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Chapter 3
Cells Physiology
•Membrane Transport-Passive-Active
Do you remember learning about?
Membrane TransportMembrane Transport Movement into and out of cells to maintain HOMEOSTASIS
Filtration
Cellular FluidsCellular Fluids
Solution
- Solvent – dissolving medium (ex. water)
- Solutes – what gets dissolved (ex. sugar, salt)
Intracellular fluid
- inside cell
Interstitial fluid
- outside cell
Passive ProcessesPassive ProcessesDiffusion
Molecules ALWAYS moving; Brownian motion
Movement from high to low concentration, or down a concentration gradient
Equilibrium - concentration is equal/balanced.
Membrane is Selective PermeabilityMembrane is Selective Permeability Allows some materials to pass, not all
3 types of diffusion in cells
- Simple diffusion - lipid-soluble or small - to pass through pores
- Facilitated diffusion - too big or not lipid-soluble; need protein carriers (channel or gated proteins)
- Osmosis - movement of water across membrane from [hi] to [lo]
Study the diagram below. It represents a container that is divided by a semi permeable membrane. A different solution in its initial state is shown on each side of the membrane.
Study the diagram below. It represents a container that is divided by a semi permeable membrane. A different solution in its initial state is shown on each side of the membrane.
1. Which substance(s) can move through the membrane? Why?2. Which direction will the molecule(s) will move? To side I or II?3. Which substance will move across fastest? Why?4. How long will the molecule(s) will continue to move?
Osmosis - How Cells Respond to Osmosis - How Cells Respond to
Different SolutionsDifferent Solutions
90% H2O10% solute
90% H2O10% solute
90% H2O10% solute
90% H2O10% solute
85% H2O15% solute
95% H2O5% solute
Isotonic(no net movement
of water)
Hypotonic Hypertonic
What solution would you give someone who is retaining water?
Why shouldn’t you drink ocean water if you are thirsty?
Another Passive ProcessAnother Passive Process
Filtration
Water & solutes forced through a membrane by pressure
Pressure gradient
(high to low)Happens in kidneys.
Active Transport ProcessesActive Transport Processes Transport substances that can’t pass because:
- too large
- not lipid-soluble
- against concentration gradient
2 common forms of active transport
- Solute pumping
- Bulk transport
Energy (ATP)
required!
Solute pumpingSolute pumping Amino acids, some sugars and ions are pumped
ATP energizes protein carriers, moves substances against concentration gradients (from low to high, or up a gradient concentration.
Sodium-PotassiumPumps
Bulk TransportBulk Transport
Exocytosis Moves out of cell by vesicle
Endocytosis
engulfed by vesicle & brought in
2 Types
- Phagocytosis – cell eating
- Pinocytosis – cell drinking
Filtration
High to Low
Pressure through
capillaries
Anything dissolved in blood
Water, urea,
sugars, ions
Channel or Gate Proteins
Protein Pumps
Any direction as needed