Physiology Exam 1 - Lecture
notes 1-3
Human Physiology (University of
Michigan-Dearborn)
, 1
Physiology Exam I
● Transport Processes
○ General Form of Biological Transport
■ Bulk flow of fluids within a compartment
■ Fluids- Gases and Liquids
● Pressure gradients
○ Fluids flow from high to low pressure
○ Transport across cell membrane is selectively permeable
■ Hydrophobic or Lipophilic (nonpolar) molecules, such as
hydrocarbons, can dissolve in the lipid bilayer and pass through the
membrane rapidly
● Move by simple diffusion across the membrane
■ Hydrophilic or Lipophobic (polar) molecules, such as sugars, do not
cross the membrane easily
● Require assisted membrane transport
■ The rate of diffusion depends on the size and solubility of the molecule
● Smaller and less polar, more rapidly it diffuses
● Membrane Transport
, 2
○ Unassisted membrane transport
■ Diffusion
● Passive process
● High to low concentration
○ Chemical Gradient
● Net movement until concentration is equal
○ Equilibrium
● Rapid over short distances
● Directly related to temperature
● Inversely related to molecular weight and size
● In open system or across a partition
● Lipophilic Molecules move by simple diffusion across lipids
● Rate dependent on solubility in lipids
● Proportional to surface area of membrane
● Fick’s law of diffusion
○ Diffusion of an uncharged solute across a membrane is
proportional to the concentration gradient of the solute,
the membrane surface area, and the membrane
permeability to the solute
○ Rate of diffusion = surface area x concentration gradient
x membrane permeability (lipid solubility/molecular size)
, 3
■ Osmosis
○ Protein-Mediated Transport
■ Facilitated Diffusion
● Concentration gradient
notes 1-3
Human Physiology (University of
Michigan-Dearborn)
, 1
Physiology Exam I
● Transport Processes
○ General Form of Biological Transport
■ Bulk flow of fluids within a compartment
■ Fluids- Gases and Liquids
● Pressure gradients
○ Fluids flow from high to low pressure
○ Transport across cell membrane is selectively permeable
■ Hydrophobic or Lipophilic (nonpolar) molecules, such as
hydrocarbons, can dissolve in the lipid bilayer and pass through the
membrane rapidly
● Move by simple diffusion across the membrane
■ Hydrophilic or Lipophobic (polar) molecules, such as sugars, do not
cross the membrane easily
● Require assisted membrane transport
■ The rate of diffusion depends on the size and solubility of the molecule
● Smaller and less polar, more rapidly it diffuses
● Membrane Transport
, 2
○ Unassisted membrane transport
■ Diffusion
● Passive process
● High to low concentration
○ Chemical Gradient
● Net movement until concentration is equal
○ Equilibrium
● Rapid over short distances
● Directly related to temperature
● Inversely related to molecular weight and size
● In open system or across a partition
● Lipophilic Molecules move by simple diffusion across lipids
● Rate dependent on solubility in lipids
● Proportional to surface area of membrane
● Fick’s law of diffusion
○ Diffusion of an uncharged solute across a membrane is
proportional to the concentration gradient of the solute,
the membrane surface area, and the membrane
permeability to the solute
○ Rate of diffusion = surface area x concentration gradient
x membrane permeability (lipid solubility/molecular size)
, 3
■ Osmosis
○ Protein-Mediated Transport
■ Facilitated Diffusion
● Concentration gradient
