Ch. 4 Cell Permeability and Transport Flashcards
Cholesterol (3)
- rigid ring lipid
- random throughout hydrophobic region
- gives plasma membrane structural strength
Carbohydrate chains (3)
- extend from the outside of plasma membrane
- attached to proteins or phospholipids
- functions: signal, coating, or receptor
Extracellular environment (3)
- outside of cell
- aqueous (contains water)
- extracellular fluid
Lipid bilayer (3)
- made of two rows of phospholipid molecules
- phosphate group head faces outward
- fatty acid tails face inward
Phosphate group head (4)
- part of the phospholipid molecule
- contains phosphate group
- polar and hydrophilic
Fatty acid tails (4)
- part of the phospholipid molecule
- tails made of two fatty acid chains
- non polar and hydrophobic
Peripheral protein (2)
- does not extend across lipid bilayer
- anchor point for cytoskeleton
Transmembrane proteins (2)
- extend through lipid bilayer
- serve as transport protein or channel across bilayer
Cytoplasm (4)
- inside cell
- aqueous (contain water)
- contains organelles
- intracellular fluid
Diffusion (3)
- substances cross the membrane
- solute moves from area of high concentration to low concentration (down concentration gradient)
- passive
Kinetic energy (2)
- driving force for passive transport mechanisms
- random collisions of molecules
Simple diffusion (2)
- water, oxygen, and steroid hormones freely cross the cell membrane
- molecules move down their concentration gradient
Facilitated diffusion (3)
- molecules are assisted by a channel or transport protein to cross the cell membrane
- ions, glucose, and amino acids
- molecules move down their concentration gradients
Osmosis (3)
- selectively permeable membrane
- if concentration of two solutions is different, a concentration gradient exists for both water and the solute
- each substance attempts to diffuse down its concentration gradient
Aquaporins
water is freely permeable through these channels
Hypotonic solution (3)
- side with the lower solute concentration
- higher water concentration
- net movement of water out of this side
Hypertonic solution (3)
- side with higher solute concentration
- lower water concentration
- net movement of water toward this side
Equilibrium (2)
- molecules become evenly distributed and in equal concentrations on either side of the membrane
- dilute hypertonic solution to reach equilibrium
Isotonic (4)
- equal solute and solvent concentration
- no further net movement from one side of the membrane to the other
- no net change in the concentration
- water will continue crossing membrane
Osmosis (rule of thumb)
water will always move from hypotonic solution toward the hypertonic solution to make solution isotonic
Osmotic pressure (2)
- pressure generated within cell as water presses against the plasma membrane
- cells change shape as water moves into or out of cell
Isotonic solution cell shape
cell does not change shape
Hypotonic solution cell shape
water diffuses into cell, swells up, potentially bursts
- net flow of water in red blood cell
Hypertonic solution cell shape
water diffuses out of cell, cell will shrink or crenate
- net flow of water out of red blood cell
Filtration (2)
- separation of particles in a solution when pressure is applied to one side of a membrane
- results in passage of small particles through membrane while larger particles unable to pass through are left behind
Hydrostatic pressure
pressure is exerted by water flow
- ex. kidneys, hydrostatic pressure exerted by blood flow pushes water and small particles out of bloodstream to form urine (large particles including cells and large proteins remain in blood)
Filtration rate
-rate that substances filter through the membrane
Active processes
require energy in the form of ATP to drive the movement across the plasma membrane
Active transport
transport of substances against concentration gradient (low concentration to high concentration)
Endocytosis
bulk amounts of substances are taken into the cell by modifying plasma membrane structure
Exocytosis
substances released from the cell into the extracellular environment
Phagocytosis (3)
- process of cell eating
- intake of large substances into the cell followed by internal digestion by cellular enzymes
- requires cell’s plasma membrane to change its shape in order to surround large substance and engulf it into the cytoplasm
Phagosome (2)
- membrane sac that forms around the substance in phagocytosis
- fuses with a lysosome to digest it
Phagocytosis in human body
bacteria and dead cells are removed by specialized white blood cells
Pinocytosis
uptake of small droplets of extracellular fluid
Solvent
water is universal solvent
Solutes
dissolved in water
- ex. sugars, proteins, electrolytes, and organic molecules
Plasma membrane (3)
- primarily composed of lipids
- hydrophobic
- selectively permeable membrane
