CELL BIOLOGY

- Overview:

A. Membranes - how stuff get in/out of cells

1. Structure

2. Functions

CELL BIOLOGY

- Overview:

A. Membranes - how stuff get in/out of cells

1. Structure

2. Functions

3. Types of "transport"

LE 7-11a

Molecules of dye Membrane (cross section)

WATER

Net diffusion Net diffusion Equilibrium

Diffusion of one solute

Types of "transport"

- DIFFUSION

LE 7-11b

Net diffusion Net diffusion Equilibrium

Diffusion of two solutes

Net diffusion Net diffusion Equilibrium

Types of "transport"

- DIFFUSION

LE 7-12Lowerconcentrationof solute (sugar)

Higherconcentrationof sugar

Same concentrationof sugar

Selectivelypermeable mem-brane: sugar mole-cules cannot passthrough pores, butwater molecules can

H2O

Osmosis

- OSMOSIS:

diffusion of water across a semi-permeable membrane from HI to LO water potential

Water Potential:

as solute conc. increases

as pressure increases

LE 7-13

Animalcell

Lysed

H2O H2O H2O

Normal

Hypotonic solution Isotonic solution Hypertonic solution

H2O

Shriveled

H2OH2OH2OH2OPlantcell

Turgid (normal) Flaccid Plasmolyzed

9% Salt

1%

9% Salt

9%Salt

9%15%

LE 7-15a

EXTRACELLULARFLUID

Channel protein SoluteCYTOPLASM

Types of "transport"

- FACILITATED DIFFUSION - for big or charged stuff

movement in the direction of the concentration gradient

LE 7-15b

Carrier protein Solute

Types of "transport"

- FACILITATED DIFFUSION - for big or charged stuff

movement in the direction of the concentration gradient

LE 7-17b

ATP

Types of "transport"

- ACTIVE TRANSPORT

AGAINST concentration gradient

MUST use ENERGY

Makes cell DIFFERENT FROM the environment.

LE 7-16

Cytoplasmic Na+ bonds tothe sodium-potassium pump

CYTOPLASM Na+[Na+] low[K+] high

Na+

Na+

EXTRACELLULARFLUID

[Na+] high[K+] low

Na+

Na+

Na+

ATP

ADPP

Na+ binding stimulatesphosphorylation by ATP.

Na+

Na+

Na+

K+

Phosphorylation causesthe protein to change itsconformation, expelling Na+

to the outside.

P

Extracellular K+ bindsto the protein, triggeringrelease of the phosphategroup.

PP

Loss of the phosphaterestores the protein’soriginal conformation.

K+ is released and Na+

sites are receptive again;the cycle repeats.

K+

K+

K+

K+

K+

LE 7-17

Diffusion Facilitated diffusion

Passive transport

ATP

Active transport

LE 7-18

H+

ATP

CYTOPLASM

EXTRACELLULARFLUID

Proton pump

H+

H+

H+

H+

H+

+

+

+

+

+

–

–

–

–

–

LE 7-19

H+

ATP

Proton pump

Sucrose-H+

cotransporter

Diffusionof H+

Sucrose

H+

H+

H+

H+

H+H+

+

+

+

+

+

+

–

–

–

–

–

–

LE 7-20a

CYTOPLASM

Pseudopodium

“Food” orother particle

EXTRACELLULARFLUID

BacteriumFood vacuole

An amoeba engulfing a bacterium viaphagocytosis (TEM)

Pseudopodiumof amoeba

1 µm

Food vacuole

PHAGOCYTOSIS

Types of "transport"

- Phagocytosis and Pinocytosis

LE 7-20b

Plasmamembrane Pinocytosis

vesicles forming(arrows) in a celllining a smallblood vessel(TEM).

0.5 µm

Vesicle

PINOCYTOSIS

Types of "transport"

- Phagocytosis and Pinocytosis

LE 7-20c

Receptor

RECEPTOR-MEDIATED ENDOCYTOSIS

Ligand

Coatedpit

Coatedvesicle

Coat protein

Coat protein

Plasmamembrane

0.25 µm

A coated pitand a coatedvesicle formedduringreceptor-mediatedendocytosis(TEMs).