EST biology (cell structure)

Which of the following doesn't contain a membrane as part of its structure

• e) Endoplasmic reticulum

• a) Chromosome

• b) Mitochondria

• c) Golgi body

• d) Chloroplast

Answer explanation

Out of the given options, a) Chromosome

does not contain a membrane as part of its structure. Chromosomes are composed of DNA and proteins and are located within the nucleus (in eukaryotic cells), but they are not membrane-bound themselves. In contrast, mitochondria, Golgi bodies, chloroplasts, and the endoplasmic reticulum are all membrane-bound organelles.

Prokaryotes & eukaryotes are both characterized by all of the following except

• e) Cell division

• a) A cell membrane

• b) Cytoplasm

• c) Mitochondria

• d) Protein synthesis

Answer explanation

The correct answer is c) Mitochondria.

Both prokaryotes and eukaryotes possess a cell membrane, cytoplasm, the ability to synthesize proteins (via ribosomes), and undergo cell division. However, mitochondria are membrane-bound organelles found only in eukaryotic cells; prokaryotic cells lack membrane-bound organelles.

The eukaryotic cells of both plants & animals possess which of the following basic structures?

• Centrioles

• Golgi apparatus

• Mitochondria

Answer explanation

Both eukaryotic plant and animal cells possess the following basic structures: Golgi apparatus and Mitochondria. Centrioles are generally present in animal cells and some lower plant forms, but are typically absent in higher plant cells.

Chloroplasts are the organelles in which

• a) There is a net gain of water

• b) Cell division is controlled

• c) Large molecules are packaged for export

• d) Light energy is converted into chemical energy

• e) Degradation of organelles occurs

Answer explanation

The correct answer is d) Light energy is converted into chemical energy.

Chloroplasts are the sites of photosynthesis, where light energy is captured and converted into chemical energy in the form of ATP and NADPH during the light reactions, which then powers the Calvin cycle to produce sugars.

Bacterial, fungal, algal & plant cells have fixed shapes because they have

• a) A plasma membrane

• b) A cell wall

• c) A large central vacuole

• d) Mitochondria

Answer explanation

The correct answer is b) A cell wall.

Bacterial, fungal, algal, and plant cells all possess a rigid cell wall, which provides structural support and a fixed shape to the cell. While they also have a plasma membrane, it is flexible. A large central vacuole is specific to plant cells, and mitochondria are present only in eukaryotic cells, neither of which are the primary reason for fixed shapes across all these diverse cell types.

A beaker is set up as shown above. Which of the following best describes what will happen?

• a) There will be a net movement of water to the distilled water compartment

• There will be a net movement of water to the protein solution compartment

• c) Equal amounts of water will move in both directions across the membrane

• e) Protein will readily move with the water across the membrane

• d) Equal amounts of protein will move in both directions across the membrane

Answer explanation

The correct answer is b) There will be a net movement of water to the protein solution compartment.

This phenomenon is known as osmosis. Water will move from the area of higher water concentration (distilled H₂O) across the semipermeable membrane to the area of lower water concentration (the 10% protein solution) until equilibrium is approached.

Which of the following structures is common to all cells

• a) Plasma membrane

• b) Chloroplasts

• c) Cellulose wall

• d) Nuclear envelopе

• e) Flagellum

Answer explanation

The correct answer is a) Plasma membrane or cell membrane,

All living cells, both prokaryotic and eukaryotic, are enclosed by a plasma membrane, which regulates the passage of substances into and out of the cell. Chloroplasts are only found in plant cells and some protists; cellulose walls are characteristic of plant cells; a nuclear envelope is present only in eukaryotic cells; and a flagellum is only present in some cell types, not all.

All the following cellular structures include membranes except

• a) Nucleolus

• b) Nuclear envelope

• c) Endoplasmic reticulum

• d) Mitochondrion

• e) Chloroplast

Answer explanation

The correct answer is a) Nucleolus.

All the other options (Nuclear envelope, Endoplasmic reticulum, Mitochondrion, and Chloroplast) are membrane-bound organelles or structures within the cell. The nucleolus is a dense, non-membranous structure located within the nucleus, primarily involved in ribosome synthesis.

Which of the following functions directly in cell locomotion?

• a) Lysosome

• b) Golgi apparatus

• c) Microtubules

• d) Chloroplasts

• e) Cell wall

Answer explanation

The correct answer is c) Microtubules.

Microtubules are key components of the cytoskeleton, forming structures like cilia and flagella (which have a 9+29+2 arrangement) and centrioles. Cilia and flagella are directly involved in the movement and locomotion of cells. Lysosomes are involved in waste breakdown, the Golgi apparatus modifies and packages proteins, chloroplasts are responsible for photosynthesis, and the cell wall provides structural support but doesn't directly contribute to locomotion

Which of the following cellular organelles is least likely to be visible with a light microscope?

• a) Chloroplast

• b) Mitochondrion

• c) Nucleus

• d) Ribosome

• e) Vacuole

Answer explanation

The correct answer is d) Ribosome.

Ribosomes are very small (approximately 20−30extnm20−30extnm in diameter) and are below the resolution limit of a standard light microscope (typically around 0.2extµm0.2extµm). While chloroplasts, mitochondria, the nucleus, and vacuoles are generally large enough to be observed with a light microscope, ribosomes require an electron microscope for clear visualization of their structure.