Cell Theory Cells are basic unit of life Cells are produced from other cells Cells maintain homeostasis Homeostasis of tissues, and higher results from the coordinated effort of many cells

The cell membrane/plasma membrane Physical isolation Regulates exchange Sensitivity Structural Support

Membrane Structure Phospholipid bilayer Hydrophillic heads at the membrane surface Hydrophobic tails on the inside

Membrane Proteins Receptor proteins- recognize certain molecules Ex. Glucose can be recognized, and stimulates absorption of glucose Carrier Proteins- transport solutes across the membrane Channels- allows water and small soluted through the membrane

Membrane Permeability Detemines which substances can enter and exit the cell Selective permeability- permits free passage of some materials, and restricts others Passive passage- requires no energy Active passage- requires energy

Transport processes Diffusion- movement of molecules from a high concentration to a low concentration Osmosis- refers to the movement of water specifically Isotonic- no flow of water into or out of the cell Hypotonic- water flows into cell Hypertonic- water flows out of cell

Filtration Hydrostatic pressure forces water and solute molecules through the membrane Ex. In capillaries this pressure pushed water and nutrients into the tissues of your body

Carrier Mediated Transport Proteins carry substance across the cell membrane Facilitated diffusion- Insoluble nutrients like glucose are transported by passively proteins

Facilitated Diffusion

Active Transport Ions or molecules are moved across the membrane using ATP Ion pumps- protein that transport ions through the membrane Ex. K+, Na+, etc.

Vesicular Transport Materials move into or out of the cell through vesicles (small sacs) Endocytosis- packaging of material outside of the cell and then dumping them into the cell

Vesicle Transport (cont.) Pinocytosis- “cell drinking” sac fills with extracellular fluid, depression forms in membrane, and gets deeper until it pinches off Phagocytosis- “cell eating” membrane surrounds solid objects outside of the cell and pinches off inside of the cell

Exocytosis Vesicle created inside the cell fused with the membrane, and discharges its contents outside the cell Opposite process of endocytosis