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CELL TRANSPORT. How substances get across the membrane…. Diffusion Across Cell Membrane. Semi-permeable membrane Allows only certain molecules across H 2 O CO 2 and O 2. Passive Transport. Movement of substances across the cell membrane Requires no energy from the cell
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Diffusion Across Cell Membrane • Semi-permeable membrane • Allows only certain molecules across • H2O • CO2 and O2
Passive Transport • Movement of substances across the cell membrane • Requires no energy from the cell • Diffusion is the simplest type of passive transport
DIFFUSION • Movement of molecules from HIGH concentration to LOW concentration • Concentration Gradient - the difference between concentrations in space • Simple diffusion only allows certain molecules across a membrane
Eventually it will hit an equilibrium(same concentration across the gradient)
OSMOSIS • A type of diffusion • Process by which WATER molecules diffuse across a membrane from high to low concentrations
10% Salt Solution • % solutions have to equal 100 • 10% salt (solute) would leave how much water (solvent)? • 90% water
Hyper = above tonic refers to the • Iso = same shape of the cell • Hypo = below
How Cells Deal With Osmosis • Animal Cells: • Contractile Vacuoles • Collects water and expels it from the cell
How Cells Deal With Osmosis Plants: • Turgor Pressure • Water pressure that is exerted against cell wall
Plasmolysis – loss of turgor pressure • Plants wilt • Cytolysis – cells burst due to hypotonic solution cell is in
Ion Channels • Transport ions such as Na, K, Ca and Cl • Can’t pass through membrane w/o channel
Active Transport • Moving molecules from a LOW concentration to a higher concentration • Moving “up” their concentration gradient • Requires energy from in cell • ATP
Active Transport • Need a pump • Sodium-Potassium Pump • Exchanges Na and K • Na to the outside • K to the inside
Other Transport Mechanisms • Endocytosis – process of ingesting macromolecules and nutrients that are too large to pass through membrane • Two types:
Pinocytosis • Transport of other fluids
Phagocytosis • Transport of large particles or whole cells • Phagocytes may fuse with lysosomes to destroy ingested bacteria or viruses
Other Transport Mechanisms • Exocytosis – process by which materials are released from the inside of the cell • Release toxins and waste products • Release proteins • Control activity of other cells