agenda 10/27 cell membrane and homeostasis 2.1 relate cell parts/organelles (plasma membrane ) to...
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Agenda 10/27Cell Membrane and Homeostasis
2.1 Relate cell parts/organelles (plasma membrane) to their functions. Explain the role of cell membranes as a highly selective barrier (diffusion, osmosis, facilitated diffusion, active transport).
Homeostasis– Maintaining a relatively constant internal environment
Cells need the proper concentration of nutrients and water, and to eliminate wastes.
The cell membrane is selectively permeable – it allows some things to pass through,
while blocking other things.
Structure of the Cell Membrane
Phospholipid bilayer – two sheets of phospholipids.
Embedded with proteins and strengthened with cholesterol molecules.
What’s a Phospholipid? 2 fatty acid chains, a phosphate group,
and a glycerol.– Hydrophilic heads face out
– hydrophobic fatty acids hang inside.
Fluid Mosaic Model The parts of the cell membrane form a
fluid that can move more or less freely. The cell membrane is a “mosaic” in that
it is composed of several different parts
Cell Membrane
Cellular Transport Diffusion – movement of particles from
an area of high concentration to an area of low concentration.– Continues until an equilibrium is reached
Osmosis
Diffusion of water across a selectively permeable membrane.
Occurs until water is balanced on both sides of the membrane.
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AquaporinsAquaporins Water Channels Protein pores used during
OSMOSIS WATERMOLECULES
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Cellular Transport [1] Passive transport – no energy is
needed to move particles (from high to low concentration).
– Facilitated diffusion –proteins act as tunnels allowing particles to cross the cell membrane
Cellular Transport [2] Active transport – energy is
needed to move particles across the membrane (from low to high concentration).
1. Transport (or carrier) proteins
2. Endocytosis (endo- = into; cyto- = cell)
3. Exocytosis (exo- = out)
Active Transport: Transport Proteins
Allow movement of particles against the concentration gradient (from low to high)
Carrier proteins –protein changes shape to open and close passages across membrane.
Carrier Protein
Active Transport: Endocytosis
Movement of larger
particles INTO the cell
ExocytosisMovement of larger
particles OUT of the cell
Osmosis
Diffusion of water across a selectively permeable membrane.
Occurs until water is balanced on both sides of the membrane.
Solutions
Solute: substance that is dissolved into something else
Solvent: the substance the solute is dissolved into
Cell Concentrations
Hypertonic solutions – more dissolved solute.
Hypotonic solutions – less dissolved solute.
Isotonic solutions – the same dissolved solute.
Osmosis
Osmosis in Cells
Animal Cells- – Crenation- cell shrivels as water leaves– Lysis- cell bursts when too much water
enters Plant Cells-
– Turgor Pressure- pressure of full central vacuole pressing out on cell wall- when low, plant wilts
Osmosis in Cells
Contractile vacuoles – expel excess water from bacterial cells that live in water to keep cells from bursting.
Turgor pressure – water pressure in a plant cell (central vacuole). Loss of turgor pressure causes wilting.
Membrane Proteins
1. Determine what particles can pass through the membrane.
2. Serve as enzymes.3. Act as markers inside and outside of
the cell (communication).
Can you identify the cell parts?
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