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