Movement of Substances Flashcards
Define ‘diffusion’.
The net movement of a substance from an area of high concentration to low concentration. No energy is required.
Explain what the term ‘concentration gradient’ means.
The difference in concentration between two areas. Greater gradient = greater difference
Explain the difference between simple diffusion and facilitated diffusion across cell membranes.
Simple diffusion: small molecules directly across the plasma membrane (e.g. water, oxygen, carbon dioxide)
Facilitated diffusion: molecules that pass through the membrane with the aid of a protein (channel or carrier).
What is osmosis?
The net movement of water from an area of low solute concentration to high solute concentration across a semi-permeable membrane.
Explain what would likely occur if cells were placed in a highly concentrated salt solution
Water would move by osmosis from a region of low solute concentration (high water concentration) in the cell to a region of high solute concentration (low water concentration) outside the cell, resulting in a decrease in cell size / mass.
Explain what would likely occur if cells were placed in a solution of pure water
Water would move by osmosis from a region of low solute concentration (high water concentration) outside the cell to a region of high solute concentration (low water concentration) inside the cell, resulting in an increase in cell size / mass.
Explain the key differences between passive transport and active transport.
Passive transport: does not require energy, molecules move with/down the concentration gradient (high concentration to low concentration)
Active transport: requires energy, molecule move against the concentration gradient (low concentration to high concentration).
Describe the process of endocytosis.
Particles approach extracellular membrane which invaginates around the substance, and pinches off forming an intracellular vesicle.
Describe the process of exocytosis. What types of molecules would use exocytosis to leave the cell?
Large molecules (such as a protein) is packaged into a vesicle at the Golgi body. Vesicle approaches cell membrane, fuses with membrane and expels contents into the extracellular environment.
