular simple organims or
multicellular complex organisms.
Schwann, Schleiden, and, Virchow are
credited with developing cell theory.
◦ In 1839 Schwann and Schleiden suggested that
cells were the basic unit of life.
◦ In 1858, Virchow concluded that all cells come
from pre-existing cells.
Cell Theory states that
1. Cells and cell products are the units of structure
and function in organisms
1. ALL cells arise from preexisting cell
Once cell theory was developed, scientists
began to study the structures and functions
of cells more in depth
Microscopes made of many lens components
◦ Lens improvements in microscope construction lead
to Compound Light Microscopes
◦ Advances in staining techniques and slide
preparation have made samples easier to see
◦ Electron Microscopes (1930s) can magnify objects
by over 1,000,000x (0.5μm)
 Enough magnification to see structure of DNA and
other organelles
Prokaryotes
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No membrane enclosed
organelles
Singular circular
chromosome
No streaming in the
cytoplasm
Cell division without
mitosis (binary fission)
Simple flagella
Small ribosomes
No know cytoskelelton
No cellulose in cell walls
Proteins bound to DNA
Eukaryotes
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Membrane enclosed
organelles
Multiple linear
chromosomes, often in
pairs
Cell division by mitosis
Complex flagella
Large ribosomes
Cellulose in cell walls
DNA wrapped around
protein
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Cell Wall, Cell membrane, flagella, Nucleoid,
Plasmid, Cillia, cytoplasm, ribosomes
Prokaryotes
◦ Simplest living cells, unicellular
 Bacteria
◦ On average 0.3 μm to 5μm
◦ Extremely adaptable
 Live in wide variety of environments
 Intestine, thermal ocean vents, ice cores everywhere
◦ No true nucleus, no organelles
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Unicellular
◦ Arrange in clusters
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Cell wall – surrounds cell
◦ Made up of lipids, carbs; no cellulose
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Plasma membrane – interior to cell wall
No nucleus
◦ DNA in circular molecule
◦ Attached to plasma membrane in Nucleoid region
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Plasmids –small ring of extrachromosomal DNA
May also have Ribosomes –
◦ Function in protein formation
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May have flagella for movement
◦ Whip like motion; propellers
Three types:
1. Rod shaped – Bacilli
2. Sphere shaped – Cocci
3. Corkscrew shaped – Spirochette or spirilla
Prokaryotes
 Various metabolisms
◦ All dependent on environmental level of O2
1. Aerobic
– Need O2, cannot grow without
1. Anaerobic – Poisoned by
SO4-) to extract energy
1. Facultative
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O2; use ions (NO3- or
– Able to use both O2 or ions;
Environment dependent
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Important function within ecosystems
Decomposers
Can have symbiotic relationship
◦ Interactions between two+ organisms
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Variety of ecosystems means variety of ways to
obtain energy & carbon source
 Energy - light (Photo) or chemical (Chemo)
 Carbon – Inorganic (Autotroph) or organic (Heterotroph)
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Photoautotroph, Chemoautotroph
Photoheterotroph, Chemoheterotroph
Eukaryotes
◦ Complex, larger
 Protists, Fungi, Plants, Animals
 Protist - unicellular eukaryotes
◦ Average size - 10 – 50 μm
◦ Have nucleus & organelles
 Specific functions; Development of
specializations
◦ Organelle - specialized structures within a
living cell
 Smallest functioning part
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Cell Walls (plants), Chloroplast (plants), Central
Vacuole (plants), Cell Membrane, Nucleus (Nuclear
Envelope, Nucleolus, DNA (Chromatin)), Rough ER,
Smooth ER, ribosomes (RNA and proteins), Golgi
Apparatus, Mitochondria, Lysosomes, Cytoplasm
((Cytosol and organelles), Cytoskeleton
(microtubules, filaments, microfilaments),
Centriole (animals)
“Control Center” of cell
◦ Houses DNA of the cell
◦ Double layer membrane
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DNA
◦ Molecule of hereditary
◦ Directs production of proteins, enzymes
 Anything that controls cell function/metabolism
◦ Most often in form of Chromatin
 Grainy thread-like, loose
◦ In cell division, becomes Chromosomes
 Tight, coiled, condensed
DNA Needs to be copied/transported out of
cell
 Molecule of heredity
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Large molecule
◦ Can’t leave nucleus – too large for nuclear pores
◦ Chromosomes cannot leave the nucleus
 Too large to fit through nuclear pores
◦ DNA is coded into message that can fit – RNA
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Ribonucleaic Acid versus DEOXYribonucleaic Acid
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Found inside the nucleus
◦ Dense, dark region
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Produces RNA – 3 types
◦ mRNA – messenger RNA
 Messenger of code from nucleus to ribosomes
◦ rRNA – Actual ribosome
◦ tRNA – Transfers individual Amino Acid to ribosome
 Uses complementary code of mRNA
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Location of protein synthesis
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Small bodies of protein/RNA
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Catalyze protein synthesis in cells
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Can be free floating in cytoplasm or bound to
a membrane
◦ Bound to Endoplasmic Reticulum
Cytoplasm
 Inside of P.M., outside of nucleus
 Thick, akin to toothpaste
 Consists of fluid - Cytosol
◦ Organized system of fluid (Cytosol) and fibers
(Cytoskeleton)
 Fibers are scaffolding that connects organelles in cell
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Membrane tubes/channels through cytoplasm
◦ Weaves throughout – connecting organelles
◦ Transport materials to organelles
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Can have ribosomes embedded
◦ Rough Endoplasmic Reticulum
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…or not.
◦ Smooth Endoplasmic Reticulum
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Proteins synthesized on E.R. can enter the E.R. move to different parts of cell where needed
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Series of membrane bound sacs stacked
together
 Looks like Smooth E.R.
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Function
◦ Modification – complete final structure of protein
 Attaching protein segments together
 Assembling 4o structure
 Packages proteins into vesicles for transport
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How does material move from ER to Golgi/out
of cell?
◦ Intercellular Endo/Exocytosis
Plasma Membrane
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Phospholipid bilayer; found in plant & animal
Cell Wall
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Rigid wall surrounding P.M. of plant cells
◦ Made up of Cellulose, complex carbs & stiff fibers
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Lysosome – membrane-bound organelle
containing digestive enzymes
◦ Made in G.A.
 Peroxisome – specific type of lysosome
Vacuole
 In plant cells
◦ Very large – holds material
90% of plants volume – H2O, organic acids,
digestive enzymes, salts, pigments
Centrioles
 Paired bundles of microtubules
◦ Help organize DNA in cell reproduction
Cillia & Flagella
 Membrane wrapped microtubule bundles
◦ Provide movement
Chloroplasts
 Use light, water, CO2 to produce sugars
◦ Phtosynthesis
 light energy  chemical energy (ATP)
Mitochondria
 Double membrane organelle
 Control energy reactions in cell
◦ Cell Respiration
◦ ATP synthesis
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10s to 1000s
What is the distinction between
unicellular and multicellular
organisms?
Unicellular organisms MUST
address all of life’s needs in order
to survive.
What are the needs that unicellular
organisms must be concerned
with?
Unicellular organisms must be able to:
1. Obtain
nutrients
2. Expel wastes
3. Exchange gas regularly/ exchange gas
produced by energy conversion reactions
4. Defend against “predators”
5. Reproduce
6. Respond to changes in environment
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Move to areas of high [O2]
Move away from areas of intense heat
Unicellular organisms team up for survival –
form colonies
Colonies – distinct group of microorganisms
growing together
Colonies
◦ Can be group of the same species (organism)
◦ Can be different species (biofilm)
Cells in colony secrete chemicals to coordinate
activities
When in colonies, groups of cells secrete
protective slime
◦ Proteins & Polysaccharides
Helps control environment inside colony
◦ pH
◦ Concentration of food
◦ Water
Each cell remains separate organism!
Remove one cell from colony – the cell does
not die
When does a colony stop being unicellular and
start being Multicellular –
When specific cells stop doing everything and
starts SPECALIZING on some things.
Is specialization good or bad?
Both - Leads to greater complexity
But cells cannot survive alone – must
cooperate.
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Volvox
Eukaryotic algae-Chlamydomonas
Lives in Fresh H2O
Cells work together
to function
If one cell dies –
colony lives
Colony – sphere of cells
Possess cells where each cell has:
Nucleus
2 Flagella
Vacuoles
Light sensing structures
Chloroplast
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However, some cells are specialized
Reproductive cells
Some cells larger/smaller
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Larger cells in rear for “swimming”
Flagella beat in synchrony - coordination between
cells
Unicellular Colony
◦ Most cells VERY similar
◦ Structures and function
Multicellular Organism
◦ Cellular specialization
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Book “Barely a multicellular organism”
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Remember – Answer is not as important as is
understanding argument for both!
Multicellular – Specialized cells dependent on
each other to divide labor successfully for
survival
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Atom  Carbon
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Molecule  C6H12O6
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Macromolecule  Starch
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Organelle  Golgi Apparatus
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Cell  Animal Cell/Plant Cell
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Tissue  Group of same cells w/ common fcn
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Organ  Group of diff. tissues w/common fcn
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Organ System  Group of diff. organs w/ common fcn
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Organism  Group of different organ systems working together
for life
◦ Muscle tissue, Connective tissue
◦ Heart, bone, skin, brain, eye
◦ Circulatory, Immune, Nervous
◦ YOU