Cell Theory O Three Parts O All living things are made up of one or more cells O Cells are the basic units of structure and function O All cells arise from existing cells

Features of Cells O Cell Membrane: O Cytoplasm:

Features of Cells O Cytoskeleton: O Ribosomes:

Cell Membrane

Passive Transport O Movement across cell membrane that requires no energy O Mostly occurs through diffusion O Diffusion: movement from area of high to low concentration

What does this mean? O Concentration gradient: difference in amount of substance in a space O Ex: sugar cube in water

Diffusion O Many molecules and ions diffuse in and out of a cell O This is due to semi-permeable membrane O Let’s some things in without energy, some things need energy to get in O Ex: Food coloring in water

Equilibrium O All cells want to reach equilibrium with concentrations O Equilibrium: when concentration is equal throughout the space O Ex: when sugar cube dissolves and water is now equal parts water and sugar throughout

Osmosis O Diffusion of water through semi-permeable membrane O Three types of solutions result from osmosis O Hypertonic solution O Hypotonic solution O Isotonic solution

Hypertonic O Water moves out of cell O Fluid outside the cell has a higher concentration of dissolved particles than the cytoplasm O Ex: salt water with egg inside

Hypotonic O Water moves into the cell O Fluid outside of cell has lower concentration of dissolved particles than cytoplasm O Ex: Water with egg in it

Isotonic O No overall water movement O Fluid inside and outside of cell appear to be similar in concentration and no water movement is needed O Ex: When egg and water meet equilibrium

Ion Channels O Some substances cross the cell membrane with help from transport proteins O Ion channels allow important ions into the cell such as sodium, potassium, calcium and chloride

Facilitated Diffusion O Carrier Proteins bind to specific substances to carry them across the cell membrane O Facilitated diffusion moves substances down their concentration gradient without using the cell’s energy

Steps for Facilitated Diffusion Step 1: a molecule outside the cell binds to a carrier protein on the cell membrane Step 2: The carrier protein transports the molecule across the cell membrane Step 3: The molecule is released from the carrier protein inside the cell

Active Transport O The transport of a substance across the cell membrane against its concentration gradient

Sodium-Potassium Pump O Transports three sodium ions out of a cell, and two potassium ions into the cell O Energy needed for process O ATP O Important in animal cells

Sodium-Potassium Pump Step 1: Three sodium ions inside the cell bind to the pump. A phosphate group from ATP also binds to the pump Step 2: The pump changes shape, transporting the three sodium ions across the cell membrane. The sodium ions are released outside the cell Step 3: Two potassium ions outside the cell bind to the pump. The potassium ions are transported across the cell membrane Step 4: The phosphate group is released and the two potassium ions are released inside the cell.

Vesicles O Some substances are too large to transport any of the above ways O Proteins for example use vesicles to move across the cell membrane

Endocytosis O Movement of a substance into a cell by a vesicle

Exocytosis O Movement of a substance to the outside of a cell

Signal Molecules O Binds to a receptor protein O Can change activity of cell in three ways: O Enables specific ions to cross the cell membrane O Cases the formation of a second messenger O Speeds up chemical reactions inside cells