Module 3: Membranes and Cellular Structure
The rate of lateral diffusion is such that a phospholipid molecule can travel from one end of a bacterium to the other in _______________ of time.
1 second
How many molecules thick are membranes? infinite 1 2 Membranes are of varying thickness, depending on their structure none of the above
2
A cell membrane protein that can cause the resistance of tumors to toxic drugs used to treat cancer is called P-glycoprotein MDR or multidrug resistance protein drug transport protein A and B all of the above
A and B
Extracellular material is taken into the cell via which process? endocytosis phagocytosis lysosome-mediated endocytosis reverse secretory mechanism A and B
A and B
Which of the following organelles has a double membrane? nucleus endoplasmic reticulum mitochondria plasma membrane A and C
A and C
Which of the following membranes would be the most fluid? Correct! A bilayer made of lipids with polyunsaturated 16- carbon fatty acids A bilayer made of lipids with saturated 18-carbon fatty acids A bilayer made of lipids with saturated 16-carbon fatty acids A bilayer made of lipids with polyunsaturated 18- carbon fatty acids All of the above are equivalent in fluidity.
A bilayer made of lipids with polyunsaturated 16- carbon fatty acids
The Fluid Mosaic Model of membrane architecture incorporates these elements: Membranes are bilaminar phospholipid matrices Globular membrane proteins may be integral or peripheral Lipids and membranes are free to diffuse in the plane of the membrane but not freely move from one leaflet to the other You Answered A and B A, B, and C
A, B, and C
Primary active transport requires ____________ to transport ions and molecules across cell membranes. glucose potassium dATP ATP entropy
ATP
An ABC domain in active transport proteins is short for Allostearic Binding Cassette Antiporter Binding Cassette ATP Binding Cassette Adenosine Binding Cassette ATP Balancing Cassette
ATP Binding Cassette
The multidrug-resistance (MDR) protein and cystic fibrosis transmembrane conductance regulator (CFTR) protein are members of the __________________ superfamily. ATP binding cassette, or ABC, transporters P-type ATPase F-type ATPAse Adenosine binding cassette, or ABC, transporter ATP bypass cassette, or ABC, transporter
ATP binding cassette, or ABC, transporters
Molecules move across cell membranes down chemical gradients by active transport passive transport/facilitated diffusion simple diffusion A, B, and C B and C
B and C
The Fluid Mosaic Model describes the architecture of: Cellular Fluids Cellular Membranes Leaflets Integral proteins Peripheral proteins
Cellular Membranes
What class of proteins move lipids from the outer leaflet to the inner leaflet? Flopases Lipases Shuffle-ases Flipases none of the above
Flipases
Particles that use simple diffusion
O2, Co2, cholesterol, vitamin D
How do proteins function to make membranes selectively permeable?
Proteins exist on the surface and may span parts or run through the entire bilayer. Proteins serve as to transport larger and charged molecules. For example, channel proteins form channels for small molecules to diffuse through (facilitated diffusion). Carrier proteins can identify and grab molecules to pull into the cell. Receptor proteins might signal to release hormones or open channels for transportation of molecules. Some proteins tag molecules for recognition and work with the immune system to later remove them or destroy them. Some proteins (aquaporins) act as channels for water.
Symporter
Secondary active transport (electrochemical gradient) drives ion same direction as gradient
What are the 3 processes used for transporting molecules across cell membranes? Facilitatated diffusion, passive diffusion, and tertiary diffusion Simple Diffusion, facilitative diffusion, and active transport Primary transport, secondary transport, and tertiary transport Gradient transport, Ion channels, and ABC transport Cotransport, Symport, Antip
Simple Diffusion, facilitative diffusion, and active transport
Which of the following statements is consistent with the structure of biological membranes? All membrane proteins are integral and associate with the hydrophobic region of the membrane. Both proteins and lipids readily undergo transverse ("flip-flop") diffusion from the inside to the outside of the membrane. Membranes are symmetric. The membrane lipids self-assemble to form the lipid bilayer. A biological membrane consists of proteins sandwiched between two layers of lipids, which is referred to as a lipid bilayer.
The membrane lipids self-assemble to form the lipid bilayer
Why are membranes impermeable to most substances?
They are impermeable because they are composed of a lipid bilayer. Large molecules, polar molecules and charged ions can't cross this barrier. Embedded proteins help glucose, ions and other important chemicals across this barrier. Smaller particles like O2 and CO2 can move through the bilayer through simple diffusion, due simply to differences in concentration inside and outside the cell.
CFTR PROTEIN
Transports chloride ions out of cell
The shape of lipids influences membrane structure and curvature. True False
True
Carbohydrate residues attached to the membrane lipids are always positioned on the intracellular side of the membrane. always positioned on the inside center of the bilayer. always positioned on the extracellular side of the membrane. always positioned equally on both sides of the membrane. also covalently attached to membrane proteins.
always positioned on the extracellular side of the membrane
What force(s) stabilize(s) the lipid bilayers? van der Waals interactions electrostatic and hydrogen bonding between the polar heads and surrounding water covalent bonds between the lipid tails covalent bonds between the lipids and membrane proteins A and B
and B
The rigid material which provides structural support to a plant cell is/are called the: plant cytoskeleton plasma membrane cell wall chloroplast anchor proteins microfilaments and microtubules
cell wall
Which of the following helps regulate membrane fluidity in animals? protein ATP cholesterol magnesium ion none of the above
cholesterol
Aspirin and Ibuprofen are NSAIDs used for treatment of mild pain, and the class of proteins being inhibited is prostaglandins thromboxanes cyclooxygenases acetylsalicylic acid arachidonic acid
cyclooxygenases
The structural components (filaments and tubules) are organelles called the: chloroplast cytoplasm cytoskeleton cell wall B and D
cytoskeleton
Secondary transporters use the energy of _____________ to pump ions or molecules acetyl-CoA ATP sodium gradients glucose
gradients
A nerve impulse or action potential is generated by the flow of ________ across the plasma membrane of neurons. glucose water ATP electrons ions
ions
The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as _______________.
melting temperature
The low incidence of protein or lipid flip-flop in a membrane preserves membrane fluidity membrane melting temperatures membrane asymmetry all of the above none of the above
membrane asymmetry
Three structures that can be formed by association of lipids are Bilaminar membranes, nanoparticles, buckyballs organelles, micelles, vacuoles micelles, liposomes, bilaminar membranes liposomes, dendrimers, membranes micelles, liposomes, unilaminar membranes
micelles, liposomes, bilaminar membranes
Poisons that kill an organism as a result of a loss of high-energy ATP molecules are most likely to target which organelle? mitochondria cytoskeleton cytoplasm endoplasmic reticulum nucleus
mitochondria
Most cell membranes are electrically polarized, the inside being _______________ relative to the outside. zwitterion negative neutral amphipatic positive
negative
A secreted protein would be processed through organelles in the following order: nucleus; secretory vesicle; Golgi complex cytoplasm; Golgi complex; cytosol; secretory vesicle endoplasmic reticulum; cytoplasmic reticulum; Golgi complex nucleus; cytoplasm; endoplasmic reticulum; Golgi complex; secretory vesicle none of the above
none of the above
The main function of the plasma membrane is to: provide the interior of the cell an enclosed environment which no molecules may cross. provide a selectively permeable barrier with the aid of transport proteins. give eukaryote and prokaryote cells structural strength. allow only the free passage of water in and out of the cell. none of the above
provide a selectively permeable barrier with the aid of transport proteins.
Antiporters and symporters are proteins that are passive diffusion primary active transporters. entropy-driven pores. ABC transporters secondary transporters.
secondary transporters.
The ability of potassium ion channels to be highly specific is because of a structure called a ___________ that causes potassium to relinquish its shell of water. ion filter sodium filter selectivity filter repulsion filter water filter
selectivity filter
The fluorescence recovery after photobleaching (FRAP) technique has been used to study membrane composition. the lateral diffusion in membranes. protein structural motifs in membranes. all of the above none of the above
the lateral diffusion in membranes.
The degree of membrane fluidity depends on the percentage of lipids that contain choline. the percentage of glycolipids. the percentage of free fatty acids. the percentage of unsaturated fatty acids. none of the above
the percentage of free fatty acids
The degree of membrane fluidity depends on: the percentage of lipids that contain choline. the percentage of glycolipids. the percentage of free fatty acids. the percentage of unsaturated fatty acids. none of the above
the percentage of free fatty acids.
The most common motif found in membrane-spanning proteins is α-helices of nonpolar amino acids that pass through the membrane. α-helices of charged amino acids that form channels via extensive hydrogen bonding. a triple helix of α-helices. a helix-turn-helix arrangement of the peptide strands. none of the above
α-helices of nonpolar amino acids that pass through the membrane
