BP Eukaryotic Cells (Ch 2 Sections 1 and 2)

Question 1

Match each of the organelles below to one of it’s main functions:

1. Nucleus
2. Mitochondria
3. Endoplastmic Reticulum
4. Ribosome

FUNCTIONS

• Energy Production
• Protein Modification
• Protein Synthesis
• Storage and transcription of DNA

Answer 1

1. Nucleus………………………………Storage and transcription of DNA
2. Mitochondria………………………Energy Production
3. Endoplastmic Reticulum…….Protein Modification
4. Ribosome……………………………Protein Synthesis

Protein synthesis occurs in ribosomes (small protein and RNA complexes) which translate mRNA into protein. The nucleus, a membrane-bound organelle, stores the cells DNA genome and is the site of DNA replication and transcription. Mitocondria, membrane-bound organelles with their own genome, produce usable chemical energy in the form of ATP. Finally, the endoplasmic reticulum serves as a protein modification site post-synthesis.

Question 2

Which of the following organelles is capable of replicating itself?

1. Mitochondria
2. Ribosome
3. Golgi apparatus
4. Endoplasic reticulum

Answer 2

1. Mitocondria

CORRECT

Mitochondria have their own DNA genome, separate from the cell’s nuclear genome. This allows the mitocondria to replicate independently of the cell cycle.

INCORRECT

RNA translation of nuclear DNA produces ribosome protein components. Therefore, ribosomes are incapable of replicating by themselves.

The golgi apparatus is a membrane-bound organelle that consists of flattened pouches (cisternae) that package proteins for intracellular transport. The Golgi apparatus does not have its own genome and therefore cannot replicate independently of the cell cycle.

The endoplasmic reticulum is a membrane-bound organelle that consists of continuous flattened membrane stacks that serve as a protein synthesis site among other functions. The endoplasmic reticulum does not have its own genome and therefore cannot replicate independently of the cell cycle.

Question 3

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?

1. Mitochondria
2. Flagellum
3. Golgi apparatus
4. Endoplasmic reticulum

Answer 3

2. Flagellum

Prokaryotic cells (such as backteria) do not contain nuclei and most other organelles. However, bacteria may have flagella, an organelle that aids in locomotion.

Prokaryotic cells do not contain internal organelles, other than ribosomes, but contain DNA free-floating in the cytosol. As the question describes a prokaryotic cell and only eukaryotic cells contain mitochondria, this answer is incorrect.

The golgi apparatus is a eukaryotic organelle that assists intracellular protein packaging and transport. Prokaryotic cells lack most organelles and don’t containa golgi apparatus.

The endoplasmic reticulum (which contains both the rough and the smooth endoplasmic reticulum is a eukaryotic organelle that serves as protein … among other functions. Prokaryotic cells lack most organelles and don’t contain an endoplasmic reticulum.

Question 4

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

1. Neurons
2. Red blood cells
3. Epithial liver cells
4. Cardiac muscle cells

Answer 4

3. Epithelial liver cells

The smooth endoplasmic reticulum (ER) is a membrane-bound organelle that participates in lipid synthesis, calcium ion storage and metabolism, and detoxification. The liver is a site of extensive detoxification and lipid metabolism. Therefore, liver cells have abundant smooth ER.

Question 5

What cell would be expected to contain the most lysosomes?

1. Red blood cell
2. Kidney cell
3. Skin cell
4. Phagocytic immune cell

Answer 5

4. Phagocytic immune cell

Phagocytic immune cells (such as macrophages) have high lysosome concentrations to digest phagocytized (engulfed) particles. Given that phagocytes break down pathogens and toxins using lysosomal enzymes, phagocytic immune cells are expected to have the highest lysosome quantity of the listed cells.

Question 6

Where do lysosomal enzymes originate?

1. They are packaged at the golgi apparatus
2. They are synthesized at the ER
3. They are pinched off from the cell membrane
4. They are imported from outside the cell

Answer 6

2. They are synthesized at the ER

Lysosomal enzymes are proteins that are synthesized in the rough ER. After synthesis, they are packaged within the golgi apparatus into lysosomes, where they break down waste.

Question 7

Which cells have flagella?

1. Macrophages
2. Muscle cells
3. Sperm cells
4. Neurons

Answer 7

3. Sperm cels

Sperm cells must propell themselves long distances in order to fertilize an egg. To propel themselves, sperm use flagella for movement.

Question 8

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

1. Giving the cell shape
2. Allowing the cell to move
3. Providing energy to the cell
4. Facilitating cytokinesis during cellular division

Answer 8

3. Providing energy to the cell

Aerobic respiration occurs in mitochondria and anaerobic respiration (glycolysis) occurs in the cytoplasm. Both respiration types provide energy to the cell. The cytoskeleton is not involved in cellular respiration and energy production.

Question 9

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

1. Cells would have difficulty completing mitosis
2. Neuronos would have difficulty secreting neurotransmitters
3. All motile cells would have difficulty moving
4. Vesicular transport would be disrputed

Answer 9

3. All motile cells would have difficulty moving

While flagellated and cilliated cells would have trouble moving, many cells (like immune system cells) rely on actin reorganization for motility, and would thus be unaffected.

Question 10

Match each of the following terms with its function:

1. Tubulin Dimer
2. MTOC
3. Centriole
4. Centrosome

FUNCTION

• Building block for microtubules
• General name for location from which microtubules extend
• Component of centrosome
• Specific name for organelle from which spindle fibers extend during mitosis

Answer 10

1. Tubulin Dimer…….Building block for microtubules
2. MTOC…………………General name for location from which microtubules extend
3. Centriole…………….Component of centrosome
4. Centrosome………..Specific name for organelle from which spindle fibers extend during mitosis

Microtubules are fibrous hollow rods that help provide and support cell shape and form the mitotic spindle in cell division, among other functions. Microtubules assemble from dynamic aggragates of tubulin (a protein) dimers. Microtubule organizing centers (MTOCs) provide a “base” for microtubule growth and is where microtubules originate. Centrosomes (the organizing centers for the mitotic spindles) are each composed of two centrioles (two barrel-shaped clusters of microtubules).

Question 11

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

1. All cells are capable of reproducing
2. The cell is the basic unit of life
3. All cells arise from pre-existing cells
4. All organisms are composed of one or more cells

Answer 11

1. All cells are capable of reproducing

Cell theory states:

• Cells are the basic unit of life
• All cells arise from pre-existing cells
• All organisms comprise of one or more cells

Question 12

In eukaryotic cells, DNA replication takes place in the:

1. nucleus
2. cytoplasm
3. mitochondria

Answer 12

1. nucleus & 3. mitochondria

Both the nucleus and the mitochondria contain their own DNA genome. In eukaryotes, mitochondrial and nuclear DNA replication occurs independently of each other and within their respective organelles.

Question 13

In which of the following structures are ribosomes assembled?

1. Nucleolus
2. Cytoplasm
3. Cell membrane
4. Mitochondrial membrane

Answer 13

1. Nucleolus

The nucleolus is a structure within a eukaryotic nucleus that is primarily responsible for ribosome synthesis and assembly. Ribosomes are RNA-protein complexes that translate mRNA into protein.

Question 14

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

1. Double membrane
2. Presence of DNA
3. membrane-embedded proteins
4. Use of binary fission

Answer 14

4. use of binary fission

While the nucleus divides during mitosis, only mitochondria replicate independently of the cell cycle (via binary fission)

Question 15

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

1. Cellular movement
2. cellular respiration
3. digestion of lipids
4. digestion of proteins

Answer 15

2. cellular respiration

Mitochondria play a critical role in aerobic cellular respiration. The aerobic reactions of cellular respiration (the critical acid cycle, the electron transport chain, and ATP synthase) occur within mitochondria. Ultimately, mitochondria produce usable energy (in the form of ATP) via cellular respiration.

Question 16

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

1. Folding and modifying newly syntesized proteins
2. Digesting toxic materials in the cytoplasm
3. Packaging proteins for leaving the cell
4. Transporting proteins to the golgi apparatus

Answer 16

1. Folding and modifying newly syntesized proteins

Ribosomes bound to the rough ER syntehsize proteins. Within the ER, newly syntesized proteins may be modified or folded with the help of chaperone proteins.

Question 17

Why is the rough ER called “rough”?

1. because it is the site of toxic waste disposal in the cell
2. Because it is studded with tRNA
3. Because it is studded with ribosomes
4. Becaue it operates at a low pH

Answer 17

3. Because it is studded with ribosomes

Ribosomes (RNA-protein complexes that synthesize proteins) stud the rough ER membrane. This is constrasted to the smooth ER (its main functions are lipid synthesis and detoxification) which lacks ribosomes, and therefore has a smooth appearance when viewed under an electron microscope.

Question 18

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

1. It synthesizes proteins from mRNA
2. It synthesizes lipids
3. It provides a site for protein production
4. It generates ATP

Answer 18

2. It synthesizes lipids

The smooth ER participates in several metabolic processes, including lipid synthesis, carbohydrate metabolism, and detoxification.

Question 19

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

1. synthesizing proteins from mRNA
2. Neutralizing toxins
3. Providing a site for protein production
4. Packaging proteins that will leave the cell

Answer 19

4. Packaging proteins that will leave the cell

The golgi apparatus packages proteins from the endoplasmic reticulum into vesicles and then transports the vesicle-enclosed proteins to their ultimate destinations.

Question 20

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

1. 1
2. 5
3. 7
4. 9

Answer 20

2. 5

Lysosomes are spherical organelles that contain enzymes that best function under slightly acidic conditions (pH 4.5-5.0) and can break down most biomolecules. Lysosomes act as the cell’s waste disposal system by digesting unwanted materials.

Question 21

How are peroxisomes and lysosomes different?

1. Peroxisomes are not packaged at the golgi apparatus
2. Peroxisomes are not membrane-bound
3. Peroxisomes do not exist in eukaryotes
4. Lysosomes do not exist in eukaryotes

Answer 21

1. Peroxisomes are not packaged at the golgi apparatus

Peroxisomes are organelles that break down a variety of compounds Peroxisomes also facilitate the detoxification of reactive oxygen species (such as hydrogen peroxide). Alternatively, lysosomes digest unwanted materials using hydrolytic enzymes and are formed by pinching off vescles from the golgi apparatus. This is contrasted to peroxisomes, which are formed within the ER but are not packaged by the golgi body.

Question 22

Place the following fibers in order of decreasing diameter:

microtubes / actin microfilaments / intermediate filaments

Answer 22

microtubules

intermediate filaments

actin filaments

Question 23

Of the options below, which are typically multimeric?

1. F-actin
2. G-actin
3. keratin
4. lamin

Answer 23

F-actin, G-actin, Lamin

Question 24

T or F?

Genetic mutations that result in malformed actin might lead to easily torn muscles.

Answer 24

TRUE

Muscles contain actin microfilaments, where their movements in conjuction with myosin and other accessory proteins causes muscle contraction. Damaged or malformed actin might lead to easily torn muscle fibers.

Question 25

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

1. chromosome duplication
2. chromosome separation
3. genetic recombination
4. chromosome condensation

Answer 25

2. chromosome separation

Chromosome separation occurs during anaphase. The cell spindle coordinates chromosome separation and is made of microtubules Microtubules are tubulin polymers.

Question 26

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

1. grow
2. stay the same length
3. shrink
4. this is impossible to predict

Answer 26

3. shrink

Capping prevents the removal of monomers to the capped end of the filament. Actin filaments capped at the (+) end would likely shrink, as actin monomers readily fall off the minus (-) end, shrinking the filament size.

Question 27

Microtubules are found in cilia or flagella in which of the following cell types?

1. Sperm cells
2. E. coli
3. tracheal epithelial cells
4. Fallopian tube epithelial cells

Answer 27

1. Sperm cells

3 tracheal epithelial cells

4. Fallopian tube epithelial cells

Question 28

T or F?

Dyneins are the accessory proteins that carry neurotransmitter-containing vescles to a neural synapse.

Answer 28

FALSE

Kinesins, NOT dyneins, move from the center of the cell towards the cells edge. Kinesins move toward the plasma membrane and the synapse, dyneins, travel from the cells edge (or synapse) towards the cell center.

Question 29

Which of the following organelles is thought to have been created when specialized bacteria survived endocytosis into other bacteria?

1. Mitochondria
2. golgi apparatus
3. lysosome
4. peroxisome

Answer 29

1. mitochondria

The endosymbiotic theory suggests that how eukaryotic cells originated: One bacteria endocytosed another prokaryote. The endocytosed prokaryote later became an organelle enclosed within the cytoplasm of the endocytosing bacteria. Endosymbiotic theory describes how mitochondria are originated. The theory’s supporting evidence includes mitochondria’s independent small circular genome that resembles a prokaryotic genome.

Question 30

A cell is isolated that contains no organelles. Which of the following cell types is this cell most likely to be?

1. Platelet
2. red blood cell
3. leukocyte
4. neuron

Answer 30

2. red blood cell

Red blood cells expel their nuclei, genetic material, and organelles during their maturation process. MCAT questions often test this understanding. For example, “mature red blood cells” would likely answer a question that asks which cell type is least helpful for studying genetic mutations.

Question 31

T or F?

If scientists induce a deleterious mutation to all voltage gated cell-surface calcium ion channels, muscular contraction will be inhibited on the basis of intracellular calcium insufficiency.

Answer 31

FALSE

While voltage-gated calcium ion channels are important to facilitating neurotransmitter release, inhibiting the channels will not directly impair muscle contraction. Muscle contraction relies on calcium ions and the majority of calcium ions are stored in reservoirs in the endoplasmic reticulum.

Question 32

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

1. Golgi body
2. mitochondrion
3. plasma membrane
4. nucleus

Answer 32

1. Golgi body, 3. plasma membrane

During protein secretion, a protein is translated from mRNA and then moves through several steps before exiting the cell. One step 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.

Question 33

T or F?

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

Answer 33

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.

Question 34

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

1. Desmosomes
2. microfilaments
3. microtubules
4. intermediate filaments

Answer 34

3. 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.

Question 35

Which of the following are most likely NOT potential functions of cytoskeletal capping proteins?

1. cell movement
2. promoting cytoskeletal polymer degradation
3. muscle contraction
4. promoting the krebs cycle

Answer 35

2. promoting cytoskeletal polymer degradation, 4. promoting the krebs cycle

Capping proteins inhibit cytoskeletal protein degradation by preventing actin polymer breakdown.

Aerobic respiration (including the Krebs cycle) occurs in mitochondria to provide cellular energy as ATP. As the Krebs cycle occurs in the mitochondria, it is likely unrelated to cytoplasmic cytoskeletal proteins, such as actin and microtubules.

Question 36

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

1. Birth defects
2. mucus buildup in the throat
3. male sterility
4. DNA replication errors

Answer 36

1. Birth defects
2. mucus buildup in the throat
3. male sterility

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) flagellum dysfunction would inhibit sperm motility.

Question 37

T or F?

Only mutations to the mitochondrial genome in mothers are heritable in offspring.

Answer 37

TRUE

Mitochondria are inherited matrilineally: Only mutations in a mother’s mitochondrial genome may be passed down to her children. Conversely, mutations in a man’s mitochondrial DNA will not be passed down to his children.