Transport in cells Flashcards
Explain the three passive transport types in cells
- diffusion: movement of particles in fluid down a concentration gradient. Cell membranes are no barrier to diffusion of small particles.
- facilitated diffusion: diffusion taking place through carrier proteins or protein channels. Protein-lined pores of cell membrane make facilitated diffusion possible.
- osmosis: special form of diffusion involving movement of solvent molecules down a concentration gradient through a partially permeable membrane, which means routes can be accumulated either side of the membrane and results int he movement of water by osmosis across the membrane.
Explain the three active transport mechanisms?
- endocytosis: movement of large molecules into cells through vesicle formation. Flood nature of cell membrane makes it possible to form vesicles.
- exocytosis: movement of large molecules out of cells through vesicle formation
- active transport: movement of substances across cell membranes directly using ATP. Proteins in membrane act as carriers or enzymes, making ATP every available to move ions or molecules through membrane.
What are gated channels?
Channels that only open if a specific molecule is present or there is an electrical change across the membrane.
Where do simple diffusion, osmosis and facilitated diffusion happen in the plasma membrane and why (for no.2)
Simple is through phospholipid bilayer
Osmosis happens through channel protein to avoid the hydrophobic centre.
Facilitated diffusion happens in protein carriers of a specific shape.
What is osmotic concentration?
A measure of concentration of solutes in a solution that have an osmotic effect.
What is the situation with a hypotonic solution?
Osmotic concentration of solutes in the solution is lower than in the cytoplasm of the cells
When the fluid is hypotonic to cytoplasm, what happens and why? What is this called?
Water enters the cell, but as it swells and presses on cell walls, it generates hydrostatic pressure, which increases until it cancels out the tendency for water molecules to move in. This is pressure potential.
What is plasmolysis?
When a plant cell is placed in a hypertonic solution and so much water leaves the celery osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away from the cell walls.
What is water potential?
Measure of potential for water to move out of a solution by osmosis.
What’s the maximum water potential?
0
What is turgor pressure?
Inward pressure exerted by plant cell wall on protoplasm of cell as the cell contents expands and press forwards, a force which opposes entry of water by osmosis.
What is the water potential equation for plants?
Turgor pressure + osmotic potential
How is the water potential different for animals and whY?
Water potential of cell is simply the osmotic potential of the cytoplasm, as there’s no cell wall to exert a hydrostatic pressure.
What is osmotic potential?
Potential of a solution to cause water to move into cell across a partially permeable membrane as a result of dissolved solutes.
How does active transport use ATP to involve the carrier protein?
The carrier system contains ATPase, which catalyses the hydrolysis of ATP, breaking one bond and forming two more to provide the energy needed by the carrier system in the membrane, or to release the transported substances.
