High School Biology : Cell Structures and Organelles

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #21 : Cell Biology

How is mitochondrial DNA (mDNA) different from nuclear DNA?

Possible Answers:

All of these answers

mDNA does not have histones 

mDNA does not have introns 

mDNA is circular rather than linear

mDNA is inherited solely from the mother

Correct answer:

All of these answers

Explanation:

Mitochondrial DNA is much smaller and simpler than nuclear DNA, meaning it does not need histones or introns. Mitochondrial DNA is also circular, like bacterial DNA, rather than linear like nuclear DNA. As the ovum is the only contributor of mitochondria to an offspring, all mDNA must therefore be inherited from the mother. 

Example Question #22 : Cell Biology

Which of the following cellular organelles is responsible for making a majority of the cell's energy?

Possible Answers:

Rough endoplasmic reticulum

Mitochondria

Golgi apparatus

Nucleus

Lysosomes

Correct answer:

Mitochondria

Explanation:

Mitochondria produces most of the energy of the cell. The nucleus stores genetic information and is the site of transcription. The rough endoplasmic reticulum is the site of translation of proteins that have destinations other than in the cytoplasm. These proteins made in the rough endoplasmic reticulum are subsequently transported to the Golgi apparatus, where they are modified, packaged, and sent to their final destinations. Lysosomes have an acidic environment in which digestive enzymes break down polymers that will eventually be recycled. 

Example Question #23 : Cell Biology

What is the "powerhouse" of the cell?

Possible Answers:

Nucleus

Cell wall

Ribosome

Mitochondria

Cell membrane

Correct answer:

Mitochondria

Explanation:

The mitochondria is responsible for making the energy for the cell by cellular respiration. It does this by taking the major breakdown products of glucose (pyruvate and NADH) and converting them into ATP by the citric acid cycle and electron transport chain. This is an oxygen-dependent process.

Example Question #1 : Understanding Ribosomes

Where are ribosomes synthesized in the cell?

Possible Answers:

Mitochondria

Nucleolus

Cytoplasm

Rough endoplasmic reticulum

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 #2 : Understanding Ribosomes

Which of the following is a function of ribosomes?

Possible Answers:

Breaking down toxic substances that are in the cell

Making new proteins

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

Containing the DNA of an organism

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 #1 : Understanding Ribosomes

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

Possible Answers:

Nucleus

Lysosomes

Ribosomes

Centrioles

Cell membrane 

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 #21 : Cell Structures And Organelles

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

Possible Answers:

Lysosomes

Ribosomes

Golgi apparatus

Smooth endoplasmic reticulum

Mitochondria

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 #1 : Understanding Ribosomes

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

Possible Answers:

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

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 contain ribosomes that closely resemble the ribosomes of bacteria

Mitochondria are a type of bacteria

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 #3 : Understanding Ribosomes

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

Possible Answers:

N and C terminus

Sugar-phosphate backbone

RNA

Amino acids

Peptidyl site

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 #4 : Understanding Ribosomes

All of the following are true of ribosomes except __________.

Possible Answers:

They are made up of two parts called subunits

They combine with messenger RNA to make proteins

All ribosomes are found in the nucleus

They synthesize 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.

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