Homeostasis

1
Homeostasis Transport

• Chapter 5

2
Homeostasis Transport
Passive Transport
Active Transport
3
Passive Transport No Energy

• No energy required to move materials with the
  concentration gradient high to low
• Diffusion movement of molecules
• Concentration gradient high to low
• Driven by kinetic energy
• Equilibrium
• Diffusion across membrane depends on
• Size of molecule
• Type of molecule
• Chemical nature of membrane lipid bilayer
  pores
• e.g. O2 CO2

4
Simple Diffusion
Equilibrium
5
Passive Transport No Energy

• Osmosis movement of water molecules
• High water to low water
• Relative solute concentration terms
• Hypotonic less solute
• Hypertonic more solute
• Isotonic equal solute
• Direction of Osmosis
• Hypotonic ? hypertonic
• Isotonic no net movement (equilibrium)

6
Passive Transport No Energy

• Osmosis (continued)
• How cells deal with osmosis
• Hypotonic
• Contractile vacuoles paramecium
• Solute pumps
• Cell wall in plant turgor pressure
• Cytolysis red blood cell
• Hypertonic
• Crenation animal cell
• Plasmolysis plant cell

7
(No Transcript)
8
Passive Transport No Energy

• Facilitated Diffusion uses carrier proteins
• Molecules carried along concentration gradient
• Carrier proteins transport molecules that are
• Too large
• Not soluble in lipids
• Example glucose

9
Passive Transport No Energy

• Diffusion through Ion Channels
• Insoluble ions (Na, K, Cl-, Ca2) move with
  concentration gradient
• Membrane proteins are ion channels - specific
• Channels gated v. open
• Gated ion channels controlled by
• Stretching cell membrane
• Electrical signals
• Chemicals in cytosol or environment
• Open - always

10
Active Transport Energy Required

• Energy required to move materials against
  concentration gradient low to high
• Cell membrane pumps carrier proteins
• Na/ K pump
• Normal cells higher Na outside, higher K
  inside
• Carrier proteins pump 3Na out and 2K in using
  ATP
• Potential Difference maintains charge outside
  cell and charge inside cell
• Important for nerve cell function

11
SODIUM POTASSIUMPUMP
12
Active Transport Energy Required

• Endocytosis Exocytosis
• For substances too large or large quantities
• Endocytosis
• Enclose external materials? form vesicle? fuse
  with lysosome or other organelles
• Pinocytosis cell-drinking
• Phagocytosis cell eating
• Unicellular feeding
• Ingest destroy bacteria viruses
• Exocytosis reverse of endocytosis

13
Endocytosis
14
Exocytosis