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somatic cells
- not germ cells (that's quite the definition)
- soma = body
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3 basic parts of a cell
- 1. cell membrane
- 2. cytoplasm = cytosol and organelles
- 3. nucleus
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4 functions of a cell membrane
- 1. physical isolation
- 2. sensitivity to/response to surroundings: detects changes outside
- 3. regulation of exchange with surroundings: enter ions, release waste
- 4. structural support: like skin cells attaching to other things to support it.
- point: cell doesn't function alone.
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context: cell membrane general composition
lipids
- 42%
- -phospholipids
- -cholesterol
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context: cell membrane general composition
proteins
- 55%
- -channels
- -receptors
- -enzymes
- -carrier proteins
- -recognition proteins
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context: cell membrane general composition
carbohydrates
- 3%
- -glycoproteins
- -proteoglycans
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context: phospholipids
3 parts of the polar head (hydrophilic)
- 1. polar group: choline, ethanolamine, inositol
- 2. phosphate
- 3. glycerol
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context: phospholipids
2 types of fatty acid tails (hydrophobic)
- 1. oleic acid
- 2. linoleic acid
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context: phospholipids
choose form:
1)unilayer
2)bilayer
- 2) bilayer
- remember the SHAMITCH :D WOW im gonna be hungry
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4 things (tidbits) about the phospholipid bilayers
- 1. phospholipid distribution is asymmetrical. sphingomyelin and phosphatidylcholine are on the outside more. the rest are inside more.
- (a. transversely and b. laterally)
- 2. phospholipid composition is dynamic. with help of FLIPPASE
- 3. membrane fluidity is dynamic. with help of CHOLESTEROL
- 4. membrane composition and function differs between cell populations
- point: phospholipids can change. YES THEY CAN!
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context: SELECTIVELY permeable cell membrane
5 factors to be let across the border (passports won't work here).
- 1. molecule size (yes, size matters) ex: O2, CO2
- 2. molecule charge ex: EtOH **water**
- 3. molecule shape
- 4. molecule lipid solubility
- 5. cell membrane's composition and arrangement
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cell membrane needs proteins to let in what 3 types of molecules?
- 1. large, polar, uncharged molecules ex:glucose, amino acids
- 2. ions and charged molecules ex: amino acids, DRUGS, Na+, K+, Cl-
- 3. lipophilic molecules ex: solubility?? (can go in, and not go in??)
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2 ways proteins contribute to cell function
- 1. is the selectively permeable part
- 2. response of cell to environment
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4 properties of membrane proteins
- 1. asymmetrical distribution
- 2. distribution of lateral proteins is dynamic (fluid mosaic model)
- 3. distribution of transverse proteins is dynamic (addition/removal of transmembrane proteins)
- 4. changes in protein conformation (PO4 , ligand binding, substrate binding)
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2 ways to classify the cell membrane proteins
- 1. position: integral vs peripheral
- 2. function: channels (leak vs gated (ligand vs voltage)), carriers, receptors, enzymes, recognition
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context: ionic gradient
T/F
ion concentrations are equal inside and out.
False!
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channel proteins
all are integral, transmembrane protein with hydrophilic central pore
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context: channel proteins
Leak channels: 4 things
- 1. selective
- 2. passive
- 3. bidirectional
- 4. open 24/7
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context: channel proteins
ligand-gated channel: 4 things
- 1. selective
- 2. passive
- 3. bi-directional
- 4. open/close only for ligand
- ex: ACh for Na+ to go in
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context: channel proteins
voltage gated channels : 4 things
- 1. selective
- 2. passive
- 3. bi-directional
- 4. open/close to change in voltage, conformation change of protein
- ex: activation of neuron
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carrier proteins: 4 things
- 1. selective
- 2. passive OR active
- 3. bi-directional
- 4. solute/ligand binds, conformational change (no flip flop)
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Receptors
- ligand binds => activation of receptor
- 1. integral
- 2. requires energy mostly
- 3. selective
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enzymes
- protein catalysts that accelerate the reaction rate
- 1. integral or peripheral
- 2. selective
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one way a cell is recognized
- cell surface proteins
- ex: for immune recognition
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3 types of carbohydrates
- 1. glycoproteins
- 2. glycolipids
- 3. proteoglycans
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3 functions of carbohydrates
- 1. receptors
- 2. cell recognition (usually faces extracellular fluid)
- 3. cell protection and lubrication
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what are the 3 mechanisms of membrane transport for solutes?
- 1. diffusion (simple vs facilitated)
- 2. transport via carrier proteins (primary and secondary active transport)
- 3. vesicular (endo vs exocytosis)
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Diffusion
- -High to low (ex: Hoover Dam)
- -goal: eliminate concentration gradient
- -influenced by: distance, size, temperature, gradient, etc.
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Context: Diffusion
Simple
- down gradient = no energy required
- lipophilic uses membrane
- ions uses leak channels
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context: diffusion
facilitated diffusion
- down concentration = no energy required
- carrier-mediated transport = carrier proteins
- -specific
- -saturated = can plateau!!!
- -regulated
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context: active transport
primary
- Low to High = requires ATP
- -carrier proteins
- ex: sodium/potassium pump (3 Na+ out, 2 K+ in)
- Kim's parents issues curfew, I have to go in at 2 although I want to go out. I have to actively go into house (cell).
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context: active transport
secondary
- -no energy required INITIALLY: energy for glucose to move in, and ATP when Na+ needs to be pumped back out.
- -carrier proteins
- ex:sodium/glucose transporter
- sodium: high to low
- glucose: low to high
- Symport
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