Cell Unit Notes

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

Prokaryotes vs. Eukaryotes  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”  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 Cytoplasm Nucleus Organelles Eukaryotic Cell Prokaryote vs. Eukaryote Prokaryotic Cell

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

 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 Prokaryotes

 Bacteria have cell membranes and most have a cell wall  Their DNA is one circular molecule  They often have many plasmids Small circular rings of DNA usually containing one gene Small circular rings of DNA usually containing one gene  Pili help bacteria “stick” to things Prokaryotes 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 Prokaryotes & Viruses

Eukaryote Cell Structures  Cell Wall Found in many organisms including plants, algae, fungi, and nearly all prokaryotes Not found in animal cells Not found in animal cells

Cell Wall The main function of the cell wall is to provide support and protection for the cell 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  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

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

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

The Cytoskeleton  Made up of three types of structures : 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

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

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

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

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

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

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

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

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

Typical Plant Cell

Typical Animal Cell

The Cell Membrane  The regulates what enters and leaves 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

Selective Permeability

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

The Lipid Bilayer  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 Protein channel Carbohydrate chains

Diffusion  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

Diffusion

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

Diffusion  Diffusion allows substances to cross the cell membrane  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!

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

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

Osmosis (cont.)  Tonicity: Ability of a solution to cause a cell to gain or lose water. Is dependent on the concentration of solutes that cannot cross a membrane (non- penetrating solutes). The more of these solutes there are, the higher the tendency that water will exit the cell and vice versa. Is dependent on the concentration of solutes that cannot cross a membrane (non- penetrating 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. The concentration of solutes is equal outside & inside of cell. This is an indicator of a stable cell environment. Water will still flow across the membrane at the same rate in both directions.

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

Osmosis (cont.)

Osmotic Pressure   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)

Osmotic Pressure

Osmosis (cont.)  Osmoregulation: Control of H 2 O balance. 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.

Osmosis (cont.)  Plant cells are very turgid (very firm) when they are surrounded by a hypotonic solution. Allows the plant to stay upright = Healthy. 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. Causes the plant cell to lose water & turgor pressure, resulting in cell death. Bacteria & fungi cells can also undergo plasmolysis.

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

Facilitated Active and Passive Transport

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

Endocytosis & Exocytosis

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