Moving Cellular Materials

Fluid Mosaic Model: A mosaic is a structure made up of many different parts. The plasma membrane of a cell is composed of different kinds of macromolecules.

Phospholipid bilayer

Passive Transport: PASSIVE TRANSPORT- DOES NOT require energy to move materials through the cell membrane

3 types of passive transport Diffusion Facilitated diffusion Osmosis

1. DIFFUSION- molecules of a substance will move from an area of high concentration to an area of low concentration, down the concentration gradient, until they reach equilibrium  

Diffusion occurs in cells when substances (O2,CO2, salts, sugars, amino acids) that are dissolved in H2O move from an area of higher concentration to an area of lower concentration.

DIFFUSION

The rate of difussion will be higher or faster when diffusion: Takes place in gas rather than in liquid Takes place at a higher temperature rather than at a lower temperature Involves small-sized molecules rather than larger-sized molecules Occurs over a steep concentration gradient

Facilitated diffusion 2. FACILITATED TRANSPORT- requires transport proteins in the cell membrane to move materials into and out of the cell either because the molecules that are transported are too big or they are polar (act against the nonpolar fatty acid tail of the lipid bilayer)

FACILITATED TRANSPORT

The ability of carrier proteins to change shape is regulated by the binding and the release of the transported molecules. Just like an enzyme that is specific for its substrate, a carrier protein is specific for the solute it transports but don not catalyse chemical reactions.

Factors that effect diffusion Temperature – The rate of diffusion increases with the increase of temperature Pressure- when pressure increases the rate of diffusion increases Concentration – the rate of diffusion is effected by the concentration of the substances. It always takes place from higher to lower concentration.

Your opinion… Why is the rate of diffusion Faster in gas than in liquid? Faster when temperature rises? Faster for small molecules compared to large molecules?

A) The rate of diffusion is faster in gas because there is more space between molecules in a gas than in a liquid. Therefore, molecular collisions that can slow down movement of molecules occur less frequently in gaseous phase than in liquid.

B) Increase in temperature increases the rate of diffusion because heat energy gained is converted into kinetic energy for more rapid random movement of molecules. C) At the same temperature, smaller molecules can move faster than bigger molecules.

Application of Diffusion Exchange of gases between alveoli in the lungs and blood Exchange of gases between leaf and atmosphere Absorption of mineral by root hair cells Exchange of gases by all living cells with the surrounding. And many more!

Osmosis 3. OSMOSIS (diffusion of water)-the movement of water molecules through a semi-permeable membrane from an area of greater water concentration or pressure to an area of lesser water concentration or pressure down the concentration gradient

OSMOSIS

3 Types of concentration involved in osmosis Hypertonic- too much solute, not enough water; if a cell is placed in this solution, cell will shrink & wrinkle Hypotonic- too much water, not enough solute; if a cell is placed in this solution, cell will swell up, expand Isotonic- equal parts water and solute; water moves in & out of the cell in dynamic equilibrium

OSMOSIS

3 Types of Passive Transport: OSMOSIS

Application of Osmosis Intake of water by root hairs and all other cells.

How Cells Deal with Osmosis? WAIT! How Cells Deal with Osmosis? How Plant Deal with Osmosis?

Cells Deal with Osmosis Some animals are only single celled organisms like the paramecium. The paramecium is a freshwater pond dweller. These paramecia are functioning in a hypotonic environment all the time so water is constantly diffusing into the organism. Paramecia have contractile vacuoles that remove excess water from their bodies. Sometimes when too much water is added, cells burst and this is called cytolysis.

Plant Deal with Osmosis Since plants have a cell wall, osmosis affects them differently. When osmosis moves water into plant cells, the cell membrane swells but stops against the strong cell wall. This is called turgor pressure. When plants don’t receive enough water, plasmolysis occurs which makes the plants wilt. The cell membrane shrinks away from the cell wall.

Thank You!