UWorld Biochemistry Flashcards
(80 cards)
What structural feature in phospholipid membrane would result in the greatest increase in cell membrane fluidity?
A.cis bond
B.trans bond
C.Carboxyl group o
D.Phosphate groups of phospholipids
A.cis bond
Fatty acids with no carbon-carbon double bonds are described as saturated because each carbon atom has the maximum number of hydrogen atoms possible. In contrast, an unsaturated fatty acid contains one (monounsaturated) or multiple (polyunsaturated) double bonds that may be in either the cis (Z) or the trans (E) configuration.
Phospholipids in the cell membrane could be separated experimentally according to their differences in:
charge.
mass.
solubility.
A.I only
B.III only
C.I and II only
D.I, II, and III
D.I, II, and III
The charge on phospholipids is determined by the structure of the polar heads. The phosphate component of the head group may be linked to various chemical groups. Positively charged groups such as choline or ethanolamine neutralize the negative charge of the phosphate, whereas neutral groups such as serine, inositol, or glycerol allow the head to maintain a net negative charge. Neutral and negative phospholipids may be separated by high-performance liquid chromatography
The glycogen branching enzyme forms a glycosidic bond between carbon 1 on the incoming glucose monomer and which of the following?
A.Carbon 3 on a glucose unit of the growing chain
B.Carbon 4 on a glucose unit of the growing chain
C.Carbon 5 on a glucose unit of the growing chain
D.Carbon 6 on a glucose unit of the growing chain
D.Carbon 6 on a glucose unit of the growing chain
When the cell is in need of glucose, glycogenolysis is upregulated, beginning with the activation of glycogen phosphorylase. Glycogen phosphorylase catalyzes the production of which of the following molecules?
A.UDP-glucose
B.UDP-galactose
C.Glucose 1-phosphate
D.Glucose 6-phosphate
C.Glucose 1-phosphate
POMT can use activated D-mannose, but not D-glucose, as a substrate. D-glucose and D-mannose are:
A.constitutional isomers.
B.enantiomers.
C.epimers.
D.anomers.
C.epimers.
O-linked D-mannose can form a glycosidic bond with any sugar that has a free anomeric carbon. Therefore it could theoretically form a glycosidic bond with all of the following sugars EXCEPT:
A.galactose.
B.ribose.
C.lactose.
D.sucrose.
D.sucrose. fructose + glucose

Klenow fragment (KF) polymerase, which has 3′-5′ but not 5′-3′ exonuclease activity
The Klenow fragment used in the experiment would be able to perform which of the following repair processes?
A.Excision of thymine dimers at the 5′ end of the growing strand
B.Replacement of nucleotides at the 3′ end of the growing strand
C.Correction of mismatched nucleotides in the middle of a completed strand
D.Removal of damaged bases from the middle of the template strand
B.Replacement of nucleotides at the 3′ end of the growing strand
DNA Poly reads in 5-3

If lower phospholipid levels in ME patients are due to inhibition of fatty acid synthesis, researchers would most likely observe which of the following?
A.Increased cytosolic NADPH.
B.Decreased mitochondrial acetyl-CoA.
C.Decreased mitochondrial fumarate.
D.Increased cytosolic lysine.
A.Increased cytosolic NADPH.

Which series depicts the order in which the precursors of steroid hormones are synthesized?
A.Isoprene → monoterpene → squalene → cholesterol
B.Cholesterol → isoprene → monoterpene → squalene
C.Monoterpene → isoprene → squalene → cholesterol
D.Isoprene → cholesterol → monoterpene → squalene
A.Isoprene → monoterpene → squalene → cholesterol
3 6 membered rings and 1 5 membered ring
During anaerobic exercise, the Cori cycle connects which two metabolic pathways?
A.Glycogenolysis and the citric acid cycle
B.The urea cycle and gluconeogenesis
C.The pentose phosphate pathway and glycogenesis
D.Gluconeogenesis and glycolysis
D.Gluconeogenesis and glycolysis
cori cycle is lactic acid cycle
Escherichia coli bacteria containing only 15N-labeled DNA were grown in media containing only 14N nucleotides. What percentage of double helices would be composed of one 15N strand and one 14N strand after three generations?
A.12.5%
B.25%
C.50%
D.100%
B.25%
Gen 1: 100% 15N
Gen 2: 50% 15N and 50% 14N
Gen 3: 25%15N and 75% 14N
Prior to inserting the STR sequences into K-ras DNA, the researchers perform MCA analysis using only the double-stranded STR sequences. Which sequence from Table 1 would have the fastest reannealing time in this experiment?
A.Sequence 1
B.Sequence 2
C.Sequence 3
D.Sequence 4

C.Sequence 3

An increase in which of the following would lead to decreased ethanol production in yeast?
A.Partial pressure of oxygen
B.Pyruvate kinase activity
C.Concentration of glucose
D.Krebs cycle inhibitors
A.Partial pressure of oxygen
ANAEROBIC
The electron transport chain results in the generation of:
A.protons, which produce an electrochemical gradient that drives phosphorylation of ADP.
B.protons, which reduce NAD+ in a coupling reaction that drives phosphorylation of ADP.
C.electrons, which produce an electrical gradient that drives phosphorylation of ADP.
D.electrons, which oxidize NADH in a coupling reaction that drives phosphorylation of ADP.
A.protons, which produce an electrochemical gradient that drives phosphorylation of ADP.
After galactose is released from GC and linearized, it contains all of the following functional groups EXCEPT:
A.an aldehyde.
B.a primary alcohol.
C.a ketone.
D.a secondary alcohol.

C.a ketone.

GC can be classified as:
A.a glycerophospholipid.
B.a phosphosphingolipid.
C.a glycosphingolipid.
D.a phosphoglycolipid.

C.a glycosphingolipid.

The amino acid methionine can be converted to succinyl-CoA to enter the citric acid cycle. How many NADH molecules can be produced by each methionine molecule that enters the citric acid cycle by this pathway?
A.1
B.2
C.3
D.4
A.1

Fatty acid synthesis proceeds according to the following reaction:
where n is a positive integer. Based on this, how many ADP and NADP+molecules will be produced during synthesis of a 16-carbon fatty acid?
A.7 ADP molecules and 14 NADP+ molecules
B.14 ADP molecules and 28 NADP+ molecules
C.8 ADP molecules and 15 NADP+ molecules
D.16 ADP molecules and 32 NADP+ molecules

A.7 ADP molecules and 14 NADP+ molecules

Von Gierke disease is a rare autosomal recessive disorder that arises from inactivating mutations in the liver enzyme glucose 6-phosphatase (G6Pase).
Which of the following processes would be directly impaired in von Gierke disease?
Glycogenolysis
Gluconeogenesis
Pentose phosphate pathway
A.I and II only
B.I and III only
C.II and III only
D.I, II, and III
A.I and II only
Pentose uses G6P
Inactivation of which enzyme is most likely to result in physiological effects similar to hypoglycemia?
A.Glucose 6-phosphate dehydrogenase
B.Pyruvate decarboxylase
C.Phosphoenolpyruvate carboxykinase
D.Acyl-CoA dehydrogenase
C.Phosphoenolpyruvate carboxykinase

Group A mice (giving G6Pase inhibitor), but not group B mice, could use which of the following dietary supplements to help maintain blood glucose levels after day 10?
A.Cholesterol
B.Alanine
C.Acetyl-CoA
D.Palmitic acid
B.Alanine

Which of the following steps in the citric acid cycle does NOT produce reduced electron carriers?
A.Conversion of isocitrate to α-ketoglutarate
B.Conversion of α-ketoglutarate to succinyl-CoA
C.Conversion of succinyl-CoA to succinate
D.Conversion of succinate to fumarate
C.Conversion of succinyl-CoA to succinate
In the electron transport chain, four electrons are required to fully reduce one O2molecule to two H2O molecules. Given this information, how many NADH molecules are required?
A.1
B.2
C.3
D.4
B.2
NADH is a 2 electron carrier (FMN in ETC)
FADH2 is a 1 electron carrier

D
Anabolism is the synthesis of complex biological molecules from simpler constituents, and it requires energy input. The energy needed for anabolic processes is generally provided by cleaving high-energy phosphodiester bondsin nucleotide triphosphates (NTPs) such as ATP, GTP, or UTP.





































