chapter 7 bio

Distinguish between peripheral and integral membrane proteins

Peripheral: Provides the framework for the plasma membrane and is attached to integral protein; loosley bound to surface of protein Integral: Go through the membrane with two hydrophilic ends; embedded in protein

describe the fluidity of the components of a cell membrane and explain how membrane fluidity is influenced by temperature and membrane composition

Phospholipids can move within the bilayer but most of the lipids and proteins drift laterally. Flip flopping doesn't happen very often. Membrane molecules are held in place by weak hydrophobic interactions When temperatures are cool, the fluid state goes to a solid one as the phospholipids pack more tightly.

integral protein

penetrate the hydrophobic core of the lipid bilayer; many are transmembrane proteins which span the membrane others only extend partway into the hydrophobic core ACTUALLY EMBEDDED IN THE BILAYER

osmosis

water diffuses across the membrane from the region of lower solute concentration to that of higher solute concentration until both sides are equal

hypotonic-animal

water enters cell faster then it leaves and the cell swells and lyses

plasmolysis

when plant cell is in hypertonic enviroment the plasma membrane pulls away from the wall which causes the plant to wilt and die

peripheral protein

not embedded in bilayer; instead they are loosley bound to the surface of the membrane

glycolipids

a membrane carb covalently bonded to lipid; involved in cell attachment and the recognition of other cells

IONS PASSIVE TRANSPORT DOWN..

their electrochemical gradient

explain how hydrophobic molecules cross cell membranes

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list six major functions of membrane proteins

1. Transport 2. Enzymatic activity 3. Cell-cell recognition 4. Intercellular joining 5. Signal transduction 6. Attachment to the cytoskeleton and extracellular matrix

three types of endocytosis

1. phagocytosis 2. pinocytosis 3. receptor-mediated endocytosis

sodium potassium pump

A pump that actively maintains the gradient of sodium ions (Na+) and potassium ions (K+) across the plasma membrane of animal cells . K+ concentration is low outside animal cell and high inside the cell. Na+ concentration is high outside an animal cell and low inside the cell. Maintains these concentration gradients using the energy of one ATP to pump three Na+ out and two K+ in.

pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

explain how cholesterole resists changes in membrane fluidity with temperature change

At high temperatures, cholestrol restrains the movement of phospholipids and reduces fluidity but, at lower temperatures, it breaks up regular packing arrangements and increases fluidity

hypertonic

Having a higher concentration of solute than another solution; if a lake becomes hypertonic to animals cells, the cells might shrivel and die

hypotonic

Having a lower concentration of solute than another solution

endocytosis

Cellular uptake of biological molecules and particulate matter via formation of new vesicles from the plasma membrane

transport protein

Facilitate movement of hydrophilic substances through the lipid bilayer ex: channel protein has a hydrophilic channel that molecules can pass thru CHANNEL PROTEIN EX: AQUAPORIN

exocytosis

Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane. EX: neurone uses exocytosis to realease neurotransmitters that signal other neurons or muscle cells

isotonic-plant

no tendency for water to enter and cells become flaccid (limp)

passive transport

Requires NO energy, Movement of molecules from high to low concentration, Moves with the concentration gradient

explain the role of membrane carbohydrates in cell-cell recongnition

The ability of a cell to distinguish other cells based on recognition of membrane carbohydrates. The glycolipids and glycoproteins attached to the outside of plasma membranes varies.

membrane potential

acts like a battery an enegy source that affects the traffic of all charged substances; b/c the inside of the cell is neg compared with the outside the membrane potential favors passive tansport of cations into the cell and anions out of the cell

phagocytosis

a cell engulfs a particle by wrapping pseudopodia around it and packaging it within the membrane enclosed sac that can be large enough to be a cavuole. THe particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes

cotransport

a single ATP powered, a single ATP powered pump that transports one solute can indirectly drive the active transport of several other solutes in this mechanism as the solute that has been actively transported diffuses back passively through a transport protein its movement can be coupled with the active transport of another substance against its concentration gradient ??

electrogenic pump

a transport protein that generates voltage across a membrane; sodium potassium pump is the major electrogenic pump for animal

tonicity

ability of a solution to cause a cell to gain or lose water

proton pump

activley transports hydrogen ions (protons) out of cell; main electrongenic pump of plants

channel protein

allows water molecules or small ions to flow very quickly; aquaporins, ion channels

explain why phospholipids are amphipathic molecules

amphipathic means the phospholipid is not just hydrophobic or hydrophillic; instead, the phospholipid possess both characteristics. The "head" portion of the phospholipid is hydrophillic and faces outward with two hydrophobic tails that face inward

why only carrier proteins in active transport?

b/c when channel proteins are open they allow solutes to flow down their concentration gradients rather than picking them up and transporting them across their gradient

amphipathic molecule

both a hydrophilic region and hydrophobic region

hypertonic-animal

cell looses water to its enviornment and shrivels

ion channels

function as gated chanels; open and close in response to a stimulus

facilitated diffusion

how polar molecules and ions diffuse passively w/help of transport proteins EITHER: channel protein or carrier protein

rule of diffusion

in the absense of other forces, a substance will diffuse from where it is more concentrated to where it is less concentrated

flaccid

limp

hypertonic-plant

loses water to its surrondings and shrivels; as the plant cell shrivels the plasma membrane pulls away from the wall (plasmolysis)

glycoprotein

membrane carb covalently bonded to a protein; acts as a recognition site for hormones and neurotransmitters. Also allows cells to attach to one another to form tissues and recognize other cells

active transport

pumps solute across membrane against concentration gradient; requires energy; enables a cell to maintain internal concentration of small solutes that differ from concentrations in the enviorment EX: an animal cell has a higher concentration of potassium ions and lower sodium ions. The plasma membrane helps maintain these steep gradients by pumping sodium out of cell and potassium in THE TRANSPORT PROTEINS: ONLY CARRIER PROTEINS

isotonic-animal

stable; no net movement of water across the plasma membrane; water flows but at the same rate

carrier proteins

such as glucose transporter, undergo subtle change in shape that tasnlocates the solute bidning site across the membrane

electrochemical gradient

the combination of the two forces driving the diffusion of ions across a membrane: chemical force (ions concentration gradient) and the electrical force (the effect of the membrane potential on the ions movement)

fluid mosic model

the membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a bi-layer of phospholipids; helps explain how membranes regulate the cells molecular traffic

diffusion

the movement of molecules of any substance so that they spread out evenly into the avaliable space; needs no input of energy

selective permeability

the plasma membrane allows some substances to cross more easily than the others; nonpolar molecule (hydrophobic) pass through easily while ions and polar (hydrophilic) molecules can not

concentration gradient

the region along which the density of a chemical substance decreases

hypotonic- plant

turgid (firm; normal); uptake of the water is eventually balanced by the wall pushing back on the cell

turgid

very firm