Exchange with the Environment Cell Transport. Cell Processes For a cell to survive, it must get...
Transcript of Exchange with the Environment Cell Transport. Cell Processes For a cell to survive, it must get...
Exchange with the Environment
Cell Transport
Cell Processes
For a cell to survive, it must get nutrients and water. It must also get rid of wastes
How can the cell get materials in and out through the cell membrane?
Cell membrane
Made up of a phospholipid bilayer and several proteins
Phospholipid: Hydrophillic phosphate head Hydrophobic fatty acid tail
Image from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phosphb.htm
Cell membrane
Cell membrane: Proteins Integral Proteins
Embedded in lipid bilayer Receptor proteins and transport proteins Transmit signal or materials into/out of the cell
Peripheral Proteins Only on one side of membrane Some act as enzymes Some act as cell markers
Fluid mosaic model of cell membrane
Phospholipid bilayer acts as a fluid Lipids and proteins can move in the layer Sterols (including cholesterol) are used to
help keep membrane structure
Cell membrane
Cell Membrane
Diffusion
The movement of particles from an area of high concentration to an area of low concentration down the concentration gradient
Occurs outside of cells and across cell membranes
Diffusion
Picture from: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html
Osmosis
The diffusion of water across a cell membrane
If solution outside a cell has more water than the cell then water will move into the cell
Osmosis
Image from: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html#c3
Movement of small particles
Not all particles are able to slip through a cell membrane through diffusion
Example: sugars and starches aren’t small enough to move between the phospholipid molecules
Types of solutions
IsotonicHas same concentration as a
cell, the cell neither loses nor gains water
HypotonicHas less concentration than
cell, cell gains water
Types of solutions
Hypertonic Has more concentration than cell,
cell loses water
Osmosis in cells
Paramecia Control water flow by using a contractile vacuole
Collect excess water and pump it out of the cell
Plant cells Live in hypotonic environment Survive because of cell wall Pressure of water against cell wall: turgor pressure Too much water leaves the cell: plasmolysis Water storage in Central Vacuole
Transport of particles
Some particles have to go through “doorways” to enter the cell Because they are too large or not
soluble through cell membrane These “doorways” are protein
channels These proteins are carrier proteins
Facilitated Diffusion
Diffusion of particles through protein channels in a cell membrane
Particles move from high concentration to low concentration
Example: glucose and salts Does NOT require energy
Image from: http://www.bios.niu.edu/sims/metabolism/metabolism1.htm
Ion Channels
Allow ions to move across the cell membrane
Specific to specific ions Some are “gated”
Active transport
Movement of particles against the normal direction of diffusion
Particles move from LOW concentration to HIGH
Requires energy from the energy molecule ATP
Example: sodium/potassium pump
Image from: http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostruct/images/u1fig7a.jpg
Image from: http://www.sp.uconn.edu/~terry/images/anim/antiport.gif
Moving larger particles Endocytosis
Cell membrane surrounds a particle, and encloses it in a vesicle
PhagocytosisWhen large particles are taken in by endocytosis
PinocytosisTransport of fluids or solutes
Image from: http://www.sirinet.net/~jgjohnso/endocytosissmall.jpg
Endocytosis
Image from: http://www.sp.uconn.edu/~bi107vc/images/cell/clathrin.jpg
Exocytosis
Used to remove large particles from the cell
Vesicles formed at the ER or Golgi move to the cell membrane for release
Exocytosis
Image from: http://www.sirinet.net/~jgjohnso/exocytosis.jpg
Image from: http://cellbio.utmb.edu/cellbio/end7.jpg
Modeling the cell membrane