The Cell Theory 1.All living things are composed of cells.
2.Cells are the basic units of structure and function in living
things. 3.New cells are produced from existing cells.
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Cell Size Typical cells range in size from 5 to 50 micrometers
in diameter. Cell shapes are directly related to its function.
Cell Structures (cont) Cell Membrane thin flexible barrier
around a cell. Cell Wall rigid layer surrounding the cell membrane
in some cells. Nucleus Control center of the cell Cytoplasm
material inside the cell membrane (excluding the nucleus).
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Prokaryotes vs. Eukaryotes
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Major Differences Prokaryotes (Pro = No) Smaller cells NO
Nucleus Lack organelles except cell membrane. Bacteria are
prokaryotes DNA is in the cytoplasm Eukaryotes (Eu = True) Larger
cells (by comparison) Have a nucleus Plants, animals, and fungi are
eukaryotes. Have specialized organelles DNA is in the nucleus
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Section 7-2 Cell Structures
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Cell Wall : The Support System Cell walls are found in many
plants, algae, fungi, and prokaryotes. The cell wall lies outside
the cell membrane Function: To provide support and protection for
the cell. Made mostly of a hard starch known as cellulose.
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The Nucleus: AKA The Control Center
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Nucleus (cont.) Function: Controls most cell processes. *
Contains DNA that controls the building of proteins.
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Nucleolus
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What is it? Small dense area within the nucleus that functions
as a protein factory
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Nuclear Envelope Porous membrane that surrounds the nucleus.
Function: Allows materials to move into and out of the
nucleus.
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Cytoskeleton Function: Gives the cell support and movement.
Made up of protein filaments.
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Movement in the cell Microtubules Hollow protein tubes that
organelles slide along. Similar to tracks Form centrioles in animal
cells during mitosis. Also form cilia and flagella on the outside
of cells to enable cells to move. Microfilaments Smaller tubes that
form a tough and flexible framework to support the cell. Play
Video: actin_cytoskeleton
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Organelles in the Cytoplasm AKA little organs
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Ribosomes The protein factories of the cell Made up of RNA
(ribonucleic acid) and proteins
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Endoplasmic Reticulum An intracellular highway Function: Area
where cell membrane parts are assembled and some proteins are
modified. Two different types of endoplasmic reticulum (ER) ..
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ER Continued Rough ER Embedded with ribosomes that build
proteins to be released from the cell. Called rough because the
ribosomes resemble bumps on the surface. Smooth ER Does not have
ribosomes, but may build lipids, regulate enzymes in muscle cells,
and break down toxic substances in the liver.
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Golgi Apparatus Shipping is our business
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Golgi Apparatus Function: The shipping, packaging, and
secreting organelle of the cell. Shaped like stacks of flattened
sacks. Packages proteins made in the rough ER into small packages
called vesicles.
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Vacuoles
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Sometimes called the waste dumps of the cell. Contain fluid
filled sacs that store water, salts, and enzymes. Vacuoles are
commonly found in plant cells and some protozoans. Vacuoles can be
very large and take up as much as 90% of a cells volume.
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Lysosomes
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Lysosome Enzyme Sacs Functions Break down food particles in the
cell Digests worn out organelles in the cell Also digests ingested
bacteria and other debris. Shapes the appendages in early
development. (Selective destruction) Common in animals, fungi, and
algae cells. Lysosome Animations
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Chloroplasts The Sugar Factory
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Chloroplasts Site of photosynthesis in plant cells, algae, and
some bacteria. Contains the green pigment, chlorophyll.
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Mitochondria AKA The Powerhouse
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Mitochondria Uses food to produce the high energy molecule ATP.
The site of cellular respiration. Found in all eukaryotic
cells.
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Mitochondria History Mitochondria contain its own DNA. This
means that it might have originated as an ancient bacteria. Your
mitochondria cells are inherited from your mother. They come from
her egg cells.
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Comparing Plant vs. Animal Cells
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Plant Cells vs. Animal Cells Plant cells have cell walls,
chloroplasts, and vacuoles which are NOT found in animal cells.
(Some animal cells may contain small vacuoles.) Plant cells rarely
have lysosomes, but animal cells do. All other organelles are
common to both.
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Movement Through the Membrane
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The Role of the Cell Membrane Cell membrane regulates what
enters and leaves the cell. Provides protection and support to the
cell. The cell membranes structure is known as a lipid bilayer.
Cell membrane has a double layer of lipids which protect the cell.
Embedded with protein molecules that form channels or pumps to move
materials across the cell membrane.
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Lipid Bilayer Hydrophilic Head, Hydrophobic Tail
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How do molecules move across the cell membrane? Diffusion The
movement of molecules from an area where they are in high
concentration to an area where they are less concentrated. Many
substances move constantly from high to low concentration. This can
be in or out of the cell. This movement continues until the
concentration on both sides is equal. (AKA equilibrium.)
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Permeability in Cell Membranes If a membrane allows a substance
to cross, it is said to be permeable to that substance. Most
membranes are selectively permeable, which means that some
substances can pass, but not others.
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Osmosis Osmosis the diffusion of water through a selectively
permeable membrane.
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Tonicity of Solutions Osmosis (and diffusion)- solutions flow
from areas of HIGH concentration to LOW concentration. Hypotonic
solution- has a high concentration of water and a low concentration
of sugar. (or salt) Hypertonic solution has a low water
concentration and a high sugar concentration. Water moves from
hypertonic to hypotonic solutions to reach equilibrium. Equal
solutions are said to be isotonic. (Iso = same or equal)
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Homeostasis (Hypotonic Solutions) An internal balance Cells
placed in a hypotonic solution like pure water will swell. In plant
cells, the swelling is limited by the cell wall but the cell does
build up turgor pressure. Animal cells may swell and even burst,
which is called cytolysis.
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Homeostasis (in Hypertonic Solutions) Cells placed in
hypertonic solutions full of salt will collapse. Plant cells will
wilt in hypertonic solutions. This is called plasmolysis. (Usually
temporary, but can lead to the death of the cell. Animal cells will
also shrink in hypertonic solutions.
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Tonicity of Fresh vs. Saltwater Environments Freshwater
environments are naturally hypotonic. Some aquatic organisms have
organelles called contractile vacuoles that pump out excess water.
Freshwater fish maintain homeostasis by frequent urination.
Saltwater environments are naturally hypertonic. Saltwater fish
maintain homeostasis by excreting salt in their urine and from
their gills as well.
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Passive Transport Does not require cell energy to move
materials across the cell membrane. 3 types 1. Occurs by diffusion
of small molecules like salt (NaCl) 2. Occurs by osmosis (diffusion
of water) 3. Occurs by facilitated diffusion which moves the sugar
glucose across the membrane through protein channels.
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Active Transport Active Transport does require energy to move
materials across a cell membrane from low concentration to high
concentration. (Normally goes from high to low.)
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Active Transport Types Sodium-Potassium pump uses cell energy
to move Na + ions outside the cell and put K + ions inside the
cell. Endocytosis- uses cell energy to transport large molecules
into a vesicle on the cell membrane. There are two types:
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Endocytosis Types Phagocytosis cell eating moves large
particles or whole cells into the cell membrane. Used by white
blood cells called phagocytes to eat bacteria.
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Endocytosis Types Pinocytosis cell drinking transports fluids
or solutes across the cell membrane.
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Exocytosis (Exo = out) Exocytosis (Opposite of endo) The
vesicles form on the inside of the membrane and pooch outwards then
rupture and release the contents. Used to release packaged
molecules like proteins. Also used by the nervous system to release
neurotransmitters.
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7-4 Diversity of Cellular Life
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A. Unicellular Organisms Are single-celled organisms that
maintain all life functions. Made up of both prokaryotes and
eukaryotes. This is the most dominant life form on Earth. Examples
are: yeast, bacteria, and some algae.
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B. Colonial Organisms Consist of groups of unicellular
organisms clustered together. Ex. volvox aureus (type of algae)
Each cell is held to other cells using cytoplasmic strands. They
are still single- celled organisms working together.
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C. Multicellular Organisms Have cells that are more complex and
also more dependant on other cells. These cells also exhibit a
division of labor. Ex: movement, coverings. Examples of
multicellular organisms include: humans, other mammals, reptiles,
etc.
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D. Levels of organization within a multicellular organism
1.Cell Functional unit but depends on other cells. 2.Tissue
composed of groups of cells alike in their structure and function.
There are 4 types in humans. a. Nervous b. Epithelial (covers and
lines the body and organs. Ex. skin c. Muscle d. Connective bones,
blood, cartilage, lymph
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D. Levels of organization within a multicellular organism 3.
Organs made up of groups of tissues working together to perform one
major task. a. The stomach is an organ made up of epithelial,
muscle, nervous, and connective tissues. b. Examples of organs are:
heart, lungs, skin, pancreas, etc.
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D. Levels of organization within a multicellular organism Organ
systems consist of groups of organs that work together to perform a
specific function for the organism. a. There are 11 major organ
systems in humans. b. Examples of organ systems are: muscular
system, skeletal system, circulatory system, etc...\..\Teacher
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