Flashcards in 1.4 Membrane Transport Deck (19)
What is simple diffusion?
Particles passing between phos. molecules, through the membrane. Non-polar molecules diffuse easily, small polar molecules slower. PASSIVE - no energy required.
Simple molecules (O2, H2O,etc.)
What is facilitated diffusion?
Diffusion through protein channels. Channels are specific to certain molecules b/c of size and shape of channel interior. PASSIVE - no energy required.
More complicated molecules, sugars and amino acids
What is diffusion (in general)
Movement of particles from an area of high concentration to an area of low concentration. Due to cont. random motion of particles. All diffusion is PASSIVE.
What is osmosis?
Diffusion of water across a semi-permeable membrane due to differences in solute concentration. H2O will pass through membrane to dilute solute and make inside and outside of cell equal conc. PASSIVE.
What is active transport?
Movement against the conc. gradient (low conc. to high conc.). REQUIRES ENERGY usually in form of ATP. Active transport is carried out by membrane proteins (protein pumps)
How do particles move across membranes?
Simple diffusion, facilitated diffusion, osmosis, and active transport
How does active transport work?
Particle enters pump from side w low conc.. Particle binds to specific site (only one type can bind). Energy from ATP is used to change shape of pump. Particle released on side w higher conc. and pump returns to original shape.
What are the three types of solutions?
Isotonic, hypotonic, hypertonic.
What is an isotonic solution?
Equal [solute] on each side of membrane so water flows equally in both directions
What is a hypotonic solution?
Lesser [solute] outside cell than inside to water flow into cell to try to equalize it. (Water flows in to dilute [solute] inside cell, cell gets large and might explode)
What is a hypertonic solution?
Higher [solute] outside cell than inside so water flows out of cell to try to equalize it. (Water flows out to dilute [solute] outside cell, cell shrinks and shrivels)
What type of solution do plant cells need? What type of solution do animal cells need?
Plant cells need hypotonic solutions so that there is enough H2O for the cell. The cell is not at risk of exploding because of the strong cell wall. Animal cells need to be in isotonic solutions since they do not have a cell wall and will explode if too full of H2O.
Endocytosis occurs when a membrane encloses a particle. Fluidity of membrane allows the membrane to move, it sinks inwardly and seals back on itself to create a vesicle. Inner layer of original membrane is outer layer of vesicle and vice versa. Vesicle breaks away and moves to cytoplasm. Requires ENERGY.
What is exocytosis?
Movement of particles out of the cell, opposite of endocytosis.
How are vesicles used to transport materials secreted by a cell.
Vesicles formed from rER transport proteins to G app. Vesicles fuse w membrane of G app. Proteins processed. Vesicles move through cytoplasm. Fuse w membrane. Exocytosis. Vesicles used to secrete substances such as hormones and digestive enzymes. Can contain cell products other than protein.
Distinguish between active and passive movements of materials across membranes, using named examples.
Passive: (facilitated) diffusion, osmosis, does not require energy, down conc gradient, no pump, e.g. oxygen through mem.
Active: active transport, exocytosis, pinocytosis, phagocytosis, requires ATP, against conc gradient, requires pumps, e.g. glucose through active transport
What are the types of endocytosis?
Phagocytosis: cell eating, Pinocytosis: cell drinking, Recepto-mediated endocytosis: specific particles
Describe how the sodium-potassium pump in neurons works.
Neuron at rest positive outside negative inside. Positives and negatives switch when Na comes in. K goes out to switch them back. Pump then works to replace Na into middle and K into outside. Pump is ACTIVE.