Cellular Transport

Introduction to Cell Transport

• Cell transport= moving materials in and out of a cell

• All living cells need to be able to:– Take in oxygen and nutrients– Get rid of wastes

• The cell membrane separates the inside of the cell from the outside.– It allows some things to enter and blocks other things

Cell Membrane Structure

Phospholipid Bilayer- double layer of phospholipids enclosing the cell

1. Bilayer:• Exterior and interior surface: heads• Between: tails

Phospholipid Bilayer

Membrane Proteins

• Membrane proteins can be used to:– transport materials thru the membrane– serve as chemical signals or receptors of chemical signals.

• Membranes also can contain cholesterol (animal cells) and glycoproteins.

Fluid Mosaic Model

• Describes the cell membrane as a fluid rather than a solid.– Phospholipids and some proteins are able to move – This is able to change its shape and form.

• http://www.youtube.com/watch?v=Qqsf_UJcfBc

Selective Permeability

• The cell membrane regulates what can pass in or out of the cell.– this maintains a stable internal environment

(homeostasis) – Factors that determine a substances’ ability to

pass thru the membrane:• Size• Shape• Composition• Polarity (polar or nonpolar)• Charge (positive or negative)

Solutions

• Solution= combination of solute and solvent

– Solute= Substance being dissolved– Solvent= thing substance is dissolved in• Universal solvent= water

*Solute dissolves in the solvent

Example: Saltwater

Concentration

• Amount of solute compared to the amount of solvent– Low concentration of solute• Lesser amount of solute dissolved

– High concentration of solute• Higher amount of solute dissolved

Particle Movement

• Brownian motion- constant random motion of all particles.

Passive Transport

Movement that does not require energy– No energy needed from the cell

• Types:– Diffusion– Facilitated Diffusion– Osmosis

DiffusionMovement from high to low concentration.– Concentration Gradient= A difference in

concentration• (A concentration gradient is when there is a difference

in concentration within a system)

– Particles will move until concentration is equal throughout the system (Dynamic Equilibrium)

Diffusion Animation

Facilitated Diffusion

• Diffusion of particles with the help of membrane proteins.1. Carrier proteins• change shape to move large molecules thru the lipid

bilayer.

Facilitated diffusion of Glucose

2. Ion channels– A tube for dissolved ions to pass thru the lipid

bilayer.• Ex. Na+ ion channel

Osmosis

The diffusion of water.– High to low concentration of water– Water will move in the opposite direction of the

solute

Types of solutions:1. Hypertonic solution- lower concentration of

water outside the cell.• water will rush out of the cell

– Causes wilting in plant cells.

Hypotonic Solution

Solution with a higher concentration of water than the cell.– water will move into the cell causing it to swell• Can cause bursting of animal cells

Isotonic solution

Equal concentration of water in the solution and the cell.– net movement of water and solute is equal– cell is in dynamic equilibrium w/ the solution

• http://www.youtube.com/watch?v=7-QJ-UUX0iY

Osmosis in plant cells

Osmosis of red blood cells

Osmotic pressure

Which way will the water move?

How Cells Deal with Osmosis

• How do cells like paramecium that live in water, not blow up?– Contractile vacuoles – organelles that remove

water from the cell.

Questions

1. Can things always diffuse in and out of the cell when they want to? – In your answer, use the words:• selectively permeable• passive transport.

2. Give a short description (in your own words) of the three types of passive transport.

Active Transport

• Movement of substances that requires cell energy. – Movement from low to high concentration– Necessary to maintain homeostasis

Proteins Pumps

• Proteins that force particles to move– Energy is used to change the shape of the protein.

– ex. Na+/K+ ion pump• Uses energy to keep a high concentration of Na+

outside the cell and K+ inside the cell.

http://www.youtube.com/watch?v=P-imDC1txWw

Na+/K+ ion pump

Endocytosis

• Ingesting large particles or large amounts of solution.– membrane pinches off around material creating a

vacuole – Types• Pinocytosis- ingesting large amounts of fluid or solutes.• Phagocytosis- ingesting large particles or whole cells.

– ex. White blood cells, Ameoba

Exocytosis

Release of large particles from the cell– excretory vesicles fuse w/ the cell membrane

releasing the material outside the cell.

• http://www.youtube.com/watch?v=DuDmvlbpjHQ

Endocytosis and Exocytosis

Endocytosis vs. Exocytosis

• Which is endocytosis? Exocytosis?