Chapter 5 Flashcards
Cell membrane function
Controls interactions with other cells
Controls passage of materials inside and outside of the cell (homeostasis) (Selectively permeable
Integral protein
Goes through the phospholipid bilayer.
Span the lipid bilayer (transmembrane proteins) Non polar regions of protein within interior of bilayer and polar regions protrude from both sides of bilayer. (Secondary Structure)
Peripheral protein
Only 1 side of phospholipid bilayer (Usually intracellular)
Anchoring molecules attach membrane protein to surface (tertiary structure)
Fluid Mosaic Model
Phospholipids in a bilayer with additional lipid, protein, and carbohydrate molecules
Properties that resemble a fluid because lipids and proteins can move relative to each other within membrane (Not rigid)
Membrane structure 4 compnents
1 Phospholipid Bilayer (flexible matrix, barrier to permeability)
2 Transmembrane proteins (Integral membrane proteins [go through phospholipid bilayer]
3 Interior protein network (peripheral or intracellular membrane proteins)
4 Cell surface markers (Glycoproteins and glycolipids)
Phospholipids are amphipathic (two natures) molecules
Hydrophobic
Hydrophilic
(Also contains cholesterol)
Saturated and unsaturated fatty acids
Saturated fatty acids make membrane less fluid than unsaturated fatty acids
Membrane proteins various functions
Transporters
Enzymes
Cell-surface receptors
Cell-surface identity markers
Cell to cell adhesion proteins
Attachments to the cytoskeleton
Transmembrane domain
Spans the lipid bilayer. Hydrophobic amino acids arranged in alpha helices. Single or multiple transmembrane domains ( multiple helices)
Pores
Beta pleated sheet proteins
Extensive nonpolar regions can create a pore through the membrane
Cylinder of beta sheets in the protein secondary structure (Beta barrel) [Interior polar and allows water and small polar molecules to pass through membrane]
Passive transport
DOES NOT require energy, goes with the concentration gradient.
1 Diffusion (simple)
2 Facilitated diffusion
3 Osmosis
Diffusion (Passive transport)
Movement of molecules from high concentration to low concentration. Will continue until concentration is at equilibrium.
Selectively permeable membrane
Hydrophobic interior repels polar molecules, but not nonpolar molecules. Nonpolar move until equilibrium. Small polar molecules have limited permeability (O2, CO2). Very limited permeability to larger polar molecules and ions.
Facilitated diffusion
Polar molecules and larger molecules with help of a protein to move across membrane.
1 Channel proteins - can be open or closed
2 Carrier proteins - need to physically bind to specific molecules and pull across membrane
Ion channels and 3 conditions to determine direction
Allow passage or ions. Gated, open or close due to stimuli
1 Relative concentration on either side or membrane
2 Voltage differences across membrane (charge of cell compared to surroundings)
3 Gated channels: Open or closed
3 Electrochemical questions
1 Where is ions more abundant and where does it want to go chemically (Conc. Gradient)
2 What is the charge of the cell and the ion? Which way does it electrically want to go
3 Is vm (membrane potential) = to Ek (equilibrium)?
Facilitated diffusion limitations
Saturated because only one molecule can enter at a time
Requires concentration difference
Osmosis
Channel to move H2O. Net diffusion of water across a membrane toward a higher solute concentration. (Moves from pure to less pure)
Water is solvent. Dissolved substances are solutes
Hypertonic Solution
Has a higher solute concentration
Hypotonic Solution
Has a lower solute concentration
Isotonic solution
Same osmotic concentration
Aquaporins
facilitates osmosis (Channels to move H2O [pores])
Osmosis in animal cells
Must maintain balance between extracellular and intracellular solute concentrations to maintain their size and shape
Crenation
Shrinking in a hypertonic solution
Lysis
bursting in a hypotonic solution
Osmosis in plant cells
Cell wall prevents major changes in cell size (Prevents lyce)
Turgor pressure - force due to internal pressure of water pushes plasma membrane against cell wall (Maintain size and shape)
Plasmolysis - plant wilt because water leaves plant cells
Central vacuole pushes on cell wall to maintain shape
Active transport. 2 types
Requires energy (ATP), against concentration gradient. (From low to high)
Direct - primary active transport
Indirect - secondary transport (Coupled transport)
Carrier proteins used in active transport include
Uniporters - move one molecule at a time
Symporters - move two molecules in the same direction
Antiporters - Move two molecules in opposite directions
Sodium-Potassium Pump (Na+ - K+)
Direct ATP for active transport, binds phosphate group to protein to open. Antiporters move 3 Na+ out of cell and 2 K+ into cell. Against concentration gradient
Plasmolysis
Plant wilt because water leaves plant cells
Secondary/Coupled transport
Indirectly uses ATP, uses symporter or antiporter. One molecule goes with conc. grad. and that energy moves a different molecule against its con. grad.
Bulk Transport types
Endocytosis (into cell) and Exocytosis (EX- EXit the cell)
Endocytosis types
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Phagocytosis
Cell takes in particulate matter (Cellular eating)
Pinocytosis
Cell takes in only fluid (Cellular drinking) (Mostly water)
Receptor-mediated endocytosis
Specific molecules are taken in after they bind to a protein receptor, formation of clathrin-coated pits and vesicles
Clathrin-coated pits and rings
After receptor mediated endocytosis pits form to trap molecules and then form vesicles with clathrin-coated rings around them
Channel Proteins
Hydrophilic channel when open. Ex ion channel
Carrier Proteins
Bind specifically to molecules they assist. Pull across membrane
