Biochem Flashcards
What is the rate limiting step of: glycolysis?
PFK-1
What is the rate limiting step of: gluconeogenesis?
Pyruvate carboxylase
What is the rate limiting step of: TA (Krebs) cycle?
Isocitrate dehydrogenase
What is the rate limiting step of: glycogenesis (glycogen synthesis)
glycogen synthase
What is the rate limiting step of: glycogenolysis
glycogen phosphorylase
What is the rate limiting step of: hexose monophosphate (HMP) shunt
G6PD
What is the rate limiting step of: fatty acid synthesis
Acetyl CoA carboxylase
What is the rate limiting step of: B-oxidation
Carnithine acyltransferase I
What is the rate limiting step of: ketogenolysis
HMG CoA synthase
What is the rate limiting step of: cholesterol synthesis
HMG CoA reductase
What is the rate limiting step of: Urea cycle
Carbomoyl phosphate synthetase I
What is the rate limiting step of: heme synthesis
d-ALA synthase
What is the rate limiting step of: pyrimidine synthesis
Aspartate transcarbomylase
What is the rate limiting step of: purine synthesis
PRPP glutamyl amido transferase
What is the only faty acid that is gluconeogenic?
propionic acid
Aldose reductase converts galactose to what?
galactitol
How many ATPs are generated from glycolysis?
8
In the mito, what complex is needed in order for pyruvate carboylase to catalyze the rxn from pyruvate to OAA?
Biotin, ATP, and CO2
What is the enzyme for the oxidative reaction in glycolysis
Glyceraldehyde dehydrogenase
What 3 substrates control the enzyme PEPCK for the conversion of OAA to pyruvate in the cytoplasm?
What is released from this rxn?
- Cortisol (stimulates PEPCK)
- Glucagon
- Guanin triphosphate (GTP)
CO2
What enzyme deficiency causes cataracts, galactosemia, and galactosuria?
Galactokinase deficiency
Addition of D-2,3-BPG to HbA does what to the O2 saturation curve?
Shift R
What is the glycolysis enzyme found only in the liver?
Glucokinase
How many ATPs are generated per acetyl CoA
12 (Not 15 - that would be the answer if you included the pyruvate to acetyl CoA step)
What enzyme is associated with the substrate-level phosphorylation in the TCA cycle?
Succinate thiokinase
The availability of OAA and acetyl CoA regulates what pathway?
TCA
What complex of the ETC is inhibited by malonate?
Complex II
In what 2 places is glycogen made and stored?
- Liver
- Mm
Liver stores are for blood glucose; mm sotres are for energy reserves
At what step of the TCA is FADH2 generated?
Succinate dehydrogenase (inhibited by malonate)
What inhbits complex III of the ETC?
Antimycin A
What inhibits the ATP/ADP translocase of the ETC?
Atractyloside
TTP is associated with what 3 enzymes?
- a-ketoglutarate dehydrogenase
- pyruvate dehydrogenase
- transketolase
What hormone stimulates glycogen synthesis
Insulin
Deficiency in what enzyme leads to insoluble glycogen formation?
a-1,6 transferase
The reduced nicotinamide adenine dinucleotide phosphate (NADPH) generated from G6PD reaction is used exclusively for what?
FA synthesis
What enzyme requires selenium to function?
GLutathione peroxidase
What are the 2 essential FA?
- Linolic acid
2. Linolenic acid
What intermediate of the HMP pathway is used to generate nucleotides?
Ribose 5-phosphate
A deficiency in what enzyme causes a decrease in oxidoreductase activity in neutrophils?
G6PD
What are the nonoxidative enzymes of the HMP shunt?
Are the rxns they catalyze reversible or irreversible?
Transketolase and transaldolase
Reversible
VLDL remnants are known as what?
IDLs
What carries triacylglycerols (TAGs) and cholesterol from the diet?
Chylomicrons
What protein is required for uptake of LDLs in the peripheral tissue?
Apoprotein B-100
What 3 apoproteins are on the surface of chylomicrons
Apoprotein B-48, CII and E
What protein carries free FA to the liver?
Albumin
in the B-oxidation path, what enzyme generates the FADH2?
Acyl CoA dehydrogenase
How many ATPs are generated per acetyl CoA in B-oxidation
5
How many ATPs are generated per acetyl CoAfrom B-oxidation if its run through the TCA cycle?
12
What is the only organ in the body that can produce ketone bodies?
Liver (in the mito)
What 2 tissues prefer ketone bodies over glucose?
- Heart mm
2. Renal cortex
What enzyme is absent in the liver so that ketogenolysis cannot occur?
Thiophorase
What path uses HMG CoA synthetase in the cytoplasm
Cholesterol biosynthesis
What 2 vitamins are inactivated when they come in contact with acetaldehyde
- Thiamine
2. Folate
What is the precursor of a sphingolipids?
Ceramide
What 2 sugars can be used to produce cerebrosides?
- Glucose
2. Galactose
Where does the energy for the urea cycle come from?
Fat metabolism
What are the 2 major carriers of nitrogen from tissues?
- Glutamine (most tissues)
2. alanine (mm)
WHat are the ketogenic aa?
leucine and lysine
What is the storage form of folate?
N-methyl folate
Where in the body is heme converted to bilirubin?
RES
What is the primary end produce of pyrimidine synthesis?
UMP
All aa have titration plateaus at what pH value?
pH of 2 and 9
What aa is a good buffer at pH of 7?
Histidine
WHat is the only way to inc Vmax?
Inc enzyme conc
What happens to affinity if you inc Km?
Affinity decreases (they are inversely proportional)
What 2 aa disrupt an a-helix?
- Glycine
2. proline
What aa is a phenol?
Tyrosine
What enzyme requires molybdenum (mo) as a cofactor?
Xanthine oxidase
What determines the rate of a reaction
the activation energy
What substrate conc is required to produce 1/2 Vmax
Km
What enzyme is stimulated by PTH to produce 1,25 Vit D3?
1-a-hydroxylase
What vit is important component of rhodopsin?
Vit A
What G protein is stimulated by activated rhodopsin?
Gt (Transducin), which dec cGMP and closes the Na+ channels, cauisng nerve transmission
What vit is connected to selenium metabolism?
Vit E
What is the activated form of vit E?
a-tocopherol
What is the MC methylated base?
Cytosine
DNA is replicated at what phase of the cell cycle?
S phase
At which end of DNA are new bases added?
3’ end
What keeps ss DNA from re-annealing during DNA replication?
ss binding proetin
what enzyme is responsible for producing a ss cut in the DNA to relieve the coil tension
topo I
What 2 aa are found in high conc in the nucleosome
- arginine
2. lysine
what 3 bases are pyrimidines
- CUT (cytosine, Uracil, thymidine)
what enzyme creates a short seq of RNA to start DNA replication
primase
what type of enzyme is reverse transcriptase?
RNA-dep DNA polymerase
What is the direction of transcription
5’ –> 3’
where is the TATA box in eukaryotes?
25 bases downstream
what causes transcription to stop in eurkaryotes?
Poly(A) site on DNA
what protein binds to the promoter region in eukaryotes to initate transcription?
TF II D
What part of the 30S ribosome binds to the shine-Dalgarno sequence?
16S subunite
What enzyme activates the aa for the tRNA?
aminoacyl-tRNA synthetase
What is needed to direct enzymes to a lysosome?
phosphorylation of mannose residues
What cofactor is needed for lysyl oxidase?
Cu2+
What part of the 50s and 60S ribosomal subunit is needed for elongation?
peptidyl transferase
In the lac operon:
- where is the repressor gene encoded?
- to which site does the repressor protein bind to inhibit transcription?
- I gene
2. operator
what amplification technique is used to generate a larger amount of DNA?
PCR
At what organ in the body is urea produced?
liver
what regulatory proteins work during fetal development to ensure that cells become a specific cell type
Homeobox genes (if there is a defect here, there can be a profound structural mutation)
Mode of inheritance seen in every generation and is passed by females?
mitochondrial inheritance
What form of continuous DNA used in cloning has no introns or regulatory elements?
cDNA, when made from mRNA
What complex of the ETC contains Cu2+?
COmplex 4
What 2 shuttles are needed to keep NAD+ in the reduced state?
Malate/aspartate and glycerol-3-phosphate shuttles
Vit required for gamma-carboxylation of many Ca2+ binding proteins
Vit K
Where is the energy for gluconeogenesis derived?
B-oxidation of FA
What aa is broken down into N2O causing an inc in cGMP of smooth mm –> vasodilation?
Arginine
what enzyme in the liver catalyzes glycerol to glycerol-3-phosphate
glycerol kinase
What shuttle is used to bring fatty acyl CoA from the cytoplasm for ketogenesis?
Carnitine acyl CoA transferase II
All the carbons in FA are derived from what source?
Cytoplasmic acetyl CoA that left the mito as citrate
What glycolytic intermediate can be used to synthesize triglycerides and phospholipids?
DHAP
What is the main inhibitor of pyruvate dehydrogenase?
Acetyl CoA (pyruvate to acetyl CoA)
What are the 2 substrate-level phosphorylations in glycolysis?
- pyruvate kinase
2. phosphoglycerate kinase
What are 8 liver specific enzymes?
- Fructokinase
- Glucokinase
- Glycerol kinase
- PEPCK
- Pyruvate carboxylase
- Galactokinase
- F-1,6-BP
- G6P
In what cycle does glucose go to the mm, where it is converted to pyruvate and then into alanine before being taken back to the liver?
Alanine cycle
In what cycle does glucose go to the mm, where it is converted to lactate, and then returned to the liver?
Cori cycle
What 4 substrates inc the rate of gluconeogenesis?
- Glucagon
- NADH
- Acetyl CoA
- ATP
What 3 substances stimulate glycogenolysis?
- Ca2+: calmodulin ratio
- epinephrine
- glucagon
What are the 2 inhibitors of complex I of the ETC?
- Rotenone
2. Amytal (barbiturates)
5 factors that constitute the pyruvate dehydrogenase complex?
- TPP
- Lipoic acid
- CoASH
- FAD
- NAD
What attaches to protons and allows them to enter into the mito without going through the ATP-generating system?
24-dinitrophenol
What are the 2 decarboxylation steps of the TCA cycle?
- Isocitrate dehydrogenase
2. alpha-ketoglutarate dehydrogenase
What are the 3 inhibitors of complex IV of the ETC?
- CN
- CO
- Azide
What 3 steps of the TCA cycle generate NADH?
Malate dehydrogenase
- Isocitrate dehydrogenase
- a-ketoglutarate dehydrogenase
NADPH generated from the HMP shunt is used for what?
FA synthesis, nucleotide synthesis, and glutathione reductase
Is the oxidative reaction of the HMP shunt reversible or irreversible?
Irreversible (G6PD and 6-phosphogluconate dehydrogenase)
At what 3 sites can the HMP shunt enter into glycolysis?
- Fructose-6-phosphate
- Glucose-6-phosphate
- glyceraldehyde-3-phosphate
What apoprotein is on the surface of LDL
Apoprotein B-100
What carries cholesterol from the tissues back to the liver?
HDLs
What apoprotein mediates the uptake of remnants by the liver?
Apoprotein E
What is the complex needed for acetyl CoA carboxylase?
Biotin
ATP
CO2 (acetyl CoA to malonyl CoA)
What are the 3 tissues where TAGs are produced?
- Liver
- MM
- Adipose
What delivers cholesterol to the tissues?
LDLs
What apoprotein is produced by the intestinal epithelium?
Apoprotein B-48
What carries TAGs to the peripheral tissues?
VLDLs
How many NADPHs are used per addition of each acetyl CoA into a fatty acid chain?
2 NADPHs/acetyl CoA
What apoprotein activates LPL in the capillary epithelium to hydrolyze TAGs
Apoprotein C-II
What apoproteins are on the surface of IDL?
Apoprotein B-100 and E
From which 2 substances are phospholipids made?
- DAGs
2. Phosphatidic acid
What apoproteins are on the surface of HDL?
Apoprotein A-I, C-II, and E
What is needed to produce a double bond in a fatty acid chain in the ER?
NADPH, O2 and cytochrome b5
What apoprotein activates lecithin cholesterol acyl transferase to esterify cholesterol from tissue?
Apoprotein A-I
What apoproteins are on the surface of VLDL
Apoproteins B-100, C-II, and E
At the end of each round of B-oxidation, what is released?
Acetyl CoA, FADH, and NADH
What hormone hydrolyzes TAGS to free FA and glyerol?
hormone-sensitive lipase?
What regulates the rate of ketone body formation?
The rate of B-oxidation
What intermediate enables propionyl CoA to enter into the TCA cycle?
Succinyl CoA
What sphingolipid is formed by the union of serine and palmitoyl CoA?
Sphingosine
What intermediate of cholesterol synthesis anchors proteins in the membranes and forms CoQ
Farnesyl pyrophosphate (FPP)
What is the complex needed for propionyl CoA carboxylase?
Biotin, ATP, and Co2
What are the 3 ketone bodies?
- Acetoacetate
- Acetone
- B-hydroxybutyrate
What is the only sphingolipid that contains choline and PO4?
Sphingomyelin (lecithin also, but is not a sphingolipid)
Sialic acid and amino sugars are needed to produce what sphingolipid?
Ganglioside
What vitamin is needed as a cofactor for decarboxylation and transaminase reactions?
B6
What are the 2 ways that nitrogen can enter into the urea cycle?
Aspartate; carbomoyl PO4
What is the only enzyme in the body that uses N5 methyl folate?
homocysteine methyl transferase
What are the glucogenic and ketogenic aa?
Phenylalanine tyrosine tryptophan isoleucine threonine
What is the pyrimidine intermediate the joins PRPP?
orotic acid
What 3 aa are used to synthesize purine ring?
- glycine
- aspartate
- glutamine
What is the primary end product of purine synthesis?
IMP
What are the 2 precursors of heme?
- glycine
2. Succinyl-CoA
What substrates are needed to produce carbamoyl PO4 (de novo pyrimidine synthesis)?
Glutamine, CO2, and ATP via carbamoyl PO4 synthetase II
What is the end product of purine catabolism?
uric acid
On a lineweaver-Burke plot, what type of binding has both plots crossing the y-axis in the same spot?
competitive, reversible inhibition (Vmax is the same, inc Km)
On the lineweaver-burke plot, what type of binding has both plots crossing the x-axis in the same spot?
Noncompetitive, reversible binding (dec in Vmax, km is same)
What is the max rate possible with a given amount of enzyme
Vmax
To what are intracellular glucose levels inversely related?
cAMP levels
DOes a saturated FA have double bonds?
no; unsaturated FA have double bonds
