1.
2 kinds of channels: aquaporins and gated channels
2.
3 abundant ingredients in membranes: lipids, proteins, carbohydrates
3.
amphipathic molecule: have both hydrophobic and hydrophilic regions
Ex: Phospholipids
4.
aquaporins: water channel proteins that facilitate massive amounts of diffusion
5.
attachment to the cytoskeleton and extracellular matrix as a function of membrane proteins: microfilaments or other elements of the cytoskeleton may be bonded to membrane proteins, a function that helps maintian cell shape and fixes the location of certain membrane proteins. Proteins that adhere to the ECM can coordinate extracellular and intracellular changes
6.
cell-cell recognition as a function of membrane proteins: some glycoproteins serve as identification tags that are specifically recognized by other cells
7.
describe integral proteins.: They penetrate the hydrophobic core of the lipid bilayer. Many are transmembrane proteins. The hydrophobic regions of an integral protien consist of one or more stretches of nonpolar amino acids usuallay coiled in (fish) helix. The hydrophillic parts of the molecule are exposed to the aqueous solutions on either side of the membrane.
8.
describe peripheral proteins: they are not embedded in the lipid bilayer at all, they are appendages loosely bound to the surface of a the membrane, often to the exposed parts of the integral proteins
9.
do membranes have disinct insides and outside faces?: yes. Carbohydrates are the only on the outside. The assymetrical distribution of proteins, lipids and carbohydrates is determined as the membrane is being built by the ER.
10.
enzymatic activity as a function of membrane proteins: a protein built into the membrane may be an enzyme with its active site exposed to the substances in the adjacent solution. In some cases, several enzymes in a membrane are ordered as a team that carries out sequential steps of a metabolic pathway
11.
flaccid: limp cells due to lack of water
12.
Fluid Mosaic Model: a model for structure of a membrane, a fluid structure with various proteins embedded in or attached to the phospholipid bilayer
13.
gated channels: stimulus causes them to open or close
14.
how are membranes affected by a decrease in temperature?: they remain fluid untin the phospholipids settle into closely packaged arrangements and the membrane solidifies.
15.
how do cells with wall balance their water uptake/loss: needs to be turgid, can survive flaccid but will usually die in plasmolysis
16.
how do hydrophilic substances cross the membrane: hydrophilic substances avoid the lipid bilayer by passing through transport proteins that span the membrane
17.
how do substances tend to diffuse?: substances will diffuse from where it is more concentrated to where it is less concentrated (diffuses down its concentration gradient)
18.
how does cell-cell recognition work?: cells recognize other cells by keying on surface molecules, often carbohydrates on the plasma membrane
19.
how does water move?: from hypertonic to hypotonic, if the substance is isotonic, water moves across the membrane at an equal rate in both directions
20.
how does water relate to cell survival?: cell survival depends on the balancing water uptake nd loss
21.
how is the temperature at which a membrane solidifies: the types of lipids that the membrane is made of determine the temperature at which it solidifies.
22.
how to cell without walls balance their water uptake/loss?: the cells are stable in isotonic environments, but they cannot tolerate excessive loss or gain of water, cells that live in hyper or hypotonic solutions use osmoregulation which controls the water balance within the cell
23.
in what way are cell membranes permeable?: The membrane's molecular organization results in its selective permeability
24.
intracellular joining as a function of membrane proteins: membrane proteins of adjacent cells may be hooked together in various kinds of junctions
25.
is a substance's concentration differences affected by the concentration differences of other substances?: no
26.
membrane structure: membranes are fluid and held together primarily by hydrophobic interactions
27.
phagocytosis: cell engulfs a particle by wrapping it in a sac which is digested by a lysosome
28.
pinocytosis: cell gulps droplets of extracellular fluids into tiny vessicles
29.
plasmolysis: when a plant shrivels, it's plasma membrane pulls away from the wall, usually fatal
30.
receptor-mediated endocytosis: very specific, extracellular substances bind to receptors on molecule (ligands)
31.
signal transduction as a function of membrane proteins: a membrane protein may have a binding site with a specific shapre that fits the shape of a chemical messenger such as a hormone. The external messenger signal may cause a conformational change in the protein that relays the message inside the cell
32.
the three types of endocystosis: phagocytosis, pinocytosis, receptor-mediated endocytosis
33.
transport as a function of membrane proteins: a protein that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute; some transport proteins hydrolyze ATP as an energy source to actively pump substances across the membrane
34.
turgid: when the cell is very firm because water is pressing on the cell wall, healthy for most plants
35.
what are some features that transport proteins share in common with enzymes?: -specialized for the solute it transports
-can be saturated
-has a maximum transport rate
-can be inhibited by imposter molecules
36.
what are some functions of membrane proteins?: tranport, enzymatic activity, signal transduction, intercellular joing, cell-cell recognition, attachment to the cytoskeleton and extracellular matrix
37.
what are the two major populations of membrane proteins?: integral proteins and peripheral proteins
38.
what are the two ways that transport proteins move molecules?: some have a hydrophilic channel used as a tunnel while other hold on to their passenger and physically move them across the membrane
39.
what determines a membrane's specific function?: the proteins embedded in it
40.
what do transport proteins not do that enzymes do?: they do not catalyze reactions
41.
what happens to the permeability of the membrane once it has solidified: it changes
42.
what is a hypertonic solution?: higher concentration of solute
43.
what is a hypotonic solution?: lower solute concentration
44.
what is a isotonic solution?: equal solute concentration
45.
what is a proton pump?: the main electrogenic pump of plants, bacteria, fungi; actively transports hydrogen ions out of the cell which transfers positive charge from the cytoplasm to the extracellular solution
46.
what is active transport?: the pumping of solutes against their gradient, requires work-energy often supplied by ATP, allows cells to maintain small concentrations of small molecules
47.
what is an electrochemical pump?: a transport proteins that generate voltage across a membrane
48.
What is cell-cell recognition?: a cell's ability to distinguish one type of neighboring cell from another
49.
what is cotransport?: when a single ATP powered pump that transports a specific solute can indirectly drive the active transport of several other solutes
50.
what is diffusion?: -the result of thermal motion (intrinsic kinetic energy of molecules)
-the tendency for molecules of any substance to spread out into the available space
51.
what is endcytosis?: when the cell takes in macromolecules and particulate matter by forming new vesicles from the plasma membrane
52.
what is exocytosis?: when a cell secretes macromolecules by the fusion of veciscles with the plasma membrane
53.
what is facilitated diffusion?: when hydrophilic substances are transported across a membrane by a protein
54.
what is membrane potential?: voltage across a membrane, affects ion movement, -50 to -200 milivolts
55.
what is osmosis?: the passive transport of water
56.
what is passive transport?: diffusion across a membrane, called passive because it doesn't have to expend energy
57.
what is the charge of the cytoplasm?: negative
58.
what is the electrochemical gradient?: the chemical force and electrical force that affect ion movement
59.
what is the sodium potassium pump?: exchanges sodium for potassium across a plasma membrane
60.
what is voltage?: electrical potential energy, separation of opposite charges
61.
what kind of carbohydrates are typically found on the membrane and used in cell-cell recognition: oligosaccarides:
-some are bonded with lipids: glycolipids
-some bonded with proteins: glycoproteins
they vary from cell to cell, but function as markers to distinguish cells
62.
What purposes dooes cell-cell recognition serve?: its crucial for sorting cells, rejection of foreing cells
63.
which cells have voltage across their membranes?: all cells
64.
which kind of lipids freeze at lower temperatures?: the membrane remains fluid to a lower temperature if it is rich in phospholipids with insaturated carbon tails because they do not pack as well as saturated carbon tails
65.
which kind of molecules cross the membrane with difficulty/cannot cross the membrane: the hydrophobic core if the membrane impedes the transport of ions and polar molecules which are hydrophilic
66.
which kind of molecules cross the membrane with ease?: hydrophobic: hydrocarbons, carbon dioxide, oxygen
