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Cell Membranes (CH.5)


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asymmetriscally distributed
membrane proteins
1 protein for every 25 phospholipid molecules - this ratio is variable
membrane proteins
inner mitochondrial membrane has __ protein(s) for every __ lipids
1, 15
myelin (coated nerve cells) have approx. ___ protein(s) for every ___ lipids
Many proteins have both ___ and ____ regions
polar, nonpolar
membrane proteins have both _____ and ______ R groups in their amino acid
hydrophilic, hydrophobic
for many protein molecules & lipid molecules, bonding is not_______
both protein molecules and lipid molecules are free to move around laterally
fluid mosaic model
2 kinds of membrane proteins
Integral & peripheral
have long hydrophobic amino acid areas
Integral membrane proteins
penetrate/ entirely cross the bilayer
Integral membrane proteins
form an alpha-helix region, interact w/ only the membrane core
Integral membrane proteins
hydrophilic R groups face the aqueous areas & interact w/ them
Integral membrane proteins
proteins that go completely through the membrane (hydrophobic)
transmembrane proteins
have a specific orientation - one side shaped such that it can act as a receptor for a signaling molecule
transmembrane proteins
the other side changes in response to the signal binding
transmembrane proteins
can't go entirely inside (do not penetrate the bilayer at all)
peripheral membrane proteins
some proteins can move around in the membrane while other membrane proteins are restricted in movement due to anchoring part of cytoskeleton. that causes ____
an unequal distribution of these proteins
some cells are speciallized to be anchored to the ___
extracellular matrix
exposed portion of the protein locks onto the ___, while internal region might tie to the _____
extracellular polymers, cytoskeleton
2 kinds of plasma membrane carbohydrates
glycolipids and glycoproteins
recognition signals for interacting w/ other cells - may change when cell becomes cancerous
recognition signals for other cells and proteins - use an "alphabet" of single sugars to create a diversity of messages
cells can arrange themselves into groups by:
cell recognition & cell adhesion
one cell specifically binds to another cell of a certain type
cell recognition
the relationship between the two cells in "cemented"
cell adhesion
is essential in the formation and maintenence of tissues and multicellular organisms - occurs because of phospholipid bilayer recognition proteins
tissue-specific & species-specific aggregation
Only cells from the same species aggregate ex:)sponge
if a sponge is disaggregated into cells, it can reaggregate into a sponge
large glycoproteins (~80% sugar) is partly embedded in the phos. bilayer
regonition proteins
species-specific recognition portion faces ______ & is exposed to the ______
outward, environment
2 kinds of binding of cells in a tissue
homotypic & heterotypic
both cells have the same type of cell surface receptor & their interaction causes them to stick together - most cases ex:) sponge cells
homotypic binding
a plug and socket - mammalian sperm & egg cell binding
heterotypic binding
line body cavities & cover body surfaces
epithelial tissues
3 kinds of specialized cell junctions
tight junctions,desmosomes, gap junctions
hold cells together by acting like spot welds on adj. cells
one cell connects its fibrous networks of other cells
seals tissues & prevents leaks - prevents substances from moving through the intercellular space
tight junctions
restrict the migration of membrane proteins and phospholipids, therefore, can help polarize & stabilize the cell
tight junctions
facilitate communication between cells - dissolve materials, electric signals
gap junctionc
process of random movement toward the state of equilibrium- individual movement is random but net movement is directional until equilibrium - from region of highrer concentration to lower concentration
in a solution, diffusion depends on:
temp, physical size of the solute, electrical charge of the diffusing material, and the conc. gradient
very fast over short distances, not adequate to distribute materials over length of the body, across layers of membranes/from 1 cell to another rapid enough to distribute small molecules & ions almost instantaneously
permeability of membranes to diff. solutes can influence diffusion rates. Ex: a steroid will diffuse readily vs. a proetein of similar size. - although both will eventually achieve equilibrium
diffusion across the bilayer
hydrophobic interior of the membrane tends to exclude hydrophilic substances except water - water readiky passes through the lipid bilayer
diffusion across the bilayer
can move through ion channels - moves rapidly through protein-lined membrane channels
membrane-lined channels through which water can move
diffusion of water across membranes net movement - a completely passive process
molecules move from a region of higher concent. to lower concent.
water will diffuse from:
region of its higher concentration (low conc. of solutes) to region of it's lower conc. (higher conc. of solutes)
two solutions of equal solute conc.
Isoionic solutions
lower total solute conc. than the soln. to which it i being compared
Hypotonic solution
higher total solute conc. than the soln. to which it is being compared
Hypertonic soln.
Integrity of cells depends on:
Ex: RBCs in the plasma
a constant solute conc.
In pure water :
Plant cells ______
Animal cells_______
-limit the amount of water intake (rigid cell wall),
-continue to take pure water in-eventually burst.
may be aided by proteins - polar substances e.g. a.a. & sugars & charged substances e.g. ions
involves proteins embedded in the plasma membrane - channel proteins and carrier proteins
facilitated diffusion
lined w/ polar a.a. - nonpolar a.a face the outside of the channel towards the fatty acid tails of the lipid mol. - e.g. ion channels
channel proteins
gated: various mechanisms for controlling the opening & closing. Once open, millions of ions/second can rush through.
Ion channels
speed and direction of ions depends on_______
conc. gradient
Ion cahnnels are ______ for one type of ion
involves not just opening a channel but actual binding to the transported substance e.g. sugars & a.a.
carrier proteins
allow diffusion in both directions
carrier proteins
conc. gradient can be kept by metabolizing the transported substance e.g. as soonas glucose enters the cell, it is metabolized, therefore the cell's glucose conc. remains low and the movement of glucose continues
carrier proteins
rate of movement through these is dependent on conc. ONLY to a point.
carrier proteins
if the limited # of carrier protein mol. are loaded w/ solute mol. they are _________
______ can limit the # of molecules that can move into the cell/unit of time
ions or molecules move across the membrane from regions of lower conc. to rgions of higher conc. (against the conc gradient)
active transport
In active trasport, ATP is used ______
directly or indirectly
3 kinds of protein driven active transport
uniport transporters, symport transporters, and antiport transporters
move a single type of solute ex: Ca2+, in one direction
uniport transporters
move 2 solutes in the same direction e.g. a.a. transport may be coupled to Na+ transport
symport transporters
Na+ moves from higher conc _____ the cell down the conc gradient to the _______ of the cell. As this occurs, a _______ is moved up the conc gradient & into the cell as well.
outside, inside, amino acid
moves two solutes in opposite directions e.g. Na+ K+ pump
antiport transporters
for each molecule of ATP used __ Na+ ions are pumped ___ and ___ K+ ions are pumped ___
3, out, 2, in
uses ATP directly for the pumping of the system
primary active transport
uses ATP indirectly to establish the ion gradient.
secondary active transport
gradient is used to move a substance e.g. in symport and antiport systems
secondary active transport
only cations e.g. Na+ K+ pump
primary active transport
in intestinal cells, glucose is move up its conc gradient, while moving Na+ down its conc gradient
secondary active transport
both Na+ & glucose enter the cell Na must be pumped out again, but the energy harvested from the glucose more than pays for this energy expense
secondary active transports
bring macromolecules, large particles, small molecules, & even other cells inside a cell e.g. proteins, polysaccarides, nucleic acids, & triglycerides - too large and charged to enter through the membrane
3 kinds of Endocytosis
phagocytosis, pinocytosis, and receptor-mediated endocytosis
involves the largest vesicles (can be entire cells) transported inside the cell
cellular feeding process of unicellular protists
white blood cells defend the body against invading foreign cells by means of ______
very small vesicles - dissolved substances and fluids are brought into the cell - nonspecific
the layer of cells separating blood capillaries from surrounding tissue aquire fluids from the blood by means of ______
similar to endocytosis, but highly specific
receptor-mediated endocytosis
In receptor-mediated endocytosis, receptor proteins are exposed on the outside of the cell in ________
coated pits
The cytoplasmic surface of a coated pit is coated by proteins, such as _____
________ is the method by which cholesterol is taken up by most mamalian cells
receptor-mediated endocytosis
cholesterol is transported throughout the body with _________
Low-density lipoproteins (LDL)
genetic disorder in which LDL receptors are deficient and there are extremely high levels of cholesterol in blood
moves materials out of the cell - vesicle membrane fuses with plasma membrane and is transported outside. ex:) waste, enzymes, hormones, neurotransmitters
involved in info. processing to initiate, modify or turn off a cell function
membranes (are more than just simple barriers)
important in energy transformation ex:) inner mitochondrial membrane: energy of feul molecules to ATP
membranes (are more than just simple barriers)
An example of membrane involved in energy transformation in thalakoid membranes of chloroplasts
light energy to chemical bond energy
involved in organizing chemical reactions into "assembly line" reactions that proceed more rapidly & efficiently
membranes (are more than just simple barriers)
actively participate in many cellular processes; continually form, move and fuse; are similar and can interconverge; major chemical dif. depend on their locations and functions.
Membranes (are dynamic)
In membrane synthesis in Euk. cells,the ___ synthesizes and distributes the phosphlipids
smooth endoplasmic reticulum (SER)
In membrane synthesis in Euk. cells, _______ form proteins that are inserted into the RER
In membrane synthesis in Euk. cells, each _____ changes its membranes to carry out specific functions
sum total of all the chem. conversions in a cell
link simple molecules to make complex ones - energy-stroing reactions
anabolic reactions

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