Cell TheoryO 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 CellsO Cell Membrane:

O Cytoplasm:

Features of CellsO Cytoskeleton:

O Ribosomes:

Cell Membrane

Passive TransportO Movement across cell membrane

that requires no energy

O Mostly occurs through diffusionO 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

DiffusionO Many molecules and ions diffuse in

and out of a cellO This is due to semi-permeable

membraneO Let’s some things in without energy,

some things need energy to get inO Ex: Food coloring in water

EquilibriumO All cells want to reach equilibrium

with concentrationsO Equilibrium: when concentration is

equal throughout the spaceO Ex: when sugar cube dissolves and

water is now equal parts water and sugar throughout

OsmosisO Diffusion of water through semi-

permeable membraneO Three types of solutions result from

osmosisO Hypertonic solutionO Hypotonic solutionO Isotonic solution

HypertonicO Water moves out of cellO Fluid outside the cell has a higher

concentration of dissolved particles than the cytoplasm

O Ex: salt water with egg inside

HypotonicO Water moves into the cellO Fluid outside of cell has lower

concentration of dissolved particles than cytoplasm

O Ex: Water with egg in it

IsotonicO No overall water movementO 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 ChannelsO 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 DiffusionO 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 TransportO 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 processO ATPO 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.

VesiclesO Some substances are too large to

transport any of the above ways

O Proteins for example use vesicles to move across the cell membrane

EndocytosisO Movement of a substance into a cell

by a vesicle

ExocytosisO Movement of a substance to the

outside of a cell

Signal MoleculesO Binds to a receptor proteinO Can change activity of cell in three

ways:O Enables specific ions to cross the cell

membraneO Cases the formation of a second

messengerO Speeds up chemical reactions inside

cells