Old MCQs Flashcards
do D-glucose and D-fructose have different chemical formulae?
no
what conformation is most stable for the 4 bases?
the chair conformation
how many bases per turn does the DNA double helix contain?
around 10
can RNA secondary structures include base pairs other than A-T and C-G?
yes
how is the base joined to the ribose in nucleic acids?
via an N-glycosidic bond
what catalytic triad does the specificity pocket of serine proteases contain?
Ser-His-Asp
can histidine act as an acid and a base in enzyme mechanisms?
no
what amino acids are exclusively ketogenic?
lysine and leucine
which amino acids are commonly phosphorylated?
tyrosine and threonine
which amino acids are found in collagen repetitive sequences?
proline and glycine
what is a gel based method to detect the presence of a specific protein in a cell extract?
Western blot
what method is used to find new protein interactions?
coimmunoprecipitation
what method is used to determine the total protein concentration in a sample?
Bradford assay
what sidechains are cell surface oligosaccharides attached to?
serine, threonine, glutamine
do fructose and glucose have the same number of carbon atoms?
yes
do fructose and glucose have a different number of carbon atoms?
no
what does stereochemistry at the anomeric carbon determine?
the shape of polysaccharides
what is the reducing end of a sugar formed by?
the anomeric carbon
what is as accurate as using a Lineweaver Burk plot?
estimation of Km and Vmax from a direct rate vs [S] plot
how many polypeptides is insulin made from?
2
what does insulin stimulate in the adipose tissue?
lipogenesis
what is insulin produced by?
pancreatic beta cells
what does insulin promote in muscle?
glycogen synthesis
how do competitive inhibitors affect Km and Vmax?
affect Km, leave Vmax unchanged
what does the serine protease oxyanion hole do?
stabilises the transition state
what do Asp proteases cleave next to?
aspartic acid residues
can enzymes form covalent bonds with reaction intermediates?
yes
what does rotation around the alpha-carbon in proteins allow?
the protein backbone to fold
do all sugars have a reducing end?
no
is deoxyribose in DNA in the L form?
no
which amino acid is most positively charged at pH 7?
arginine
which amino acid has a side chain attached to sugars in N-linked oligosaccharides?
aspartic acid
which amino acid has an aromatic, hydrophobic sidechain?
Phe
what does the Greek key motif describe?
how 4 beta-strands are packed together
do secondary structures always maximise side chain hydrogen bonds?
no
what are the 2 nucleotides in NAD and FAD connected by?
5’-3’ phosphodiester bonds
what is the pantothenate?
vitamin precursor for a cofactor essential for acyl transfer
are prosthetic groups integral to the protein they’re attached to?
yes
which amino acids are aromatic?
Tyr, Trp, Phe
which amino acids have side chains that are positive at pH 6?
Asp, Lys, His
which amino acids can be phosphorylated?
Ser, Thr, Tyr
which is stronger: binding between 2 strands of an anti-parallel beta sheet or binding between 2 strands of a parallel beta sheet?
anti-parallel
what can accommodate the linkage between 2 strands of an anti-parallel beta-sheet?
short structural loop called a hairpin
what are beta-sheets and alpha-helices exclusively held together by?
hydrogen bonds
what is scurvy caused by?
reduced hydroxylation of proline residues, weakening collagen fibres
which has a higher Km for glucose: glucokinase or hexokinase?
glucokinase
how many immunoglobulin domains do IgG antibodies consist of?
12
is haem a prosthetic group?
yes
what is the iron atom coordinated within in oxy-haemoglobin?
a porphyrin ring
what does carbon monoxide compete with?
oxygen for binding to the haem groups
what binding kinetics does haemoglobin bind oxygen with?
sigmoidal
which amino acid residues can be glycosylated?
Thr, Asn, Ser
where is most glycogen stored: muscle or liver?
muscle
what is glycogen a polymer of?
glucose linked to a protein at 1 end
does glycogen synthase require UTP?
no
what does cAMP phosphodiesterase hydrolyse cAMP upregulates to?
AMP
what does hydrolysis of cAMP upregulates to AMP downregulate?
glycogen breakdown
what upregulates glycogen breakdown by allosteric activation of PKA?
cAMP
what allosterically activates PKA?
cAMP
what ATP levels are needed for ketone body formation in liver cells?
high
what NADH levels are needed for ketone body formation in liver cells?
high
what activity level of pyruvate dehydrogenase is needed for ketone body formation in liver cells?
less active
what Acetyl-CoA levels are needed for ketone body formation in liver cells?
high
what is an amino acid directly involved in the urea cycle?
arginine
what is an enzyme which specifically catalyses triacylglycerol hydrolysis to diacylglycerol in fat cells?
adipose triglyceride lipase
what is the enzyme that catalyses the final step in synthesis of the ketone body acetoacetate?
hydroxymethylglutaryl-CoA lyase
what is an enzyme activated by calcium ions in skeletal muscle?
phosphorylase kinase
what is an inhibitor of carnitine acyltransferase I?
Malonyl-CoA
what is an activator of acetyl-CoA carboxylase?
citrate
what is an enzyme located on the inner mitochondrial membrane?
succinate dehydrogenase
what is an allosteric activator of pyruvate carboxylase?
acetyl-CoA
what is an allosteric activator of glycogen phosphorylase?
5’-adenosine monophosphate (AMP)
do skeletal muscle cells contain acetyl-CoA carboxylase?
yes
what causes phenylketonuria?
when phenylalanine hydroxase can’t convert phe to tyr
what do most fish secrete nitrogen as?
ammonia
what is excess ammonia in tissue added to?
glutamate
what does alanine do?
carries ammonia from skeletal muscle to liver
is the glycolytic reaction catalysed by fructose bisphosphate aldolase exergonic or endergonic?
highly endergonic
what regulates protein kinase A activity?
binding to cAMP
what is an allosteric modulator which regulates the balance between glycolysis and gluconeogenesis acting on PFK1?
fructose 2,6-bisphosphate
what is an intermediate in both the citric acid cycle and gluconeogenesis?
oxaloacetate
what is the product of hexokinase?
glucose 6-phospate
how many ATP molecules result from the oxidation of FADH2?
1.5
how many ATP molecules result from the complete oxidation of acetyl-CoA?
10
how many ATP molecules result from the complete oxidation of palmitoyl-CoA?
106
what does the carbonic anhydrase reaction mechanism rely on?
a histidine-bound zinc atom
where does fatty acid synthesis occur?
in the cytosol
what is most acetyl-CoA in the liver normally converted into?
ketone bodies
what is acetyl-CoA carboxylase subject to?
phosphorylation and allosteric regulation
what supplies reducing equivalents for fatty acid synthesis?
NADPH2
what does the proton motive force depend on?
both the proton gradient and the total charge gradient across the inner mitochondrial membrane
in the oxygen electrode experiment with glutamate added, what does the maximum rate of oxygen uptake not occur until?
until ADP and inorganic phosphate are added
what is the TCA cycle enzyme succinate dehydrogenase part of?
the electron transport chain
what do birds use for the secretion of nitrogen?
uric acid
what is alanine secreted by?
muscle
what is arginine an intermediate in?
the urea cycle
is the reaction that glutamate dehydrogenase catalyses reversible?
yes
what do GPCRs replace bound GDP with?
GTP
where is the final orientation of a plasma membrane protein established?
at the er
into which organelle are fully folded proteins imported from the cytosol?
nucleus
which organelle is the site where sugar residues are first attached to secreted proteins?
endoplasmic reticulum lumen
which organelle is the location of the Sec61 translocon complex?
endoplasmic reticulum membrane
what mediate recovery from receptor-activated intracellular signalling?
Ca2+ pumps and PLC
what is a small molecule inactivated by dephosphorylation?
IP3
what activates protein kinase C?
diacylglycerol
where do COPII vesicles transport proteins from and to?
from the ER to the Golgi apparatus
where are misfolded proteins in the ER lumen exported to?
the cytosol
what state are proteins in before transport to peroxisomes?
fully folded
where are signal peptides removed?
within the ER lumen
which group is added to proteins in the Golgi?
mannose-6-phosphate
what is IP3 inactivated by?
dephosphorylation
what binds lysosome enzymes in the ER?
mannose-6-phosphate
what does clathrin contribute to?
the endocytosis of LDL receptors
where can glycosylated proteins be modified?
within the Golgi apparatus
what is a protein with the ability to phosphorylate tyrosine residues?
EGF receptor (or other tyrosine kinase receptor)
what protein degrades cAMP?
phosphodiesterase
what protein can hydrolyse GTP
Gq
what proteins mediate fusion of vesicles during intracellular trafficking?
SNARE proteins
what do glucagon, adrenaline and vasopressin have in common?
all stimulate cell signalling cascades using cAMP as a common intracellular signal transduction molecule
what is PKA catalytic activity regulated by?
binding to cAMP
what is required for calcium flow through voltage gated calcium channels?
ion-ion repulsion
what can modify the response of voltage gated calcium ion channels to membrane potential?
phosphorylation
what does IP3 stimulate?
release of Ca2+ from the ER
what does caffeine inhibit?
degradation of cAMP
what does PKA binding to cAMP do?
stimulates PKA activity
is the lumen of lysosome alkaline?
no
what can ligand-gated ion channels be classified as?
allosteric receptors
how do SNARE proteins force inbound vesicles closer to target organelle membranes?
they wind around each other
what domain in Grb2 binds to the active receptor tyrosine kinase?
SH2 domain
what protein switches off small G proteins?
GTPase activating protein
what protein kinase is activated by binding to an active small G protein?
MAP kinase
what is a scaffold protein which directs intracellular co-localisation of PKA and other proteins?
AKAP
what is an enzyme that hydrolyses phosphatidylinositol 4,5-bisphosphate generating IP3 and DAG?
PLC
