Biology chapter 7

Aquapores

A channel protein in the plasma membrane that specifically facilitates osmosis, the diffusion of free water across a membrane

passive and active transport.

Active transport moves substances against their concentration gradient. Active transport requires energy, usually in the form of ATP. Active transport is performed by specific proteins embedded in the membranes. Active transport allows cells to maintain concentration gradients that differ from their surroundings. Passive transport move substances down the concentration gradient where not work must be done. The diffusion of a substance across a biological membrane is passive transport because it requires no energy from the cell to make it happen.

Explain how an electrogenic pump creates voltage across a membrane

By pumping electrons across the membrane leaving one side more positive and making one side more negative which results in a voltage charge

channel and carrier proteins.

Channel proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel. They provide corridors that allow a specific molecule or ion to cross the membrane. (Channel proteins include: Aquaporins, for facilitated diffusion of water. And Ion channels that open or close in response to a stimulus (gated channels)) Carrier proteins undergo a subtle change in shape that trans-locates the solute-binding site across the membrane. These proteins bind to molecules and change shape to shuttle them across the membrane. A transport protein is specific for the substance it moves.

Explain how large molecules are transported across a cell membrane

Into the cell by endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane. There are three types of endocytosis. In pinocytosis, molecules are taken up when extracellular fluid is "gulped" into tiny vesicles. In phagocytosis a cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle. In receptor-mediated endocytosis, binding of ligands to receptors triggers vesicle formation. A ligand is any molecule that binds specifically to a receptor site of another molecule. By leaving the cell is through exocytosis, transport vesicles migrate to the membrane, fuse with it, and release their contents to the outside of the cell.

hypertonic, hypotonic, and isotonic solutions

Isotonic: solutions have equal solute concentrations. Hypertonic: solution has a higher solute concentration than the other solution. Hypotonic: solution has a lower solute concentration than the other solution.

Explain how membrane fluidity is influenced by temperature and membrane composition

Membranes switch from a fluid sate to a solid state as temperature cools because the lipids became compressed by lower temperatures but the temperature required to switch it to a solid state would depend on the type of lipid. Unsaturated fatty acids are more fluid than saturated fatty acids because unsaturated fatty acids a have a kink in there lipid chain from a double bond with a hydrogen so do not compact easily in the membrane as the saturated fatty acids do because they have the full amount of hydrogen in there chains with just single bonds so there is not kink in the chain composition so they compact very closely and uniformly. Cholesterol is a steroid that effects these behaviors in membrane fluidity with temperature. In warm temperature it will restrain movement of lipids and in colder temperatures it maintains fluidity by preventing the lipids from packing tightly.

osmosis, simple diffusion, and facilitated diffusion

Osmosis is the diffusion of water across a selectively permeable membrane. Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration. Simple diffusion substances diffuse down their concentration gradient, the difference in concentration of a substance from one area to another. In facilitated diffusion, transport proteins speed the passive movement of molecules across the plasma membrane. Transport proteins are transmembrane proteins that allow passage of hydrophilic substances across the membrane.

peripheral and integral membrane proteins.

Peripheral proteins are bound to the surface of the membrane where they function as recognition sites and integral proteins penetrate the hydrophobic core of the membrane functioning as channel proteins

Name two electrogenic pumps

The sodium-potassium pump is the major electrogenic pump of animal cells. The main electrogenic pump of plants, fungi, and bacteria is a proton pump.

Explain how transport proteins facilitate diffusion

Transport proteins are transmembrane proteins that allow passage of hydrophilic substances across the membrane by use of channel proteins or carrier proteins which both move down the gradient. Or some transport proteins facilitate diffusion by active transport.

Ampiphathic molecules

have both fat loving and water loving characteristics.

Diffusion

the spontaneous movement of a substance down its concentration or electrochemical gradient from a region where it is more concentrated to a region it is less concentrated.