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what is the function of membrane
sets external boundaries for cells and separates compartments
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what are the 7 common features of membranes
- sheetlike, and form boundaries between cell compartments
- contain lipids, proteins, and CHO
- lipids forms a bilayer due to amphiphilic nature
- function are mediated by specific proteins; pumps, channels, receptors, energy transducers, enzymes
- membrane components associate through noncovalent interactions
- asymmetrical
- lipid and proteins diffuse rapidly along the plane of the membrane
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what is the melting temperature of saturated fatty acids (Tm)
high
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what is the melting temperature of unsaturated fatty acids
lower
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what does and increase in cholesterol do to the membrane
decrease fluidity
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What are the common monosaccharides associated with membranes
- glucose
- galactose
- fructose
- mannose
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what molecules are important for cell to cell recognition
- glycoproteins
- glycolipids
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How are ABO blood groups different from each other?
Each blood group has unique antigens (polysaccharides) on the glycoproteins of the RBC membrane. The different polysaccharide chains are classified as A,B,O,AB
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Are CHO asymmetric and where are they found
- asymmetric
- outside of the cell
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what are the types of membrane lipids
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what is sphingomyelin and where is it found
- a membrane lipid
- brain, blood cells, lung surfactant
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what are glycolipids
identical in structure to sphingolipids except the phosphoryl choline head group is replaced with a monosaccharide
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what are the types of membrane proteins?
- peripheral membrane proteins: extracellular or intracellular, can be easily removed
- extracellular proteins: includes protein ligands specific for cell surface receptors. Includes proteins of the extracellular matrix
- intracellular proteins: attaches to lipid anchors or integral proteins. Can be modified covalently by lipids or modified as oncoproteins
- integral membrane proteins: span across the bilayer, has both intra and extra cellular domains. Difficult to remove unless destroying the membrane
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what are the classes of integral membrane proteins
- antigens
- receptors
- translocators
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what is the structure of a transmembrane domain
a-helical
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antigens
integral membrane proteins that are recognized by antibodies
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receptors
required for the specific action of hormones, transmitters, and growth factors
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what are two classes of membrane receptors
- growth factor receptor tyrosine kinases (RTKs)
- small molecule 7 transmembrane helix receptors
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What are RTKs
- binds to hormones such as insulin
- intracelluar domain: contains lots of tyrosine residues
- extracellular domain: binds to ligand
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what are small molecule 7 transmembrane helix receptors
- binds to hormone epinephrine and glucagon
- most small molecule 7 transmembrane receptors are G-proteins
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function of transporters (translocators)
- acts as a selective permeability barrier
- transport is either active or passive
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what is active transport
- transport of molecules across cell membrane using energy
- ex: Na/K ATPase, found in all mammals
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what is the function of Na/K ATPase
pumps 3 Na+ ions out and two K+ into cell expending one ATP molecule
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what is passive transport
transport of molecules along electrochemical gradient
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