Molecular Biology: Enzymes and Ribosomes

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Questions and Answers

What type of bond is formed between the amino group of an incoming amino acid and the carboxyl group of a polypeptide chain during protein synthesis?

Ionic bond

Disulfide bond

Hydrogen bond

Peptide bond (correct)

Which transport mechanism is used for the import of proteins into the nucleus?

Vesicular transport

Transmembrane transport

Gated transport (correct)

Active transport

What is the primary transport mechanism for exporting proteins from the nucleus?

Vesicular transport

Simple diffusion

Gated transport (correct)

Transmembrane transport

Which of the following mechanisms is used for returning proteins from the Golgi apparatus to the endoplasmic reticulum?

Vesicular transport Signup and view all the answers

What characterizes lysosomes in terms of pH levels?

Maintain a pH of about 2.0 to 2.5 Signup and view all the answers

Which transport mechanism is primarily involved in importing proteins into mitochondria?

Transmembrane transport Signup and view all the answers

What feature do lysosomes maintain that aids in their function?

Contain heavily glycosylated membrane proteins Signup and view all the answers

Which of the following statements about affected individuals and their mothers is correct?

An affected woman almost always has an affected mother. Signup and view all the answers

Which of the following statements about the endoplasmic reticulum lumen is true?

It is continuous with the perinuclear space Signup and view all the answers

What processes are involved in recombination?

Crossing over and independent assortment. Signup and view all the answers

Which isotope was used to label the viral protein in the Hershey and Chase experiment?

Sulfur-35. Signup and view all the answers

Which of the following contains repetitive DNA and heterochromatin?

Centromere. Signup and view all the answers

Which of the following enzymes does not assist in the unwinding of DNA for replication?

Primase. Signup and view all the answers

What is the RNA sequence transcribed from the DNA strand 5′ GTACCGTC 3′?

5′ GACGGUAC 3′. Signup and view all the answers

Which statement correctly describes nonsense mutations?

They convert a codon for an amino acid into a stop codon. Signup and view all the answers

At neutral pH, which structure better represents the amino acid serine?

Neutral form with an amino group, a carboxyl group, and a carbon chain. Signup and view all the answers

What role does telomerase play in human cells?

It has an RNA component that serves as a template. Signup and view all the answers

Which term describes the structure that appears during the cell cycle where cells commit to divide?

Restriction point Signup and view all the answers

In which meiosis stage do sister chromatids separate?

Meiosis II Signup and view all the answers

What is the expected direction of DNA strand synthesis at the replication fork?

5′ to 3′ direction Signup and view all the answers

In a schematic representation of the cell cycle, which phase is typically represented by the letter 'M'?

Mitosis Signup and view all the answers

Which of the following correctly identifies the function of the early endosome?

Serves as a sorting compartment for internalized materials Signup and view all the answers

What occurs during the G1 phase of the cell cycle?

Cell growth and metabolic activity Signup and view all the answers

In which cellular structure can the secretory vesicle be found?

Cis Golgi network Signup and view all the answers

What type of enzyme is responsible for synthesizing RNA using a DNA template?

RNA polymerase Signup and view all the answers

Which statement describes how amino acids are linked to tRNA by aminoacyl-tRNA synthetase?

By forming a bond between the carboxyl group of the amino acid and the 3' or 2' hydroxyl group of the tRNA. Signup and view all the answers

In what direction is the mRNA read during translation?

5' to 3'; N- to C-terminus Signup and view all the answers

What happens during peptidyl transfer at the ribosome?

The carboxyl end of the polypeptide is released from the P-site tRNA and joined to the free amino group of the A-site tRNA. Signup and view all the answers

What is the primary function of RNA polymerase in the cell?

To synthesize RNA Signup and view all the answers

What is the term for a form of a gene that has a slightly different sequence but encodes the same type of RNA or protein?

allele Signup and view all the answers

What serves as the attachment point on the chromosome for spindle microtubules during cell division?

centromere Signup and view all the answers

Which of the following options accurately describes the connection between amino acids and tRNA?

Amino acids are linked to tRNA by an ester bond. Signup and view all the answers

What role do the A and P sites serve during translation?

They facilitate the formation of peptide bonds. Signup and view all the answers

How many sets of chromosomes do diploid cells have?

two sets Signup and view all the answers

During which phase of cell division do microtubules attach to the kinetochores of the chromosomes?

prometaphase Signup and view all the answers

Which statement correctly describes the overall directionality of peptide chain synthesis?

From N-terminus to C-terminus. Signup and view all the answers

What is the expected proportion of offspring with green seeds from a yellow offspring crossed with a green plant, assuming yellow seeds are dominant?

50% Signup and view all the answers

Which chromosome constitution will never result in a viable human baby?

YY Signup and view all the answers

What possible blood types can result from a couple with blood types AB and A?

A, B, and AB only Signup and view all the answers

Which statement is likely true regarding a child with an autosomal recessive trait when both parents are phenotypically normal?

The parents are both heterozygous for the trait. Signup and view all the answers

Study Notes

Enzyme Depiction

The enzyme depicted in the schematic drawing is RNA polymerase
This enzyme synthesizes RNA using one of the DNA strands as a template

Aminoacyl-tRNA Synthetase

Aminoacyl-tRNA synthetase activates a specific amino acid by linking it to its corresponding tRNA
The linkage occurs between the carboxyl group of the amino acid and the 3' or 2' hydroxyl group of the tRNA.

Ribosome Function

On the ribosome, mRNA is read from 5' to 3', and the polypeptide chain is synthesized from the N-terminus to the C-terminus.
Ribosomes translate mRNA into proteins during translation.
During translation elongation, ribosomes translocate along the mRNA from the 5' end to the 3' end in three-nucleotide sets.

Elongating Ribosome

An elongating ribosome binds to appropriate tRNAs in both the A and P sites.
The carboxyl end of a growing polypeptide chain is released from the P-site tRNA, then joined to the free amino group of the amino acid linked to the A-site tRNA.

Protein Transport Processes

Import into the nucleus and the other cellular pathways use different transport processes.
G - Gated transport
T - Transmembrane transport
V - Vesicular transport

Lysosomes

Lysosomes are the principal site of cellular digestion.
They maintain an acidic pH of about 2.0 to 2.5.
They contain F-type ATPases that pump protons into the organelles,
They are not homogeneous in size and shape.

Telomerase Enzyme

Telomerase in human cells has an RNA component.
It extends the telomeres using its RNA polymerase activity.
Telomerase's RNA polymerase activity does not use a DNA template to polymerize the telomeric DNA sequences.

Replication Fork

The strand labeled A in a replication fork diagram is known as the lagging strand.
This strand is extended from 5' to 3', but the replication fork moves in the opposite direction.
This produces discontinuously polymerized strands.

Restriction Point

The restriction point in a mammalian cell cycle is located during the G1 phase.

Meiosis and Mitosis

Meiosis II is more similar to mitosis than meiosis I.
Sister chromatids separate during meiosis II, not meiosis I.

Gene Form

The form of a gene that slightly differs from other forms yet encodes a similar RNA or protein is called an allele.

Chromosome Attachment

The centromere is the attachment point on the chromosome for spindle microtubules.

Diploid Cells

Diploid cells normally contain two sets of chromosomes.

Prometaphase

During prometaphase, microtubules attach to the kinetochores of chromosomes.

Mendel's Peas

In Mendel's peas, yellow seeds are dominant over green seeds.
A cross between a pure-breeding yellow seed plant and a pure-breeding green seed plant will result in all offspring with yellow seeds.
If a yellow seed offspring is crossed with a green seed plant, the expected proportion of plants with green seeds in the next generation will be 50%.

Human Chromosome Constitutions

A viable human male or female requires a complete set of chromosomes.
The chromosome constitution of a YY human cannot lead to a viable human baby.

Blood Types

Blood types A and B are codominant to each other.
Blood type O is recessive to both A and B.
The possible blood types of offspring from an AB type parent and an A type parent are A, B, and AB

X-Linked Recessive Traits

An affected man often has phenotypically normal parents
An affected man usually has a mother who carries the recessive allele
All the sons of a woman with an affected X-linked recessive trait will not be affected

Recombination

Recombination occurs through crossing over and independent assortment.

Hershey-Chase Experiment

In the Hershey-Chase experiment, the isotope 35S was used to label viral proteins.

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Description

This quiz focuses on the functions of crucial enzymes in molecular biology, including RNA polymerase and aminoacyl-tRNA synthetase. It also covers the role of ribosomes in protein synthesis and the process of translation. Test your understanding of these vital cellular processes!