Chapter 5 Membrane Structure and Function
Read chapter 5 in textbook Read Lab 1 (Osmosis and Diffusion) Read
appropriate lab and lecture pages in pages in CliffsAP Cell Surface
SEM Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function
Topics 5.1 Plasma Membrane Structure and Function 5.2
5.3Permeability of the Plasma Membrane 5.4Modification of Cell
Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function5.1 Plasma Membrane
Structure and Function All cells have a plasma membrane Functions
differently in different cells All have same basic makeup Currently
the fluid mosaic model is thought to be the best representation
Mills AP Biology 2012 Chapter 5 Membrane Structure and Function
5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Actively functioning part of cell without it cells die
Selectively permeable Composed of double layer of phospholipid with
free floating proteins imbedded in it (proteins can float
laterally) Also contains glycolipids, cholesterol and glycoproteins
Mills AP Biology 2012 Chapter 5 Membrane Structure and Function
5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Hydrophilic phosphate heads Hydrophobic fatty acid
tails water soluble substances cannot pass easily ( amino acids,
sugars, proteins, nucleic acids) substances soluble in lipids can
pass more easily (O2, CO 2) Mills AP Biology 2012 Chapter 5
Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Fluid Mosaic Membrane is fluid because phospholipids
are oil consistency at body temperature Proteins can float around
between phospholipds Membrane is mosaic because it has a wide range
of movable proteins imbedded in it Mills AP Biology 2012 Chapter 5
Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Mosaic Quality Proteins give unique qualities to cells
RBC has over 50 different proteins associated with it Proteins are
of two major types Peripheral proteins Integral proteins Proteins
can account for 50% of wt of membrane Mills AP Biology 2012 Chapter
5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Peripheral Proteins Occur on inside or outside of
membrane Dont span the membrane Often attached to integral protein
Function: Can have structural role Sometimes enzymatic Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Integral proteins Most span the entire membrane Have
hydrophilic and hydrophobic portions Function as : Receptors
Channels or pores Carriers Enzymes Cell recognition Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Integral Proteins Channel protein Mills AP Biology
2012 Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Integral Proteins Carrier/Transport protein Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Integral Proteins (usually) Cell recognition proteins,
fingerprints of the cell These glycoproteins and/or glycolipids are
specific for each species, for individuals within a species and
even for different types of cells within the same individual Mills
AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Integral Proteins Receptor protein Mills AP Biology
2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Integral Proteins Enzymatic protein Mills AP Biology
2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Junction Protein Junction Proteins: Tight junctions
join cells so that a tissue can fulfill a function, as when a
tissue pinches off the neural tube during development. Without this
cooperation between cells, an animal embryo would have no nervous
system. Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure
and Function Glycoproteins Most proteins that abut the
extracellular space are associated with branching sugar groups
(glycocalyx) Branching carbohydrates Cell surface sticky Distinct
for each cell type - also mark cells as self Mills AP Biology 2012
Cystic Fibrosis Problem with a membrane protein
Or (on hard drive) cystic fibrosis membrane protein Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function Permeability
of the Plasma Membrane
How do substances get into and out of cells? Pg CliffsAP What
determines whether or not a substance will enter or exit a cell?
Outside of cell - interstitial fluid (intercellular fluid,
extracellular fluid) Inside of cell - intracellular fluid Must
maintain balance each has its own make up Membrane selectively
permeable if cell looses this property, cell will die Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function Permeability
of the Plasma Membrane
Selectively (differentially) permeable membrane Properties due in
part to: Hydrophilic phosphate heads Hydrophobic fatty acid tails
Small, non charged, lipid soluble substances (O2, alcohol) pass
easily Some small polar molecules (water, carbon dioxide) pass
fairly easily Large and or charged substances and macromolecules
need help to pass water soluble substances cannot pass easily (
amino acids, sugars, proteins, nucleic acids) Mills AP Biology 2012
Chapter 5 Membrane Structure and Function Permeability of the
Plasma Membrane
Active processes Active transport Bulk transport endocytosis
pinocytosis phagocytosis receptor mediated endocytosis transcytosis
exocytosis E needed from cell (ATP) Passive processes Diffusion
Facilitated diffusion Osmosis(water diffusion) Filtration no E
needed from cell Mills AP Biology 2012 Chapter 5 Membrane Structure
and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Passive Process - Diffusion down concentration gradient
distributes until equilibrium reached influenced by: distance,
temperature, weigh, concentration small particles, lipid soluble
particles can diffuse across membrane. O2, CO2, steroids, general
anesthetics (lipid soluble), water (small), alcohol-can diffuse.
Mills AP Biology 2012 Chapter 5 Membrane Structure and Function
5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Passive Process - Osmosis (diffusion of water) water
molecules move from area of greater water concentration to area of
lesser water concentration across a selectively permeable membrane
Mills AP Biology 2012 Mills AP Biology 2012 Isotonic, hypotonic,
hypertonic
Osmotic pressure Isotonic, hypotonic, hypertonic Mills AP Biology
2012 Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Tonicity Hypertonic Mills AP Biology 2012 Chapter 5
Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Tonicity Hypotonic Mills AP Biology 2012 Chapter 5
Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Tonicity Isotonic Osmosis demo site: Mills AP Biology
2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Passive Process - Facilitated Diffusion uses a carrier
molecule protein channels and protein carriers Proteins are
specific to the substance they transport amino acids and sugars too
large for pores and arent lipid soluble Na, K, Cl ions too large,
also charged rate depends on binding rate and concentration down
concentration gradient glucose carrier activated by insulin Mills
AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Water molecule Sodium molecule Mills AP Biology 2012
Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Facilitated Diffusion ..\..\Biology\Biology Clipart
Movies Animations Sounds\Biology movies\Facilitated Diffusion.dir
Mills AP Biology 2012 Mills AP Biology 2012 Chapter 5 Membrane
Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across
a Membrane Passive Process - Filtration molecules forced through
membrane by blood pressure this is how tissue fluid formed blood
pressure too high --->tissue edema urine formed in kidneys down
a pressure gradient Mills AP Biology 2012 Chapter 5 Membrane
Structure and Function
Active processes active transport bulk transport endocytosis
pinocytosis phagocytosis receptor mediated endocytosis exocytosis E
needed from cell (ATP) Passive processes diffusion facilitated
diffusion osmosis (water diffusion) filtration no E needed from
cell Mills AP Biology 2012 Active Process - Active Transport
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Process - Active Transport moves particles up
concentration gradient from low concentration to high involves
carrier proteins-pumps often coupled reactions ( Na - K pump) very
important for homeostasis useful for amino acids, sugars and ions
Mills AP Biology 2012 Chapter 5 Membrane Structure and Function
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Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane NORMAL CONDITIONS More K inside cell than outside More Na
outside cell than inside Na - K Pump Pumps ions up concentration
gradients. 2 K into cell for every 3 Na out of cell. Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Transport Animation ..\..\Biology\Biology Clipart
Movies Animations Sounds\Biology movies\active transport
animation.mov Mills AP Biology 2012 Active Process - Bulk
Transport
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Process - Bulk Transport Exocytosis moves particles
out of cell requires energy nerve cells use to secrete
neurotransmitter Transcytosis ferries particles across cell
Endocytosis moves particles into cell requires energy particles too
large for diffusion or active transport three types: pincytosis
phagocytosis receptor mediated endocytosis Mills AP Biology 2012
Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Process - Endocytosis - Pinocytosis liquid
droplets, cell drinking small (0.1um) vesicles most cells use, esp.
cells that function in absorption Mills AP Biology 2012 Different
stages of the pinocytosis, an endocytic process, in an endothelial
cell. The vessel lumen is to the right; the underlying connective
tissue is to the left. Notice the thin gray (electron-dense) line
of the basal lamina immediately along the left border of the cell.
1 = Vesicle open to the outside of cell, facing the extracellular
matrix; 2 = Vesicle partially enclosed by cell membrane; 3 =
Vesicle limited by membrane and wholly within cytoplasm of cell.
The elongate nucleus lies in the center of the cell. Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Process - Endocytosis - Phagocytosis cell eating
vesicles larger WBCs, macrophages combine with lysosome, get
digested Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Phagocytosis animation..\..\Biology\Biology Clipart Movies
Animations Sounds\Biology movies\phagocytosis animation and
tutorial.swf Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane ActiveProcess - Endocytosis - Receptor mediated
endocytosis moves specific particles (ligands) receptor proteins on
cell membrane insulin, cholesterol taken into cells this way Mills
AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Process - Exocytosis Moves particles out of cell
vesicles form within cell proteins can be secreted this way Mills
AP Biology 2012 Mills AP Biology 2012 Chapter 5 Membrane Structure
and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a
Membrane Active Process -Transcytosis Ferries particles from one
side of cell to other important in HIV transmission Mills AP
Biology 2012 Passage of Molecules into and out of Cells
Uses energy Name Direction Requirement Examples Passive Processes
No Diffusion Osmosis Toward lower concentration Concentration
gradient Lipid soluble molecules, water, gasses Facilitated
diffusion Concentration gradient and carrier Some sugars and amino
acids Active Processes Yes Active Transport Toward greater
concentration Carrier Other sugars, amino acids and ions Exocytosis
Toward outside Vesicle Macromolecules Endocytosis Toward inside
Vacuole Cells and subcellular material Mills AP Biology 2012
Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Many cells have modifications that are exterior to the
plasma membrane Plants, bacteria, algae and fungi have cell walls
Animals have extracellular matrix Mills AP Biology 2012 Chapter 5
Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Extracellular Matrix of Animal Cells Meshwork of
insoluable glycoproteins and proteoglycans Fills spaces between
cells, supports cells Influences cell development, migration, shape
and function Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Desmosomes (Adhesion junctions) spot welds, scattered like
rivets binds cells together and reduces tension Found in skin,
heart muscle, neck of uterus,stomach, bladder Mills AP Biology 2012
Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Tight junctions protein molecules in adjacent cells fuse
together Impermeable,zipperlike junction digestive tract
epithelium, nephrons capillaries of brain Mills AP Biology 2012
Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Gap junctions allow chemical substances to pass from one
cell to another, adjacent channel proteins join Found in
electrically excitable tissue - heart muscle, smooth muscle
important in embryonic cells prior to circulatory system Mills AP
Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and
Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell
Surfaces Plant Cell Walls Freely permeable, variable in thickness
All plants have a primary cell wall composed cellulose, pectin and
noncellulose polysaccharides Some plants (esp woody) have a
secondary cell wall composed of lignin and cellulose Plasmodesmata
(only in plants) Narrow, membrane lined channels that connect cells
cytoplasm Mills AP Biology 2012 Read Connecting the Concepts on pg
101
THE END Mills AP Biology 2012