Biochemistry Chapter 8: Biological Membranes Flashcards
(28 cards)
Fluid mosaic model
Accounts for the presence of lipids, proteins, and carbohydrates in a dynamic, semisolid plasma membrane that surrounds cells.
lipid rafts
assemblies of lipids that move freely in the plane of the membrane
flippases
specific membrane proteins that maintain the bidirectional transport of lipids between the layers of the phospholipid bilayer in cells.
Triacylglycerols and free fatty acids
phospholipid precursors and are found in low levels in the membrane
glycerophospholipids
replace one fatty acid with a phosphate molecule which is often linked to other hydrophilic groups
cholesterol
present in large amounts and contributes to the membrane fluidity and stability
Waxes
present in very small amounts, if at all; they are most prevalent in plants and function in waterproofing and defense.
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
can form a protective glycoprotein coat and also function in cell recognition.
Gap junctions
allow for the rapid exchange of ions and other small molecules between adjacent cells.
Tight junctions
prevent paracellular transport, but do not provide intercellular transport
Desmosomes and hemidesmosomes
anchor layers of epithelial tissue
Concentration gradients
Help to determine appropriate membrane transport mechanisms in cells
Osmotic pressure
the pressure applied to a pure solvent to prevent osmosis and is used to express the concentration of the solution
Passive transport
does not require energy because the molecule is moving down its concentration gradient or from an area with higher concentration to an area with lower concentration
osmosis
describes the diffusion of water across a selectively permeable membrane
Facilitated diffusion
uses transport proteins to move impermeable solutes across the membrane.
Active transport
requires energy in the form of ATP or an existing favorable ion gradient
- Can be primary or secondary
Symport
both molecules flow in the same direction across the membrane
Antiport
Molecules flow in opposite direction across the membrane
Primary active transport
directly transports molecules across a membrane.
Secondary active transport
aka coupled transport
uses energy to transport molecules across the membrane w/o direct coupling to ATP. Instead it uses energy from one particle going down concentration to another going up.
