membrane structure & function
DESCRIPTION
Membrane Structure & Function. Membrane Models. 1972- Present Fluid-Mosaic Model. 1935-1970 Sandwich Model. Membrane Transport (Passive). 1. 2. Glucose, amino acids. Diffusion. Steepness of concentration gradient Temperature Mass of diffusing substance Surface area - PowerPoint PPT PresentationTRANSCRIPT
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Membrane Structure & Function
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Membrane Models
1935-1970SandwichModel
1972- PresentFluid-MosaicModel
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Membrane Transport(Passive)
Glucose, amino acids
1 2
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Diffusion
• Steepness of concentration
gradient• Temperature• Mass of diffusing
substance• Surface area• Diffusion
distance
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2 types of membrane transportPassive vs Active
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Channel-mediated Facilitated Diffusion of Potassium ions through a Gated K +
Channel
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Glucosetransporter
Glucosegradient
Glucose
Extracellular fluid Plasma membrane Cytosol
1
Glucosetransporter
Glucosegradient
Glucose
Extracellular fluid Plasma membrane Cytosol
1
2
Glucosetransporter
Glucosegradient
Glucose
Glucose
Extracellular fluid Plasma membrane Cytosol
1
2
3
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http://trc.ucdavis.edu/biosci10v/bis10v/media/ch04/tonicity.html
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Crenation
HemolysisCytolysis
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Plasmolysis – the shriveling of the cell membrane due to loss of water (osmosis)
Turgor pressure – the force directed against the cell wall after the influx of water (osmosis)
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Filtration is movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.
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Requires Energy:ex.: thyroid gland concentrates Iodine glucose is completely absorbed by digestive tract sodium potassium pump
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Active TransportI. Solutes are transported across plasma membranes with the use of energy, from an area of lower concentration to an area of higher Concentration *Sodium-potassium pump*Thyroid gland*Intestines (glucose)II. 2 sources of energy
1. ATP (Primary active transport)2. Energy stored in Ion concentration gradients (Secondary active transport)
**40% of a cell’s ATP is used for Primary active transport Cyanide shuts down active tranport by turning off ATP production
1
3 Na+
K+
gradient
Cytosol
1
3 Na+ expelled
3 Na+
ADP P
P
2 K+
importedK+
gradient
Na+
gradientNa+/K+ ATPase
Extracellular fluid
Cytosol
2K+
ATP2 3 4
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Secondary Active Transport Mechanisms
• Antiporters carry two substances across the membrane in opposite directions (Digitalis)
• Symporters carry two substances across the membrane in the same direction
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Endocytosis – taking in large amounts of material (bulk flow)
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• Ex. LDL cholesterol (bad cholesterol)
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