7.3: CELL TRANSPORT

(across the cell membrane!)

Vocabulary

• Osmosis

• Diffusion

• Facilitated Diffusion

• Active Transport

• Endocytosis

• Exocytosis

• Protein Pumps• Facilitated Diffusion

• Osmotic Pressure

• Isotonic

• Hypertonic

• Hypotonic

• Protein Pumps

Background Info…• Every living cell contains a liquid interior

(cytoplasm) and is surrounded by a liquid.

• The cell (plasma) membrane separates what is inside the cell from what is outside of the cellinside the cell from what is outside of the cell

• What is the MAJOR function of cell membrane?– regulate the movement of molecules from one side of

the membrane to the other.• In other words—control what gets in and what gets out!

Selectively permeable: • property of biological membranes which

allows some substances to pass more easily than others

Transport proteins:

• membrane proteins that transport

SPECIFIC molecules or ions across

biological membranes

GLUCOSE

Binding

TransportRecovery

Dissociation

Movement across the cell membrane can be:

1) PASSIVE

� cell does not have to spend

energy

� substance moves from where it

is MORE concentrated to where

it is LESS concentrated.it is LESS concentrated.

2) ACTIVE� cell “spends” energy to move a

substance from where it is LESS concentrated to where it is MORE concentrated (“UPHILL”)

Passive Transport: DIFFUSION

• movement of a substance from where it is conc. to where it is less conc. (“down where it is less conc. (“down a concentration gradient”)

Passive Transport: OSMOSIS

• diffusion of WATER

across a selectively

permeable membrane; permeable membrane;

water moves DOWN its

concentration gradient

INSIDE

THE CELL

OUTSIDE

THE CELL

– the direction of water movement water

can be described/predicted based on if

the cell’s environment is:

• ISOTONIC: equal solute concentration compared to inside a cell

• HYPERTONIC: greater solute

concentration than inside a cellconcentration than inside a cell

• HYPOTONIC: lower solute concentration compared to inside a cell

WATER MOVES FROM

HYPO TO

HYPERTONIC!!!

In animal cells:

• in a HYPERTONIC environment,

water exits the cell;

cells shrivel and usually die

• in a HYPOTONIC environment,

water moves into cell,

causing it to swell and

possibly burst

In cells with cell walls (i.e. plant cells):

• in a HYPERTONIC environment, water exits the cell; cells shrivel and usually die

• in a HYPOTONIC environment, water moves into cell, causing it to swell; cells become more TURGID.

Passive Transport: FACILITATED DIFFUSION

• diffusion of solutes across a membrane, with the help of transport proteins

(passive transport because it is movement (passive transport because it is movement down a concentration gradient; cell does not need to spend any energy)

ACTIVE TRANSPORT: energy-requiring process; molecules are moved across the cell membrane AGAINST their concentration gradient (“uphill”)

ACTIVE TRANSPORT: ENDOCYTOSIS & EXOCYTOSIS

• transport of large molecules (e.g. proteinsand polysaccharides) into or out of the cell

ENDOCYTOSIS EXOCYTOSIS

*importing large

molecules by forming

vesicles out of the cell

membrane

**vesicle forms in a small **vesicle forms in a small

region of cell membrane

***used by cells to bring in

larger, extracellular

substances (e.g. proteins)

ENDOCYTOSIS EXOCYTOSIS

*exporting large

molecules by vesicles

fusing w / the cell

membrane

**vesicle buds from ER **vesicle buds from ER

or Golgi and migrates to

cell membrane

***used by cells to

export products (e.g.

cells in pancreas

secreting insulin)

2 types of Endocytosis:

1) Phagocytosis: solid particles (“cell

eating”)

2) Pinocytosis: fluid droplets (“cell

drinking”)

Phagocytosis

Pinocytosis

What are the 3 types of passive What are the 3 types of passive transport across a membrane?transport across a membrane?

a)a) Diffusion, osmosis, and Diffusion, osmosis, and exocytosisexocytosis

b)b) ExocytosisExocytosis, , endocytosisendocytosis, and , and b)b) ExocytosisExocytosis, , endocytosisendocytosis, and , and phagocytosisphagocytosis

c)c) Diffusion, facilitated diffusion, and Diffusion, facilitated diffusion, and osmosisosmosis

d)d) Diffusion, osmosis, and Diffusion, osmosis, and endocytosisendocytosis