MCAT- Eukaryotic Cells

Which of the following is NOT a tenet of cell theory?

Answer: A. All cells are capable of reproducing The statement that all cells are capable of reproducing is not part of cell theory and is also not strictly true (e.g., mature erythrocytes have no nucleus and cannot reproduce). Cell Theory States: Page #1

Which of the following is a function of the rough endoplasmic reticulum?

Answer: A. Folding and modifying newly synthesized proteins Bound ribosomes synthesize proteins that are fed into the rough endoplasmic reticulum, where they are folded with the help of chaperone proteins and modified.

How are peroxisomes and lysosomes different?

Answer: A. Peroxisomes are not packaged at the Golgi apparatus Peroxisomes are organelles that break down a variety of compounds such as fatty acids and amino acids. These organelles also facilitate the detoxification of reactive oxygen species such as hydrogen peroxide. Lysosomes are organelles that possess hydrolytic enzymes that digest unwanted materials. Lysosomes are formed by pinching off as vesicles from the Golgi apparatus, but this is not true of peroxisomes.

In which of the following structures are ribosomes synthesized?

Answer: A. The nucleolus The nucleolus is a structure within the nucleus of eukaryotic cells that is primarily responsible for the synthesis and assembly of ribosomes, which are macromolecular complexes of RNA and proteins used for the synthesis of other proteins required by the cell.

If a person had a genetic mutation that impaired the microtubules from forming efficiently, which of the following would NOT occur?

Answer: All motive cells will have difficulty moving While flagellated and ciliated cells would have trouble moving, many cells, like those of the immune system, rely on actin reorganization in order to move, and would thus be unaffected.

At which of the following pH levels would a lysosome's enzymes function best?

Answer: B. 5 Lysosomes are spherical structures that contain enzymes that function best under slightly acidic conditions (pH 4.5-5.0) and can break down most types of molecules, thereby acting as the waste disposal system of the cell by digesting unwanted materials.

True or false: Secretory proteins are transported from the endoplasmic reticulum to the trans-face of the Golgi apparatus.

Answer: B. False This statement is false. Secretory proteins are transported from the endoplasmic reticulum to the cis-face of the Golgi appartus. There, they will undergo packaging as they are transported first to the medial- then trans-face of the Golgi apparatus, before release in the form of vesicles that can subsequently fuse with the plasma membrane to exocytose their contents.

Which of the following is a function of the smooth ER?

Answer: B. It synthesizes lipids The smooth ER participates in several metabolic processes, including lipid synthesis, carbohydrate metabolism, and detoxification.

Why is the rough ER called "rough"?

Answer: C. It is studded with ribosomes The rough endoplasmic reticulum is studded with ribosomes, the complexes that synthesize proteins. This stands in contrast to the smooth endoplasmic reticulum, which has a smooth surface when examined with an electron microscope.

A microfilament capped at the plus (+) end would tend to:

Answer: C. Shrink Capping prevents the addition or removal of monomers to the capped end of the filament. Actin filaments capped at the plus (+) end would tend to shrink, as actin monomers readily fall off the (-) end.

A loss-of-function mutation in a gene that codes for tubulin would most directly inhibit which of the following processes in meiosis?

Answer: Chromosome seperation Chromosome separation during anaphase depends on the spindle, which is made of microtubules. Microtubules are composed of tubulin.

In which of the following processes do mitochondria play the biggest role?

Answer: D. Mitochondria play a critical role in energy production by way of aerobic cellular respiration. The citric acid cycle occurs in the mitochondrial matrix, and the electron transport chain complexes and ATP synthase are embedded in the inner membrane. These generate ATP in the presence of oxygen.

Which of the following is a function of the Golgi apparatus?

Answer: D. Packaging proteins that will leave the cell. Proteins from the endoplasmic reticulum are packaged by the Golgi apparatus and transported as vesicles to their ultimate destinations.

Which of the following is NOT a similarity between nuclei and mitochondria?

Answer: D. Use of binary fission While the nucleus divides during cell division, only mitochondria replicate independently of the cell cycle via binary fission.

Which of the following types of cells are most likely to contain large amounts of smooth ER?

Answer: Epithelial liver cells The liver is a site of extensive detoxification and lipid metabolism, and thus liver cells have abundant smooth endoplasmic reticulum (ER).

True or false: Dyneins are the accessory proteins that carry neurotransmitter-containing vesicles to a neural synapse.

Answer: False This statement is false. It is kinesins, not dyneins, that move from the center of the cell towards the edge, including towards the plasma membrane and the synapse. Dyneins travel in the opposite direction.

A cell is isolated that contains DNA but does not contain a nucleus. Which of the following organelles would most likely be part of this cell?

Answer: Flagellum Cells that do not contain nuclei are prokaryotes, such as bacteria, and do not contain most other organelles. However, bacteria may contain flagella, which aid in locomotion.

A protein exiting a cell, such as a peptide-hormone, would pass through which of the following organelles during its exit? Select all that apply.

Answer: Golgi body & plasma membrane Protein secretion is a process by which a protein is translated inside of a cell, and then moves through a series of steps before exiting the cell. One of these steps occurs at the Golgi apparatus, where proteins are packaged and sorted for distribution. The plasma membrane would be the final stop for a protein exiting the cell.

In eukaryotic cells, DNA replication takes place in the: I. nucleus. II. cytoplasm. III. mitochondria.

Answer: I and III only. Recall that both the nucleus and the mitochondria contain DNA. Therefore, replication can take place in both of these organelles.

Of the options below, which of the following are typically multimeric? Select all that apply.

Answer: Keratin, F-actin, and Lamin F-actin is the polymeric form of actin, meaning it is made of multiple actins polymerized together.Keratin - an intermediate filament - is multimeric. Lamin - an intermediate filament - is multimeric.

Which of the following would be significantly increased by mutations affecting microtubule function? Select all that apply.

Answer: Male sterility, mucus buildup in the throat and birth defects Mutations affecting microtubules would cause birth defects by impacting the ability for chromosomes to be "pulled apart" during anaphase of meiosis.Mutations affecting microtubules would cause mucus buildup in the throat by inhibiting throat epithelial cells' ciliary action, which normally clears debris in the throat.Mutations affecting microtubules could cause male sterility in at least two ways: 1) chromosomal nondisjunction might affect cellular functionality, and 2) cilia dysfunction would inhibit sperm motility.

Place the following fibers in order of decreasing diameter: microtubules, actin microfilaments, and intermediate filaments.

Answer: Microtubules, intermediate filaments, actin filaments(aka microfilaments)

Which of the following organelles is capable of replicating itself?

Answer: Mitochondria Mitochondria have their own nucleic acids, separate from the nuclear DNA. This allows them to replicate independently of the cell cycle.

Which cell would be expected to contain the most lysosomes?

Answer: Phagocytic immune cell A phagocytic immune cell, such as a macrophage, would have a high concentration of lysosomes to digest phagocytized (engulfed) particles. Red blood cells, kidneys, and the skin are not as highly involved in waste detoxification.

Which of the following are most likely NOT potential functions of cytoskeletal capping proteins? Select all that apply.

Answer: Promoting the Krebs cycle and promoting cytoskeletal polymer degradation This is the opposite of what capping proteins do - inhibition of cytoskeletal protein degradation.Aerobic respiration occurs in mitochondria to provide energy to cells in the form of ATP. Since the Krebs cycle is one of these processes that takes place in the mitochondria, this is likely unrelated to cytoplasmic cytoskeletal proteins such as actin and microtubules.

Which of the following have flagella?

Answer: Sperm cells Flagella are used by sperm cells for movement.

Where do lysosomal enzymes originate?

Answer: They are synthesized at the ER. The enzymes in lysosomes are proteins, which are synthesized by ribosomes in the rough ER and packaged by the Golgi bodies. Since this question asks where these enzymes originate (or begin), the answer is the ER.

True or false: Genetic mutations that result in malformed actin might lead to easily-torn muscles.

Answer: True This statement is true. Actin microfilaments are found in muscle fibers, where their movement in conjunction with myosin and other accessory proteins causes muscle contraction. Damaged or malformed actin might lead to weak muscle fibers.

Which of the following is NOT a purpose of a cell's cytoskeleton?

Answer: providing energy to the cell Aerobic respiration occurs in the mitochondria and anaerobic respiration via glycolysis occurs in the cytoplasm.

Microtubules are found in cilia or flagella in which of the following cell types? Select all that apply.

Answer: sperm cells, tracheal epithelial cells, and fallopian tube epithelial cells Sperm cells contain flagella. In eukaryotes, both cilia and flagella are composed of microtubules. Tracheal and fallopian tube epithelial cells contain cilia. In eukaryotes, both cilia and flagella are composed of microtubules. Tracheal and fallopian tube epithelial cells contain cilia. In eukaryotes, both cilia and flagella are composed of microtubules.

True or false: Only mutations to mitochondrial DNA in mothers are heritable in offspring.

Answer: true This statement is true. Mitochondria are inherited through the maternal lineage - DNA mutations inside of a mother's mitochondria may be passed down to children. Conversely, mutations in a man's mitochondrial DNA will not be passed down to his children.

Neurotransmitters are delivered by kinesins, taken from the cell body of a neuron to the axon terminal. Neurons must have extensive:

C. Microtubules Microtubules are tracks made of tubulin which extend out from the microtubule organizing center of a cell. They are heavily implicated in transporting cargo around a cell - for example, vesicles containing neurotransmitters. Kinesins and dyneins are motor proteins which "walk" along microtubules like a road.

Match each of the organelles below to one of its main functions.

Nucleus: Storage and transcription of DNA Mitochondria: Energy production Endoplasmic Reticulum: Protein modification Ribosome: Protein synthesis

Match each of the following terms with its function.

Tubulin dimer: Building block for microtubules MTOC: General name for location from which microtubules extend Centriole: Component of centrosome Centrosome: Specific name for organelle from which spindle fibers extend during mitosis Microtubules are assembled from tubulin dimers, MTOCs provide a "base" for microtubule growth, and centrosomes (the organizing centers for the mitotic spindle) are each composed of two centrioles.