CELL TRANSPORT

Tomato plantmust take in nutrientsfrom the soil.

Potassium

Nitrogen

Phosphorus

Every living cell exists in a liquid environment.

One of the most important functions of the cell membrane is to keep the cell’s internal conditions relatively constant.

INFoodGlucoseO2H2O

OUTWasteHormoneCO2H2O

What structure in the cell regulates what substances enter the cell?

The cell membrane regulates and controls which substances enter and leave the cell.

There are two basic methods by which substances enter/exit the cell:

(1) Passive transport --- no energy needed

(2) Active transport --- requires energy

Passive transport is the movement of substances across a cell membrane from an area of higher concentration to an area of lower concentration. (requires no energy )

aasugar saltO2

Higher Concentration

Lower Concentration

InsideCell

What are some characteristics of the cell membrane?

Outside Cell

Nonpolar---oily

InsideCell

Small nonpolar substances such as CO2, O2, and small lipids can pass through the cell membrane by diffusion.

lipidsCO2 O2

Outside Cell

Diffusion is the movement of substances from a region of higher concentration to a region of lower concentration.

High Conc

Low Conc

Low Conc

Low Conc

higher conc lower conc

Equilibrium is the condition in which the concentration of a substance is equal throughout a region. Even at equilibrium, molecules continue to move randomly.

Which way will fat move?

inside cell

outside cell

fat

fat

fat fat

fatfat

fat

fat

fat

fatfat

LOW

HIGH

fatfat

fat

fat

fat fatThat’s diffusion!

InsideCell

How do polar molecules like glucose get across the nonpolar membrane?

Outside Cell

Nonpolar--oily

glucoseglucose

glucose

By Facilitated Diffusion

Channel Proteins

Facilitated Diffusion: The diffusion of substances across the cell membrane through channel proteins. passive

transportNo energyinput

substance substance

higherconc

lowerconc

InsideCell

Proteins in the cell membrane create channels making it easy for certain molecules to pass.

Channel Proteins

glucose glucose

InsideCell

Outside Cell

Polar molecules like glucose diffuse across the membrane by moving through pores formed by channel proteins.

Channel Proteins

glucose glucose

OsmosisWater is very important, so we talk about water separately.

Cell survival depends on balancing water uptake & loss.

freshwater balanced saltwater

Normal plant cell

******

Osmosis is the movement of water across a cell membrane from a region of higher conc to a region of lower conc.

Osmosis is the diffusion of water across a cell membrane.

high concH2O

low concH2O

Cell

mem

bran

e

high concH2O

low concH2O

Cell

mem

bran

e

How does water move?

Always from an area of higher concentration to an area of lower concentration.

The direction of osmosis depends on the relative concentration of solutes on the two sides of the membrane.

low conc solute high conc solute Less watermore water

solute

How does water move?

low conc solute high conc solute Less watermore water

solutemore water less water

Cells are always surrounded by some kind of solution.

The solution surrounding cells may be: (1) isotonic (2) hypotonic (3) hypertonic

An isotonic solution has the same concentration of solute molecules as the cell.

iso = same10 %solute

10 %solute

Water moves in and out at the same rate

iso = same2 %salt

2 %salt

isotonic solution

iso = same5 %glucose

5 %glucose

isotonic solution

A hypotonic solution has a lower concentration of solutes than a cell. This means the concentration of water is greater outside the cell than inside.

Water will move intothe cell

Hypo = more water

10 %solute

25 %solute

The cell will swell.

Less solute

1 %salt

5 %salt

hypotonic solution

1 %glucose

2 %glucose

hypotonic solution

A hypertonic solution has a higher conc of solutes than a cell.

The water conc is lower outside the cell than inside.

Water will move out of the cell

The cell will shrivel.

25 %solute

5 %solute

Hyper = less water more solute

5 %salt

2 %salt

hypertonic solution

3 %glucose

1 %glucose

hypertonic solution

Summing Up!Passive Transport:

Movement from high to lowNo energy

Examples: diffusion facilitated diffusion

osmosis

Contractile vacuole in Paramecium