Biochemistry Ch 8. Biological Membranes Flashcards
Fluid mosaic model
Accounts for the presence of lipids, proteins, and carbohydrates in a dynamic, semisolid plasma membrane that surrounds cells
Phospholipid bilayer components
Lipids primary component both by mass and mole fraction, has proteins embedded in it, carbohydrates and extracellular ligands also present
Biological membranes movement
Not static, lipids move freely in the plane of the membrane and can assemble into lipid rafts, proteins and carbohydrates may also move within the membrane but are slowed by their relatively large size, flippases also cause movement
Lipid rafts
-
Flippases
Specific membrane proteins that maintain the bidirectional transport of lipids between the layers of of the phospholipid bilayer in cells
Triacylglycerols membrane
Acts as a phospholipid precursors, along with free fatty acids, and are found in low levels in the membrane
Free fatty acids membrane
Acts as a phospholipid precursors, along with triacylglycerols, and are found in low levels in the membrane
Glycerophospholipids membrane
Replace one fatty acid with a phosphate group, which is often linked to other hydrophilic groups
Cholesterol membrane
Present in large amounts and contributes to membrane fluidity and stability
Waxes membrane
Present in very small amounts, if at all, they are most prevalent in plants and function in waterproofing and defense
Proteins membrane
Located within the cell membrane and can act as transporters, cell adhesion molecules, and enzymes
Transmembrane proteins
Can have one or more hydrophobic domains and are most likely to function as receptors or channels
Embedded proteins
Most likely part of a catalytic complex or involved in cellular communication
Membrane associated proteins
May act as recognition molecules or enzymes
Carbohydrates membrane
Can form a protective glycoprotein coat and also function in cell recognition
Glycoprotein coat
Created by carbohydrates in biological membranes
Extracellular ligands membrane
Can bind to membrane receptors, which function as channels or enzymes in second messenger pathways
Cell cell junctions
Regulate transport intracellularly and intercellularly
Gap junctions
Allow for the rapid exchange of ions and other small molecules between adjacent cells
Tight junction
Precent paracellular transport, but do not provide intercellular transport
Paracellular transport
-
Desmosomes
Anchor layers of epithelial tissue together
Hemidesmosomes
Anchor layers of epithelial tissue together
Concentration gradients
Help to determine appropriate membrane transport mechanisms in cells
Osmotic pressure
A colligative property, the pressure applied to a pure solvent to prevent osmosis and is used to express the concentrations of the solution, conceptualized as a “sucking” pressure in which a solution in drawing water in, proportional to its concentration
Colligative property
-
Passive transport
Does not require energy because the molecules is moving down its concentration gradient or from an area with higher concentration to an area with lower concentration
Simple diffusion
Does not require a transporter, small, nonpolar molecules passively move from an area of high concentration to an area of low concentration until equilibrium is achieved
Osmosis
Describes the diffusion of water across a selectively permeable membrane
Facilitated diffusion
Uses transport proteins to move impermeable solutes across the cell membrane
Active transport
Requires energy in the form of ATP or an existing favorable ion gradient, may be primary or secondary depending on the energy source
Secondary active transport
Classified as either symport or antiport
Endocytosis
Method of engulfing material into cells
Exocytosis
Method of releasing material to the exterior or cells
Pinocytosis
Ingestion of liquid into the cell in vesicles form from the cell memebrane
Phagocytosis
Ingestion of larger, solid molecules
Membrane potential
Maintain by the sodium-potassium pump and leak channels
Nernst equation
Calculates the electrical potential created by one ion
Goldman-Hodgkin-Katz voltage equation
Calculates the resting potential of a membrane at physiological temperature, is derived from the Nernst equation
Outer mitochondrial membrane
Different from the cell membrane, highly permeable to metabolic molecules and small proteins
Inner mitochondrial membrane
Different from the cell membrane, surrounds the mitochondrial matrix where the citric acid cycle produces electrons used in the electron transport chain and where many other enzymes important in cellular respiration are location, does not contain cholesterol
