T.15 Ribozimas

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Questions and Answers

What is the primary role of metal ions in ribozyme catalytic activity?

To coordinate peptide bond formation
To stabilize the RNA's active site (correct)
To initiate the splicing reaction
To facilitate substrate positioning

What is the resulting bond formed during the splicing reaction catalyzed by ribozymes?

Phosphodiester bond (correct)
Glycosidic bond
Disulfide bond
Peptide bond

What is the primary goal of in vitro selection experiments in the context of ribozyme evolution?

To understand the structure of ribozymes
To study the RNA world hypothesis
To develop new therapeutic strategies
To evolve new ribozyme functions (correct)

What is the location of the peptidyl transferase center (PTC) in the ribosome?

In the large subunit of the ribosome (D) Signup and view all the answers

What is the resulting product of RNA cleavage catalyzed by ribozymes?

A 2',3'-cyclic phosphate and a 5'-hydroxyl group (D) Signup and view all the answers

What is the potential application of RNA cleavage ribozymes in RNA-based therapies and diagnostics?

To selectively degrade specific RNA molecules (D) Signup and view all the answers

What is the hypothesized role of RNA in the early stages of life?

To serve as a catalyst and genetic material (C) Signup and view all the answers

What is the proposed advantage of peptides and proteins over RNA?

Their higher turnover rate and efficiency (A) Signup and view all the answers

What is the primary difference between ribozymes and modern enzymes?

Their composition (RNA vs. protein) (B) Signup and view all the answers

What is the proposed origin of introns?

They were present in the last universal common ancestor (LUCA) (D) Signup and view all the answers

What is the current role of ribozymes in modern cells?

They are residual and still used for specific RNA-based reactions (B) Signup and view all the answers

What is the suggested advantage of ribonucleoproteins over RNA?

Their ability to recognize more types of substrates (A) Signup and view all the answers

What is the hypothetical sequence of events in the evolution of enzymes?

RNA → ribonucleoproteins → protein-based enzymes (B) Signup and view all the answers

What is the primary difference between the 'RNA world' hypothesis and other theories of early life?

The primacy of RNA as a genetic material and catalyst (B) Signup and view all the answers

What is the suggested reason for the persistence of ribozymes in modern cells?

Their vestigial nature as remnants of the 'RNA world' (B) Signup and view all the answers

What is the characteristic that distinguishes viroids from viruses?

They are RNA particles that fold into a hammerhead structure (C) Signup and view all the answers

What is the function of the hammerhead ribozyme?

To auto-cleave itself (A) Signup and view all the answers

What is the characteristic of ribointerruptores?

They can adopt different structures depending on the environment (A) Signup and view all the answers

What is the difference between ribozymes and proteic enzymes?

Ribozymes have a lower KM than proteic enzymes (B) Signup and view all the answers

What is the primary function of the glmS ribozyme?

To cleave RNA molecules (D) Signup and view all the answers

What is the characteristic of RNA molecules that can act as ribozymes?

They can fold into a specific three-dimensional structure (A) Signup and view all the answers

What is the advantage of ribozymes over proteic enzymes?

They are more specific than proteic enzymes (B) Signup and view all the answers

What is the difference between ribozymes and RNase P?

RNase P is a type of ribozyme that can cleave RNA molecules (A) Signup and view all the answers

What is the characteristic that sets ribozymes apart from traditional enzymes?

Their composition as RNA molecules (B) Signup and view all the answers

What is the term used to describe the process of RNA molecules autocatalyzing their own cleavage and splicing?

Autoescission (D) Signup and view all the answers

What is the proposed role of RNA molecules in the early stages of life on Earth?

Catalysts of chemical reactions (D) Signup and view all the answers

What is the limitation of RNA molecules as catalysts compared to protein molecules?

Their lower efficiency and efficacy (A) Signup and view all the answers

What is the type of bond that is formed or broken during the autoescission reaction of RNA molecules?

Phosphodiester bond (A) Signup and view all the answers

What is the functional group that is capable of catalyzing reactions in RNA molecules?

Hydroxyl group (D) Signup and view all the answers

What is the role of the ribonucleasa P enzyme in the context of RNA processing?

Cleavage of RNA molecules (C) Signup and view all the answers

What is the term used to describe the process of RNA molecules catalyzing their own cleavage and re-ligation?

Autocatalysis (B) Signup and view all the answers

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Study Notes

Catalytic Activity

Ribozymes are RNA molecules that catalyze specific chemical reactions, including peptide bond formation and RNA cleavage
Catalytic activity is dependent on the RNA's tertiary structure, which creates a binding site for substrates
Ribozymes can accelerate chemical reactions by as much as 10^10-fold, making them comparable to protein enzymes
Catalytic activity is often dependent on metal ions, such as Mg2+, which stabilize the RNA's active site

Splicing

Ribozymes can catalyze the splicing of RNA molecules, a process essential for removing introns and joining exons
Splicing involves two sequential transesterification reactions, resulting in the formation of a phosphodiester bond
Group I and group II introns are two types of self-splicing ribozymes, which can catalyze their own splicing reactions
Splicing reactions are often dependent on the presence of metal ions and specific RNA structures

Ribozyme Evolution

Ribozymes are thought to have evolved before protein enzymes, playing a key role in the RNA world hypothesis
The evolution of ribozymes is closely tied to the evolution of RNA structures and functions
In vitro selection experiments have been used to evolve new ribozyme functions, such as ligase activity
The evolution of ribozymes has implications for the development of new therapeutic strategies

Peptidyl Transferase

The peptidyl transferase center (PTC) is a ribozyme that catalyzes peptide bond formation during protein synthesis
The PTC is located in the large subunit of the ribosome and is composed of RNA
The PTC uses a mechanism involving substrate positioning and metal ion coordination to facilitate peptide bond formation
The PTC is a key target for antibiotic development, as it is essential for bacterial protein synthesis

RNA Cleavage

Ribozymes can catalyze the cleavage of RNA molecules, resulting in the formation of a 2',3'-cyclic phosphate and a 5'-hydroxyl group
RNA cleavage is a key step in many cellular processes, including RNA degradation and RNA processing
The hammerhead and hairpin ribozymes are two well-studied examples of RNA cleavage ribozymes
RNA cleavage ribozymes have potential applications in RNA-based therapies and diagnostics

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