High School Biology : Understanding Ribosomes

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #24 : Cell Structures And Organelles

Where are ribosomes synthesized in the cell?

Possible Answers:

Cytoplasm

Rough endoplasmic reticulum

Nucleolus

Mitochondria

Correct answer:

Nucleolus

Explanation:

Ribosomal subunits and rRNA are both created in the nucleolus in order to create functional ribosomes. The nucleolus is a specialized structure for ribosome production and is found within the nucleus.

Mitochondria are responsible for generating cellular energy. The rough endoplasmic reticulum helps modify proteins. The cytoplasm is the aqueous matrix found within the cell.

Example Question #1 : Understanding Ribosomes

Which of the following is a function of ribosomes?

Possible Answers:

Making new proteins

Breaking down toxic substances that are in the cell

Containing the DNA of an organism

Transporting materials in and out, as well as within the cell

Correct answer:

Making new proteins

Explanation:

Ribosomes are composed of ribosomal RNA (rRNA) and proteins. Their primary function is to bind mRNA and tRNA to build proteins. Ribosomes are the fundamental structure necessary for translation and protein formation.

The nucleus houses the DNA of the cell, the cytoskeleton and specialized proteins transport compounds within the cell, and the smooth endoplasmic reticulum breaks down toxic substances, such as alcohol.

Example Question #2 : Understanding Ribosomes

Which organelle is most involved in the formation of bonds between amino acids?

Possible Answers:

Cell membrane 

Nucleus

Ribosomes

Lysosomes

Centrioles

Correct answer:

Ribosomes

Explanation:

Ribosome are structures in the cell where the assembly of polypeptide chains takes place by joining together individual amino acids. 

The process of making a protein starts when DNA is transcribed to mRNA in the nucleus. After some modification, the mRNA exits the nucleus and enters the cytoplasm of the cell. 

In the cytoplasm, the small ribosomal subunit binds to mRNA at the start codon. tRNA (which is attached to an individual amino acid) and the large ribosomal subunit join as well, to complete the complex. tRNA translocates from the A-site to the P-site, and a new tRNA binds to the A-site. A peptide bond forms between the two amino acids bound to the tRNA molecules in the A and P sites of the ribosome. A new tRNA then enters the A-site, pushing the previous tRNA molecules to the P-site and E-site respectively and the process continues to elongate the peptide chain. This continues until the stop codon is encountered. 

None of the other cell structures are involved in the formation of proteins. The nucleus stores genetic information, the cell membrane separates the interior of the cell from its environment, lysosomes degrade waste in the cell, and centrioles organize the mitotic spindle fibers. 

Example Question #3 : Understanding Ribosomes

Which of the following cell structures is composed of proteins and RNA, and serves as the apparatus on which proteins are synthesized?

Possible Answers:

Ribosomes

Lysosomes

Mitochondria

Golgi apparatus

Smooth endoplasmic reticulum

Correct answer:

Ribosomes

Explanation:

A ribosome is an organelle consisting of two subunits, each composed of ribosomal RNA and protein. Ribsomes are the site of protein systhesis, or translation.

Mitochondria produce energy by aerobic metabolism. Lysosomes contain intracellular digestive enzymes. The major function of lysosomes is to digest old or damaged macromolecules, especially proteins. The smooth endoplasmic reticulum is a series of interconnected channels in the cytoplasm that synthesize lipids and remove cellular toxins. The Golgi apparatus modifies and packages protein and lipids according to their destinations. 

Example Question #4 : Understanding Ribosomes

Why do scientists posit that mitochondria existed as aerobic bacteria a long time ago?

Possible Answers:

Mitochondria are not classified as an organelle

Mitochondria do not have their own DNA and must consume other organelles in order to produce DNA

Mitochondria are a type of bacteria

Mitochondria contain ribosomes that closely resemble the ribosomes of bacteria

Mitochondria cannot interact with the rest of the cell and are treated as foreign objects in the body

Correct answer:

Mitochondria contain ribosomes that closely resemble the ribosomes of bacteria

Explanation:

Endosymbiosis is a theory widely supported by cell biologists, which states that the mitochondria of eukaryotes very likely evolved from aerobic bacteria living within a host cell. There are three pieces of evidence for this:

1) Mitochondria can only arise from existing mitochondria via a replication mechanisms similar to binary fission.

2) Mitochondria have their own genomes, which more closely resemble the genomes of bacteria than those of eukaryotes. 

3) The protein manufacturing machinery (ribosomes) of mitochondria more closely resemble the machinery of bacteria than those found in the cytoplasm of eukaryotes. 

Example Question #5 : Understanding Ribosomes

Which of the following is not characteristic found within a fully functional ribosome?

Possible Answers:

RNA

Sugar-phosphate backbone

Amino acids

Peptidyl site

N and C terminus

Correct answer:

Sugar-phosphate backbone

Explanation:

A sugar phosphate backbone is characteristic of a DNA sequence. While fully functional ribosomes are composed of a mix of functional RNA and protein the sugar-phosphate components within the RNA do not comprise the backbone of the entire ribosome. This question also requires the knowledge that an amino acid chain has an N and C terminus. Last, it is important to note that the Peptidyl site is where the bond between two amino acids is synthesized. 

Example Question #6 : Understanding Ribosomes

All of the following are true of ribosomes except __________.

Possible Answers:

They are made up of two parts called subunits

All ribosomes are found in the nucleus

They synthesize proteins

They combine with messenger RNA to make proteins

Correct answer:

All ribosomes are found in the nucleus

Explanation:

Ribosomes synthesize proteins and are made up of two parts called subunits that come together during the process of translation with messenger RNA (mRNA).  Ribosomes are not found in the nucleus.  They are found floating freely in the cytoplasm or bound to rough ER.

Example Question #31 : Cell Biology

Many people consume alcohol and drugs on a daily occasion. The body needs a detoxification system against these toxins to prevent harmful accumulation of metabolites from the breakdown of these toxins. What organelle is responsible for this detoxification?

Possible Answers:

Golgi apparatus

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Nucleus

Correct answer:

Smooth endoplasmic reticulum

Explanation:

Smooth endoplasmic reticulum is primarily responsible for the production of lipids and for the detoxification of drugs and toxins from the body. 

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