Cell: The Unit of Life Chapter-Wise Test 11

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A protein is synthesised for secretion outside a eukaryotic cell. Which sequence most logically represents its movement through the cell?

Ribosome on RER → ER-derived vesicle → cis face of Golgi → Golgi cisternae → trans face → secretion
Free ribosome → lysosome → trans face of Golgi → cis face → secretion
Nucleolus → SER → mitochondrial matrix → Golgi apparatus → secretion
Ribosome on RER → trans face of Golgi → cis face → nuclear pore → secretion
1

Secretory proteins are synthesised on ribosomes attached to RER. Materials from the ER reach the cis or forming face of the Golgi, move through its cisternae and are released from the trans or maturing face.

Three cells show the following features:

Cell P: cell wall, plastids and a large central vacuole
Cell Q: centrioles but no cell wall or plastids
Cell R: naked circular genomic DNA, 70S ribosomes and no membrane-bound organelles

Which classification is correct?

P—animal cell; Q—plant cell; R—fungal cell
P—prokaryotic cell; Q—animal cell; R—plant cell
P—plant cell; Q—animal cell; R—prokaryotic cell
P—plant cell; Q—prokaryotic cell; R—animal cell
3

A plant cell possesses a cell wall, plastids and a large central vacuole. Centrioles are characteristic of animal cells and absent from almost all plant cells. Naked circular DNA and absence of membrane-bound organelles identify a prokaryotic cell.

A substance blocks every nuclear pore without damaging the nuclear envelope itself. Which effect would follow most directly?

The cell wall would no longer protect the cell from mechanical damage.
Cristae would lose their ability to increase mitochondrial surface area.
The tonoplast would stop accumulating ions inside the vacuole.
Movement of RNA and protein molecules between the nucleus and cytoplasm would be impaired.
4

Nuclear pores are passages formed where the two nuclear-envelope membranes fuse. RNA and protein molecules move through them in both directions between the nucleus and cytoplasm, so blocking the pores would directly obstruct this exchange.

Consider the following statements about transport across the plasma membrane:

I. A neutral solute may move from higher to lower concentration without expenditure of energy.
II. A polar molecule may require a carrier protein because it cannot readily cross the non-polar bilayer.
III. Movement from lower to higher concentration requires energy and represents active transport.

Which option correctly evaluates the statements?

Only statements I and II are correct.
Statements I, II and III are correct.
Only statements II and III are correct.
Only statement III is correct.
2

Neutral solutes may diffuse down their concentration gradient without energy. Polar molecules require carrier proteins to cross the non-polar bilayer. Movement against a gradient is active transport and requires energy supplied through ATP.

Two cylindrical structures are examined:

Structure P has nine peripheral microtubule doublets and two central microtubules.
Structure Q has nine peripheral microtubule triplets connected to a central hub by radial spokes.

Which identification is correct?

P—axoneme of a cilium or flagellum; Q—centriole
P—centriole; Q—bacterial flagellum
P—bacterial pilus; Q—axoneme of a cilium
P—centriole; Q—axoneme of a flagellum
1

The axoneme of a eukaryotic cilium or flagellum usually has a 9+2 arrangement of peripheral doublets and central microtubules. A centriole has nine peripheral triplets connected to a proteinaceous hub by radial spokes.

A normally walled bacterium suffers severe damage specifically to its cell wall, while its plasma membrane and glycocalyx remain present. Which consequence is most consistent with the functions of the damaged structure?

Its ribosomes will change directly from 70S to 80S.
Its genomic DNA will become enclosed by a nuclear envelope.
Its fimbriae will immediately become locomotory flagella.
Its shape and structural stability will be compromised, increasing the risk of bursting or collapsing.
4

The bacterial cell wall determines cell shape and supplies strong structural support that prevents bursting or collapsing. Damage to it would therefore affect shape and stability without converting ribosomes, DNA organisation or surface structures into different components.

Organelle P is a membrane-bound vesicle containing hydrolytic enzymes that function best at acidic pH. Organelle Q is double-membrane-bound, has cristae and produces ATP during aerobic respiration. Which identification is correct?

P—vacuole; Q—chloroplast
P—lysosome; Q—mitochondrion
P—Golgi apparatus; Q—centriole
P—microbody; Q—nucleus
2

Lysosomes are membrane-bound vesicles containing hydrolytic enzymes that are optimally active at acidic pH. Mitochondria are double-membrane organelles whose inner membrane forms cristae and whose aerobic respiratory activity generates ATP.

The thylakoid system of a chloroplast is extensively damaged, but the stroma and chloroplast envelope remain intact. Which combination would be most directly affected?

Circular DNA and 70S ribosomes present in the stroma
Enzymes involved in carbohydrate and protein synthesis in the stroma
Chlorophyll-containing membranes, grana organisation and the light reactions
The double membrane forming the chloroplast envelope
3

Chlorophyll occurs in the thylakoids, and stacks of thylakoids form grana, which are the sites of light reactions. Circular DNA, ribosomes and enzymes for carbohydrate and protein synthesis occur in the stroma and may remain present.

A researcher makes two observations:

I. Every examined plant and animal tissue consists of cells or products of cells.
II. An increase in cell number occurs through division of already existing cells.

Which conclusion integrates both observations?

Living organisms are composed of cells and products of cells, and new cells arise from pre-existing cells.
Only plants are composed of cells, while animal tissues arise from non-cellular material.
Cells can arise independently from abiotic materials whenever growth occurs.
Cell theory applies only to unicellular organisms capable of independent existence.
1

The observations combine the two central principles of cell theory: living organisms are composed of cells and products of cells, and new cells arise through division of pre-existing cells.

Organelles X and Y both contain circular DNA and 70S ribosomes. X has cristae, while Y contains thylakoids surrounded by stroma. Which interpretation is best supported?

X and Y are parts of the endomembrane system because both contain DNA.
X is a lysosome, while Y is a vacuole specialised for ion accumulation.
X performs photosynthesis, while Y carries out intracellular digestion.
X is a mitochondrion involved in aerobic respiration, while Y is a chloroplast involved in photosynthesis; both possess components for internal protein synthesis.
4

Cristae identify X as a mitochondrion, while thylakoids and stroma identify Y as a chloroplast. Mitochondria perform aerobic respiration and generate ATP; chloroplasts trap light energy. Their circular DNA and 70S ribosomes support some protein synthesis within both organelles.

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