Download A Look at Cells

A Look at Cells—Cell Theory, Structure, & Function NOTES
(Powerpoint Notes)
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These notes are based on the information in chapter 3 of your text. There is absolutely no guarantee that every last thing you need to
know is here. You need to LISTEN in class, READ the chapter, and PAY ATTENTION to the other activities we do in class. You are
responsible for any and all material you are exposed to or have access to (except the entire internet  ).
Cells are the smallest unit of life that can carry out all the functions of a living organism;
not discovered until the invention of the microscope.
Organisms can be very broadly classified on the number of cells they are made of. Unicellular organisms are made
of only 1 cell; they are the smallest of all living organisms. Ex) some bacteria, many protists
Other living organisms are made of many cells and are called
Multicellular Ex) Plants, animals, and
fungi
Shape is related to function
Blood cells (hemocytes) - round to move through vessels
Nerve - long to carry message to spinal cord
Muscle cells for contracting and relaxing
The Discovery of Cells
Robert Hooke gave the cell its name when viewing cork from an oak tree
Anton Van Leewenhoek invented the first “real” microscope and later viewed living
organisms (for the first time) in pond water
Brown discovered the nuclei of a cells by observing epidermal cells of orchids.
Cell Theory
Schleiden, a botanist, said “all plants are made of cells”
Schwann, a zoologist, said “all organisms are made of cells”
Virchow, a physician, said “all new cells come from other cells”
These 3 pieces of information are incorporated into the modern cell theory which states:
* Cells are the basic unit of life
* All organisms are made of cells
* All cells come from other cells
Basic Cell Structures
All cells have some structures in common. All cells have:
 Cell membrane - phospholipids and protein
 Cytoplasm - everything inside the cell except the nucleus/DNA
 Cytoskeleton - system of fibers
 DNA/RNA - the genetic material
 Ribosomes - proteins are made on these
Cell Membrane See Fig. 11 & 12, p. 60-61
Function: homeostasis
1. controls what enters and leaves the cell
2. boundary separating the cell from its environment
Structure:
1. Thin layer of lipids embedded with proteins
2. semipermeable (aka selectively permeable)
3. 2 phospholipid layers called a bilayer
4. hydrophilic head (water loving)
5. hydrophobic tail (water fearing)
Cytoplasm
Function:
Contains or “suspends” structures called organelles inside the cell
Structure:
1. Jelly-like base, consisting mainly of water and organic compounds; called the cytosol
2. Other structures within the cytoplasm vary.
3. Contains the cytoskeleton
Cytoskeleton:
Function:
Provides support and a place to anchor
other organelles
Structure:
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Composed of protein fibers 3 types:
Actin fibers
microtubules
intermediate fibers
DNA
All cells contain DNA at some point in their lives
Structure:
complementary strands in a double helix
Function :
Carries the genetic code
replicates itself to pass the genetic code on to its daughter cells
Ribosomes
Structure:
Spheres composed of RNA and Protein
Function:
Site of protein synthesis
free are shown in the electron micrograph.
Ribosomes are also attached to the ER
“Typical” animal Cell
“Typical” plant Cell
note the cell wall!
Nucleus – Found only in eukaryotes (all except bacteria)
Function:
Control headquarters for the cell (brain)
Structure:
 Found in the cytoplasm
 Contains the genetic material – chromosomes – made of DNA and
Proteins
 Surrounded by a double membrane called the Nuclear Envelope or
Nuclear Membrane
 Inside is a Nucleolus that makes ribosomes
Overview of Organelles
Eukaryotic cells contain a variety of organelles other than the nucleus. These include:
2
• Endoplasmic Reticulum (ER) –
transport system of tubes (1 & 4)
•Golgi– stacked sacs that package and
distribute materials through the cell (2)
3
1
Vesicles – membrane-bound sacs for
transport of proteins (3)
4
•Vacuoles – tiny membrane-bound storage
containers
•Lysosomes (animal cells only) – contain digestive
enzymes, “suicide sacs”
•Mitochondria – function in the 2nd part of
Respiration, taking the energy from small carbon
compounds and storing it in ATP; have their own
DNA
“powerhouse of cell”
•Centrioles– function in cell division (animal cells only);
always 2 present at right angles to each other; referred
to collectively as the centrosome
•Chloroplast – type of plastid containing chlorophyll; functions in photosynthesis
(plant cells and a few protists only) ; have their own DNA
•Central Vacuole (plant cells only) – large central
structure for storing water and its solutes
Organelles—A Closer Look at a Few
Nucleolus: Location—within the nucleus; Structure—knot of chromatin; Function—produce ribosomes
Endoplasmic Reticulum (Rough): Structure—Network of membranes near nucleus, contains ribosomes on
surface; Function—transports proteins made by the attached ribosomes through the cell to the golgi.
Endoplasmic Reticulum (Smooth): Structure—Network of folded membranes throughout cell, Contains no
ribsomes on surface; Function—Makes lipids and breaks down toxic substances.
Golgi Apparatus: Location—in the cytoplasm; Structure—closely stacked, flattened membrane sacs; Function—
stores, packages, and transports products (proteins) inside for use outside; vesicles (a bit of golgi pinches for
transport of stored materials)
Lysosome: Not found in plants; Structure—saclike, contains digestive enzymes; Function—digests food particles,
old organelles
Mitochondria: Found in ALL eukaryotic cells; Strucure--oval, complex matrix of folded membranes to increase
surface area; Function—changes energy stored in food into a more useful form, the energy storage molecule called
adenosine triphosphate (ATP)
Centrioles: Found in Animal cells only; Structure—9 sets of 3 protein fibers; Function—aid in the division of
chromosomes during mitosis.
Microtubules: Location—throughout the cell’s structure; Structure—thick filaments made of protein; Function—
gives structure & shape to cells and anchors organelles
Microfilaments: Location—thoughout the cell structure; Structure—thin, protein tubes; Function—allows for
elasticity and movement within cells
Vesicles: Location—inside or outside of the plasma/cell membrane; Structure—bits of membrane from the plasma
membrane or the golgi apparatus; Function--Vesicles fuse with the cell membrane may be used to release or
transport chemicals in or out of the cells. Exocytosis out of the cell; Endocytosis into the cell
Vacuole: Location—cytoplasm; Structure—sac of fluid surrounded by a membrane; Plants--large in size, Animals—
small in size; Function—sites of storage of water, ions and some nutrients. Plants: allows plants to maintain turgor
pressure.
Chloroplast: Location—plant cells and some protests; Structure—double phospholipids bilayer, Inner layer
(stacks=grana; Non stacked area = stroma); Function—capturing radiant energy and converting it to chemical
energy, chlorophyll is the green pigment that traps the energy from the sun.
Vesicles, golgi, and ER are all involved in protein production in the cell. They are found in both plant and
animals cells.
Mitochondria are found in both plant and animal cells. They are involved in cellular respiration.
ONLY IN ANIMALS:
Centrioles are only found in animal cells. They were thought to be involved in cell division. Lysosomes contain
digestive enzymes for breaking down toxins and worn out organelles, invading cells, or “food” for phages.
ONLY IN PLANTS:
Choloroplasts are found only in plant cells. They take in light energy and store it in carbohydrates during
photosynthesis. Note the cell wall (contains cellulose, provides structure & support) and large central vacuole
(stores water) in the diagram of a plant cell. They are also found only in plant cells.
Flagella and Cilia: Location—outside of cells; Structure—Cilia (short hair-like), Flagella (long whip-like tail);
Function--locomotion=movement, Cilia (tiny, flutters of movement), Flagella (one big wave motion)
Some Cell Web Sites for Further Study
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http://sun.menloschool.org/~cweaver/cells/
•http://www.borg.com/~lubehawk/cell.htm
•http://www.rkm.com.au/CELL/
•http://www.enchantedlearning.com/subjects/biology/cells/
•http://web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm
•http://www.rkm.com.au/BACTERIA/bacterial-cell.html
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http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html#Golgi%20Apparatus%20and%20Dictyosomes