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Exam 3 slide flash cards

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1
Q

The Calvin benson cycle consist of what three phases

A

Carboxylation
Reduction
Regeneration

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2
Q

Which of the following statements about the Calvin-Benson cycle is incorrect?

a) It is used by most autotrophs to fix CO2
b) In eukaryotes, it occurs in the stroma of chloroplasts
c) It consists of 3 phases: carboxylation, reduction, and regeneration
d) It requires 2 ATPs and 3 NADPHs to incorporate one CO2 molecule
e) The enzyme RuBisCO catalyzes the addition of CO2 to ribulose 1,5-bisphosphate

A

d) It requires 2 ATPs and 3 NADPHs to incorporate one CO2 molecule

Explanation: The correct statement is that three ATPs and two NADPHs are used during the incorporation of one CO2 molecule in the Calvin-Benson cycle [1][2].

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3
Q

Which enzyme catalyzes the addition of CO2 to ribulose 1,5-bisphosphate (RuBP) in the carboxylation phase of the Calvin-Benson cycle, and what is the result of this reaction?

A) RuBisCO; formation of two 3-phosphoglycerate molecules
B) Phosphofructokinase; formation of fructose 1,6-bisphosphate
C) Pyruvate carboxylase; formation of oxaloacetate
D) Transketolase; formation of sedoheptulose 7-phosphate

A

A) RuBisCO; formation of two 3-phosphoglycerate molecules

Explanation: The enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) catalyzes the addition of CO2 to ribulose 1,5-bisphosphate (RuBP), forming a 6-carbon intermediate that splits into 2 molecules of 3-phosphoglycerate (PGA) [1].

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4
Q

In the Calvin-Benson cycle, which of the following statements correctly describes the reduction and regeneration phases?

A) 3-phosphoglycerate is reduced to glyceraldehyde 3-phosphate, and fructose is produced

B) Glyceraldehyde 3-phosphate is oxidized to 3-phosphoglycerate, and glucose is produced

C) 3-phosphoglycerate is reduced to glyceraldehyde 3-phosphate, and Ribulose 1,5-bisphosphate is reformed

D) Ribulose 1,5-bisphosphate is reduced to 3-phosphoglycerate, and glucose is produced

A

C) 3-phosphoglycerate is reduced to glyceraldehyde 3-phosphate, and ribulose 1,5-bisphosphate is reformed

Explanation: According to the information provided, in the reduction phase, 3-phosphoglycerate is reduced to glyceraldehyde 3-phosphate. In the regeneration phase, ribulose 1,5-bisphosphate (RuBP) is reformed, allowing the cycle to repeat. Additionally, carbohydrates such as fructose and glucose are produced during these phases [1].

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5
Q

What other alternative CO2-fixation pathway can be used by autotrophs, and what is its key characteristic compared to the Calvin-Benson cycle?

A

Answer:
The Reductive TCA cycle is mentioned as an alternative CO2-fixation pathway. Its key characteristic is that it runs in the reverse direction of the oxidative TCA cycle

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6
Q

Which metabolic pathway shares enzymes with gluconeogenesis? [1]

A) Calvin-Benson cycle
B) Embden-Meyerhof pathway
C) Reductive TCA cycle
D) Pentose phosphate pathway

A

B) Embden-Meyerhof pathway

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7
Q

Which of the following statements about gluconeogenesis is correct?

a) Gluconeogenesis uses only carbohydrate precursors to synthesize glucose-6-phosphate
b) Gluconeogenesis shares no enzymes with the Embden-Meyerhof pathway
c) Gluconeogenesis involves the synthesis of glucose-6-phosphate from non-carbohydrate precursors
d) Gluconeogenesis requires only one enzyme specific to the pathway

A

*Answer: c) Gluconeogenesis involves the synthesis of glucose-6-phosphate from non-carbohydrate precursors**

Explanation:
Gluconeogenesis is the process of synthesizing glucose-6-phosphate from non-carbohydrate precursors [1]. It shares some enzymes with the Embden-Meyerhof pathway but also involves three reactions catalyzed by enzymes specific to gluconeogenesis:
- Two enzymes convert pyruvate to phosphoenolpyruvate
- One enzyme is involved in forming fructose 6-phosphate from fructose 1,6-bisphosphate

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8
Q

Which of the following statements about the synthesis of monosaccharides is correct?

a) Monosaccharides are synthesized without the involvement of nucleotides
b) Uridine diphosphate glucose (UDPG) is not involved in monosaccharide synthesis
c) Several sugars are synthesized while attached to a nucleoside diphosphate such as uridine diphosphate glucose (UDPG)
d) Monosaccharides are always synthesized as free molecules in the cell

A

The correct answer is c) Several sugars are synthesized while attached to a nucleoside diphosphate such as uridine diphosphate glucose (UDPG)

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9
Q

What two key components are involved in the complex process of peptidoglycan synthesis?

A
  1. In the cytoplasm:
    • UDP-NAM and UDP-NAG are synthesized
    • Pentapeptide (5P) is added to UDP-NAM
    • UDP-NAM-5P is transferred to BP, forming Lipid I
    • UDP-NAG transfers NAG to Lipid I, forming Lipid II
    • Flippase flips Lipid II to the periplasmic side
  2. In the periplasm:
    • NAG-NAM-5P is added to the end of the peptidoglycan chain
    • BP flips back over to the cytoplasm [3]
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9
Q

Explain the role of bactoprenol phosphate (BP) in peptidoglycan synthesis.

A

transports NAG-NAM-pentapeptide units acoss the cell to cytoplasm

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10
Q

How are cross-links formed in the peptidoglycan structure?

A

Transpeptidation reaction occurs to form crosslinks

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11
Q

What multiple steps and methods contribute to the process Amino Acid synthesis?

A

Contributing Processes
- Inorganic nitrogen assimilation
- Sulfur assimilation
- Amino acid biosynthetic pathways
- Anaplerotic reactions

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12
Q

Which of the following are potential sources of nitrogen for inorganic nitrogen assimilation in cells?

a) Ammonia (NH3)
b) Nitrate (NO3-)
c) Nitrogen gas (N2)
d) All of the above

A

d) All of the above

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13
Q

Describe the two main mechanisms by which ammonia (NH3) can be incorporated into carbon skeletons during inorganic nitrogen assimilation in microorganisms. Explain how these mechanisms differ and their importance in amino acid biosynthesis

A
  1. Reductive amination
  2. Glutamine synthetase-glutamate synthase pathway

These mechanisms are crucial for incorporating nitrogen into organic compounds, particularly amino acids. Once ammonia is incorporated, nitrogen can be transferred to other carbon skeletons by transaminases, facilitating the synthesis of various amino acids.

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14
Q

Question:
Which two enzymes are involved in the process of assimilatory nitrate reduction, and what are their specific roles?

A

Answer:
1. Nitrate reductase: Catalyzes the reduction of nitrate to nitrite
2. Nitrite reductase: Catalyzes the reduction of nitrite to ammonia
​

This process allows bacteria to reduce nitrate to ammonia and then incorporate it into an organic form

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15
Q

Which of the following statements about nitrogen fixation is correct?

a) It is the process of reducing atmospheric gaseous nitrogen to ammonia
b) It is catalyzed by the enzyme nitrogenase
c) It is found in most bacteria and archaea
d) Both a and b are correct
e) All of the above are correct

A

Answer: d) Both a and b are correct

Explanation:
Nitrogen fixation is indeed the process of reducing atmospheric gaseous nitrogen to ammonia, and it is catalyzed by the enzyme nitrogenase. However, it is not found in most bacteria and archaea, but only in a few species [1].

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16
Q

Exam Question:

Sulfur is an essential element for microbial cells. Which of the following statements correctly describes sulfur assimilation in microorganisms?

a) Sulfur is only needed for the synthesis of amino acids
b) Sulfur is obtained exclusively from intracellular amino acid reserves
c) Sulfur is required for the synthesis of amino acids and several coenzymes
d) Inorganic sulfate cannot be used as a sulfur source by microorganisms
e) Coenzyme A does not require sulfur for its synthesis

A

Correct Answer: c) Sulfur is required for the synthesis of amino acids and several coenzymes

Explanation: According to the information provided, sulfur is needed for:
- Synthesis of amino acids (specifically cysteine and methionine)
- Synthesis of several coenzymes (such as coenzyme A)
​
Additionally, the slide mentions that sulfur can be obtained from either external sources, intracellular amino acid reserves, or inorganic sulfate [1].
(Add Clarifier)

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16
Q

Which of the following statements correctly describes the use of sulfate as a sulfur source in microorganisms?

A) Sulfate is reduced to SO3(2-) and then to H2S before being used to synthesize cysteine
B) Assimilatory sulfate reduction is the same as dissimilatory sulfate reduction
C) Sulfate activation does not involve the formation of phosphoadenosine 5’-phosphosulfate (PAPS)
D) Cysteine is made by combining hydrogen sulfide with alanine

A

Answer: A

Explanation:
The correct answer is A. According to the information provided, in assimilatory sulfate reduction, sulfate is reduced to SO3(2-) and then to H2S, which is then used to synthesize cysteine. This process involves sulfate activation through the formation of phosphoadenosine 5’-phosphosulfate (PAPS), followed by the reduction of sulfate

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16
Q

Question:
Anaplerotic reactions play a crucial role in cellular metabolism. Which of the following statements best describes the purpose and function of anaplerotic reactions?

a) They are responsible for breaking down complex carbohydrates into simple sugars
b) They replenish TCA cycle intermediates that are used in amino acid biosynthesis
c) They are involved in the synthesis of fatty acids from acetyl-CoA
d) They catalyze the formation of peptide bonds during protein synthesis

A

Correct Answer: b) They replenish TCA cycle intermediates that are used in amino acid biosynthesis

Anaplerotic reactions are essential because:
* TCA cycle intermediates are used in many amino acid biosynthetic pathways
* These reactions replenish the intermediates to maintain the cycle’s function
* They ensure a balance between the use of precursor metabolites for biomass and energy extraction [1]

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17
Q

What is a nucleoside? What is a Nucleotide?

A

Nucleoside= Nitrogenous base+ pentose sugar
Nucleotide=Nucleoside +phosphate

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18
Q

Question:
Which of the following processes is NOT involved in the incorporation of inorganic phosphate (Pi) through the formation of ATP?

A) Photophosphorylation
B) Oxidative phosphorylation
C) Substrate-level phosphorylation
D) Glycolysis

A

Answer: D) Glycolysis

Explanation: According to the information provided, inorganic phosphate (Pi) is incorporated through the formation of ATP by three processes: photophosphorylation, oxidative phosphorylation, and substrate-level phosphorylation. Glycolysis is not mentioned as one of these processes [1].

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19
Q

Question:
Purine biosynthesis is a complex process involving multiple molecules. Which of the following statements accurately describes this process?

a) Purine biosynthesis primarily uses three different molecules to form the final purine skeleton
b) The initial products of purine biosynthesis are deoxyribonucleotides
c) Seven different molecules contribute parts to the final purine skeleton
d) Purine biosynthesis begins with the formation of pyrimidines

A

Answer: c) Seven different molecules contribute parts to the final purine skeleton [1]

Explanation:
The document states that purine biosynthesis is a complex pathway in which seven different molecules contribute parts to the final purine skeleton. Additionally, it mentions that the initial products are ribonucleotides, not deoxyribonucleotides [1].

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20
Q

Question:
Which of the following statements about pyrimidine biosynthesis is NOT correct?

a) The process begins with aspartic acid and high-energy carbamoyl phosphate
b) Ribonucleotides are the initial products of the pathway
c) Deoxyribose forms of uracil and cytidine nucleotides are created by oxidation of ribose
d) Pyrimidines are cyclic nitrogenous bases consisting of a single ring

A

Answer: c) Deoxyribose forms of uracil and cytidine nucleotides are created by oxidation of ribose

Explanation: This statement is incorrect. According to the information provided, deoxy forms of uracil and cytidine nucleotides are formed by reduction of ribose to deoxyribose, not oxidation [1].

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21
Q

Fatty acids are synthesized from what intermediates and by what complex?

A
  1. acetyl- CoA
  2. malonyl-CoA
  3. NADPH
    by
    Fatty acid synthase complex
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22
Q

Phospholipids and Triacylglycerol are made from Fatty acids and glycerol phospahte. What intermediate is important to the formation of these compounds?

A

Phosphatidic Acid

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23
Q

7:

Question:
Lipopolysaccharides (LPS) are crucial components of the Gram-negative bacterial outer membrane. Describe the synthesis and assembly process of LPS molecules, including:

a) The two main branches involved in LPS synthesis
b) Where Lipid A is synthesized
c) The sequence of steps in LPS assembly

A

Answer Key:
1. Two main branches: Lipid A-core branch and O-antigen branch

  1. Lipid A is synthesized in the cytoplasm
  2. Sequence of steps:
    • Lipid A synthesized in cytoplasm
    • Saccharides added
    • LPS flips to periplasm
    • O antigen added
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24
Q

How does DNA appear in Bacteria ?

A

circular

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25
Q

The location in which DNA is unwound?

A

Replication fork

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26
Q

Describe the process of bidirectional DNA replication in bacteria, including:

  • The shape of bacterial DNA
  • The number of origins of replication
  • The direction of replication
  • The key structure where DNA unwinding occurs
A

Answer Key:

  • Bacterial DNA is typically circular
  • Replication starts from a single origin
  • Replication proceeds bidirectionally (in both directions) from the origin
  • DNA unwinding occurs at the replication fork
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27
Q

Question:
What is the replisome in bacterial DNA replication, and how does it function during the initiation of replication?

A

Answer:
The replisome is:
- A complex of 12 proteins involved in DNA replication
- Composed of two replisomes that move in opposite directions away from the origin of replication
- Includes helicase, which:
- Forms a ring that encircles the DNA
- Disrupts hydrogen bonds
- Provides the force to move the replisome along the DNA

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28
Q

Question:
Which of the following statements correctly describes the DNA polymerase III holoenzyme in E. coli?

A) It consists of a single core enzyme
B) It is composed of 3 core enzymes, each with three different proteins
C) It plays a minor role in DNA replication
D) It is responsible for synthesizing RNA primers

A

Answer: B) It is composed of 3 core enzymes, each with three different proteins

Explanation:
The DNA polymerase III holoenzyme in E. coli is a complex enzyme that plays a major role in DNA replication. It is composed of:
- 3 core enzymes
- Each core enzyme consists of three different proteins
- Two of these core enzymes replicate one DNA strand, while the third replicates the other strand.

29
Q

what synthesizes short complementary strands of RNA Primers?

A

Primase

30
Q

True or false Dna A Protiens bind to oriC to separate strands and the SSB attach

A

False: It binds to oriC but causes a bending and separation of strands

31
Q

Proof reading is carried out from 3’ end of growing strand by

A

DNA Polymerase III

32
Q

What is the leader sequence transcibed into?

A

mRNA

33
Q

The Shine-Dalgarno sequence is not important for translation initiation T O F

A

False

34
Q

What is the purpose of the trailer sequence

A

prepares RNA polymerase for terminator sequence

35
Q

Genes coding for tRNA and rRNA are transcribed from different promoters? T o F

A

False

they are from single promoter

36
Q

What is an operon in bacteria ?

A

An operon in bacteria is:
- A group of genes encoding proteins involved in related processes
- Transcribed by a single promoter

37
Q

What are the 5 components that make up the core enzyme in Bacterial RNA polymerase ?

A

two alpha subunits
Beta
Beata ‘
and omega

38
Q

what has no catalytic activity but helps the core enzyme recognize the start of genes ?

A

Sigma factor

39
Q

Core enzyme and sigma factor make up what ?

A

RNA Polymerase Holoenzyme

40
Q

Exam Question:

What are the key features of the bacterial sigma promoter and their functions in transcription initiation?

A

Answer Key:
- The sigma promoter has two important sequences:
1. The -35 sequence (TTGACA):
- Located 35 base pairs upstream of the transcription start site
- Recognized by the sigma factor, helping to position the RNA polymerase holoenzyme

  1. The -10 sequence (TATAAT):
    • Located 10 base pairs upstream of the transcription start site
    • Marks where DNA strands begin to separate for transcription
41
Q

What are the termination mechanisms for transcription?

A

Intrinsic termination and Factor dependent

42
Q

Exam Question:

Describe the structure and key features of transfer RNA (tRNA) as presented in the document. Include information about its size, shape, and important functional elements.

A

Answer Key:

  1. Size: tRNA molecules are 70-95 nucleotides long
  2. Structure:
    • Forms a cloverleaf structure due to base pairing within the molecule
    • Folds into an L-shaped three-dimensional structure
  3. Key Feature - Anticodon:
    • Located on the anticodon arm
    • Complementary to the mRNA codon
  4. Functional Importance:
    • Carries amino acids during protein synthesis
    • The 3’ CCA end of aminoacyl-tRNA binds to 16S rRNA during translation
43
Q

What is the process of amino acid activation and what enzymes are involved?

A

Answer Key:
- Amino acid activation involves the attachment of an amino acid to the tRNA acceptor stem
-
- This process is catalyzed by aminoacyl-tRNA synthetases
- Key points:
- There are at least 20 different aminoacyl-tRNA synthetases
- Each synthetase is specific for a single amino acid
- tRNAs attach to their specific (cognate) amino acids

44
Q

What is the role of 23S rRNA in translation?

A

Answer:
The 23S rRNA acts as a ribozyme that catalyzes peptide bond formation during protein synthesis [1].

45
Q

Which of the following correctly describes the initiation of protein synthesis in bacteria?

A) IF1 and IF2 bind to the 50S subunit, allowing mRNA to enter
B) mRNA binds to the 50S subunit before the 30S subunit attaches
C) IF2+GTP+fMet-tRNA enter the P site, followed by mRNA binding to the 30S subunit
D) The 50S subunit binds to the 30S subunit before IF1 and IF2 are released

A

C) IF2+GTP+fMet-tRNA enter the P site, followed by mRNA binding to the 30S subunit

46
Q

what aids in the recognition of stop codons?

A

Release factors

47
Q

Function of Peptidyl transferase?

A

hydrolyzes the bond linking the polypeptide to the tRNA

48
Q

Question: What is a polyribosome in bacteria?

A) A complex of DNA with several RNA polymerases
B) A complex of mRNA with several ribosomes
C) A complex of tRNA with several amino acids
D) A complex of proteins with several chaperones

A

Correct Answer: B

Explanation: According to the information provided, a polyribosome is defined as a complex of mRNA with several ribosomes. This structure allows bacteria to increase efficiency by coupling RNA polymerase activity and translation.

49
Q

Protiens that help protiens fold are called ?

A

Chaperones

50
Q

Which of the following statements about protein translocation and secretion is NOT correct?

A) More than 1/3 of proteins leave the cytoplasm
B) Translocation is the movement of proteins from cytoplasm to or across the plasma membrane
C) The Sec system is the general secretion pathway
D) The Tat system secretes only unfolded proteins
E) YidC is involved in folding and translocating plasma membrane proteins

A

The correct answer is D. The Tat system actually secretes only folded proteins, not unfolded ones

51
Q

Which of the following statements is true about bacterial gene expression?

A) All bacterial genes are expressed constantly
B) Constitutive genes encode enzymes for specialized metabolic pathways
C) Genes that encode enzymes of the central metabolic pathway are typically constitutive
D) Regulated genes are always expressed regardless of environmental conditions

A

The correct answer is C. Constitutive genes, also known as housekeeping genes, encode enzymes of the central metabolic pathway and are constantly expressed as the cell needs a constant supply of these active enzymes

52
Q

Question: How does the presence of lactose affect the production of β-galactosidase in bacterial cells?

A) It has no effect on β-galactosidase production
B) It decreases β-galactosidase production to 3 molecules
C) It increases β-galactosidase production from 3 to 3,000 molecules
D) It completely stops β-galactosidase production

A

C

The information provided shows that in the absence of lactose, there are 3 β-galactosidase molecules, while in the presence of lactose, this number increases to 3,000 β-galactosidase molecules . This demonstrates the inducible nature of the gene encoding β-galactosidase, where its expression is dramatically increased in response to the presence of its substrate, lactose.

53
Q

what does B-galactosidase do in the presence of lactose ?

A

Hydrolyzes lactose into galactose and glucose

54
Q

Which of the following correctly describes transcriptional control mechanisms?

A) Negative control involves an activator protein binding to enhance transcription
B) Positive control involves a repressor protein blocking RNA polymerase
C) Negative control involves a repressor protein binding to inhibit transcription
D) Positive control involves RNA polymerase blocking the operator

A

The correct answer is C

  • Negative control: Involves a repressor protein binding to the operator, which inhibits transcription initiation by blocking RNA polymerase from binding .
  • Positive control: Involves an activator protein binding to sites upstream of the promoter, which encourages RNA polymerase to bind .
55
Q

Which of the following statements about the lac repressor is correct?

A) It binds to the operator site when lactose is present
B) It inhibits transcription when lactose is absent
C) It is encoded by the lacZ gene
D) It promotes transcription of the lac operon genes

A

The correct answer is B

According to the information provided, the lac repressor binds to the operator and inhibits transcription when no lactose is present

56
Q

When lactose is present in the cell, which of the following occurs in the lac operon regulation?

A) The lac repressor binds more tightly to the operator
B) Allolactose binds to the repressor, preventing it from binding to the operator
C) The number of β-galactosidase molecules decreases
D) The lac repressor degrades lactose directly

A

The correct answer is B

When lactose is present:
* Lactose permease brings lactose into the cell
* β-galactosidase converts lactose to allolactose
* Allolactose binds to the repressor, preventing it from binding to the operator
* This allows transcription of the lac operon genes to proceed

57
Q

What is the primary function of the tryptophan (trp) operon?

A) To synthesize lactose
B) To break down arabinose
C) To produce enzymes needed for tryptophan synthesis
D) To regulate the production of β-galactosidase

A

The correct answer is C) To produce enzymes needed for tryptophan synthesis

Explanation:
The trp operon contains five structural genes that code for enzymes needed to synthesize tryptophan. It operates under negative transcriptional control by the trp repressor and only functions in the absence of tryptophan. When tryptophan is present, it acts as a corepressor

58
Q

what is attenuation ?

A

Termination of the transcriptipon within the leader region

59
Q
  1. The arabinose operon is controlled by:
    a) Only negative transcriptional control
    b) Only positive transcriptional control
    c) Both positive and negative transcriptional control
    d) Neither positive nor negative transcriptional control
A

c

60
Q

When arabinose is absent:
a) AraC monomers bind to DNA
b) AraC dimerizes and binds to two different sites on DNA
c) AraC does not bind to DNA at all
d) Transcription of arabinose enzymes is activated

A

b

creates an inhibtion

61
Q
  1. In the presence of arabinose:
    a) DNA remains folded, inhibiting transcription
    b) AraC dimerizes and binds to two different sites
    c) Arabinose binds to AraC, interfering with dimerization
    d) Transcription of arabinose enzymes is inhibited
A

c

transcription occurs

62
Q
  1. The folding pattern of a riboswitch is altered by:
    a) Temperature changes
    b) pH changes
    c) Binding of an effector molecule
    d) Interaction with ribosomes
A

c

63
Q

Question: How do riboswitches regulate translation in Gram-positive bacteria?

A) By altering the folding of mRNA
B) By blocking the binding of RNA polymerase
C) By occluding the Shine-Dalgarno sequence
D) By degrading the mRNA

A

Correct Answer: C) By occluding the Shine-Dalgarno sequence

Correct Answer: C) By occluding the Shine-Dalgarno sequence

This change in folding occludes the Shine-Dalgarno sequence, preventing the ribosome from binding and thus stopping translation initiation

64
Q
  1. What is the main function of a two-component signal transduction system?
    a) To regulate gene expression
    b) To link external events to internal gene expression
    c) To phosphorylate proteins
    d) To produce second messengers
A

Correct answer: b

65
Q
  1. Which component spans the plasma membrane in a two-component system?
    a) Response regulator
    b) Sensor kinase
    c) Phosphate group
    d) Gene
A

Correct answer: b

66
Q
  1. What happens to the response regulator in a two-component system?
    a) It phosphorylates itself
    b) It spans the membrane
    c) It undergoes a conformational change
    d) It transfers phosphate to the sensor kinase
A

Correct answer: c

66
Q
  1. How do phosphorelay systems differ from two-component systems?
    a) They involve fewer proteins
    b) They don’t use phosphorylation
    c) They transfer phosphoryl groups to many proteins
    d) They only occur in eukaryotes
A

Correct answer: c

67
Q
  1. What is the role of alternate sigma factors in bacterial gene expression?
    a) They inhibit RNA polymerase activity
    b) They direct RNA polymerase to specific subsets of bacterial promoters
    c) They degrade mRNA transcripts
    d) They activate translation of proteins
A

b

68
Q
  1. Which of the following is NOT mentioned as a second messenger in bacterial global control?
    a) Cyclic adenosine monophosphate (cAMP)
    b) Guanosine tetraphosphate (ppGpp)
    c) Cyclic dinucleotides (c-di-GMP)
    d) Cyclic guanosine monophosphate (cGMP)
A

d

69
Q

Which statement best describes the action of second messengers?
a) They are produced in response to an external signal
b) They are always present in high concentrations in the cell
c) They only affect a single gene at a time
d) They are directly involved in DNA replication

A

a

70
Q

Which of the following statements about telomerase activity is correct?

A) Telomerase uses a DNA template for DNA synthesis
B) The G-tail serves as a primer for RNA synthesis
C) Telomerase maintains chromosome length by lengthening the 5’ end
D) Telomerase has reverse transcriptase activity and uses an internal RNA template

A

The correct answer is D.

71
Q

The purpose of the Tata box

A

houskeepign of genes and absent for regulated genes

72
Q

Which of the following is NOT mentioned as a modification required for initial transcripts before they are ready to be translated?

A) Addition of a 5’ cap
B) 7-methylguanosine addition
C) Removal of introns/splicing together exons
D) Addition of a 3’ poly-A tail
E) Phosphorylation of the transcript

A

E

Explanation:
The image lists the following modifications:
* Addition of a 5’ cap—7-methylguanosine
* Removal of introns/splicing together exons
* Addition of a 3’ poly-A tail

These modifications help protect the mRNA from degradation and signal that it is ready for transport to the cytoplasm. The cap also aids in recognition of mRNA by ribosomes in the cytoplasm.

73
Q

Which of the following is NOT a product of the spliceosome’s function?

A) Mature mRNA that goes to the ribosome
B) Lariat-excised RNA molecule
C) Protein molecules
D) Joined exons

A

The correct answer is C) Protein molecules.

Explanation:
* The spliceosome is described as a ribozyme that removes introns from pre-mRNA
* It produces two main products:
1. Mature mRNA that goes to the ribosome
2. Lariat-excised RNA molecule (the removed intron)
* The spliceosome joins exons together
* While the spliceosome is made of proteins and RNA molecules, it does not produce protein molecules as a product of its splicing function

Micro BIO (13 decks)

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