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BIOL 1202:02 Chapter 7 Notecards

Terms in this set (62)

What is the boundary that separates the living cell from its surroundings?
The plasma membrane
selective permeability
A property of biological membranes that allows some substances to cross more easily than others.
transport proteins
membrane proteins that help move substances across a cell membrane
Phospholipids are
the most abundant lipid in the plasama membrane
phospholipids are amphipatic molecules, they contain
hydrophobic and hydrophilic regions
Proteins are NOT randomly distributed in the membrane
True
membranes are held together by
weak hydrophobic interactions
as temperature cools, membranes swutch from a
fluid state to a solid state
Membranes rich in unstaturated fatty acids are more fluid than those rich in saturated fatty acids.
True
the steroid cholesterol has different effects on the membrane fluidity of animal cells at different temps
True
At warm temps, cholesterol
restrains movement of phospholipids
At cool temps it maintains fluidity by:
preventing tight packing
Phospholipids form the main fabric of the membrane
true
peripheral proteins
bound to the surface of the membrane
integral proteins
penetrate the hydrophobic core
integral proteins that span the membrane
transmembrane proteins
cell-surface membranes can carry out several functions such as
1. transport
2. enzymatic activity
3. signal transduction
4. cell-cell recognition
5. intercellular joining
6. attachment to the cytoskeleton and extracellular
Cells recognize each other by
binding to surface molecules, often carbohydrates, on the plasma membrane
membrane carbohydrates may be covalently bonded to _____ or ______
lipids or proteins
A cell must exchange materials with its surroundings, a process controlled by
the plamsa membrane
plasma membranes are selectively permeable which
regulates the cell's molecular traffic
hydrophobic (nonpolar) molecules, such as _______ can dissolve in the lipid bilayer and pass through the membrane rapidly
hydrocarbons
proteins built into the membrane play key roles in
regulating transport
transport proteins allow
passage of hydrophilic substances across the membrane
Aquaporins
channel proteins that facilitate the passage of water
a transport protein is specific for the substance It moves
true
Diffusion
the tendency for molecules to spread out evenly into the available space
substances diffuse down their concentration gradient which is
the region along which the density of a chemical substance increases or decreases
The diffusion of a substance across a biological membrane is
passive trasnport because no energy is expended by the cell to make it happen
osmosis
diffusion of water across a selectively permeable membrane
Tonicity
the ability of a surrounding solution to cause a cell to gain or lose water
isotonic solution
Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane
hypertonic solution
Solute concentration is greater than that inside the cell; cell loses water
hypotonic solution
Solute concentration is less than that inside the cell; cell gains water
Hypertonic or hypotonic environments create ________ problems for organisms that have cells without rigid walls
osmotic
Osmoregulation
the control of solute concentrations and water balance
turgid
swollen as from a fluid; bloated - firm
flaccid
to limp, in the case of the surroundings are isotonic
in a hypertonic environment
plant cells lose water
Plasmolysis
the membrane pulls away from the cell wall causing the plant to wilt
facilitated diffusion
transport proteins speed the passive movement of molecules across the plasma membrane
transport proteins include
channel proteins and carrier proteins
channel proteins
provide corridors that allow a specific molecule or ion to cross the membrane
Aquaporins facilitate
diffusion of water
ion channels
facilitate the diffusion of ions
gated channels
open or close in response to a stimulus
facilitated diffusion is still passive because
the solute moves down its concentration gradient, and the transport requires no energy
Active transport requires
energy, usually in the form of ATP
all proteins involved in active transport are
carrier proteins
sodium-potassium pump
a transport protein that is energized by transfer of a phosphate group from the hydrolysis of ATP - major pump of animal cells
membrane potential
The voltage across a cell's plasma membrane.
electrochemical gradient
two combined forces that drive the diffusion of ions across a membrane
electrogenic pump
a transport protein that generates voltage across a membrane - can help store energy that can be used for cellular work
cotransport
occurs when active transport of a solute indirectly drives transport of other substances
small molecules and water enter or leave the cell through the _______ or via transport proteins
lipid bilayer
Bulk transport requires
energy
in exocytosis
transport vesicles migrate to the membrane, fuse with it, and release their contents
in endocytosis the cell takes in macromolecules by:
forming vesicles from the plasma membrane
three types of endocytosis
phagocytosis,
pinocytosis,
receptor-mediated endocytosis
Phagocytosis
a cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle.
Pinocytosis
molecules dissolved in droplets are taken up when extracellular fluid is "gulped" into tiny vesicles
receptor-mediated endocytosis
binding of ligands to receptors triggers vesicle formation
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