 All living things are composed of cells
 Cells are the basic functional units of life
 New cells are produced from existing cells

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Prokaryotes smaller & simpler
Contain a cell membrane & cytoplasm
Sometimes a cell wall
Also have ribosomes
No nucleus
All bacteria are prokaryotes
DNA is “free – floating”
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Eukaryotes
Have a nucleus containing DNA
Most have specialized structures called organelles
All plants, animals, protists, and fungi are eukaryotes
Larger and more complex

Cell membrane
Prokaryotic Cell
Cytoplasm
Eukaryotic Cell
Cell membrane
Cytoplasm
Nucleus
Organelles

 Prokaryotes are simple, living organisms that can reproduce on their own
 They have diverse ways of obtaining nutrients:
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Photosynthesis
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Chemosynthesis
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Heterotrophic consumers

 Bacteria (prokaryotes) live in every habitat possible and are the most numerous of all living things on our planet
 All living things depend upon bacteria – including, especially, humans!

 Archea represent the “ancient bacteria” and they live in extreme environments such as boiling water or extremely salty environments
 They are the oldest living organisms on this planet. Evidence suggests that they were present during the early stages of Earth over
3.9 billion years ago

 Bacteria have cell membranes and most have a cell wall
 Their DNA is one circular molecule
 They often have many plasmids
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Small circular rings of
DNA usually containing one gene
 Pili help bacteria
“stick” to things
Many bacteria have a flagellum or many flagella to help them move

 Viruses are extremely small particles not considered to be “alive”
 They act like parasites because they can ONLY reproduce in a host
 They consist of a protein coat and contain either
DNA or RNA inside

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Found in many organisms including plants, algae, fungi, and nearly all prokaryotes
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Not found in animal cells

The main function of the cell wall is to provide support and protection for the cell
Plant cell walls are made of cellulose

 The nucleus is the “control center” of the cell
 The nucleus controls most cell processes and contains the hereditary information of
DNA
 Almost all eukaryotic cells, including plant and animal, contain a nucleus

 Nucleolus – small dense region in nucleus where ribosomes are produced
 Nuclear envelope – double membrane layer surrounding the nucleus (aka.
Nuclear membrane)

 A network of protein filaments that help the cell maintain it’s shape
 It is also involved in many forms of
Microtubule movement
Microfilament

 Made up of three types of structures :
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Microtubules – hollow tubes of protein that help maintain cell shape and serve as “tracks” for organelles to travel on
Intermediate Filaments – smaller than microtubules – gives a cell its strength
Microfilaments – long thin fibers that support cell movement and support

 Ribosomes
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Organelle that
“assembles” proteins
(Protein Synthesis)
A ribosome is made up of 2 parts:
• a protein
• rRNA (ribosomal
RNA)
Ribosomes make proteins from the “coded” instructions of the DNA inside the nucleus
Ribosomes

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An internal membrane where parts of the cell membrane are made and some proteins are modified
The Rough
Rough endoplasmic reticulum
Endoplasmic Reticulum is where protein synthesis occurs
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Ribosomes are on it’s surface making it appear “rough”

 The Smooth
Endoplasmic
Reticulum does not have any ribosomes on it’s surface
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It contains enzymes that make lipids (fats)
Smooth endoplasmic reticulum

Golgi apparatus
 After proteins are assembled and produced by the
Rough ER they move to the Golgi Complex where :
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Carbohydrates (sugars) and lipids (fats) are attached to the protein
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They are then sent to their final destination

 Small organelles that are filled with digestive and other enzymes
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They break down lipids
(fats), carbohydrates
(sugars), and proteins from food particles so it can be used by the rest of the cell
Lysosomes also break down “old” organelles that have outlived their function
Basically, they “take out the trash”

 Serve as a storage for water, salts, proteins, and “carbs” (plant and animal cells)
 In Plants :
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They usually have one large vacuole filled with water to support structures like leaves and flowers
Vacuole

 The producer!
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They use sunlight to power a familiar process called
Photosynthesis
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The green pigment
(color) chlorophyll is what gives leaves their color and is found inside chloroplasts
Chloroplast

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The “powerhouse” of the animal and plant cell!
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Mitochondria use energy from food to make highenergy compounds (ATP)
The cell uses these highenergy compounds for growth, development, and movement
In that way, the mitochondria makes “fuel” for the cell

 The cell membrane regulates what enters and leaves the cell
 It also provides support and protection
 The cell takes in food and water and eliminates wastes through the cell membrane
 The cell membrane is selectively permeable

 Most cell membranes are made up of a doublemembrane layer called the lipid bilayer
 Along with lipids the membrane also has proteins that are “stuck” in it (see below)

 Along with the proteins are “carbohydrate chains” that are attached to the protein
 These “chains” act like an identification card or
“face” so the cell can be recognized
Carbohydrate chains
Protein channel

 All living cells are surrounded by and full of liquid
 Even a cactus in the desert has moist cells in it’s living tissue
 One of the most important functions of the cell membrane is to regulate the movement of molecules from one side of the membrane to the other

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The concentration of a solution is the relative “purity” of a liquid
There can be a high concentration to a low concentration
A solution will move in the direction of high concentration to low concentration and this is called
Diffusion

 Diffusion allows substances to cross the cell membrane without requiring the cell to use energy
 This is very important since energy must be conserved – even at the cellular level!

 Osmosis is the movement of water across a semi-permeable membrane.
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Important part of homeostasis

 Selective permeability means that only select
“things” can pass through the membrane
 Osmosis is “the diffusion of water across a selectively permeable membrane”

 Tonicity: Ability of a solution to cause a cell to gain or lose water.
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Is dependent on the concentration of solutes that cannot cross a membrane (nonpenetrating solutes). The more of these solutes there are, the higher the tendency that water will exit the cell and vice versa.
 Isotonic solution: No net movement of H
2
O occurs.
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The concentration of solutes is equal outside & inside of cell.
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This is an indicator of a stable cell environment.
Water will still flow across the membrane at the same rate in both directions.

 Hypertonic solution:
H
2
O will move out of the cell (lose H
2
O).
Concentration of solutes is greater outside of cell.
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Increases in salinity causes cells to lose
H
2
O such as a freshwater plant placed into saltwater.
 Hypotonic solution:
H
2
O will enter cell.
Concentration of solutes is greater inside of cell.
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This can cause cells to lyse (burst) & die.

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Isotonic – means that on both sides of the cell membrane it is the same
“concentration”
Hypotonic – the cell fills up with water and is in danger of “bursting”
Hypertonic – the cell loses much of its water concentration and can
“shrink”
(Animal Cells react differently than plant cells because of the cell wall that plant cells have)

 Osmoregulation:
Control of H
2
O balance.
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Paramecium lives in pond water (hypotonic to cell). It has a plasma membrane that is less permeable to H
2
O to slow the uptake of H
2
O.
• Also has a contractile vacuole that pumps out
H
2
O as fast as it enters.

 Plant cells are very turgid
(very firm) when they are surrounded by a hypotonic solution.
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Allows the plant to stay upright = Healthy.
 If plant cells are in an isotonic environment, the cells will become flaccid
(limp) = Unhealthy.
 If plant cells are in a hypertonic environment, they will undergo plasmolysis.
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Causes the plant cell to lose water & turgor pressure, resulting in cell death.
Bacteria & fungi cells can also undergo plasmolysis.

 This is diffusion across the cell membrane with the
“help” of proteins
 It still flows from a high to low concentration

 Active transport requires
“action” or energy in order to move these particles across the cell membrane
 The input of energy along with special proteins on the surface of the cell can move any particles across any “gradient”
 Gradient – relative concentration of a solution

 The removal of large amounts of material from the cell is known as exocytosis
 The vesicle fuses with the cell membrane and forces its contents out of the cell