NOTES – Transport Through The Cell Membrane

NOTES – Transport Through NOTES – Transport Through The Cell MembraneThe Cell Membrane

What is cell transport?What is cell transport? Cell TransportCell Transport – when substances – when substances

move into or out of cellsmove into or out of cells In order to get into or out of the cell, In order to get into or out of the cell,

substances must pass through the cell substances must pass through the cell membrane membrane

Substances in a living thing naturally Substances in a living thing naturally move from areas of high concentration move from areas of high concentration (where there is a lot of that substance) (where there is a lot of that substance) to areas of low concentration (where to areas of low concentration (where there is less of that substance)there is less of that substance)

What are the 2 types of cell What are the 2 types of cell transport?transport?

1.1. Passive TransportPassive Transport – When substances – When substances move in or out of move in or out of cells from areas of cells from areas of high concentration high concentration to areas of low to areas of low concentration concentration

Passive Transport - Diffusion

Diffusion - the process by which molecules spread from areas of high concentration, to areas of low concentration (H L)

Dynamic Equilibrium - When molecules are evenly spread throughout a space

Passive Transport - Osmosis

Osmosis is the process by which WATER moves from areas of high concentration to areas of low concentration (H L)

Relationship between diffusion of solute molecules and

osmosis Diffusion and osmosis happen in

opposite directions Diffusion is the movement of solute Osmosis is the movement of solvent

(water) Solutions that have relatively high

concentrations of solute, have relatively low concentrations of solvent, and vice versa

Passive TransportPassive Transport EX. If there is a lot of sodium outside of a cell, the EX. If there is a lot of sodium outside of a cell, the

sodium moves into the cell by diffusion and water sodium moves into the cell by diffusion and water moves out of the cell by osmosis moves out of the cell by osmosis

Two Solutions Are Separated By A Selectively Permeable Membrane

Solution A has a high concentration of solute compared to solution B

Solution B has a high concentration of water compared to Solution A

So what happens?

Two Solutions Are Separated By A Selectively Permeable Membrane

Solute moves through the membrane from Solution A to Solution B (Diffusion)

Solution A becomes less concentrated, Solution B becomes more concentrated

Two Solutions Are Separated By A Selectively Permeable Membrane

Water moves through the membrane from Solution B to Solution A (Osmosis)

Solution B becomes more concentrated, Solution A becomes less concentrated

Two Solutions Are Separated By A Selectively Permeable Membrane

Dynamic equilibrium is reached

Solute and Water move back and forth equally

Rate of Diffusion The rate (speed) of diffusion is influenced

by 3 factors: A. Temperature: As Temp. increases,

the rate of diffusion also increases T D B. Concentration: As the Conc.

increases, the rate of diffusion also increases C D

C. Pressure: As the Pressure increases, the rate of diffusion DECREASES P D

Passive Transport - Facilitated Diffusion

Facilitated Diffusion - the movement of molecules from H L, through protein molecules in the cell membrane

The Rime of the Ancient Mariner

By Samuel Taylor Coleridge (written in 1797-98)

Water, water, every where, And all the boards did

shrink; Water, water, every where, Nor any drop to drink.

Salt-Cured Meat

Meat or fish preserved or cured with salt The only widely available method of

preserving food until the 19th century Salt prevents the growth of bacteria by

drawing water out of bacteria cells by osmosis

Salted meat was a staple of the mariner's diet in the Age of Sail. It was stored in barrels, and often had to last for months spent out of sight of land.

What are the 2 types of cell transport?

2. Active Transport – When the cell uses energy to move substances in or out from an area of low concentration to an area of high concentration (L H)

Active TransportActive Transport The cell must USE ENERGY because The cell must USE ENERGY because

substances do not naturally move substances do not naturally move from low concentration to high from low concentration to high concentration concentration

The cell must also use energy to The cell must also use energy to move very large particles into or out move very large particles into or out of the cellof the cell

Bulk Transport Bulk Transport - the movement of large

amounts of material into or out of the cell Endocytosis – movement into the cell Exocytosis – movement out of the Both processes occur when the material is

too large to pass through the cell membrane

Two Types of Endocytosis

A. Phagocytosis = “cell eating” cell takes in large solid molecules

Ex: white blood cell engulfing a bacteria

B. Pinocytosis = “cell drinking” cell takes in large amount of fluid

Video Clip of Active Transport

Another way to look at it…Another way to look at it…

What are the effects of passive transport on cells? As the cell’s external environment

changes, passive transport causes water and other substances to continuously move into and out of cells

Turgor Pressure – pressure in a cell caused by water

Plant cells need the correct amount of turgor pressure to stay rigid

Elodea Cells Before and After Placement in a Hypertonic

Solution

1. What happens if there is a lower concentration of substances outside the cell?

1. What happens if there is a lower concentration of substances outside the cell?

1. What happens if there is a lower concentration of substances outside the cell?

Type of Solution Hypotonic

Turgor Pressure High

Cell Shape Swollen

Plant Cell - Hypotonic

Cell is turgid (rigid from high turgor pressure)

2. What happens if the concentration of substances outside of the cell is equal to the cytoplasm

2. What happens if the concentration of substances outside of the cell is equal to the cytoplasm

2. What happens if the concentration of substances outside of the cell is equal to the cytoplasm

Type of Solution Isotonic

Turgor Pressure Normal

Cell Shape Normal (Flaccid if plant)

Plant Cell - Isotonic

Cell is flaccid (turgor pressure not quite high enough to maintain rigidity)

3. What happens if there is a higher concentration of substances outside of the cell?

3. What happens if there is a higher concentration of substances outside of the cell?

3. What happens if there is a higher concentration of substances outside of the cell?

Type of Solution Hypertonic

Turgor Pressure Low

Cell Shape Shriveled

Plant Cell - Hypertonic

Cell is plasmolyzed (turgor pressure too low to hold membrane against cell wall)

Animal Cells in Different Solutions

Cytolysis – animal cell bursts in hypotonic solution Crenation – when a cell shrinks in a hypertonic

solution

Osmotic Effects on Cells

How do I figure out the direction of passive transport? Look at the solution outside of the cell.

Compared to the cytoplasm, is the concentration of substances higher, lower, or equal?

Diffusion – Which way will the substances move? (into cell, out of cell, in or out equally)

Osmosis – Which way will water move? (into cell, out of cell, in or out equally)

To sum up…To sum up… If there is a lot of substance outside a If there is a lot of substance outside a

cell, substance moves in (diffusion), cell, substance moves in (diffusion), water moves out (osmosis) and the cell water moves out (osmosis) and the cell shrivelsshrivels

If there is a lot of substance inside a cell, If there is a lot of substance inside a cell, substance moves out (diffusion), water substance moves out (diffusion), water moves in (osmosis) and the cell swellsmoves in (osmosis) and the cell swells

These processes happen naturally These processes happen naturally (passive transport), if the cell wants the (passive transport), if the cell wants the opposite to happen, it must use energy opposite to happen, it must use energy (active transport)(active transport)

Cells need a steady Cells need a steady supply of energy for supply of energy for active transport active transport otherwise they would otherwise they would not be able to adjust to not be able to adjust to their environmenttheir environment

Cell Transport Animations http://www.northland.cc.mn.us/biolog

y/Biology1111/animations/transport1.swf