Upload
joella-carroll
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
Maintaining BalanceMaintaining Balance• Homeostasis – process of
maintaining the cell’s internal environment
• Cannot tolerate great change• Boundary between cell and the
environment• What provides this?
Plasma MembranePlasma Membrane• Fluid Mosaic Model
• Selective Permeability
• Phospholipid bilayer
–Hydrophobic; Fatty Acid Tail –Polar Head; Hydrophilic
• Cholesterol – Provides stability
• Transport Proteins
• Carbohydrates
• Other Proteins– Cell recognition (immune
system)
Recall Following TermsRecall Following Terms• Solution
• Diffusion
• Concentration gradient
• Results in uniform concentration
OsmosisOsmosis• Cells try to reach equilibrium• Diffusion of water across a
selectively permeable membrane; 3 results– Isotonic– Hypertonic Tonicity– Hypotonic
HypertonicHypertonic• Solute concentration of solution
higher than cell • More dissolved particles outside
of cell than inside of cell • Hyper = more (think
hyperactive); Tonic = dissolved particles
• Water moves out of cell into solution
• Cell shrinks
HypotonicHypotonic• Solute concentration of solution
lower than cell • Less dissolved particles outside
of cell • Hypo = less, under (think
hypodermic, hypothermia); Tonic = dissolved particles
• Water moves into cell from solution
• Cell expands (and may burst)
Active vs. Passive Active vs. Passive • Active vs. Passive Transport• Passive requires no energy from
the cell• Active requires cells to use
energy, usually ATP
Passive TransportPassive Transport• Have to move with the
concentration gradient• Diffusion• Osmosis• Facilitated Diffusion- involves
use of transport proteins but still follow rule of diffusion
Active TransportActive Transport• Movement of materials against
concentration gradient• Transport proteins• Endocytosis – cell takes in
material• Exocytosis – expulsion or
secretion of materials from cell