Chapter 8 Review Cell & Molecular

Describe the movements of O2, CO2, glucose, H2O, H2CO3- , Cl- , Na+ and K+ across the plasma membrane of a red blood cell.

1)Capillaries of body tissue/Carbonic anhydrase. (O2, CO2, HCO3-, Cl-) 2)osmosis (H2O) 3) Facilitated Diffusion of Glucose by Glucose Transporter GLUT1 4)Na+/K+ Pump

Na+/glucose symporter

Example of indirect active transport; a membrane transport protein that simultaneously transport glucose and sodium ions into cells, with the movement of sodium ions down their electrochemical gradient driving the transport of glucose against its concentration gradient.

Beta-barrel

Has a water-filled pore at its center.

CF transmembrane conductance regulator (CFTR)

Is an ion channel; and unlike most of the ABC-type ATPases, it does not use ATP to drive transport. Instead, ATP hydrolysis appears to be involved in opening the channel.

• Describe the function of the CFTR protein.

Is an ion channel; and unlike most of the ABC-type ATPases, it does not use ATP to drive transport. Instead, ATP hydrolysis appears to be involved in opening the channel.

Glucose transporter (GLUT)

Membrane carrier protein responsible for the facilitated diffusion of glucose.

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

osmosis

Movement of water through a semipermeable membrane driven by a difference in solute concentration on the two sides of the membrane.

counter- ions

Oppositely charged ion within a solution for any given ion.

plasmolysis

Outward movement of water that causes the plasma membrane to pull away from the cell wall in cells that have been exposed to a hypertonic solution.

• What is the difference between porin and aquaporin?

Porins- transmembrane protein that forms pores for the facilitated diffusion of small hydrophilic molecules; found in the outer membranes of mitochondria, chloroplasts, and many bacteria. AQP-Any of a family of membrane channel proteins that facilitate the rapid movement of water molecules into or out of cells in tissues that require this capability, such as the proximal tubules of the kidneys.

turgor pressure

Pressure that builds up in a cell due to the inward movement of water that occurs because of a higher solute concentration inside the cell than outside; accounts for the firmness, or turgidity, of fully hydrated cells or tissues of plants and other organisms.

secretion

Production and release of a substance from a cell

• Compare and contrast: simple diffusion, facilitated diffusion, and active transport.

Simple diffusion- Diffusion that doesn't involve a direct input of energy or assistance by carrier proteins. (Shared FD)-Down electrochemical gradient -small polar mol (H2O, Glycerol) (Difference) -small nonpolar mol (O2, CO2) -large nonpolar (oils, steroids) Facilitated diffusion-Movement of specific molecules across cell membranes through protein channels. Kinetic properties required. (membrane protein required, saturation kinetics and Competitive inhibitions) (Shared AT)-Large polar (glucose) -Ions (Na+, K+, Ca2+) Active transport- The uphill transport of large polar molecules and ions . Requires a protein transporter and an input of energy. It may be powered by ATP hydrolysis, the electrochemical potential of an ion gradient, or light energy. Thermodynamic properties required & Kinetic properties required.

"Down" the concentration gradient

Simple or facilitated diffusion of a molecule involves exergonic movement "down" the concentration gradient (negative Delta G)

The three main factors affecting diffusion of solutes

Size, polarity, and charge

osmolarity

Solute concentration on one side of a membrane relative to that on the other side of the membrane; drives the osmotic movement of water across the membrane.

active transport

The uphill transport of large polar molecules and ions . Requires a protein transporter and an input of energy. It may be powered by ATP hydrolysis, the electrochemical potential of an ion gradient, or light energy. Active transport powered by ATP utilizes four major classes of transport proteins; P-type, V-type, F-type, and ABC-type ATPases. Example: the ATP -powered Na+/K+ pump (a P-type ATPase), which maintains electrochemical potentials for sodium and potassium ions across the plasma membrane of animal cells. Active transport driven by an electrochemical potential usually depends on a gradient of either sodium ions or protons. Example: The inward transport of nutrients across the plasma membrane is often driven by the symport of sodium ions that were pumped outward by the Na+/K+ pump . As they flow back into the cell, they drive inward transport of sugars, amino acids, and other organic molecules. Active transport powered by light energy. Ex: Halobacterium photons absorbed by bacteriorhodospin.

uniporter

Uniport: membrane protein that transports a single kind of molecule or iron from one side of a membrane to the the other.

concentration gradient

What determines the movement of a molecule across the membrane that has no net charge

coupled transport

When two solutes are transported simultaneously and their transport is coupled such that transport of either stops if the other is absent.

ATP synthase

alternative name for an F-type ATPase when it catalyzes the reverse process in which the exergonic flow of protons down their electrochemical gradient is used to drive ATP synthesis; Examples: CFoCF complex found in chloroplast thylakoid membranes and the FoF! complex found in mitochondrial inner membranes and bacterial plasma membranes.

multidrug resistance (MDR) transport protein

an ABC-type ATPase that uses the energy of ATP hydrolysis to pump hydrophobic drugs out of cells.

carbonic anhydrase

an enzyme that catalyzes the interconversion of dissolved bicarbonates and carbon dioxide.

anion exchange protein

antiport carrier protein that facilitates the reciprocal exchange of chloride and bicarbonate ions across the plasma membrane membrane.

chloride-bicarbonate exchanger

facilitates the reciprocal exchange of chloride (Cl-) and bicarbonate (HCO3-) ions in opposite directions across the plasma membrane.

directionality

having two ends that are chemically different from each other; used to describe a polymer chain such as a protein, nucleic acid, or carbohydrate; also used to describe membrane transport systems that selectively transport solutes across a membrane in one direction.

Na+/K+ ATPnase (pump)

membrane carrier protein that couples ATP hydrolysis to the inward transport of potassium ions and the outward transport of sodium ions to maintain the NA+ and K+ gradients that exist across the plasmas membrane of most animal cells. An alloseteric protein exhibiting two alternative conformational states referred to as E1 & E2.

ion channels

membrane protein that allows the passage of specific ions through the membrane; generally regulated by etiher changes in the membrane potential or binding of a specific ligand (lignand-gated channels)

channel protein

membrane protein that forms a hydrophilic channel through which solutes can pass across the membrane without any change in the conformation of the channel protein.

carrier protein

membrane protein that transport solutes cross the membrane by binding to the solute on one side of the membrane and then undergoing a conformational change that transfers the solute to the other side of the membrane.

transport proteins

membrane proteins that help move substances across a cell membrane. Includes both carrier proteins and channel proteins.

direct active transport

membrane transport in which the movement of solute molecules or ions across a membrane is coupled directly to an exergonic chemical reaction, most commonly the hydrolysis of ATP.

indirect active transport

membrane transport involving the cotransport of two solutes in which the movement of one solute down its gradient drives the movement of the other solute up its gradient..

alternating conformation model

membrane transport model in which a carrier protein alternates between two conformational states, such that the solute-binding site of the protein is open or accessible first to one side of the membrane and then to the other.

membrane transport

movement of substances into and out of the cell

ATPase pumps

proteins driven directly by ATP hydrolysis

electrochemical potential

transmembrane gradient of an ion, with both an electrical component due to the charge separation quantified by the membrane potential and a concentration component; also called electrochemical gradient.

porins

transmembrane protein that forms pores for the facilitated diffusion of small hydrophilic molecules; found in the outer membranes of mitochondria, chloroplasts, and many bacteria.

antiporter

transporter that carries two ions or small molecules in opposite directions

ABC-type ATPases/ ABC transporters

type of transport ATPase characterized by an "ATP-binding cassette", with the term cassette used to describe catalytic domains of the protein that binds ATP as an intergral part of the transport process.

membran potential (Vm)

voltage across a membrane created by ion gradients usually the inside of a cell is negatively charged with respect to the outside.

"Up" the concentration gradient

Active transport involves endergonic movement "up" the concentration gradient (positive Delta G) and requires some driving force.

aquaporins (AQPs)

Any of a family of membrane channel proteins that facilitate the rapid movement of water molecules into or out of cells in tissues that require this capability, such as the proximal tubules of the kidneys.

symporter

Both solutes move jin the same direction.

simple diffusion

Diffusion that doesn't involve a direct input of energy or assistance by carrier proteins.

bacteriorhodopsin

Transmembrane protein complexed with rhodosin, capable of transporting protons across the bacterial cell membrane to create a light-dependent electrochemical proton gradient.