Plasma Membrane, Cell Transport, and Enzymes Flashcards
What is simple diffusion? Equilibrium?
-The movement of particles from an area of high concentration to an area of low concentration.
-Diffusion occurs until equilibrium is reached. (Movement in both directions is equal).
Is energy required for diffusion? Examples of diffusion transports.
-Energy is not required.
-Diffusion relies on the energy of molecular motion.
-The kinetic energy contained by the particles results in random molecular motion and molecular collisions, which results in diffusion.
-O2, CO2, lipid soluble molecules.
What is osmosis?
-Osmosis is the diffusion of water across a selectively permeable membrane.
-During osmosis water moves from an area of high water molecule concentration to an area of low water molecule concentration.
Is energy required for osmosis? How does water move by osmosis through the plasma membrane?
-Water can move through the nonpolar fatty acid tails of phospholipids in the phospholipid bilayer, because they’re loosely packed, and water is a small enough molecule.
-Water moves rapidly and in larger quantities through channel proteins called aquaporins. The channels within the protein are hydrophilic.
What is facilitated diffusion?
-Facilitated diffusion is the movement of particles from an area of high concentration to an area of low concentration.
Is energy required for facilitated diffusion? What particles are moved by facilitated diffusion?
-The use of specific protein carriers, which is a function of integral membrane proteins.
-The two types of transport proteins are carrier and channel proteins.
-Integral membrane proteins can either act as carrier or channel proteins.
How do carrier proteins transfer materials?
-They have a specifically shaped binding site that fits only a specifically shaped molecule.
-When the molecule attaches a subtle change occurs in the three-dimensional shape of the transport protein that allows the binding and release of the molecule.
-A carrier protein can move the molecule in either direction. The direction do transport depends on the concentration gradient.
How do channel proteins allow particles to move across?
-Channel proteins provide a pathway that allows specific particles to cross.
-Some channel proteins are gated and open when stimulated, allowing a specifically shaped molecules to cross. (Ex. calcium in nerve cells)
What is active transport?
-The movement of particles from an area of low concentration to an area of high concentration (against the concentration gradient).
Is energy required for active transport? What is active transports require the use of?
-Active transport is an active mechanism since energy is required.
-ATP powers active transport by transferring its terminal phosphate group directly to the transport/integral protein. This results in a change shape which allows the substance to be moved across.
-Active transport requires the use of specific protein carriers. This is a function of integral membrane proteins.
Does active transport achieve equilibrium? What does active transport move?
-Active transport does not achieve equilibrium.
-Active transport is commonly used to move ions (glucose and amino acids).
-Ex. Iodine ions into cells of thyroid glands. Sodium ions and potassium ions across the neuron plasma membrane.
What is endocytosis? What are the two forms of endocytosis?
-Endocytosis is the movement of large particles to inside of the cell through the formation of a vesicle or vacuole by the plasma membrane.
-Endocytosis is an active mechanism because energy is required.
-The two forms are phagocytosis and pinocytosis.
What is phagocytosis?
-It is used by a cell to engulf very large particles. (Ex. Bacteria, viruses, yeast cell)
-Extensions of the plasma membrane called pseudopods wrap around the particle and enclose it in a large vesicle or vacuole.
-Within the cell a lysosome will fuse with the vesicle, allowing hydrolytic enzymes to digest the particle.
What is pinocytosis?
-It is used by the cell to engulf moderately sized particles.
-Macromolecules including proteins and polysaccharides.
-The plasma membrane indents drawing the particle and a small amount of surrounding fluid into the small pocket which pinches off and forms a vesicle.
-Within the cell a lysosome will fuse with the vesicle, which allows hydrolytic enzymes to digest the particle.
-This is non specific because all dissolved solutes are taken in.
What is exocytosis?
-Exocytosis is the movement of large particles to the outside of the cell by the fusing of vesicle with the plasma membrane.
-It then becomes a vesicle membrane, which becomes part of the plasma membrane. The contents of the vesicle are released outside the cell.
-Exocytosis is an active mechanism because ATP is required. Particles released from the cell by exocytosis have often been packaged into secondary vesicles by the Golgi body.
-Ex. Insulin released by cells in the pancreas. Ovaries release estrogen.
