Cellular Transport Notes
About Cell Membranes
1.All cells have a cell membrane
2.Functions: a.Controls what enters
and exits the cell to maintain an internal balance called homeostasis
b.Provides protection and support for the cell
3.Structure of cell membrane
Lipid Bilayer -2 layers of phospholipidsa. Phosphate head is polar (water
loving)b. Fatty acid tails non-polar (water
fearing)c. Proteins embedded in membraned. Steroids and cholesterol are
embedded within the cell membrane.They provide support and flexibility.
About Cell Membranes (continued)
Phospholipid
Lipid Bilayer
Proteins
Polar heads love water & dissolve.
Non-polar tails hide from water.
Carbohydrate cell markers
Fluid Mosaic Model of the
cell membrane States that the membrane
is in constant motion
• 4. Cell membranes have pores (holes) in ita.Selectively permeable: Allows some
molecules in and keeps other molecules outb.The structure helps it be selective!
About Cell Membranes (continued)
Pores
Cell Membrane
Cholesterol in the Membrane
Outside of cell
Inside of cell (cytoplasm)
Lipid Bilayer
Proteins
Transport Protein Phospholipids
Carbohydratechains
Structure of the Cell Membrane
Go to Section:
Animations of membrane
structure
Cell Transport
• There are three types of cellular transport– Passive Transport– Active Transport– Cytosis
Types of Cellular Transport
• Passive Transport cell doesn’t use energy
1. Diffusion2. Facilitated Diffusion3. Osmosis
• Active Transportcell does use energy
1. Protein Pumps2. Endocytosis3. Exocytosis
high
low
This is gonna
be hard work!!
high
low
Weeee!!!
•Animations of Active Transport & Passive
Transport
Cytosis
Passive Transport: 1. Diffusion
1. Diffusion: random movement of particles from an area of high concentration to an area of low concentration.
(High to Low)• Diffusion continues until all
molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out.
http://bio.winona.edu/berg/Free.htm
Simple Diffusion Animation
What determines the rate of diffusion?There 4 factors:
1. The steepness of the concentration gradient. The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.
2. Temperature. Higher temperatures give molecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster.
3. The surface area. The greater the surface area the faster the diffusion can take place. This is because the more molecules or ions can cross the membrane at any one moment.
4. The type of molecule or ion diffusing. Large molecules need more energy to get them to move so they tend to diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.
Passive Transport
• The diffusion of water is called OSMOSIS.
Passive Transport - Osmosis
A good way to remember which way water will move is to remember that the water will ALWAYS move TOWARDS the solutes (salt).
• 3.Osmosis: diffusion of water through a selectively permeable membrane
• Water moves from high to low concentrations
•Water moves freely through pores.
•Solute (green) to large to move across.
Osmosis animationPassive Transport: 3. Osmosis
Passive Transport
• We have special names for the different types of situations where osmosis occurs in cells.
Passive Transport
• We have special names for the different types of situations where osmosis occurs in cells.
Hypotonic SolutionHypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!
Hypertonic SolutionHypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)
Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!
shrinks
Isotonic SolutionIsotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)
What type of solution are these cells in?
A CB
Hypertonic Isotonic Hypotonic
Summary
• Isotonic Solutions are those where the concentration of the solution EQUALS the concentration of the cell.
• Hypertonic Solutions are those where the concentration of the solution is MORE than the concentration of the cell.
• Hypotonic Solutions are those where the concentration of the solution is LESS than the concentration of the cell.
What is the solution?
10% Salt
40% Salt
40% Salt
10% Salt
15% Salt
15% Salt
Hypotonic Hypertonic Isotonic
What is the cell?
10% Salt
40% Salt
40% Salt
10% Salt
15% Salt
15% Salt
Hypertonic Hypotonic Isotonic
Remember!
In osmosis, goes towards the
!
Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane a.Transport Proteins are
specific – they “select” only certain molecules to cross the membrane
b.Transports larger or charged molecules
Facilitated diffusion (Channel Protein)
Diffusion (Lipid
Bilayer)
Passive Transport: Facilitated Diffusion
Carrier Protein
A B
• http://bio.winona.edu/berg/Free.htm
High Concentration
Low Concentration
Cell Membrane
Glucosemolecules
Proteinchannel
Passive Transport: 2. Facilitated Diffusion
Transport Protein
Through a
Cellular Transport From a- High
Low
Facilitated Diffusion:• Molecules will randomly move
through the opening like pore, by diffusion. This requires no energy, it is a PASSIVE process. Molecules move from an area of high concentration to an area of low conc.
Active Transport
• Active transport is when the cell membrane “imports” or “exports” substances that are needed that do not travel by diffusion.
• Usually, this means obtaining substances against the concentration gradient
• Substances go from areas of LOW concentration to areas of HIGH concentration
Active Transport
Types of Active Transport
1. Protein Pumps -transport proteins that require energy to do work
•Example: Sodium / Potassium Pumps are important in nerve responses.
Sodium Potassium Pumps (Active Transport using proteins)
Protein changes shape to move molecules: this requires energy!
Active Transport
• Active Transport uses energy called ATP.• Active Transport = ATP
• Accomplished by the proteins embedded within the cell membrane.
Active Transport• The lack of efficient pumps can be classified as
a disease.– Sodium Deficiency can cause muscle spasms, and
Liddie's Syndrome.– Potassium deficiencies can cause an irregular heart
beat, epileptic seizures in infancy, and deafness.• Examples of active transport include:
– Kidney's removing sodium– Thyroid obtaining iodine– Gills removing salt from water– Plants obtaining minerals through the roots.
Summary
Cytosis: A type of Active Transport
• Large amounts of some substances can be taken in and out of a cell directly by the membrane.
Endocytosis
Exocytosis
Types of Active Transport
• Endocytosis:– Uses energy (ATP)• Cell membrane in-folds around
food particle• Endocytosis of large particles is
called phagocytosis, “cell eating” • Endocytosis of small particles is
called Pinocytosis, “cell drinking”• forms food vacuole & digests food• This is how white blood cells eat
bacteria!
PhagocytosisYour white blood cells can keep you healthy by using PHAGOCYTOSIS
The LYSOSOMES digest the bacteria cell and then spit it out of the cell.
Types of Active Transport
3. Exocytosis: movement of material out of
cytoplasm of the cell using ATP
• membrane surrounding the material fuses with cell membrane (like endocytosis backwards)
• how cells get rid of wastes
Endocytosis & Exocytosis animations
Vesicles and Vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of
the cell.