Module 7 Flashcards
A hydropathy plot of a protein serves to:
predict whether a given protein sequence contains membrane-spanning segments.
Lipid rafts:
are less fluid than the surrounding membrane.
When membrane bilayers are frozen and then fractured, they tend to split along the middle thus separating the two leaflets. This may be because:
the hydrophobic interactions that hold the membrane together are weakest at this point.
What is the purpose of having cholesterol in mammalian plasma membranes?
It enables the membrane to stay fluid more easily when temperature drops.
Phospholipids can laterally diffuse along the plane of the membrane OR Phospholipids can laterally diffuse along the plane of the membrane.
Phospholipids can laterally diffuse along the plane of the membrane.
How do fatty acids with double bonds help keep membranes fluid when temperatures drop?
The double bonds form kinks in the fatty acid tails and prevent tight packing.
Which of these molecules pass through a cell membrane most easily?
small and hydrophobic
Which of the following statements is correct about simple diffusion?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
The enzyme that catalyzes the critical regulatory step of the cholesterol biosynthesis pathway is
HMG CoA reductase.
What do you predict will happen when you transfer a phospholipid bilayer from water to oil?
The membrane is expected to invert its normal structure such that the polar head groups hide inside of the bilayer and the non-polar fatty acid tails face out to the oil.
Cells have different types of receptors on their surface. After receptor-mediated endocytosis, where would you expect to find these receptor molecules?
on the inside surface of the vesicle
Glucose- H+ symporter is a proton based secondary active transport mechanism that brings glucose into a cell. Which of these treatments would increase the rate of glucose transport into the cells?
Decrease extracellular pH
Which of these is true for the action of Na+/K+ ATPase on the plasma membranes of cells?
3 Na+ out, 2 K+ in, coupled to hydrolysis of 1 ATP to ADP + Pi.
What is the molecular basis of potassium channel’s ability to select for K+ over Na+?
The differential interaction of these cations with the selectivity filter
How does muscle contraction increase when the action of the Na+/K+ ATPase is inhibited?
The inhibition of the transporter increases [Na+ ] in the cells and therefore decreases Ca2+ export.
Intestinal transepithelial glucose transport uses a symport to transport glucose up its concentration gradient via cotransport of
glucose with Na+
An integral membrane protein can be extracted from a membrane with:
a solution containing detergent.
Membrane depolarization can cause the opening of _______________ channels.
voltage-gated
When the proteins of the Na+/K+ ATPase are first synthesized on the ER membrane, what side of this membrane will the ATP-binding site be on?
It will be on the cytoplasmic side of the ER.
When examined by FRAP, certain integral membrane proteins are significantly less mobile than others. What accounts for this reduced mobility?
Lipid rafts
Why do aquaporins fail to transport H+ whereas some can transport glycerol?
hydrogen bonds with amino acids
What key mechanistic features results in large differences in transport rates of uniporters vs. ion channels?
Transporters undergo conformational change
Describe the mechanism of how the muscle Ca2+ ATPase pumps Ca2+ ions from the cytosol into the sarcoplasmic reticulum.
E1 binds better to cation than E2
Describe fluid mosaic model. What experimental evidence supports the fluid mosaic model of biomembranes?
noncovalent interactions between molecules allow movement
Propose a rationale for why the coupling of the import of amino acids or sugars into cells is typically to Na+ ion import.
Na+ is high outside of cell
