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C2-04 Transport Through the Cell Membrane
Diffusion/Osmosis/Active Transport
10
Biology
Professional
09/15/2010

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Cards

Term

 

 

Extracellular Fluid (ECF) Nutrient Levels

Definition

  • Sodium (Na+)= 142
  • Potassium (K+)= 4.2
  • Calcium (Ca+2)= 1.2
  • Glucose= 85 mg/dl
  • pH= 7.4

Term

 

 

 

Intracellular Fluid Nutrient Levels

Definition

  • Sodium (Na+)= 10
  • Potassium (K+)= 140
  • Calcium (Ca+2)= .0001
  • Glucose = 0-20 mg/dl
  • pH= 7.0

Term

 

 

Mechanisms of Solute Movement Through The Cell Membrane

Definition

1) Simple Diffusion

2) Facilitated Diffusion

3) Active Transport

a. primary active transport

b. secondary active transport

Term

 

 

 

Simple Diffusion

Definition

Net movement of solutes through the cell membrane down their concentration gradients, so no energy requirement
No carrier proteins are required

Lipid soluble substances easily cross the plasma membrane (O2, N2, CO2, ETOH )
Most other small lipid insoluble molecules such as water move through transmembrane protein pores (passive transport)

Term

 

 

 

Factors Influencing Diffusion

Definition

1.   Membrane Permeability (P)

2.Concentration Difference across the membrane
3.Pressure difference across the membrane

4.   Effect of Electrical Potential 

  Nernst Equation  

Term

 

 

 

Factors Affecting Membrane Permeability 

Definition

1)Thickness of the membrane
2)Lipid solubility of the substance diffusing
3)Number of protein channels available for passage
4)Molecular size of the diffusing substance

Term

 

 

 

Primary Active Transport

Definition

Active Transport is carrier-facilitated to move substances against their concentration gradient

 

Allows for the concentration of certain solutes inside the cell even if external concentrations are quite low, and vice versa

It requires energy – direct cleavage of ATP or other high-energy phosphate compound on the carrier protein

Saturation of carrier occurs, same as in facilitated diffusion

Prototype example is Na+/K+ “pump” 

Term

 

 

 

Na+/K+ ATPase

Definition

Present in all cells in the body
Has three internal binding sites for Na+ and two external sites for K+ (2 K+ move in, 3 Na+ move out)
Electrogenic pump (3 + out, 2 + in)
Maintains the plasma membrane resting potential

Term

 

 

 

Secondary Active Transport

Definition

Utilization of ion gradients generated by 1° active transport to move a second solute against its concentration gradient

Examples include:  Na+/ glucose co-transporter, Na+/ amino acid co-transporter, Na+/Ca2+ counter-transporter, Na+/H+ counter-transporter

Term

 

 

 

Osmosis 

Definition

Process of water moving from a high concentration to a low concentration through a semi-permeable membrane
Water equilibrates across the membrane moving to regions where solute concentration is higher
Net movement of water into or out of a cell can cause the cell to shrink or swell
Can create pressure differences if solutes are trapped on one side of a membrane (osmotic pressure)

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