Cell Bio exam II
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Cell Bio exam II
Chap 11, cell membrane, Buff state, BIO 214
*has the small molecule choline attached to a phosphate group as its hydrophilic head
*molecules with both hydrophilic and hydrophobic parts are termed:
Pure phospholipids that will form closed spherical vesicles called:
Whats the two major properties of hydrocarbon tails that affect how tightly they pack in a bilayer?
Length and # of double bonds
A shorter hydrocarbon chain length will _________ the tendency of the hydrocarbon tails to interact, and _________the fluidity of the bilayer
At higher temps the cell makes membrane lipid makes _________ tails that contain ________ double bonds
* allows membrane proteins diffuse rapidly
* allows membrane lipidsand proteins to diffuse
* ensures that membrane molecules are evenly distributed
* allows membranes to fuse with one another
enzymes that catalyze the transfer of lipids from one monolayer to the other
Why is the enzyme scramblases important?
because new phospholipids are only deposited on the cytosolic half of the bilayer, this enzyme rearranges them so the bilayer is even
How does a membrane with two different monolayers become asymmetrical?
Golgi has enzymes called flippases, picks specific phospholipids and flips them to the cytosolic layer
monolayer that faces the cytosol
monolayer that faces away from the cytosol
which side of the membrane is glycolipids found?
What happens when enzymes add sugar to the noncytosolic lipid molecule heads?
glycolipid molecule will remain trapped in this monolayer, nothing can transfer it to the other side
membrane proteins that extend through the bilayer
membrane proteins that are directly attached to the bilayer either trans, or w/lipid monolayer, or lipid-linked are called
integral membrane proteins
Membrane Proteins that are not directly attached to the bilayer
peripheral membrane proteins
the two parts of a transmembrane protein that allow for it to be a part of the bilayer
hydrophobic side chain bonded with hydrophilic polypeptide backbone
example of a b sheet protein
porin proteins, form, large, water-filled pore that allow the passage of small nutrients, metabolites, and inorganic ions
why are detergents good at separating bilayers?
have only a single hydrophobic tail, shaped like cones, thus aggregate into micelles.
interacts and seperates
example of a membrane transport protein that pumps H+ out of the cell
Differences in plant/bacteria vs animal cell walls
: proteins, sugars
: fibrous proteins call cell cortex
protein in red blood cell that maintains its shape
localized areas within the bilayer where particular proteins are confined
the surface that faces the gut contents
a barrier formed along the line where the cell is sealed to adjacent epithelial cells
*membrane proteins cannot diffuse past
proteins that have short chains of sugars linked to them
proteins that contain one or more long polysaccharide chains
sugar coating located on the outside of the plasma membrane that consists of all carbohydrates
membrane proteins that shift small molecules from one side of the membrane to the other by changing shape
membrane proteins that form tiny hydrophilic pores across membranes then a substance can pass through via diffusion
membrane proteins that only permit passage of inorganic ions
molecules that can cross the membrane slowly
* inorganic ions
* amino acids
how do hydrophilic molecules cross the membrane
membrane proteins that accelerate transport of hydrophilic molecules
molecule order of most to no crossing of the membrane
ions-not at all
most import inorganic ions
electrical imbalances generate a voltage difference across the membrane called:
exchange of anions and cations across the membrane will be balanced
voltage difference across the cell membrane
resting membrane potential
the interior of the cell is more _______ charged than the exterior
what does the transport protein transfer?
molecules or ions that fit into specific binding site on the protein
How does the channel protein discriminate?
by the size and electrical charge of molecules
When molecules spontaneously flow downhill from higher to lower concentration
movement of a solute against its concentration gradient
how is active transport carried out?
protein transporters called pumps
the two net forces driving a charged solute across a cell membrane
concentration gradient + membrane potential=
* determines the direction that each solute will flow by passive transport
water moves passively across cell membranes down its concentration gradient
specialized channel proteins for H2O
total concentration of solute particles inside the cell
plant cells osmotic swelling pressure
what actively transports a solute against its electrochemical gradient
what moves a solute along its electrochemical gradient?
3 types of pumps
pump that hydrolyze ATP to drive uphill transport
pump that link the uphill transport of one solute across a membrane to the downhill transport of another
pumps found mainly in bacterial cell, use sunlight energy to drive uphill transport
how does the Na+ pump work?
uses ATP to expel Na+ and bring in K+
*coupling, only when appropriate ions are available for transport
How does the Ca+ pump work?
ATPase, coupling, removing Ca2+ out of cell into the extracellular that has a higher concentration
what does Ca2+ do in the cell?
intracellular signal to trigger processes
when a gradient of any solute across a membrane can be used to drive the active transport of a second molecule
coupled pump moves both solutes in the same direction across the membrane
pump that moves only one type of solute across the membrane
coupled pump that moves solutes in opposite directions across the membrane
what kinds of electrochemical gradient pump do animals rely on?
Na+ pumps and Na+-driven symport
what kind of electrochemical gradient pumps to plants, fungi and bacteria rely on?
H+ pumps and H+-driven symport
How does the H+ pump work?
pumps H+ out, creates acid pH in medium surrounding the cell
2 channels that form relatively large, aqueous pores
gap junctions btwn cells
porins outer membrane of mitochondria
narrow, highly selective pores/channels
* facilitate the flow of water across plasma membrane
* prohibits the movement of ions
* ion selectivity
* not continusously open-gated
* does not undergo conformational changes
* fastest transporter
whats the main inorganic ions that an ion channel transports?
these channels randomly flicker open and closed no matter what the conditions are inside or outside the cell, allows free movement
most common leak channel
K+ leak channel
when the flow of positive and negative ions across the membrane is balanced
resting membrane potential
* K+ leak channel closed
type of gated channel that is controlled by the membrane potential
type of gated channel that is controlled by the binding of some molecule to the channel
type of gated channel that is controlled by a mechanical force applied to the channel
when the membrane potential of the plasma membrane shifts to less negative value
what happens when theres a negative membrane potential and the plasma membrane depolarizes?
voltage-gated Na+ channels open
How does the depolarized axonal membrane return to resting potential?
voltage-gated K+ channels opening in response to depolarization
channel responsible for the maintenance of resting membrane potential of a plasma membrane
channel responsible for generation of action potentials of a nerve cell axon
Voltage-gated Na+ channel
channel responsible for the return of membrane to resting potential after action potential at the nerve cell axon
voltage-gated K+ channel
channel responsible for stimulation of neurotransmitter release on plasma membrane of nerve terminal
voltage-gated Ca2+ channel
channel responsible for excitatory synaptic signaling of the muscle cell
Acetylcholine receptor/gated cation channel
channel responsible for excite synaptic sign of neurons
glutamate receptors/gated cation channels
channel responsible for detection of sound vibrations in auditory hair cell
mechanically=activated cation channel
The ER, Golgi apparatus, peroxisomes, endosomes and lysosomes are all part of what is collectively called:
Possible way membrane bound organelles may have come to be:
where does the synthesis of virtually all proteins begin?
ribosomes in the cytosol
exceptions of proteins that are synthesized inside specific organelles instead of in the cytosol
how is it determined where protein is going to be synthesized?
amino acid sequence contains sorting signal
3 ways a protein is transported across membranes
enclosure of the nuclear DNA
part of nuclear envelope that contains proteins that act as binding sites for chromosomes and nuclear lamina
Inner nuclear membrane
finely woven meshwork of protein filaments that line the inner face of membrane and provides structural support for the nuclear envelope
the signal that directs a protein from the cytosol into the nucleus is called:
nuclear localization signal
the nuclear localization signal on proteins destined for the nucleus is recognized by cytosolic proteins called:
nuclear import receptors
What protein helps the newly made proteins inside mitochondria and chloroplast and helps refold them again?
enzyme that also synthesizes certain phospholipids
THe most extensive membrane system in a eukaryotic cell
What are the two kinds of proteins that are transferred form the cytosol to the ER?
Water soluble proteins
Prospective transmembrane proteins
translating mRNA with ribosomes binded to it
The two protein components that help guide ER signal sequences to the ER membrane
1. Signal-recognition particle(SRP)
2. SRP receptor
binds to both the ribosome and the ER signal sequence after ribosome
embedded in the ER membrane , recognizes the SRP
site of detoxification in a cell
Site of glycosolation
type of Golgi that's facing the nucleus
type of Golgi that's facing away from the nucleus