B2 - Cells Flashcards
What is the phospholipid bilayer?
The phospholipid bilayer is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells.
What is an aqueous solution?
An aqueous solution is a solution in which the solvent is water.
What is the cell membrane?
Also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment. The cell membrane consists of a lipid bilayer that is semipermeable.
What is the core of the membrane?
Biological membranes usually involve two layers of phospholipids with their tails pointing inward, an arrangement called a phospholipid bilayer. Cholesterol, another lipid composed of four fused carbon rings, is found alongside phospholipids in the core of the membrane.
What is the freeze fracture electron?
It consists of physically breaking apart (fracturing) a frozen biological sample; structural detail exposed by the fracture plane is then visualized by vacuum-deposition of platinum-carbon to make a replica for examination in the transmission electron microscope.
What is a solute and solvent?
The solvent is the material that usually decides the solution’s physical state (solid, liquid or gas). The solute is the product that the solvent dissolves. A solution of salt and water, for example, has water as the solvent and salt as the solute.
What is permeability?
Many words semi-permeable, permeable, high permeability, low permeability. Passing through a barrier with ease (High permeability/Low permeability depends on size and polarity). Small non-polar molecules have a high permeability.
What is the concentration gradient?
Water likes to move down its concentration gradient (high to low).
What is simple diffusion (passive)?
Successfully moves between barrier or membrane from an area of high concentration to an area of low concentration without using any energy and no other structures are involved like a channel or pump. Two substances that do this are oxygen and carbon dioxide, both small and non-polar.
What is a integral protein?
They’re embedded into one or both (transmembrane protein) the phospholipid layers of the membrane. Integral proteins have at least one part that is hydrophobic that interacts with the non-polar cellular core.
What is a peripheral protein?
They’re attached to the surface of the bilayer. These proteins are hydrophilic and their properties are repelled by the cell membrane core and can not sit within the phospholipid bilayer. They are attached to the hydrophilic head and can bind with the integral proteins.
What is the aquaporin?
They’re integral protein channels that allow water to move across the cell membrane at a faster rate. Water, although polar, can move in and out of the cell membrane through simple diffusion or through the aquaporin depending on what is dissolved in the water.
What is facilitated diffusion?
Passive movement of substances across the cell membrane through a protein channel, which is an integral trans protein membrane. This is facilitated because the proteins need help to pass across the cell membrane. This is a passive movement (no energy) that also uses a concentration gradient. Some things cannot move directly through the cell membrane bilayer but with the help of some specific transmembrane proteins it is possible for polar molecules and ions to move through. These channels usually only allow one substance through the channel and often have an open and closed state. Examples: aquaporin and calcium channels.
What is osmosis?
Due to the difference in the concentration of substances dissolved in water (solutes).
What is active diffusion:
Exact opposite of simple and facilitated diffusion. Energy in the form of ATP is used to move materials across the cell membrane against their concentration gradient. Low concentration to a high concentration. This requires energy. Integral protein called pump proteins: moves from a low concentration to a high concentration but only moves in one direction. Example: Sodium potassium pump: Build a concentration gradient on either side of the membrane. The pump works to move sodium to the exterior and potassium to the interior of the cell. It starts with 3 sodium ions attached to the protein which stimulates the hydrolysis of ATP. It uses this energy to alter its shape and release the sodium ions to the outside of the cell, while still in the shape two potassium ions enter the cell and bind to the structure releasing the potassium to the inside of the cell so that the process can start again.
