Cell

Which one of the following statements about lysosomes is NOT correct ?

[amp_mcq option1=”They are waste disposal system of the cell” option2=”They breakdown all inorganic materials” option3=”These are also referred to as "suicidal bags"” option4=”Lysosomes stop entry of foreign materials” correct=”option2″]

The statement “They breakdown all inorganic materials” is NOT correct about lysosomes.

Lysosomes contain hydrolytic enzymes (like proteases, lipases, carbohydrases, nucleases) that break down organic macromolecules (proteins, lipids, carbohydrates, nucleic acids), waste materials, and cellular debris. They are not equipped to break down inorganic substances.

Statement A is correct as they function in waste disposal. Statement C is correct as they are often called “suicidal bags” because their rupture can lead to the digestion of the cell itself. Statement D is also technically incorrect as lysosomes digest foreign material *after* it has entered the cell (e.g., through phagocytosis), rather than stopping its entry. However, option B is fundamentally wrong about the nature of the substances they break down.

Eukaryotic cells are much more complex as compared to prokaryotes. Which one of the following structures is exclusively present in a eukaryotic cell ?

[amp_mcq option1=”Cell wall” option2=”Plasma membrane” option3=”Nucleic acid” option4=”Mitochondria” correct=”option4″]

Mitochondria are membrane-bound organelles responsible for cellular respiration in eukaryotic cells. They are absent in prokaryotic cells. The other options are present in both types of cells: Cell walls are present in plant and fungal eukaryotes as well as bacterial prokaryotes. Plasma membrane is the outer boundary of all cells. Nucleic acids (DNA and RNA) are the genetic material found in all cells.

Eukaryotic cells are characterized by the presence of a nucleus and membrane-bound organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and chloroplasts (in plants and algae), which are absent in prokaryotes.

Prokaryotic cells lack a true nucleus and complex membrane-bound organelles. Their genetic material is located in a nucleoid region. Eukaryotic cells compartmentalize cellular functions within organelles, contributing to their complexity.

The digestive enzymes are present in

[amp_mcq option1=”mitochondria” option2=”vacuoles” option3=”lysosomes” option4=”ribosomes” correct=”option3″]

The correct answer is lysosomes.

Lysosomes are membrane-bound organelles within eukaryotic cells that contain a variety of hydrolytic enzymes, often referred to as digestive enzymes. These enzymes function best in an acidic environment (pH ~4.5-5.0) and are responsible for breaking down waste materials, cellular debris, and pathogens within the cell through processes like autophagy and phagocytosis.

Mitochondria are responsible for cellular respiration and energy production. Vacuoles in animal cells are typically small and involved in storage or transport. Ribosomes are the sites of protein synthesis.

Which one of the following will be resulted when an animal cell is surrounded by a medium with lower concentration of water?

[amp_mcq option1=”Cell will lose water” option2=”No change in movement of water” option3=”Cell will gain water” option4=”Cell will swell up” correct=”option1″]

The correct answer is Cell will lose water.

Osmosis is the movement of water across a semi-permeable membrane from a region of higher water potential (lower solute concentration) to a region of lower water potential (higher solute concentration). A medium with a “lower concentration of water” means it has a higher concentration of solutes compared to the cell’s cytoplasm; such a medium is hypertonic to the cell. Therefore, water will move by osmosis from inside the cell (higher water concentration) to the surrounding medium (lower water concentration).

If the medium had a *higher* concentration of water (lower solute concentration, hypotonic), the cell would gain water and swell. If the medium had the *same* concentration of water (isotonic), there would be no net movement of water. In a hypertonic solution, animal cells lose water and crenate (shrink).

The breakdown of glucose in cytoplasm results in the formation of

[amp_mcq option1=”pyruvate and energy” option2=”pyruvate and carbon dioxide” option3=”pyruvate and oxygen” option4=”pyruvate and nitrogen” correct=”option1″]

The breakdown of glucose begins in the cytoplasm through a process called glycolysis. Glycolysis breaks down one molecule of glucose into two molecules of pyruvate. This process also produces a small amount of ATP, which is a form of energy for the cell.

Glycolysis occurs in the cytoplasm and converts glucose into pyruvate, yielding energy (ATP).

Carbon dioxide is released during the subsequent stages of cellular respiration (Krebs cycle and oxidative phosphorylation) if oxygen is present, which occur in the mitochondria. Oxygen is consumed during oxidative phosphorylation. Nitrogen is not directly involved in the breakdown of glucose for energy production.

Which one of the following statements about animal cells and plant cells is correct?

[amp_mcq option1=”Animal cells have only cell membrane not cell wall, whereas plant cells have only cell wall not cell membrane.” option2=”Animal cells have only cell membrane not cell wall, but plant cells have both.” option3=”Both animal and plant cells have cell membrane and cell wall.” option4=”Only some cells of animals have cell wall and all plant cells have cell membrane.” correct=”option2″]

Animal cells are surrounded only by a cell membrane. Plant cells have both a cell membrane and a rigid cell wall located outside the cell membrane.

The presence of a cell wall is a defining characteristic of plant cells (and fungal, algal, and bacterial cells) that is absent in animal cells. Both plant and animal cells have a cell membrane.

The cell membrane regulates the passage of substances into and out of the cell and is present in all known cell types. The plant cell wall provides structural support, protects the cell, and prevents excessive water uptake.

In prokaryotic organisms, nuclear region is not surrounded by a membrane. This undefined nuclear region is known as

[amp_mcq option1=”Nucleic acid” option2=”Nucleoid” option3=”Nucleolus” option4=”Nucleosome” correct=”option2″]

In prokaryotic organisms (like bacteria and archaea), the genetic material (DNA) is located in a region of the cytoplasm that is not enclosed by a nuclear membrane. This ill-defined, irregularly shaped region where the genetic material is concentrated is called the nucleoid.

Prokaryotes lack membrane-bound organelles, including a true nucleus. Eukaryotic cells, on the other hand, have a membrane-bound nucleus containing their genetic material.

– Nucleic acid refers to the genetic material itself (DNA or RNA).
– Nucleolus is a dense structure found within the nucleus of eukaryotic cells, involved in ribosome synthesis.
– Nucleosome is a structural unit of a eukaryotic chromosome, consisting of a length of DNA coiled around a core of histone proteins.

Which one of the following cell organelles may play a role in expelling excess water and wastes in case of unicellular organisms ?

[amp_mcq option1=”Lysosome” option2=”Vacuole” option3=”Golgi body” option4=”Endoplasmic reticulum” correct=”option2″]

In many freshwater unicellular organisms like *Paramecium* or *Amoeba*, contractile vacuoles are specialized organelles that collect excess water that enters the cell by osmosis and periodically expel it out. This process is crucial for osmoregulation, preventing the cell from bursting in a hypotonic environment. Wastes can also be expelled via this mechanism or through other means like diffusion or exocytosis.

– Vacuoles in unicellular organisms can include contractile vacuoles, which are vital for maintaining osmotic balance by expelling excess water.
– Lysosomes are involved in intracellular digestion.
– Golgi body (or Golgi apparatus) is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.
– Endoplasmic reticulum is involved in protein and lipid synthesis.

Contractile vacuoles are found mainly in protists living in freshwater habitats. Their rate of pulsation is regulated by the osmotic potential of the surrounding medium; they pump faster in more dilute environments. While primarily for water expulsion, they also contribute to the removal of some metabolic wastes.

Mitochondria are able to produce their own

[amp_mcq option1=”Nucleus” option2=”Proteins” option3=”Chloroplasts” option4=”Digestive enzymes” correct=”option2″]

The correct answer is B) Proteins.

Mitochondria contain their own DNA and ribosomes, enabling them to synthesize some of the proteins they need for their function. This makes them semi-autonomous organelles.

Mitochondria are often called the “powerhouses” of the cell because they generate most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy. They are believed to have originated from symbiotic bacteria, which is supported by the presence of their own DNA (circular, similar to bacterial DNA) and ribosomes (70S, similar to bacterial ribosomes).

Net movement of water from a dilute to a concentrated solution through a selectively permeable membrane is called

[amp_mcq option1=”Diffusion” option2=”Dispersion” option3=”Osmosis” option4=”Absorption” correct=”option3″]

The description “Net movement of water from a dilute to a concentrated solution through a selectively permeable membrane” is the definition of osmosis.
A) Diffusion is the net movement of particles (solute or solvent) from a region of higher concentration to lower concentration, which can occur with or without a membrane. It is driven by a concentration gradient.
B) Dispersion refers to the spreading out of particles or substances.
C) Osmosis is specifically the movement of solvent (usually water) across a selectively permeable membrane from an area of higher water potential (dilute solution, lower solute concentration) to an area of lower water potential (concentrated solution, higher solute concentration). This movement occurs down the water potential gradient and fits the description perfectly.
D) Absorption is the process by which one substance is taken into another, either physically or chemically. While osmosis results in the absorption of water by the concentrated solution, “osmosis” is the specific term for the described process of water movement across a membrane due to concentration differences.

– Osmosis is the movement of solvent (water) across a selectively permeable membrane.
– Water moves from a region of higher water concentration (dilute solution) to lower water concentration (concentrated solution).
– Diffusion is the general movement of particles from high to low concentration.

A selectively permeable (or semi-permeable) membrane allows certain molecules or ions to pass through by diffusion, and occasionally specialized facilitated diffusion. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Osmosis is a specific type of diffusion involving the solvent.