Chapter 3 Flashcards
Cells
Basic, living, structural, and functional units of the body.
What are the three main parts of a cell?
Plasma membrane, cytoplasm, and nucleus.
Plasma membrane
Form the cell’s flexible outer surface, separating the cell’s internal environment from the external environment. It is a selective barrier that regulates the flow of materials into and out of a cell. Plays a key role in communication among cells and between cells and their external environment.
Fluid mosaic model
Model used to describe plasma membrane. According to this model, the molecular arrangement of the plasma membrane resembles a continually moving sea of fluid lipids that contain a mosaic of many different proteins.
Lipid bilayer
The basic structural framework of the plasma membrane; two back-to-back layers made up of three types of lipid molecules.
What are the three types of lipids molecules that make up the lipid bilayer?
Phospholipids, cholesterol, and glycolipids.
Phospholipids
About 75% of the plasma membrane lipids; lipids that contain phosphorus.
Cholesterol
About 20% of the plasma membrane lipids; a steroid with an attached –OH (hydroxyl) group.
Glycolipids
About 5% of the plasma membrane lipids; lipids with attached carbohydrate group.
The bilayer arrangement occurs because the lipids are ______ molecules, meaning _______.
Amphipathic; they have both polar and nonpolar parts.
How are the phospholipids arranged in the bilayer arrangement?
The polar part of phospholipids is their phosphate containing “head” which is hydrophilic. The nonpolar part are the two fatty acid “tails”, which are hydrophobic. Because “like seeks like”, the phospholipid molecules arrange themselves in the bilayer with their hydrophilic heads facing outwards, towards the watery fluid on either side - cytosol or ECF. The hydrophobic tails in each half of the bilayer point toward one another.
Cholesterol molecules are ______ amphipathic.
Weakly.
What are the two types of membrane proteins?
Integral proteins and peripheral proteins.
Integral proteins
Membrane proteins that are firmly embedded in the membrane, and extend into or through the lipid bilayer. Integral proteins are amphipathic.
Transmembrane proteins
Membrane proteins that span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid. Most integral proteins are transmembrane proteins.
Glycoproteins
Membrane proteins with carbohydrate group attached to the ends that protrude into the extracellular fluid. Many integral proteins are glycoproteins.
Glycocalyx
Sugary coat formed by the carbohydrate portions of glycolipids and glycoproteins. The pattern of carbohydrates in the glycocalyx varies from one cell to another. Therefore, the glycocalyx acts like a molecular “signature” that enables cells to recognize one another. Eg. A white blood cells ability to detect a “foreign” glycocalyx is one basis of the immune response that helps us destroy invading organisms.
Peripheral proteins
Membrane proteins that are not firmly embedded in the membrane. They are attached to the polar heads of membrane lipids or to integral proteins at the membrane’s inner or outer surface.
What are the six membrane functions?
Ion channels, carriers, receptors, enzymes, linkers, cell identity markers.
Ion channels
Pores or holes that specific ions can flow through to get into or out of the cell. Most ion channels are selective, as they allow only a single type of ion to pass through.
Carriers
AKA transporters; selectively move a polar substance or an ion from one side of the membrane to the other.
Receptors
Serve as cellular recognition sites. Each type of receptor recognizes and binds a specific type of molecule. Eg. Insulin receptors bind to the hormone insulin.
A specific molecule that binds to a receptor is called a ______ of that receptor.
Ligand.
Enzymes
Catalyze specific chemical reactions at the inside or outside surface of the cell.