BIOCHEM Chp.8 Membrane Flashcards
How do phospholipids move through the membrane?
they move easily through simple diffusion
What is a lipd raft?
a collection of similar lipids with or without associated proteins that serve as attachment points for other biomolecules and play a role in biosignaling
What are flippases?
enzymes that assist in the flip of phospholipids b/w the layers of the cell membrane
What are the components of the membrane?
lipids, glycoproteins carbs, and nucleic acids
What are Fatty Acids?
Carboxylic acids that contain a hydrocarbon chain and terminal carboxyl group
What are triacylglycerols?
storage lipid proteins that contain 3 FA chains esterified to a glycerol molecule
What is an unsaturated FA?
healthier fats because they have one or more double bonds and exist in lipid form at room temp. in the membrane, it imparts fluidity
What is a saturated FA?
animal fat that exits as solid at room temp. in the membrane, they decrease overall fluidity
What is the role of glycerophospholipid?
they can produce a hydrophilic surface layer on very-low-density lipoproteins
they serve a structural role in the membrane and second messengers in single transduction
provide an attachment point for water-soluble groups such as choline and inositol
What is the structure of sphingolipids?
a hydrophilic region and 2 Fatty acid-derived hydrophobic tails
What are some examples of sphingolipids?
ceramide, sphingomyelins, cerebrosides and gangliosides
What is the role of cholesterol?
regulation of membrane fluidity and the synthesis of steroids
How does cholesterol regulate membrane fluidity?
at lower temperatures, cholesterol prevents the formation of crystal structures in the membrane, increasing fluidity. At high temperatures, cholesterol limits the movement of phospholipids within the bilayer and decreases fluidity to help hold the membrane intact
What are waxes?
a class of lipids that is extremely hydrophobic. it is composed of a long-chain FA and a long-chain alcohol which contributes to its high melting point
What is the diff b/w transmembrane and embedded proteins?
transmembrane proteins pass completely through the lipid bilayer whereas embedded proteins are associated with only the interior (cytoplasmic) or extracellular surface of the membrane
What proteins make up the integral membrane proteins?
transmembrane and embedded proteins
How are membrane-associated/peripheral proteins bound to the membrane?
through electrostatic interactions with the lipid layer especially at lipid rafts or with coupled receptors
What are examples of membrane receptors?
ligand-gate channels, G protein-coupled receptors
What are CAMS?
cell adhesion molecules are proteins that allow cells to recognize each other and contribute to proper cell differentiation and development
What are gap junctions/connexins?
connexins are formed by the alignment and interactions of pores composed of six molecules of connexin
What is the role of gap junctions/connexins?
they permit rapid movement of water and some solutes directly between cells and do not prevent paracellular transport of materials
What is the role of tight junctions?
they prevent solutes from leaking into the space b/w cells via a paracellular route
Where are tight junctions found?
in epithelial cells and functions as a physical link b/w cells as they form a single layer of tissue
What is the purpose of desmosomes?
they bind adjacent cells by anchoring their cytoskeleton
Where are desmosomes found?
at the interface b/w 2 layers of epithelial tissue
How are desmosomes formed?
by interactions b/w transmembrane proteins associated with intermediate filaments inside adjacent cells
What is the function of hemidesmosomes?
to attach epithelial cells to underlying structures, especially the basement membrane
What is passive transport?
passive transport doesn’t require energy (change is G is neg), because particles are moving down its concertation gradient from areas of high to low concentrations, and the primary thermodynamic motivator is an increase in entropy (change in S)
What is active transport?
active transport requires energy (change is G is pos), and the primary thermodynamic motivator is an increase in enthalpy (change in H)/heat, solutes are moved against its concentration gradient
What are examples of passive transport?
simple and facilitated diffusion, osmosis
What is simple diffusion?
the movement of substrates down their CG directly across the membrane. only particles that are permeable to the membrane can undergo simple diffusion
What is osmosis?
the simple diffusion of water from high water (low solutes) to low water (high solute) concentration
When is a hypotonic state created?
when solutes inside the cell are higher than the surrounding solution
What happens in a hypotonic solution?
water rushes in and the cells swell sometimes to the point of lysing/bursting
When is a hypertonic state created?
when the solution is more concentrated than the cell
What happens in a hypertonic solution?
water rushes out of the cells swell
When is an isotonic state created?
when the next movement of water inside and outside of the cell are equimolar
What are examples of colligative property?
osmotic pressure (dependent on the concentration of the dissolved particles), vapor pressure depression (Raoult’s law), BP elevation, and freezing point depression
What is the equation for osmotic pressure?
II = i MRT
M is the molarity of the solution, R is the ideal gas constant, T is the absolute temp in kelvins, i is van’t Hoff Factor which is the number of particles obtained from the molecule when in solution
What is the relationship b/w osmotic pressure and molarity of a solution?
it is directly proportional
What is facilitated diffusion?
the movement of molecules (large, polar, charged) that are impermeable to the membrane through integral membrane proteins or channels
What is the difference b/w channels and carriers?
carriers are only open to one side of the cell membrane at any given point. channels may be in an open or closed conformation, and when open, they are exposed to both sides of the cell membrane
What is the energy source of primary active transport?
ATP through the use of transmembrane ATPase. it is important in maintaining the membrane potential of neurons
What is the energy source of secondary active transport?
it harnesses the energy released by one particle going down its electrochemical gradient to drive a different particle up its gradient
What is the diff b/w symport, antiport secondary active transport?
symport - when both particles flow in the same direction across the membrane
antiport - when the particles flow in opposite directions
When does endocytosis occur?
when the cell membrane engulfs material to bring it into the cell
What is the diff b/w pino and phagocytosis?
pinocytosis is the endocytosis of fluids and dissolved particles, whereas phagocytosis is the ingestion of large solids such as bacteria
What are clathrins?
vesicles that carry out invagination
When does exocytosis occur?
when secretory vesicles fuse with the membrane, reading material from inside the cell to the extracellular environment
What is the membrane potential at resting and during depolarization?
resting: -40 to -80 mV
depolarization: +35 mV
What is the role of sodium-potassium ATPase?
to maintain a low concentration of sodium ions and a high concentration of potassium ions intracellular by pumping 3 sodium ions out for every 2 potassium ions pumped in
Where does the ETC take place?
in the cristae of the inner mitochondria
Where does the TCA occur?
in the mitochondrial matrix
What are the functions of transmembrane, embedded, and membrane-associated proteins?
transmembrane functions as receptors or channels
embedded proteins are involved in catalytic complex and cellular communication
membrane-associated act as recognition molecules or enzymes on the extracellular surface
How is membrane potential maintained?
through leak channels and the sodium-potassium pump
