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Cells: Cell physiology and transport
lecture 9/13/11
41
Anatomy
Undergraduate 1
09/13/2011

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Term
Why is transport important?
Definition
Natural Gradients
Food/Oxygen/CO2
Unnatural Gradients
Excitability
Cells create an unequal distribution of ions across a cell membrane to store membrane potential for responsiveness
Membranes do this with the help of proteins
Term
Transport Proteins: Recall that-
Definition
The membrane is hydrophobic-
There are proteins in the membrane
Term
Plasma membranes are
Definition
selectively permeable
Term
Two types of transport:
Definition
Passive
Active
Term
Passive processes
Definition
No cellular energy (ATP) required
Substance moves down its concentration gradient
Term
Active processes
Definition
Energy (ATP) required
Occurs only in living cell membranes
Term
What determines whether or not a substance can passively permeate a membrane?
Definition
Lipid solubility of substance
Channels of appropriate size
Presence of Carrier proteins
Term
Passive Processes: Simple Diffusion
Definition
Nonpolar lipid-soluble substances diffuse directly through the phospholipid bilayer
Term
Certain molecules (glucose, amino acids, and ions) use carrier proteins or channel proteins which:
Definition
Exhibit specificity (selectivity)
Rate is determined by number of carriers or channels which assists to regulate activity and quantity
Term
Facilitated Diffusion -
Definition
Using Carrier Proteins
Term
Transmembrane integral proteins transport:
Definition
specific polar molecules (sugars and amino acids)
Term
Binding of substrate causes:
Definition
shape change in carrier
Term
Facilitated Diffusion -
Definition
Aqueous channels formed by transmembrane proteins selectively transport ions or water
Term
Facilitated Diffusion Two types:
Definition
Leakage channels - Always open
Gated channels - Controlled by chemical or electrical signals
Term
osmosis
Definition
Movement of a solvent across a selectively permeable membrane
Term
isotonic
Definition
isotonic environment happens when an equal concentration exists inside and outside the cell
Term
hypertonic
Definition
greater solute concentration within cell
Term
hypotonic
Definition
greater solute concentration outside cell
Term
Passive Processes:
Definition
Simple diffusion
Facilitated diffusion
osmosis
Term
Active Processes:
Definition
use energy (ATP) for membrane transport
Two types of active processes:
Active transport
Vesicular transport
Term
active transport requires:
Definition
carrier proteins (solute pumps)
Term
active transport does:
Definition
Moves solutes against their concentration gradient
Term
Types of active transport:
Definition
Primary active transport
Secondary active transport
Term
Sodium - Potassium pump
Definition
Na+- K+ ATP
Located in all plasma membranes
Involved in primary and secondary active transport of nutrients and ions
Maintains electrochemical gradients (or membrane potential) essential for functions of muscle and nerve tissues
Term
Secondary Active Transport
Definition
Depends on an ion gradient created by primary active transport
Energy stored in ionic gradients is used indirectly to drive transport of other solutes
Term
Vesicular Transport
Definition
Transport of large particles, macromolecules, and fluids across plasma membranes
Requires cellular energy (ATP)
Term
Vesicular Transport 3 types:
Definition
Exocytosis - transport out of cell
Endocytosis - transport into cell
Transcytosis - transport into, across, and then out of cell
Term
Exocytosis -
Definition
transport out of cell
Term
Endocytosis -
Definition
transport into cell
Term
Transcytosis -
Definition
transport into, across, and then out of cell
Term
Substance (vesicular) trafficking -
Definition
transport from one area or organelle in cell to another
Term
Phagocytosis –
Definition
solids pseudopods engulf solids and bring them into cell’s interior
Term
Pinocytosis -
Definition
plasma membrane infolds, bringing extracellular fluid and solutes into interior of the cell
Term
Exocytosis:
Definition
material being moved out of the cell
Term
Membrane Potential:
Definition
Separation of oppositely charged ions across a membrane creates a membrane potential
Term
Resting Membrane Potential (RMP):
Definition
Voltage measured in resting state in all cells Results from diffusion and active transport of ions (mainly Na+ and K+)

Sodium / Potassium pump maintains the RMP!
Term
Important Roles of Cell Adhesion Molecules
Definition
Anchor cells to extracellular matrix or to each other
Assist in movement of cells past one another
-CAMs of blood vessel lining attract white blood cells to injured or infected areas
Stimulate synthesis/decom. of adhesive membrane junctions
Transmit intracellular signals to direct cell migration & proliferation
Term
Important Roles of Cell Membrane Receptors
Definition
Contact signaling - touching and recognition of cells like in an immune response
Chemical signaling - interaction between receptors in neurotransmitters and hormones
Alter activity of cell proteins allowing enzymes or chemically gated ion channels to become active
G proteins - receptors affecting an ion channel or enzyme or causing the release of an internal second messenger – thus more intracellular responses
Term
Contact signaling -
Definition
touching and recognition of cells like in an immune response
Term
Chemical signaling -
Definition
interaction between receptors in neurotransmitters and hormones
Term
G proteins -
Definition
receptors affecting an ion channel or enzyme or causing the release of an internal second messenger – thus more intracellular responses
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