Download Cell Physiology

Chapter 3
Cells Physiology
Do you remember learning about?
•Membrane Transport
-Passive
-Active
Membrane Transport
 Movement into and out of cells to maintain HOMEOSTASIS
Filtration
Cellular Fluids
 Solution
- Solvent – dissolving medium (ex. water)
- Solutes – what gets dissolved (ex. sugar, salt)
 Intracellular fluid
- inside cell
 Interstitial fluid
- outside cell
Passive Processes
Diffusion
 Molecules ALWAYS moving; Brownian motion
 Movement from high to low concentration, or
down a concentration gradient
 Equilibrium - concentration is equal/balanced.
Membrane 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.
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
Different Solutions
90% H2O
10% solute
85% H2O
15% solute
95% H2O
5% solute
90% H2O
10% solute
90% H2O
10% solute
90% H2O
10% 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 Process
Filtration
 Water & solutes
forced through a
membrane by
pressure
 Pressure gradient
(high to low)
Happens in kidneys.
Active 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
Solute 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-Potassium
Pumps
Bulk Transport
Exocytosis
 Moves out of cell by vesicle
Endocytosis
 engulfed by vesicle & brought in
 2 Types
- Phagocytosis – cell eating
- Pinocytosis – cell drinking
Filtration
Any
direction as
needed
High
to Low
Channel
or Gate
Proteins
Pressure
through
capillaries
Anything
dissolved
in blood
Water,
urea,
sugars,
ions
Protein
Pumps