Cell Diagram: College of Dupage

• 1. What is the type of bond within a single water molecule?
• 2. A carboxyl group is symbolized by what?
• 3. Briefly explain what happens in a hydrolysis reaction.
• 4. Is maltose a monosaccharide, disaccharide, lipid, or protein?

• 5. Are lipids hydrophobic or hydrophilic?
• 6. What is the difference between a saturated vs unsaturated fatty acid?
• 7. What does the secondary structure of protein refer to?
• 8. How does an enzyme work?

• 9. What is the difference between filtration and diffusion?
• 10. What happens to a rbc in a hypertonic solution?
• A hypotonic solution?

Plasma membrane is oily film made of lipids with diverse proteins embedded in
Phospholipid bilayer
– Hydrophillic heads facing water on either side of cell membrane
– Hydrophobic tails directed to center
Proteins
-integral or transmembrane
-peripheral

Plasma Membrane www.susanahalpine.com/anim/Life/memb.htm

• Defines boundaries of the cell
• Governs interactions with other cells
• Controls passage of materials into and out of cell

III. Movement Across Membrane
A. Selective Permeability
Depends on
1. Size of particle
2. Solubility in lipids
3. Charge on particle
4. Carrier molecules in membrane

Movement across membrane occurs through:
• Lipid bilayer
• Membrane channels
• With carrier molecules
• In vesicles

Passive vs. Active Transport
Requires
___________
• Primary Active
Transport
• Secondary Active
Transport

B. Non-mediated Transport Mechanisms
1. Diffusion
2. Osmosis
3. Filtration
• Passive
• Requires no energy

B. Non-Mediated Transport Mechanisms
DIFFUSION = when molecules move from a higher to a lower concentration.
What type of things might affect the rate of diffusion?
a. Magnitude of concentration gradient b. Temperature c. Size of diffusing particles d. Viscosity (thickness) of solvent
Diffusion Animation: biologycorner.com

Osmosis: Diffusion of water across the membrane
Water moves from an area of more water to an area of less water

Osmotic Pressure
Whenever dissolved substances such as glucose or protein are confined in a space by a selectively permeable membrane, they can pull water into the compartment by osmosis.
The strength of the osmotic pull is directly related to the concentration of the solution.
The greater the concentration, the greater the pulling, or osmotic pressure.

Tonicity =the ability of a solution to affect fluid volume and pressure within a cell
Environment surrounding cells may contain amounts of dissolved substances (solutes) that are… equal to less than greater than
…those found within the cell.
Tonicity
Isotonic: no net movement of water between cell and environment
Hypertonic: a higher concentration of solute.
Hypotonic : a lower concentration of solute.
Water will always move toward a hypertonic environment!!
Diagrams:
Cell: College of DuPage
Osmosis www.scienceaid.co.uk/biology/plants/osmosis.html
Blood Cells: Mariana Ruiz

Effects of tonicity on RBCs:
Water moves from an area of more water to an area of less water www.tvdsb.on.ca/WESTMIN/science/sbi3a1/cells/Osmosis.htm

Isotonic solutions: normal saline (0.9% NaCl),
5%D/W, and Ringer’s solution
Under special conditions, hypotonic or hypertonic solutions may be administered IV.
Most IV solutions are isotonic.

Filtration- due to a pressure gradient

Mediated Transport Mechanisms
Characteristics
1. Specificity- carrier exhibits specificity for certain ligand, just as an enzyme does for its substrate
2. Saturation- once all carriers occupied, adding solutes will not make the process go any faster
Three types
1. Facilitated Diffusion
2. Active Transport
3. Bulk Transport

Passive
-Proteins assist in diffusion of molecules across plasma membrane.
-Movement only occurs in the presence of a concentration gradient.
-Some molecules move across the membrane more quickly if diffusion is facilitated by a carrier molecule.

www.susanahalpine.com/anim/Life/memb.htm
www.northland.cc.mn.us/biology/biology1111/animations/passive3.swf
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation_how_osmosis_works.html
www.tvdsb.on.ca/WESTMIN/science/sbi3a1/cells/Osmosis.htm
www.education.uoit.ca/lordec/ID_LORDEC/capillary_fluid/capillary_fluid_LO.swf
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation_how_facilitated_diffusion_works.html

What are three examples of non-mediated transport mechanisms?

What are three examples of non-mediated transport mechanisms?
1. Diffusion
2. Osmosis
3. Filtration

What are three examples of non-mediated transport mechanisms?
1. Diffusion
2. Osmosis
3. Filtration
Are these active transport or passive transport?

1. Osmosis is best defined as the movement of
A) molecules from an area of high concentration to an area of lower concentration
B) molecules from an area of low concentration to an area of higher concentration
C) water molecules across a membrane from an area of low water concentration to an area of higher concentration
D) water molecules across a membrane from an area of high water concentration to an area of lower concentration
2. A red blood cell placed in a hypertonic solution will
A) Expand
B) Burst
C) Shrink
D) Have no change in shape
3. Facilitated diffusion requires
A) Enzymes
B) Carrier proteins
C) lipid carriers
D) carbohydrate carriers

• The main difference between filtration and diffusion is

Active Transport
Transport of solute across membrane up (against) concentration gradient
Analogous to a pump moving water uphill.
ATP Driven Active Transport
Energy from adenosine triphosphate (ATP) drives substances across the plasma membrane with the aid of carrier molecules.
Examples: Sodium-potassium pump, bring amino acids into cell, pump Ca2+ out of cell
Diagram:
Cell, College of DuPage

• Needed because Na+ and
K+ constantly leak out of the cell
• One ATP utilized to exchange three Na+ pushed out for two K+ brought in to cell

• Regulation of cell volume
• Heat production (thyroid hormone increases number of pumps; heat a by-product
• Maintenance of membrane potential in all cells
• Secondary active transport (no ATP used)

• Transport large particles or fluid droplets through membrane in vesicles (uses ATP)
• Exocytosis
• Endocytosis
– Phagocytosis
– Pinocytosis
– Receptor mediated endocytosis

Taking in droplets of ECF
– Occurs in all human cells
Membrane caves in, then pinches off into the cytoplasm as pinocytotic vesicle

 Transport of a substance across a cell
 Capture on one side and release on the other side
 Receptor mediated endocytosis moves it into cell and exocytosis moves it out the other side