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UNIT 3: CELLS
T H E O RY, T Y P E S , S T R U C T U R E S , M O V E M E N T
UNIT 3 TOPIC 1: THE CELL THEORY
By the end of this topic, I will be able to…
1. List the three components of the cell theory
2. Describe the importance of each of the contributors to the cell
theory
– Virchow, Schleiden, Schwann, Leeuwenhoek, Hooke
3. Relate the invention of the microscope to the development of the
cell theory
THE CELL THEORY
Three components:
1. All living things are composed of cells
2. Cells are the basic unit of structure and function in living
things
3. All cells come from preexisting cells
HOW DID WE GET THE CELL THEORY?
What tool do we need to see most cells?
The microscope!
People you should know involved with this tool:
• Anton van Leeuwenhoek – he used to grind lenses and
assemble them together to make microscopes
• Robert Hooke – he observed fleas and cork; while looking at
cork, he saw what he called cells. He discovered plant cells (he
did not know this) AND coined the term cell.
– Why did he call them “cells?”
• When he looked at the cork (in 1665), he saw what looked like
thousands of chambers, or little boxes, and called them cells (like a prison
cell or monastery cell, where monks live)
WHAT HOOKE SAW (HIS DRAWINGS)
Fleas
Flies
Snowflakes
Cells
LEEUWENHOEK(1678)
• Worked on ways to make superior lenses (again, he would grind and
reassemble lenses together)
– Did NOT invent the microscope (it was invented nearly 40 years before he was born- in
the 1590s)
• Developed a lens tube with a magnifying power of 270x
• He was the first to see and describe bacteria, yeast, and “animalcules” (little
animals)
– Observed the animalcules in pond water and on his own dental scrapings (plaque)
– His observations are among the first observations ever recorded for bacteria
WHAT LEEUWENHOEK SAW
YEARS AND YEARS OF NO PROGRESS….
Nothing really drastic happens between the work of Hooke/Leeuwenhoek and our next
scientists for close to two centuries
Why?
Likely, because people believed in spontaneous generation and were unwilling to believe anyone
telling them otherwise.
What’s that?
The belief that something living can come from something non-living. We will revisit this in
evolution later this year!
LOUIS PASTEUR
Finally put an end to the debate on where living things come from and disproved spontaneous
generation with his famous experiment:
Living things only come from living things
1838-1839
Two German scientists, Matthias Schleiden and Theodor Schwann, continue studying living things.
• 1838 – Matthias Schleiden (botanist, so studies plants) concluded that all plants are made of
cells
• 1839 – Theodor Schwann (physiologist) concluded that all animals are made of cells
AND FINALLY, VIRCHOW
1855: Rudolph Virchow concluded that all cells come from
preexisting cells (part 3 of the cell theory)
THE CELL THEORY
The 3 Basic Components of the Cell Theory were now complete:
1. All organisms are composed of one or more cells. (Schleiden &
Schwann)(1838-39)
2. The cell is the basic unit of life in all living things. (Schleiden &
Schwann)(1838-39)
3. All cells are produced by the division of preexisting cells.
(Virchow)(1858)
LANGUAGE TARGET: 30-ISH MINUTES
• In the small space in your notes, sketch a timeline highlighting development of
the cell theory
• After you have the dates/people/events/images set out, create your timeline on
the slip of paper available to you in the front
• When done, work on microscope parts handout
Timeline Component Value (points)
Date (Year) 2.5 (.5 points per date)
Person with description of work 5 (1 point per person with description)
Image (COLORED) relating to work 2.5 (.5 points per image)
UNIT 3 TOPIC 1 ENRICHMENT: THE MICROSCOPE
By the end of this topic, you should be able to…
1. Label a microscope and explain the function of each part
2. Bring a specimen into focus when using a compound light
microscope
3. Write about the history of the microscope
HISTORY OF THE MICROSCOPE
• The first microscope is believed to have been invented in/around the 1590s by
Hans and Zacharias Jansen
– Zacharias was a spectacle maker that is credited with inventing the first microscope.
However, he was born ~1580, so he would have been very young in 1590.
– It is believed his father, Hans, assisted him in the building of the first microscope.
HOOKE & LEEUWENHOEK
• These two made improvements on the microscope by modifying the lenses.
• Leeuwenhoek's instruments consisted of simple powerful magnifying glasses,
rather than the compound microscopes (microscopes using more than one
lens) of the type used today or in Zacharias Jansen's original microscope
design.
• Leeuwenhoek's design is extremely simple, using a single lens mounted in a tiny
hole in a brass plate that makes up the body of the instrument. The specimen
was then mounted on a sharp point that sticks up in front of the lens. Its
position and focus could be adjusted by turning the two screws. The entire
instrument was only 3-4 inches long, and had to be held up close to the eye,
requiring good lighting and great patience to use.
TODAY’S MICROSCOPEPLEAS E NOTE … WE WI LL ONLY BE DI S CUS S I NG THE COMPOUND LI G HT MI CR OS COPE (WE MAY A DDR ES S THE S EM AND TEM L ATER I N THE COUR S E)
• The scopes we use in class are compound microscopes
– Have more than one lens
• Convex lenses are used to build the microscopes (and glasses)
– These lenses bend light and focus it in one spot
– Bending Light: The objective (bottom) convex lens magnifies and focuses (bends) the image inside
the body tube and the ocular convex (top) lens of a microscope magnifies it (again).
Ocular Lens
(Magnifies Image)Objective Lens
(Gathers Light,
Magnifies
And Focuses Image
Inside Body Tube)
Body Tube
(Image Focuses)
PARTS OF THE MICROSCOPE• Objective lenses
• Body tube
• Ocular lens
• Nosepiece
• Stage clips
• Diaphragm
• Light source
• Arm
• Stage
• Adjustment knobs
• Base
TOP FUNCTIONS
• Ocular Lens (eyepiece): magnifies the specimen (typically 10x) and what you
look through to observe the specimen
• Body Tube: holds the objective lens(es) the proper distance from the ocular
lens
• [Revolving] Nosepiece: holds the objective lens(es); turn this to switch
objective/magnification
• Arm: holds the body tube/nosepiece/objective lenses; used to support the
microscope; always carry with one hand on the arm
• Objective Lenses: increase/decrease magnification; change power; use the
nosepiece to switch between objective lenses
MIDDLE FUNCTIONS
• Stage: flat surface used to hold the specimen/slide
• Stage clips: two clips used to hold the slide/specimen in place; always use
these!
• Diaphragm: controls the amount of light coming through the
specimen/slide
• Coarse adjustment knob: moves the stage up and down (quickly) for
focusing your image
– This is the larger of the two adjustment knobs
– Never use this on high power!
BOTTOM FUNCTIONS
• Fine adjustment knob: this is the smaller of the two adjustment
knobs and it is used to move the stage slightly to sharpen the image
• Light source: projects light upwards through the slide/specimen,
diaphragm, and lenses
– Usually a light, though can be a mirror
• Base: supports the microscope; always carry with one hand on the
base
MAGNIFICATION
• To determine your magnification…you just multiply the ocular lens by the
objective lens
• Ocular 10x Objective 40x:10 x 40 = 400
Objective Lens have
their magnification
written on them.
Ocular lenses usually magnifies by 10x
So the object is 400 times “larger”
CARING FOR A MICROSCOPE
• Clean only with a soft cloth/tissue
• Make sure it’s on a flat surface
• Don’t bang it
• Carry it with 2 HANDS…one on the arm and the other on the base
USING A MICROSCOPE
• Start on the lowest magnification
• Don’t use the coarse adjustment knob on high
magnification…you’ll break the slide!!!
• Place slide on stage and lock clips
• Adjust light source
• Use fine adjustment to focus
UNIT 3 TOPIC 2: CELL TYPES AND STRUCTURES
By the end of this topic, you should be able to…
1. Discuss similarities and differences between prokaryotic and eukaryotic cells
2. Identify a cell as being prokaryotic or eukaryotic based on cellular components
3. Explain the function of cellular organelles
4. Compare and contrast plant and animal cells
5. Explain how cells work together in multicellular organisms
TYPES OF CELLS• There are MANY types of cells (skin, brain, liver…), but cells are generally classified as
either prokaryotic or eukaryotic.
• Some things that all cells, regardless of type, have in common are:
1. Water- nearly 70% of the mass of each cell is water
2. Macromolecules-
1. Every cell contains a genetic code (nucleic acids)
2. Every cell has hundreds of proteins with unique functions, like cellular
communication or transport or structure (keratin)
3. Every cell contains lipids that are used for energy storage, cell communication,
and protective barriers (cell membrane contains lipids, as does nuclear membrane)
4. Every cell contains carbohydrates, also used in cellular communication, energy
storage, and used for structural support
3. Cell membrane, cytoplasm, and ribosomes
REVISITING UNIT 2 ☺
BEFORE CONTINUING…• What is the monomer for:
– Carbohydrates:
– Lipids:
– Proteins:
– Nucleic acids:
• Explain what the phrase “water is polar” means
– How does this allow water to dissolve so many solutes?
• Describe how invention of the microscope helped scientists understand cells
ANSWERS• What is the monomer for:
– Carbohydrates: monosaccharides/simple sugars
– Lipids: fatty acids/ triglycerides
– Proteins: amino acids (build a polypeptide)
– Nucleic acids: nucleotides
ANSWERS• What is the monomer for:
– Carbohydrates: monosaccharides/simple sugars
– Lipids: fatty acids/ triglycerides
– Proteins: amino acids (build a polypeptide)
– Nucleic acids: nucleotides
• Explain what the phrase “water is polar” means
There is an uneven distribution of electrons, giving one side (the oxygen) a partially negative
charge and the other side (the hydrogen) a slightly positive charge
– How does this allow water to dissolve so many solutes?
The negative end attracts positive molecules and the positive end attracts negative
molecules
• Describe how invention of the microscope helped scientists understand cells
ANSWERS• What is the monomer for:
– Carbohydrates: monosaccharides/simple sugars
– Lipids: fatty acids/ triglycerides
– Proteins: amino acids (build a polypeptide)
– Nucleic acids: nucleotides
• Explain what the phrase “water is polar” means
– How does this allow water to dissolve so many solutes?
• Describe how invention of the microscope helped scientists understand cells
Before the microscope was invented, cells could not been seen. Once the microscope was
invented, scientists could see individual cells as well as what is inside of them.
EXAMPLES OF CELLS
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
TYPES OF CELLSAgain, there are two general types:
1. Prokaryotic: pro means before, kary refers to karyon (kernel)
1. Before kernel (before nucleus)
2. Older, simpler, smaller… bacteria
2. Eukaryotic: eu means true
1. True kernel (true nucleus)
2. Younger, more complex, larger… animal, plant, protist, fungi
PROKARYOTIC CELLS
• Smaller than eukaryotic cells (smaller surface area to volume ratio)
– Size is important because the smaller the cell, the easier it is to have nutrients
reach inner parts of the cell (they also get through the cell quicker)
• Eukaryotic cells have organelles that assist in moving nutrients/waste
• DNA is circular and located in the cytoplasm (“nucleoid region”)
• Less complex than eukaryotic cells (no membrane bound organelles)
– Do contain ribosomes (site of protein synthesis)
• Surrounded by a cell wall outside of the cell membrane
EVOLUTION OF CELLS• Prokaryotic cells likely appeared on earth
approximately 3.8 billion years ago
– We will look at how these cells could have
developed later in the year (evolution unit)
• It involves conditions of earth’s early
atmosphere (lacked oxygen) and the
synthesis of organic molecules
– Photosynthetic bacteria evolved ~3 billion years
ago (oxygen released into atmosphere)
• Eukaryotic cells evolved around 2.7 billion years ago
– Endosymbiotic theory
• Multicellular organisms evolved roughly 1.7 billion
years ago (plants & animals)
CELLSNote that
archaebacteria and
eubacteria are both
closer to eukaryotic
cells than they are to
one another. Scientists
have found that
archaebacterial genes
are more similar to
eukaryotic genes than
they are to eubacterial
genes, suggesting that
archaebacteria share a
common line of
evolutionary descent
with eukaryotes.
ENDOSYMBIOTIC THEORY
Define theory (again): A well-substantiated explanation of some aspect of the
natural world, based on a body of facts that have been repeatedly confirmed
through observation and experiment.
The endosymbiotic theory explains how scientists believe that eukaryotic cells
evolved from prokaryotic cells
ENDOSYMBIOSIS
What is happening?
Essentially, a larger prokaryotic cell engulfs (but does not digest) a smaller
prokaryotic cell. The smaller cell is then living within the larger cell and
operating as a specialized organelle.
EUKARYOTIC CELLS• Larger than prokaryotic
• More complex
– Contain specialized organelles
• Exist either as single-celled organisms or as part of multicellular organelles
– Human body is made of more than 200 kinds of cells! These cells work together to make up five main types of tissue: epithelial, connective, blood, nervous, and muscle tissue.
– Recall: cells of the same organism contain the same DNA, but not all of the genes are activated in every type of specialized cell
• Each type of cell is modified to work in the way the organism needs it to (may differ in size, shape, or function)
SPECIALIZED CELLSA stem cell is a non-
specialized cell that can
either replicate itself
(produce more stem cells)
or differentiate into a
specialized cell. A stem cell
can differentiate into a liver
cell, but a liver cell cannot
change into a nerve cell. A
cell specializes (often) during
interphase before cell
division. Stem cells are
either embryonic (derived
from an embryo) or can be
adult stem cells
(undifferentiated cells from a
mature organism).
GENERAL EUKARYOTIC CELL
• Cell membrane
• Cilia/flagella
• Cytoplasm
• Cytoskeleton
• Nucleus
• Ribosomes
• Endoplasmic Reticulum
• Golgi Body
• Mitochondria
• Lysosome
• Vacuole
• Chloroplast
• Cell wall
PLANT V ANIMAL CELL
PLANT ANIMAL
Chloroplasts/ Cell wall/ Large Vacuole Lysosome
CELL MEMBRANE• Also referred to as the plasma
membrane
• Surrounds the cytoplasm
• Is the outermost part of animal
cells, but not for plant cells
• Plays a large roll in cell transport
(topic 3 this unit)
– Controls movement of
materials into and out of the
cell
– Selectively permeable (does
not allow all things into the
cell)
CILIA/FLAGELLA
• Used for cell movement
• Cilia:
– Shorter/greater in number
– Move fluids using sweeping
motion
• Flagella:
– Longer and typically one per
cell
– Propels cell using whip-like
motions
CYTOPLASM
• Suspends the organelles
• Jelly-like fluid within the cell
membrane
• Also known as the cytosol
CYTOSKELETON• A structure that maintains the shape and size of cells
• A network of microtubules (thicker) and microfilaments (thinner)
– Long protein strands
NUCLEUS• The control center of the cell,
housing the DNA (master copy of
a cell’s genetic material)
• The nucleus is surrounded by the
nuclear membrane, which has lots
of little pores (RNA exits through
these)
• Within the nucleus is the
nucleolus, and this is where
ribosomes are produced
RIBOSOME
• Small particles of RNA and protein scattered
throughout the cytoplasm
• This is the site of protein synthesis (proteins are
made here)
ENDOPLASMIC RETICULUM• An interconnected network of flattened sacs
• Joins with the outer membrane of the
nucleus
• Two types:
– Rough ER: coated in ribosomes (makes
proteins)
– Smooth ER: lacks the ribosomes on its
exterior
• Known as the “highway” or the
transportation system because it folds and
moves proteins
– Sends them to the golgi apparatus/body
GOLGI APPARATUS (GOLGI BODY)
• Made of membrane-bound sacs
• Processes, sorts, and packages cellular
components (proteins and lipids) “Post
Office”
• Can produce lysosomes
• Works directly with the ER
MITOCHONDRIA• Acts as the powerhouse of the cell
– Produces ATP, the energy currency of
the cell
• Contains DNA (not unique to an individual
though, runs through the family- get it from
your mom because it is carried in the
female egg)
• Double membrane
• Varies from 1 to 10,000 mitochondria in a
single (specialized) cell
– Muscle cells contain lots of
mitochondria. Why? Need lots of energy!
LYSOSOME• Membrane-enclosed organelles with lots
of enzymes used to break down polymers
– Lysis = to break or to burst
• Functions as the digestive system of the
cell
• Maintain an acidic pH within the
lysosome
• Debate as to whether this is only found
in animal cells… leaning towards this
organelle being found in both animal and
plant cells
VACUOLE• Fluid filled organelle that stores enzymes,
waste, and water
• Often the largest organelle in plant cells- can
take up to 80% size of the cell (much smaller in
animal cells)
CHLOROPLAST• Found only in plant cells, this
is the location of
photosynthesis
– Converts light energy to
chemical energy
• Double membrane
• Contains DNA
• Green in color because it
contains the pigment
chlorophyll
CELL WALL
• Found in plant cells (and
bacteria and fungi), not in
animal cells
• Located outside the cell
membrane
• Leads to plant cells having a
square/rectangular shape
• Supports and protects the cell
• Made of cellulose (in plant
cells)
– Remember, this is a
polysaccharide!
CENTRIOLES
• Only found in animal cells-
located near nucleus
• Assists in cell division
– Develops spindle fibers
ANIMAL CELL
Mitochondria
Nucleus
Golgi
Cytoplasm
ER
Ribosomes
Cell Membrane
PLANT CELL
Cytoplasm
Vacuole
Cell wall
Cell membrane
Chloroplast
Nucleus
Mitochondria
ER
Ribosome
Golgi body
UNIT 3 TOPIC 3: CELL TRANSPORT
By the end of this topic, you should be able to…
1. Label a cell membrane with its components and explain the function of each component
(carbohydrates, phospholipid head/tail, proteins)
2. Explain what “a cell membrane is selectively permeable means”
3. Explain why the cell membrane is known as the Fluid Mosaic Model
4. Compare and contrast passive transport (diffusion, facilitated diffusion, osmosis) with active
transport (endocytosis, exocytosis)
5. Discuss the importance of surface area to volume ratio
THE CELL MEMBRANE
• Task: regulate movement
into and out of the cell
• Parts you need to know:
1. Lipid bilayer
2. Carbohydrate
3. Proteins (integral and
peripheral)
4. Cholesterol
ARRANGEMENT OF LIPID BILAYER• 2 sheets of phospholipids (a lipid with a head &
two tails)
– Head = hydrophilic
• Hydro: water
• Philia: love, fondness, affinity for
– Arranged on the outsides of the
bilayer due to it’s love for water
(constant contact)
– Tails = hydrophobic
• Hydro: water
• Phobia: fear of or aversion to
– Arranged on the inside of the bilayer
so it is away from water
OTHER COMPONENTS, 1• Carbohydrates
– Attach as a chain to membrane proteins
or lipids
• Glycoprotein- carbohydrates
attached to protein
• Glycolipid- carbohydrates attached
to lipid
– Protect the cell
• These are used for cell recognition
– Differentiate between things that
can enter the cell and things that
cannot enter the cell
OTHER COMPONENTS, 2• Proteins
– Allow for interactions between cells and
transport of materials
– Integral proteins: embedded within the cell
membrane
• Usually transmembrane (extends the length
of the membrane to connect the inside of
the cell with the outside)
• Can act as pathways for materials to enter
and exit the cell
– Peripheral proteins: attached to the exterior
(outside) of the lipid bilayer (or other
membrane)
• Wingmen for other membrane proteins
(partner with other proteins- can be used
for transport from one part of the cell to
another by attaching to these other
proteins)
OTHER COMPONENTS, 3• Cholesterol
– Maintains the integrity of cell
membranes
• Without cholesterol, cell
membranes would be too
fluid and too permeable
– Used to maintain fluidity
of the cell membrane by
preventing crystallization
of the tails in the bilayer
– Involved with cell to cell
communication (due to closeness
with proteins on the cell
membrane)
FLUID MOSAIC MODEL• Fluid combination of
phospholipids, cholesterol, and
proteins
– Separate but loosely attached
molecules
– Different parts of the
membrane float in a fluid-like
space
– Dynamic and scattered with
these different molecules
(mosaic-like)
SO HOW DO THINGS GET INTO AND OUT OF CELLS?• By moving across a concentration gradient (moving from one side of the cell
to the other)
– Concentration: mass of solute in a given volume of solution
• Cell transport
– Passive: no energy required, solutes move down the concentration gradient
– Active: energy required, solutes move up the concentration gradient
SIMPLE DIFFUSION
• Molecules move down the concentration
gradient
– from an area of high concentration to
an area of low concentration
• Passive
– No energy required
• Oxygen and carbon dioxide move
through cells using simple diffusion
FACILITATED DIFFUSION• Some substances, like glucose,
are too large to fit through the
cell membrane without
assistance
• These larger molecules must
use channel proteins to be
carried across the cell
membrane
• Still moving down the
concentration gradient and still
a passive process
OSMOSIS
• This is the movement (diffusion) of
water across a cell membrane
• Passive process
• Molecules move down the
concentration gradient
– Movement depends on type of
solution (hypertonic, isotonic,
hypotonic)
SOLUTION TYPES
HYPERTONIC
Solution outside the cell has a higher solute
concentration and lower water
concentration than inside the cell
• Water LEAVES the cell
HYPOTONIC
Solution outside the cell has a lower solute
concentration and higher water
concentration than inside the cell
• Water ENTERS the cell
SOLUTION TYPES, CONT.
ISOTONIC
The concentration of solute (and water) is
the same outside the cell as inside the cell
• Water moves equally in both directions
• No NET movement
REAL LIFE EXAMPLE: RED BLOOD CELLS
• Red blood cells
• Plant cells
REAL LIFE EXAMPLE: PLANT CELL
ACTIVE TRANSPORT• Movement up the concentration gradient
– From areas of low concentration to areas of high concentration
• Active because this requires energy (ATP)
• Molecular pumps are used to transport materials across the membrane
– Each pump moves one type of molecule
ENDOCYTOSIS AND EXOCYTOSIS
• Endocytosis
– Endo = within
– Cyto = cell
• Movement INTO the
cell
• Exocytosis
– Exo = exit/leave
– Cyto = cell
• Movement OUT OF
the cell
ENDOCYTOSIS• Two types: phagocytosis and pinocytosis
– Phagocytosis: essentially, cell eating
(bringing solids into the cell)
• Ph sounds like fuh… same start
as food (solid)
– Pinocytosis: essentially, cell drinking
(bringing liquids into the cell)
• Think pina colada, which is a
drink!
• In either case, the material is brought into
the cell through vesicles that form around
the material
EXOCYTOSIS
• Products of the ER are
packaged into vesicles at
the Golgi and are then sent
to and released at the cell
membrane
SURFACE AREA TO VOLUME RATIO• Each part of the cell relies on the cell surface. As a
cell grows, its volume grows and the cell membrane
expands. The volume increases quicker than the
surface area.
– Surface area available to pass materials to a unit
volume of the cell steadily decreases.
• If the cell grows too big, not enough material can
come into the cell to accommodate the larger cell
volume.
– cell must divide into smaller cells with favorable
surface area/volume ratios, or cease to function.
• The important point is that the surface area to the
volume ratio gets smaller as the cell gets larger.