All Flashcards
Define passive transport.
Movement of substances across a membrane without energy input, moving down the concentration gradient.
Define active transport.
Movement of substances across a membrane requiring energy (ATP), moving against the concentration gradient.
What is simple diffusion?
Movement of a substance from high to low concentration directly across the membrane, without assistance.
What is facilitated diffusion?
Movement of a substance from high to low concentration with the help of a transport protein.
Define osmosis.
The facilitated diffusion of water across a selectively permeable membrane.
What is endocytosis?
The process by which cells engulf substances by inward folding of the cell membrane, forming a vesicle.
What is exocytosis?
The process by which cells release substances by fusion of vesicles with the cell membrane.
Define phagocytosis.
A type of endocytosis where the cell engulfs large particles or cells ('cellular eating').
Define pinocytosis.
A type of endocytosis where the cell engulfs extracellular fluid with dissolved solutes ('cellular drinking').
What is receptor-mediated endocytosis?
A type of endocytosis where specific molecules bind to receptors on the cell surface, triggering vesicle formation.
What are the general steps of endocytosis?
- Cell membrane invaginates. 2. Substance is enclosed in the invagination. 3. Membrane pinches off, forming a vesicle inside the cell.
What are the general steps of exocytosis?
- Vesicle containing substance moves to cell membrane. 2. Vesicle membrane fuses with cell membrane. 3. Substance is released outside the cell.
Describe the process of phagocytosis.
- Cell extends pseudopodia around a particle. 2. Pseudopodia fuse, enclosing the particle in a vacuole. 3. Vacuole fuses with a lysosome for digestion.
Outline the process of receptor-mediated endocytosis.
- Specific molecules bind to receptors on the cell surface. 2. Receptors cluster together in coated pits. 3. Coated pit invaginates and forms a coated vesicle. 4. Vesicle is internalized into the cell.
Compare and contrast simple and facilitated diffusion.
Simple diffusion: No protein required, directly across membrane. Facilitated diffusion: Requires a transport protein, still down concentration gradient.
What are the key differences between passive and active transport?
Passive: No energy required, down concentration gradient. Active: Energy (ATP) required, against concentration gradient.
Differentiate between endocytosis and exocytosis.
Endocytosis: Brings substances into the cell. Exocytosis: Releases substances out of the cell.
Compare phagocytosis and pinocytosis.
Phagocytosis: 'Cellular eating', engulfs large particles. Pinocytosis: 'Cellular drinking', engulfs extracellular fluid.
What are the similarities and differences between facilitated diffusion and active transport?
Similar: Both use transport proteins. Different: Facilitated diffusion doesn't require energy and moves down the concentration gradient, while active transport requires energy and moves against the concentration gradient.