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Questions and Answers
What triggers the proteolytic degradation of reductase?
What triggers the proteolytic degradation of reductase?
What happens to SREBP when cholesterol levels fall?
What happens to SREBP when cholesterol levels fall?
How does the proportion of protein in a lipoprotein affect its density?
How does the proportion of protein in a lipoprotein affect its density?
Which lipoprotein is responsible for scavenging excess cholesterol?
Which lipoprotein is responsible for scavenging excess cholesterol?
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What is the main consequence of a defect in LDL receptors?
What is the main consequence of a defect in LDL receptors?
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What characterizes the core of lipoprotein particles?
What characterizes the core of lipoprotein particles?
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How does LDL enter peripheral tissues?
How does LDL enter peripheral tissues?
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What is the potential consequence of a point mutation?
What is the potential consequence of a point mutation?
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What happens to LDL after it is hydrolyzed in the cell?
What happens to LDL after it is hydrolyzed in the cell?
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How do somatic mutations differ from germline mutations?
How do somatic mutations differ from germline mutations?
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What happens during insertion mutations?
What happens during insertion mutations?
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Which type of mutation results in a premature stop codon?
Which type of mutation results in a premature stop codon?
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How do DNA repair systems operate?
How do DNA repair systems operate?
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Which statement about amino acid mutations is true?
Which statement about amino acid mutations is true?
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Which type of mutation only affects the nucleotide level?
Which type of mutation only affects the nucleotide level?
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What is the consequence of environmental stress on mutations?
What is the consequence of environmental stress on mutations?
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Which enzyme catalyzes the formation of 5-phosphoribosyl-1-amine from PRP and glutamine?
Which enzyme catalyzes the formation of 5-phosphoribosyl-1-amine from PRP and glutamine?
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What is the final product of the purine pathway?
What is the final product of the purine pathway?
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Which amino acid is added to IMP to form AMP?
Which amino acid is added to IMP to form AMP?
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Which of the following substances acts as a suicide inhibitor in nucleotide synthesis?
Which of the following substances acts as a suicide inhibitor in nucleotide synthesis?
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What is required for the conversion of ribonucleotide diphosphates to deoxyribonucleotides?
What is required for the conversion of ribonucleotide diphosphates to deoxyribonucleotides?
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What important role does 5-phosphoribosyl-1-amine serve in purine metabolism?
What important role does 5-phosphoribosyl-1-amine serve in purine metabolism?
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Which nucleotide is formed when IMP is hydrated and oxidized?
Which nucleotide is formed when IMP is hydrated and oxidized?
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Which compound provides a necessary carbon group for the synthesis of TMP from dUMP?
Which compound provides a necessary carbon group for the synthesis of TMP from dUMP?
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What role do human accelerated regions (HARs) mainly play in the human genome?
What role do human accelerated regions (HARs) mainly play in the human genome?
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How do nuclear hormone receptors regulate transcription after binding with their ligand?
How do nuclear hormone receptors regulate transcription after binding with their ligand?
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Which domain of nuclear hormone receptors is responsible for binding to DNA?
Which domain of nuclear hormone receptors is responsible for binding to DNA?
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What effect does histone acylation have on DNA?
What effect does histone acylation have on DNA?
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What process involves cutting and splicing RNA after transcription?
What process involves cutting and splicing RNA after transcription?
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Which statement is true about the function of RNA polymerase I?
Which statement is true about the function of RNA polymerase I?
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What happens to some receptors in their unbound state?
What happens to some receptors in their unbound state?
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What initiates the release of repressors from nuclear hormone receptors?
What initiates the release of repressors from nuclear hormone receptors?
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What distinguishes TAGs from glycerophospholipids?
What distinguishes TAGs from glycerophospholipids?
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Which compound is commonly formed as a precursor in the synthesis of phospholipids?
Which compound is commonly formed as a precursor in the synthesis of phospholipids?
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How is phosphatidate activated in the synthesis pathway?
How is phosphatidate activated in the synthesis pathway?
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Which head group is the most abundant in phosphatidylcholine?
Which head group is the most abundant in phosphatidylcholine?
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What occurs during phosphatidylcholine synthesis when there is a deficiency of choline?
What occurs during phosphatidylcholine synthesis when there is a deficiency of choline?
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Which of the following statement is true regarding dietary choline requirements?
Which of the following statement is true regarding dietary choline requirements?
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What drives the activation of serine or inositol in the phospholipid synthesis pathway?
What drives the activation of serine or inositol in the phospholipid synthesis pathway?
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What role does excess cholesterol play in the metabolization of food energy substrates?
What role does excess cholesterol play in the metabolization of food energy substrates?
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What is the role of GTP in the formation of the 70s complex?
What is the role of GTP in the formation of the 70s complex?
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During prokaryotic elongation, what is the function of elongation factor?
During prokaryotic elongation, what is the function of elongation factor?
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What distinguishes eukaryotic translation from prokaryotic translation?
What distinguishes eukaryotic translation from prokaryotic translation?
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Why do stop codons in prokaryotes require release factors (RF)?
Why do stop codons in prokaryotes require release factors (RF)?
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What is the first amino acid incorporated during eukaryotic protein synthesis?
What is the first amino acid incorporated during eukaryotic protein synthesis?
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What occurs when the ribosomal complex encounters a stop codon?
What occurs when the ribosomal complex encounters a stop codon?
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What is an essential feature of eukaryotic mRNA that helps in translation?
What is an essential feature of eukaryotic mRNA that helps in translation?
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Which of the following is NOT a characteristic of prokaryotic genes?
Which of the following is NOT a characteristic of prokaryotic genes?
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Study Notes
Chapter 29 Notes
- Fatty acids are often subcomponents of complex lipids, like glycerophospholipids, which have a glycerol backbone and two fatty acyl chains.
- Phospholipids have a head group, and phosphatidate is a common precursor, formed from DHAP and phosphorylated glycerol.
- Phosphatidylcholine is the most abundant phospholipid in mammals, and its synthesis is influenced by dietary choline.
- If choline stores are adequate, phosphatidylcholine will be synthesized by methylating phosphatidylethanolamine.
- Cholesterol synthesis is primarily in the liver, though other tissues can also synthesize it.
- The pathway involves several stages: stage one is converting excess food/energy into acetyl-CoA, which gets converted to cholesterol and energy. Stage two and three occur in the endoplasmic reticulum, making isopentenyl phosphate, starting with 3 acetyl-CoA.
Chapter 30 Notes
- Amino acids are formed from the digestion of proteins and from the breakdown of defective or excess proteins.
- Aminotransferases transfer amino groups to a-ketoglutarate, forming glutamate, and releasing pyruvate, and other related intermediates
- The urea cycle converts ammonia into urea for excretion.
- This cyclical process occurs primarily in the liver in humans.
- It is catalyzed by carbamoyl phosphate synthetase (CPSI) and requires two ATP, and is an irreversible reaction.
- The final step of the urea cycle cleaves arginine into urea and ornithine catalysed by arginase
- Aromatic amino acids are both ketogenic and glucogenic
- Phenylketonuria (PKU) is a genetic disorder where phenylalanine is not degraded properly and results in the accumulation of phenylalanine and related metabolites in the body.
- Elevated phenylalanine levels disrupt brain growth and metabolism, which causes phenylpyruvate to be excreted in the urine.
Chapter 32 Notes
- Nucleotides are composed of a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and a phosphate group.
- Nucleotides can be mono-, di-, or tri-phosphate.
- Nucleotides can be synthesized de novo (from scratch) or via salvage pathways.
- The purine synthesis pathway produces IMP, which gets further processed into AMP and GMP.
- The pyrimidine synthesis pathway produces UMP, which can be further modified to form other pyrimidine nucleotides.
- Deoxyribonucleotides are formed from ribonucleotides via reduction.
Chapter 33 Notes
- Mutations are changes in nucleotide sequence.
- Mutations can be classified as point mutations (single nucleotide changes) or large-scale mutations (e.g., deletions, duplications, inversions).
- Point mutations can be synonymous (no change in amino acid), neutral (minor change in amino acid), missense (change to a different amino acid), or nonsense (change to a stop codon).
- Large-scale mutations can cause significant changes in the resulting protein.
- Genetic screening of newborns can detect individuals with conditions like phenylketonuria (PKU).
Chapter 34 Notes
- DNA replication is a semiconservative process, where each new DNA molecule contains one original strand and one newly synthesized strand.
- DNA polymerase needs a 3'-OH group to add nucleotides (5' → 3' direction).
- Enzymes like topoisomerases help in unwinding and restoring supercoils during replication.
- Leading strands are synthesized continuously, while Okazaki fragments are synthesized discontinuously on lagging strands.
- Topoisomerases are responsible for resolving supercoiling during DNA replication.
- Both prokaryotic and eukaryotic DNA polymerases have exonuclease activity to correct replication errors and remove mismatches.
- Telomeres are repetitive DNA sequences at chromosome ends that protect against degradation.
Chapter 35 Notes
- Point mutations are single nucleotide changes in the DNA sequence and can result in silent mutations, neutral mutations, missense mutations, or nonsense mutations.
- Large-scale mutations are changes affecting larger segments of the chromosome, including insertions, deletions, duplications, and inversions.
- Synonymous mutations do not affect the amino acid sequence.
- Nonsynonymous mutations change the amino acid sequence.
- Large-scale mutations can lead to significant phenotypic changes, including genetic diseases.
Chapters 36 and 37 Notes
- RNA is synthesized from a DNA template by RNA polymerase, which is sensitive to α-amanitin.
- RNA polymerase I synthesizes rRNA; RNA polymerase II synthesizes mRNA precursors (pre-mRNA); and RNA polymerase III synthesizes tRNA.
- Eukaryotic mRNA undergoes extensive processing, including 5' capping, 3' polyadenylation, and splicing of introns.
- Transcription factors bind to promoter regions to regulate the initiation of transcription.
- Enhancers and response elements influence the strength of transcription.
Chapter 38 Notes
- RNA polymerase I, II, and III synthesize rRNA, mRNA precursors, and tRNA, respectively, and are sensitive to different inhibitors.
- RNA processing involves 5' capping, 3' polyadenylation, and splicing of introns in pre-mRNA.
- Alternative splicing creates multiple mRNAs from a single gene, increasing proteomic diversity.
Chapter 39 Notes
- The genetic code is a triplet code where each three-nucleotide codon specifies a particular amino acid.
- The genetic code is degenerate, meaning multiple codons can specify the same amino acid.
- Transfer RNA (tRNA) molecules are adaptor molecules that carry amino acids to the ribosome.
- tRNA molecules have an anticodon that base-pairs with the mRNA codon.
- Aminoacyl-tRNA synthetase is an enzyme that attaches the correct amino acid to its corresponding tRNA.
Chapter 40 Notes
- Translation is the process of protein synthesis, where ribosomes read mRNA to synthesize proteins.
- Ribosomes have three binding sites: A site, P site, and E site.
- Initiation factors (IFs) and elongation factors (EFs) are needed for the initiation and elongation steps of translation.
- Termination factors (RFs) are needed to terminate translation.
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