1. Cellular Processes
Every cell must be able to carry on the processes of life.
Each must move substances through its membrane, metabolize foods, excrete wastes, and most need to be able to reproduce themselves.
Every cell also performs a specialized function for the body.

2. Membrane Transport
Membrane transport occurs due to the fluid environment on both sides of the cellular membrane.
The intracellular fluid is a solution inside the cell containing small amounts of gases, nutrients, and salts inside the cell.
The interstitial fluid has a similar composition and continually bathes the exterior of the cells.
Selective permeability of the cell membrane allows transport between the two fluids.

3. Transport through Cell Membrane
Transport across the cell membrane can be classified as physical (passive) or physiological (active).
Passive transport does not require energy and can occur in both live and dead cells.
Active transport requires energy and can only occur in live cells.

4. Passive Processes
Passive transport involves the net movement of ions or molecules through the membrane.
Substance always move in the downhill direction or from high concentration to low concentration.
Passive transport processes include: diffusion, osmosis, filtration, and dialysis.

5. Diffusion
Diffusion means the scattering or spreading out of particles.
Diffusion always occurs from high to low concentration and will continue until equilibrium is reached.
Ex. Oxygen and CO2 in the lungs

6. Osmosis
Osmosis is the diffusion of a solvent, usually water, through a selectively permeable membrane.
Selectively permeable means that not all substances can go through it.

7. Filtration
Filtration is the net movement of fluid and solutes through a membrane due to pressure.
Filtration pressure is the force of a fluid pushing against a surface.
Filtration is the major mechanism for moving substances through the wall of blood capillaries. Important in the kidneys.

8. Dialysis
Dialysis is a method of transport in which diffusible substances are separated from non-diffusible substances in a solution.
The movement of particles is controlled by changing the concentration gradient of solute and solvent.

9. Dialysis

10. Facilitated Diffusion
Facilitated diffusion does not require energy, and materials move down a concentration gradient – from higher to lower concentration.
An example is movement of glucose into a cell where there is not much glucose.
Fac. Diffusion requires protein molecules (carrier proteins) to help the process

11. Concentration vs Pressure Gradient
Concentration gradient is the difference in concentration of substances across a membrane.
Pressure gradient is the difference in pressure across a membrane, which causes solute containing fluid to move across the membrane.

12. Tonicity of Cells and Solutions
Hypertonic, Isotonic & Hypotonic are used as comparative terms for either cells or solutions outside the cell. Hyper – more than; hypo – less than; iso – same as.
Hypertonic- containing more solute than the other (therefore a lower concentration of solvent/water)
Hypotonic- containing less solute than the other (therefore a higher concentration of solvent/water)
Isotonic- cell is in dynamic equilibrium with solution, same concentrations of solute & water inside both.

13. Tonicity & Direction of osmosis

14. How differences in Tonicity affect Red Blood cells

15. Active Processes
Active transport is a process that requires energy to move substances against a concentration gradient or “uphill.”
The source of energy is from metabolic processes that occur within the cell. (ATP)
Every cell has various physiological pumps to move material across cell membranes.
Ex. Sodium pump in nerve cells

16. Types of Active Transport
Phagocytosis (bulk) and pinocytosis (liquid) are two examples of active transport –both endocytosis.
They consist of the same steps:
1.)Segment of cell membrane forms a pocket around particle.
2.) Membrane pinches off around the particle.
3.) Particle is released into cell.

17. Exocytosis & Receptor-mediated Endocytosis
Exocytosis is the removal of materials from the cell, the opposite process from endocytosis; not a selective process.
Receptor mediated endocytosis – entry of materials is triggered by activation of protein molecules in the
membrane; it is a
selective process.