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
...
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