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BIOCHEM Midterm I Exam

Terms in this set (25)

What correctly describes lipids?
1. triglycerides, used for energy storage in adipose tissue, are composed of glycerol molecule condensed with 3 fatty acids
2. most of the structure of lipids is very non-polar, formed almost exclusively of carbon and hydrogen atoms
3. lipids are the most efficient energy storage molecules in cells
4. diglycerides, which occur in cell membranes, are composed of a glycerol, usually two long fatty acid chains, and a more hydrophilic "head" group
Phosphatidylethanolamine (PE)
terpenes
formed from 2 or more 2-methyl-1,3-butadiene molecules
wax ester
Which of the following is a cellular function of glycophospholipids?
involvement in nerve impulse transmission
The crystal structure of the octameric membrane protein Wza is shown below. Which of the following structural motifs in the transmembrane are utilized by the protein
transmembrane alpha-helical barrel
Which of the following allows hydrophilic molecules (ions and larger polar molecules) to pass through the cells membrane?
integral membrane proteins
Which of the following is the least common type of motion in biological membrane?
flip-flop (transverse) diffusion of phospholipids from one monolayer to the other
Singer and Nicholson's fluid mosaic model of membrane structure presumed all of the following statements to be true EXCEPT
a. the phospholipid bilyaer is a fluid matrix
b. membranes are about 5-10nm thick
c. proteins can move laterally across a membrane
d. proteins can be anchored to the membrane by covalently linked lipid chains
e. transverse motion of lipid molecules can occur occasionally
d. proteins can be anchored to the membrane by covalently linked lipid chains
Phospholipids consist of a hydrophilic head and two hydrophobic tails within the same molecule. This amphipathic nature of the molecules allows to form a lipid layer, a universal component of all cell membranes. Which of the following is the major driving force to stabilize the lipid layer?
hydrophobic forces on the phospholipid fatty acid carbon chains
Which of the following correctly describes the hydropathy plot shown below?
each peak indicates the hydrophobic segment of transmembrane protein
Which of the following amino acid sequences is generally found in the membrane-spanning domain of integral membrane proteins?
-Leu-Val-Met-Phe-Ale-Ile-
When ATP formation is inhibited by small molecules, the rate of transport of a substance into a cell is drastically reduced. Which of the following transport system explains this phenomenon?
active transport
What molecule carries activated actyl-CoA from the outer mitochondrial membrane to the inner mitochondrial membrane?
carnithine
Which of the following CORRECTLY describes the activation of fatty acids by acetyl-CoA synthetase?
a. acyl-CoA synthetase condenses fatty acids with CoA, with simultaneous hydrolysis of ATP to AMP to PPi
b. An acyl-adenylate intermediate is formed before the fatty acyl-CoA thioester is produced
c. formation of a CoA ester is energetically expensive
d. all of them
e. the subsequent hydrolysis of pyrophosphate drives the reaction forward
d. all of them
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