The Cell as the The Cell as the Fundamental Unit of Fundamental Unit of

Life: Life: Membrane Membrane Transport ProcessesTransport Processes

Selectively permeable- allows certain substances to pass through

By 2 ways: active or passive transport

Passive- downhill

Active- uphill (needs energy)

Plasma Membrane Function:Plasma Membrane Function:

Passive: downhill reaction• Simple diffusion• Osmosis• Facilitated diffusion• Filtration

Active: uphill reaction, needs ATP• Exocytosis• Endocytosis

- Pinocytosis- Phagosytosis

No Barrier: Substances “spread out”

High concentration to low concentration

e.g.: Red dye placed in glass of water

Passive Diffusion

Substances diffuse

High concentration to low concentration

Pores in membrane must be large

“Down the concentration gradient”

Dynamic equilibrium, equal rates in both directions

Passive Diffusion

Biological membrane:

Facilitated

Diffusion

Carrier proteins:

• Bind specific molecule & change shape

• Pass molecule through middle of protein

Passive Diffusion: OsmosisOsmosis- diffusion of a water through a semi-permeable membrane

•Moves down concentration gradient

e.g. Two sugar solutions of different concentrations separated by porous membrane which lets water through but not sugar

What will happen?

Passive Diffusion: Terms & Osmosis

More concentrated to less concentrated Until concentration same on both sides: isotonic

Passive Diffusion: Osmosis &Terms

Concentration of solute less: solution is hypotonic.

Concentration of solute greater: solution is hypertonic.

Passive Diffusion: Osmosis: Outcomes to Living Cells (Animal)

Animal cells No cell walls

Isotonic environment: Influx of water equals the efflux of water No change in cell shape

Passive Diffusion: Osmosis: Outcomes to Living Cells (Animal)

Hypotonic solution: Water enters cell Bursts, or lyses

Hypertonic solution: Water leaves cell Shriveled, or crenate

Passive Transport and Facilitated Diffusion

Passive transport & facilitated diffusion do NOT require

ATP

Active Transport

DOES require the input of

ATP

Transport proteins AGAINST concentration

gradient

outside cell

inside cell

ATPATP

Role of ATP in Energy Role of ATP in Energy MetabolismMetabolism

ATP ATP ADP + P ADP + Pii + Energy + Energy

EndocytosisEndocytosis

ExocytosisExocytosis

SecretionSecretion

ExocytosisExocytosis

nuclei

mucus

Membrane Permeability

Cell membrane:

selectively permeable

4 factors that determine permeability lipid solubility

molecular size

polarity

charge

1

2

3

4

Lipid solubility Most important factor

Hydrophobic molecules Passively diffuse Hydrocarbons, carbon dioxide, & oxygen

Molecular Size and Polarity

Larger molecules, less permeable Lower kinetic energy Small pore sizes in the membrane

Polar molecules hydrophilic, less permeable Very small, polar uncharged (water) molecules can diffuse

-+

Molecular Size

Polarity

Charge

Charged molecules hydrophilic, less permeable Surrounded by coat of water (hydration shell), increases the size