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Exploring the Cell-iverse
by Sijie Mao
What are Cells?
What are cells?
- the smallest form of living things
- make up all living things
In order to survive, most cells must be able to:
- move
- reproduce
- maintain proper levels of chemicals
- consume food
- gain energy from food
- recycle materials
- get rid of waste
- make proteins
- adapt to their environment
What do they do?
A cell’s job or function, can differ depending on
what kind it is:
- a uni-cellular organism
- a cell part of multi-cellular organism
•in a muli-cellular organism, cells may transport
oxygen throughout your body (red blood cells), they
may also produce enzymes for digestion (pancreatic
cell) and work together to form muscle and allow you
to move (muscle cells)
Basic Structure
- all cells have a cell membrane
- many cells also have a cell wall
- many cells have a nucleus
- all cells have cytoplasm, which includes all of the
cell’s contents (ie: organelles, “mini organs” of the
cell) outside of its nucleus
Are all cells the same?
Are all cells the same?
All living things are made up of cells either as uni-cellular (onecelled), a bacteria cell, or multi-cellular (many-celled) organisms,
a squirrel
As cells serve many different functions, they cell should also be
expected to have different shapes and sizes.
- cells range from 0.0001 mm wide as bacteria to 3 m long as
nerve cells
- some cells have cube, rod or spherical shape (bacteria) while
others have an ever-changing shape (animal cells)
all cells are either prokaryotes or eukaryotes
Prokaryotes
Prokaryotes have:
- no nucleus, but posesses a nucleoid
- cytoplasm in which contents are scattered (no
membrane-bound organelles)
- a simple structure
- a cell wall
- cell membrane
- no cytoskeleton
The following are prokaryotic cells:
- bacteria cells
Eukaryotes
Eukaryotes have:
- a nucleus
- many membrane-bound organelles contained in the
cytoplasm
- cytoskeleton
- more complex structure than prokaryotes (also
larger than prokaryotes)
- a cytoskeleton
The following are eukaryotic cells:
- animal cells
- plant cells
- protist cells
- fungi cells
Test your knowledge of cells with this quiz.
Tour of the Plant Cell
Tour of the Animal Cell
The Plasma Membrane
What is it?
- the skin of the cell
- a selectively-permeable (only some things can
pass through) fluid-y membrane that
surrounds the whole cell
- found in all cells
What is it made of?
- two layers of phospholipids called the lipid
bilayer
- proteins
What does it do?
- holds the cell together
- keeps all of the cell’s contents inside
- separates the cell from its environment
- controls what enters and leaves (ie: waste) the
cell
- protection
Transport through the Plasma Membrane
Transport of Small Materials
- requires no energy, uses diffusion (materials try to
move across the membrane to an area of lower
concentration of itself)
- travel through proteins that create small openings
on the plasma membrane
Transport of Large Materials
- requires energy (active transport)
- phagocytosis (transport into the cell): part of the
plasma membrane breaks off and form a pocket
around the materials, then fuses back into the
membrane, bringing the materials in
- exocytosis (out of the cell): materials are enclosed
in a membrane bubble (vesicle) for transport by
organelles in the cell, fuses with the plasma
membrane, forcing the materials out
The Lipid Bilayer
Lipids
- all lipids contain a hydrophyllic (attracted to
water) and hydrophobic (repelled by water) end
Bilayer
- each side of the membrane facing the fluid of the
interior/exterior of the cell are the hydrophyllic
ends of the lipids
- while the ends of the lipids that are hydrophobic
stay in between, away from the fluid in/around the
cell
Membrane Shape
- because the hydrophyllic ends of the lipids, the
lipids tend to move around as fluid moves, causing
the cell membrane to be fluid-like, with an everchanging shape
The Cell Wall
What is it?
-a lining around the cell, containing small holes to
allow materials to enter or exit
- found only in plant cells
What is it made of?
-mainly made of cellulose, a flexible elastic-y material
* cellulose is a carbohydrate fiber
- also made of protein fibers
What does it do?
- protection
- gives cells a stiffer form, a defined shape
- provides support
- prevents collapse of cell when contents expand or
shrink
- keeps the cell’s contents inside the cell
The Cytoskeleton
What is it?
- the skeleton and muscles of the cell
- a series/web of tubes and filaments found
throughout the cell
- found in eukaryotic cells
What is it made of?
- three types of protein fibers:
•microtubules
•microfilaments
•intermediate filaments
What does it do?
- helps maintain the shape of the cell, support
- allows movement in the cell (moving of organelles
and the entire cell)
The Endoplasmic Reticulum
What is it?
- the production facilility/line of the cell
- a series of membranes that are an extension of the
nuclear membrane
- found in eukaryotic cells
What is it made of?
- a series of membranes
What does it do?
-there are two types:
•rough endoplasmic reticulum: has ribosomes, the area
where proteins are made, forms transition vesicles (a
bubble-like sac that envelopes the proteins and
transports them to the golgi apparatus or plasma
membrane)
•smooth endoplasmic reticulum: lacking ribosomes,
makes enzymes to make and break down lipids and other
nutrients and protect the cell from toxins
The Nucleus
What is it?
- the control center or brain of the cell
- a large structure surrounded by two membranes (the nuclear
envelope)
- found in eukaryotic cells
What is it made of?
- a nuclear envelope controls what enter and leave the nucleus,
pores on the envelope allow entry/exit
- chromatin (DNA bound to proteins)
What does it do?
- area where RNA (carries commands from the nucleus) is made
- where ribosomes are made (the nucleolus)
- makes instructions/commands for other areas in the cell
- controls cell function
- stores most of the genetic code (DNA, the cell’s identity)
Centrioles
What is it?
- a pair of cylindrical structures near the nucleus
- found in animal cells
What is it made of?
- each made of microtubules built into a shape of a
cylinder
What does it do?
- helps in cell division by separating chromosomes
to opposite ends of the cell
- forms cilia and flagella in cells
Ribosomes
What is it?
- if the cell was a factory, ribosomes would be the
machinery that produces products
- small spherical structures on the rough endoplasmic
reticulum or moving in the cytoplasm
- found in all cells
What is it made of?
- proteins and RNA
What does it do?
- changes the information carried by RNA into proteins
(makes proteins)
- ribosomes attached to the surface of the rough
endoplasmic reticulum produce proteins for transport
outside the cell, lysosomes and the plasma membrane
- free-moving ribosomes in the cytosol, make/provide
proteins for the cytoplasm
Peroxisomes
What is it?
- a spherical membrane-bound organelle
- found in eukaryotic cells
What is it made of?
-proteins
- filled with enzymes
What does it do?
- makes and breaks down toxins used for digestion
- protects cell from its own toxins/ digestive
enzymes
Lysosomes
What is it?
- the stomach of the cell
- a spherical membrane-bound organelle made by the
golgi apparatus
- found in animal cells
What is it made of?
- proteins
- filled with various kinds of enzymes
What does it do?
- breaks down un-needed materials (ie: organelles
that have stopped working) in the cell
- breaks down food (helps in digestion)
- breaks down foreign materials (ie: bacteria)
- can seal wounds in the plasma membrane when it
fuses to the membrane to allow materials to exit
Plastids
What is it?
- membrane-bound organelles that store things
- found in plant cells and some protist cells
What is it made of?
- lipids (fat), protein membranes
What does it do?
There are three types of plastids:
Chloroplast
Chromoplast
•a membrane-bound organelle
•stores carotenoid (red, orange and yellow
pigment) and chlorophyll (green pigment)
Leucoplast
•a color-less membrane-bound organelle
•changes sugar into starch to be stored
•stores starches
Chloroplast
What is it?
- a green membrane-bound, organelle
What is it made of?
- possibly was originally a bacteria cell
- contains chlorophyll, a pigment that makes
chloroplast green
- contains three membranes
• a smooth, permeable (anything can go through)
outer membrane
• a smooth inner membrane that controls what enters
and exits (selectively permeable)
• thylakoid membranes (a sac-like structure)
What does it do?
- chlorophull makes sugar/food from abosorbed light
energy (performs photosynthesis)
Mitochondria
What is it?
- the power plant of the cell, the intestines (where food
is further broken down)
- membrane-bound organelle covered in two
membranes
- found in eukaryotic cells
What is it made of?
- possibly originally a bacteria cell
• contains cristae on the wrinkly inner membrane
•smooth outer membrane
- contains own DNA
What does it do?
- turns food into energy (ATP) that the cell can use
more quickly to function
- recycles and breaks down nutrients/un-needed
materials
The Golgi Apparatus
What is it?
- the packaging plant also where final touches are
made on the products
- series of membranes located between the
endoplasmic reticulum and the surface of the cell
What is it made of?
- enzymes that allow the golgi to do its job
What does it do?
- adds lipids and carbohydrates to proteins to
make more complex materials
- packages the materials into shuttle vesicles
(portions of the golgi which pinch off, carrying
the proteins for transport through the cell to
other organelles and export out of the cell)
Vacuoles
What is it?
- the storage area of the cell
- a large storage sac, found mostly in plant cells
(usually has one main vacuole)
- smaller vacuoles can be found in some animal cells
What is it made of?
- a membrane
What does it do?
- serves as storage for plants
- stores water, nutrients, wastes
- helps control pressure/movement in the cell
Journal
November 21: research
November 27: research/slides
November 1: research/slides
December 2: slides
December 3: slides
December 4: slides/images
December 8: touch up/quiz
Quiz
Choose the best answer.
Which is a function of a cell?
Which is a NOT a feauture of a prokaryotic cell?
A) making proteins
A) has a simple structure
B) adapting to their environment
B) has no membrane-bound organelles
C) getting rid of wastes
C) has a nucleus
D) all of the above
D) has a cell wall
What’s the difference between plant cells and
animal cells?
How are the functions of the plasma membrane and
the cell wall different?
A) plant cells have cell walls
A) cell wall provides rigidity and a defined shape to the
cell while cell membrane controls what enters/leaves
the cell
B) animal cells have centrioles
C) plant cells have vacuoles
D) both A and B
B) only cell wall provides protection
C) only cell membrane provides support
D) none of the above
Quiz
What is the skeleton and muscles of the cell?
A) the endoplasmic reticulum
B) the cytoskeleton
C) the cell wall
D) eukaryotes
Which structure makes enzymes for the cell?
A) the rough endoplasmic reticulum
B) the smooth endoplasmic reticulum
C) the golgi apparatus
D) lysosomes
Which part of the nucleus is responsible for
making ribosomes?
A) the nucleolus
B) the nuclear envelope
C) chromatin
D) none of the above, the endoplasmic reticulum
makes ribosomes
What cylindrical structure helps in cell division?
A) the vacuole
B) plastids
C) ribosomes
D) centrioles
Quiz
What acts as a messenger for the nucleus?
A) DNA
B) chromatin
C) RNA
D) centrioles
What makes proteins for the cell?
A) the endoplasmic reticulum
B) ribosomes
C) RNA
D) the golgi apparatus
Where does digestion of food first take place in the
cell?
A) mitochondria
B) peroxisomes
C) lysosomes
D) both A and C
Where does photosynthesis take place in the plant
cell?
A) chromoplast
B) leucoplast
C) chloroplast
D) the cell membrane
Quiz
What has its own separate DNA in the cell?
What is an example of a multicellular organism?
A) mitochondria
A) a human
B) chloroplast
B) a tree
C) prokaryote
C) bacteria
D) both A and B
D) both A and B
What serves as the cell’s storage area?
A) the golgi apparatus
B) vacuoles
C) microtubules
D) none of the above
Resources
Miller Levine. Prentice Hall Biology. Pearson Education, Inc. New Jersey 2002
Davidson, Michael W. “Introduction to Cell and Virus Structure.”
[http://www.microscopy.fsu.edu/cells/index.html]
"Cell (biology)." Microsoft® Encarta® Online Encyclopedia 2002. [http://www.encarta.com ]
University of Arizona. “Cell Biology.” [http://www.biology.arizona.edu/cell_bio/cell_bio.html ]
Sullivan, James A. “Cells Alive!” [http://www.cellsalive.com ]
Andrew Radar Studios. “Cells and Cell Structure.” [http://www.biology4kids.com/files/cell_main.html ]
“ThinkQuest Internet Challenge Library.” ThinkQuest, Inc. [http://library.thinkquest.org ]
Purves, William K. Sadava, David Orians, Gordon H.
Heller, Craig. “The Cell.” [http://www.thelifewire.com ]
Kimball, John W. “Kimball’s Biology Pages.”[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages ]
Krupp, Dave. “Lecture 16.” [http://imiloa.wcc.hawaii.edu/krupp/BIOL101/present/lcture16 ]
Resources
Krempels, Dana M. “The Cell: Smallest Living Level of Organization.”
[http://fig.cox.miami.edu/Faculty/Dana/105F00_4.html ]
Franklin Institute. “Parts of the Cell.”[http://sln.fi.edu/qa97/biology/biopoint4.html
MSPCA.” Squirrel.”[http://www.livingwithwildlife.org/wildlifehelp/ animals/squirrel.jp]
The Nobel Foundation. “The Nobel Prize in Physiology or Medicine 1999.”
[http://www.nobel.se/medicine/educational/poster/1999]
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