AP Biology : Cell Structures

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #26 : Understand Functions Of Organelles In The Cell

DNA can be found in which of the following cellular compartments of a eukaryotic cell?

Possible Answers:

Nucleus, mitochondria, chloroplasts and cytoplasm

Nucleus only

Nucleus, mitochondria, and chloroplasts

Nucleus and mitochondria only

Correct answer:

Nucleus, mitochondria, and chloroplasts

Explanation:

While most of a cell's DNA is located in the nucleus, some DNA is found in the mitochondria and chloroplasts. The DNA found in plasmids supports the endosymbiotic theory. The cytoplasm of eukaryotes does not contain free floating DNA like in prokaryotes.

Example Question #141 : Cell Structures

What are extranuclear genes and what are their functions?

Possible Answers:

Extranuclear genes are genes located outside the nucleus that aid in DNA replication and protein synthesis

Extranuclear genes are additional genes within the nucleus that play a role in DNA replication and protein synthesis

Extranuclear genes are genes located outside the nucleus that do not play a significant role within the cell 

None of these

Extranuclear genes are additional genes within the nucleus that do not play a significant role within the cell 

Correct answer:

Extranuclear genes are genes located outside the nucleus that aid in DNA replication and protein synthesis

Explanation:

Extranuclear genes, also known as cytoplasmic genes, are genes located outside the nucleus. They can be found in other parts of the cell, such as the mitochondrion, chloroplasts, and other plastids. Each of these organelles is thought to have originally been an independent prokaryotic cell, ingested by another cell, known as the endosymbiotic theory. Each of these organelles has its own DNA and works in cooperation within the nuclear DNA. 

Example Question #141 : Cell Structures

Which of the following statements is true?

Possible Answers:

Ribosomes house chromosomes and synthesize DNA

The smooth endoplasmic reticulum synthesizes proteins

The Golgi apparatus synthesizes lipids and metabolizes carbohydrates ingested by the cell

The mitochondrion is responsible for breaking down damaged organelles and ingested substances

Peroxisomes are composed of enzymes that create hydrogen peroxide, which is then converted to water 

Correct answer:

Peroxisomes are composed of enzymes that create hydrogen peroxide, which is then converted to water 

Explanation:

Ribosomes are organelles composed of two subunits of ribosomal RNA and proteins. There are two types: free ribosomes, which are found in the cytosol of the cell, and bound ribosomes, which are bound to the rough endoplasmic reticulum. Their primary purpose is to synthesize proteins. Messenger RNA will bring amino acids to the ribosomes, where proteins are then synthesized. The endoplasmic reticulum is an organelle that is composed of bounded tubules and sacs and is continuous with the nuclear envelope. It is composed of two parts: the smooth endoplasmic reticulum and the rough endoplasmic reticulum. The smooth endoplasmic reticulum synthesizes lipids, metabolizes carbohydrates, stores calcium, and detoxifies the cell of drugs and poisons. The rough endoplasmic reticulum, studded with ribosomes, aids in protein synthesis. The mitochondrion is bound by a double membrane; the inner membrane has many infoldings called cristae. This increases the surface area of the organelle and therefore increases productivity. Known as the “powerhouse of the cell,” the mitochondrion creates ATP for the cell through a process known as cellular respiration. Peroxisomes are specialized metabolic organelles bound by a single membrane. They contain enzymes that transfer hydrogen atoms from substrates to oxygen, producing hydrogen peroxide. Hydrogen peroxide is then converted to water. The Golgi apparatus is a stack of flattened membranous sacs. Its purpose is to modify proteins, carbohydrates, and phospholipids. Polysaccharides are also synthesized here. Besides synthesis and modification of these macromolecules, the Golgi apparatus also sorts products and sends them to other parts of the cell through vesicles. 

Example Question #142 : Cell Structures

In the study of cell biology, organelles can be examined using __________.

Possible Answers:

a magnifying glass

an electron microscope

the naked eye

a light microscope

Correct answer:

an electron microscope

Explanation:

Organelles, for the most part, are too small to be clearly defined by a simple light microscope. Although, larger organelles may be seen with a light microscope, they cannot be well-studied using them. An electron microscope can achieve remarkable magnification and resolution. Some electron microscopes can even resolve individual molecules or atoms. Also note that an egg (chicken, human, ostrich etc.) is a single cell. We can study the nucleus (yolk) with the naked eye, but this is a special case, and the question does not provide us any information that would make this a reasonable assumption.

Example Question #631 : Cellular Biology

What is the process by which a cell intakes extracellular fluid in "gulps" via tiny vesicles?

Possible Answers:

Phagocytosis

Exocytosis

Simple diffusion

Pinocytosis

Correct answer:

Pinocytosis

Explanation:

Pinocytosis is the uptake of extracellular fluids. The cell accomplishes this by creating vesicles from the cell membrane around droplets of extracellular fluid and carrying them inside the cell. This process is unspecific in which substances it carries into the cell (not receptor-mediated). Exocytosis involves the same concept, but in the other direction (from inside the cell out). Simple diffusion does not involve the creation of vesicles, rather it involves substances freely diffusing through the plasma membrane from areas of high concentration to areas of low concentration without the net input of energy.    

Example Question #632 : Cellular Biology

In eukaryotes the organelles that convert energy to forms the cells can use for work are __________.

Possible Answers:

mitochondria only

rough endoplasmic reticulum only

both mitochondria and chloroplasts

chloroplasts only

Correct answer:

both mitochondria and chloroplasts

Explanation:

Both mitochondria and chloroplasts convert energy to work in eukaryotes. Mitochondria are the sites for the catabolic process that creates ATP in animals. In plants, chloroplasts are the sites of photosynthesis where solar energy is converted to chemical energy.  

Example Question #633 : Cellular Biology

Cristae are located in __________.

Possible Answers:

the stroma

mitochondria

the plasma membrane

chloroplasts

Correct answer:

mitochondria

Explanation:

Cristae are found in mitochondria. Mitochondria are enclosed by an envelope of two membranes. The inner membrane is convoluted with infoldings called cristae. This is an adaption that increases the surface area of the inner membrane of the mitochondria so that ATP synthesis can be maximized. The chloroplast equivalent of cristea are the thylakoid membranes. The stroma is the matrix equivalent of the chloroplast. The plasma membrane is not nearly as convoluted as the inner mitochondrial membrane.

Example Question #634 : Cellular Biology

What are the distinct, threadlike structures that contain the genetic information that is passed from one generation of cells to the next?

Possible Answers:

Chromosomes

Golgi apparatus

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Correct answer:

Chromosomes

Explanation:

The chromosomes are the threadlike structures that contain genetic information.  Rough endoplasmic reticulum is involved in protein synthesis.  Smooth endoplasmic reticulum is involved in lipid synthesis.  The Golgi apparatus is involved in modification and delivering of proteins within the cell and for secretion outside the cell.

Example Question #635 : Cellular Biology

Eukaryotic cells have this structure that is a network of protein filaments that helps the cell to maintain its shape.

Possible Answers:

RNA

DNA

Cytoskeleton

Smooth endoplasmic reticulum

Correct answer:

Cytoskeleton

Explanation:

The cytoskeleton is a network of protein filaments in eukaryotic cells that helps the cell to maintain its shape.  Smooth endoplasmic reticulum is involved in lipid synthesis.  DNA is the genetic code molecules in the nucleus.  RNA is involved in protein synthesis.

Example Question #636 : Cellular Biology

Which of the following is true regarding active transport?

Possible Answers:

The cell uses energy and protein pumps to move molecules across the membrane.

Osmosis occurs across the lipid bilayer.

The cell does not use energy and diffusion occurs.

The cell uses energy to bond molecules to the phosphate heads.

Correct answer:

The cell uses energy and protein pumps to move molecules across the membrane.

Explanation:

In active transport, the cell uses energy (ATP) through the protein pumps to move molecules across the membrane.  This process does not involve osmosis, which is a form of passive transport.

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