Cell

Which one of the following cell organelles is known as ‘suicide bags’ of a cell ?

[amp_mcq option1=”Lysosomes” option2=”Plastids” option3=”Endoplasmic reticulum” option4=”Mitochondria” correct=”option1″]

Lysosomes are membrane-bound organelles found in animal cells that contain a variety of hydrolytic enzymes. These enzymes are capable of breaking down waste materials, cellular debris, and invading pathogens. Under certain conditions, such as during programmed cell death (apoptosis) or severe cell damage, the lysosomal membrane can rupture, releasing these enzymes into the cytoplasm and digesting the cell itself. Due to this self-digestion capability, lysosomes are often referred to as the “suicide bags” of the cell.

Lysosomes contain digestive enzymes that can break down cellular components, leading to cell self-destruction under specific circumstances.

Plastids are involved in photosynthesis and storage in plant cells. The endoplasmic reticulum is involved in protein and lipid synthesis. Mitochondria are the primary sites of cellular respiration and ATP production.

Which one of the following is active transport ?

[amp_mcq option1=”It is the movement of a substance against a diffusion gradient with the use of energy from respiration.” option2=”It is the movement of a substance against a diffusion gradient without the use of energy.” option3=”It is the movement of a substance against a diffusion gradient with the use of energy from photosynthesis.” option4=”It is the movement of a substance along a diffusion gradient with the use of energy from respiration.” correct=”option1″]

Active transport is a process where substances move across a cell membrane against their concentration gradient (or electrochemical gradient), meaning from a region of lower concentration to a region of higher concentration. This movement requires the cell to expend metabolic energy, typically in the form of ATP, which is primarily generated through cellular respiration.

Active transport is characterized by the movement against a concentration gradient and the requirement of energy expenditure by the cell.

In contrast, passive transport processes like diffusion and osmosis do not require energy and involve movement along the concentration gradient. Facilitated diffusion uses transport proteins but still moves substances along the gradient without direct energy input from the cell.

Match List-I with List-II and select the correct answer using the code given below the Lists :

List-I (Cell Organelle)	List-II (Function)
A. Mitochondria	1. Photosynthesis
B. Chloroplast	2. Protein synthesis
C. Ribosomes	3. Intracellular digestion
D. Lysosomes	4. ATP formation

Code :

[amp_mcq option1=”A-3, B-1, C-2, D-4″ option2=”A-2, B-1, C-4, D-3″ option3=”A-4, B-1, C-2, D-3″ option4=”A-4, B-2, C-1, D-3″ correct=”option3″]

The correct match is A-4, B-1, C-2, D-3.

Mitochondria are known as the powerhouses of the cell because they are the primary sites of cellular respiration, generating ATP. Chloroplasts are organelles found in plant cells and algae where photosynthesis takes place. Ribosomes are responsible for protein synthesis. Lysosomes contain hydrolytic enzymes that break down waste materials and cellular debris through intracellular digestion.

This question tests basic knowledge of the functions of major eukaryotic cell organelles. Understanding the primary role of each organelle is fundamental in biology.

Biological catalysts are protein molecules which

• 1. speed up a chemical reaction
• 2. remain unchanged after reaction
• 3. function optimally at 37 °C
• 4. do not have an enzymatic activity

Select the correct answer using the code given below.

[amp_mcq option1=”1 only” option2=”1, 2 and 3″ option3=”2 and 3 only” option4=”1, 3 and 4″ correct=”option2″]

Biological catalysts (enzymes) are protein molecules that speed up chemical reactions, remain unchanged after the reaction, and function optimally at around 37 °C (in the human body).

– Biological catalysts are enzymes, which are indeed protein molecules (with a few exceptions like catalytic RNA).
– Statement 1 is correct: Enzymes are catalysts, meaning they increase the rate of a chemical reaction without being consumed in the process.
– Statement 2 is correct: Like all catalysts, enzymes are not permanently altered or used up during the reaction and can be reused.
– Statement 3 is generally correct in the context of human enzymes: Many enzymes in the human body function optimally at physiological temperature, which is around 37 °C. However, the optimal temperature varies greatly among enzymes from different organisms (e.g., enzymes from thermophilic bacteria function at much higher temperatures). Assuming the question refers to typical biological contexts like the human body, this statement is considered correct.
– Statement 4 is incorrect: Biological catalysts *are* enzymes, and their activity *is* enzymatic activity. This statement directly contradicts the definition.
– Based on the statements, 1 and 2 are universally true for catalysts. Statement 3 is true for a common subset of biological catalysts (human enzymes). Statement 4 is false. The option including 1, 2, and 3 is the most fitting choice.

Enzymes are highly specific for the substrates they act upon and the reactions they catalyze. Their activity is influenced by factors such as temperature, pH, and the presence of inhibitors or activators.

Which of the following cells do not contain nucleus?

• 1. Root hair cells
• 2. Red blood cells
• 3. Platelets
• 4. Monocytes

Select the correct answer using the code given below.

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1, 2 and 4″ option4=”2, 3 and 4″ correct=”option2″]

Mature red blood cells and platelets are cells/cell fragments in the human body that do not contain a nucleus.

– Statement 1: Root hair cells are specialized epidermal cells of plant roots involved in water and nutrient absorption. They are eukaryotic cells and *do* contain a nucleus, cytoplasm, and other organelles.
– Statement 2: Mature mammalian red blood cells (erythrocytes) are anucleated, meaning they lose their nucleus during maturation. This allows them to maximize the space available for hemoglobin, increasing oxygen-carrying capacity.
– Statement 3: Platelets (thrombocytes) are not complete cells but are small, irregular fragments of cytoplasm derived from megakaryocytes found in bone marrow. They lack a nucleus. They play a crucial role in blood clotting.
– Statement 4: Monocytes are a type of white blood cell (leukocyte) and are part of the immune system. They are large, mononuclear cells, meaning they *do* contain a prominent, often kidney-shaped or lobed nucleus.
– Therefore, among the given options, only red blood cells and platelets lack a nucleus.

The absence of a nucleus in mature red blood cells and platelets is a characteristic feature that distinguishes them from most other cells in the human body. This specialization enhances their specific functions (oxygen transport and blood clotting, respectively).

Microbodies found to be present in plant and animal cells contain

[amp_mcq option1=”broken down membranes” option2=”enzymes” option3=”acidic fluids” option4=”waste metabolites” correct=”option2″]

Microbodies are a class of small, membrane-bound organelles found in eukaryotic cells. They contain a variety of enzymes involved in metabolic reactions, such as breaking down fatty acids (in peroxisomes and glyoxysomes) or detoxification (in peroxisomes).

Microbodies are known for containing enzymes involved in specific metabolic pathways.

Examples of microbodies include peroxisomes (present in both plant and animal cells, involved in breaking down fatty acids and detoxification) and glyoxysomes (found specifically in plant cells, involved in converting stored lipids into carbohydrates during seed germination). Lysosomes contain acidic fluids and enzymes for degradation but are distinct from microbodies.

Which cells in human body have no nucleus?

[amp_mcq option1=”Muscle cells” option2=”Phagocytic cells” option3=”Red blood cells” option4=”Ciliated cells” correct=”option3″]

The correct answer is C. Red blood cells in the human body have no nucleus.

Mature mammalian red blood cells (erythrocytes) are unique among human cells in that they extrude their nucleus during development. This anucleated state, along with the absence of other organelles like mitochondria, maximizes the space available within the cell for hemoglobin, which is essential for oxygen transport.

Most other cells in the human body, including muscle cells, phagocytic cells (like white blood cells), and ciliated cells, contain a nucleus which houses the genetic material and controls cellular activities. The lack of a nucleus means that mature red blood cells cannot divide or synthesize proteins and have a limited lifespan.

In plant cells, RNA is present in

[amp_mcq option1=”cytoplasm only” option2=”nuclei and cytoplasm only” option3=”nuclei, cytoplasm, mitochondria, chloroplast and endoplasmic reticulum” option4=”nuclei, cytoplasm, mitochondria, chloroplast and ribosomes” correct=”option4″]

In plant cells, RNA is found in various locations: the nucleus (where transcription occurs and various RNAs are synthesized and processed), the cytoplasm (containing mRNA, tRNA, rRNA, and free ribosomes), mitochondria (with their own genetic material and protein synthesis machinery, including rRNA and tRNA), chloroplasts (similarly having their own genetic material and protein synthesis machinery, including rRNA and tRNA), and ribosomes (which are themselves composed of rRNA and proteins, and are the sites of protein synthesis using mRNA and tRNA).

RNA’s presence in mitochondria and chloroplasts reflects their endosymbiotic origin and semi-autonomous nature, possessing their own genetic systems.

Endoplasmic Reticulum (ER) is involved in protein synthesis via ribosomes attached to its surface (RER), but RNA itself is not considered a component of the ER membrane or lumen; it is associated with the ribosomes on the ER.

Which one of the following statements is correct about the cell membrane ?

[amp_mcq option1=”It is made up of cellulose.” option2=”It is a permeable structure for all substances.” option3=”It is flexible and enables the cell to engulf many materials.” option4=”It does not allow diffusion of gases like oxygen and carbon dioxide.” correct=”option3″]

Statement C is correct about the cell membrane.

The cell membrane is primarily composed of a lipid bilayer with embedded proteins (fluid mosaic model). This structure is flexible and allows the cell to change shape and engulf substances from the external environment through processes like endocytosis (e.g., phagocytosis and pinocytosis), which is essential for functions like nutrition or defence.

Statement A is incorrect; cellulose is the main component of the plant cell wall, not the cell membrane. Statement B is incorrect; the cell membrane is selectively permeable, meaning it controls which substances can pass through it. Statement D is incorrect; small nonpolar molecules like oxygen and carbon dioxide can readily diffuse across the lipid bilayer of the cell membrane.

Osmosis is the process of movement of water molecules from its

[amp_mcq option1=”higher concentration to its lower concentration through a cell wall.” option2=”lower concentration to its higher concentration through a fully permeable membrane.” option3=”higher concentration to its lower concentration through a fully permeable membrane.” option4=”higher concentration to its lower concentration through a semi-permeable membrane.” correct=”option4″]

Osmosis is defined as the net movement of solvent molecules (typically water) from a region of higher solvent concentration (or higher water potential) to a region of lower solvent concentration (or lower water potential) through a selectively permeable or semi-permeable membrane.

– The key components of osmosis are the movement of *solvent* (water), the direction from *higher to lower* water concentration/potential, and the presence of a *semi-permeable membrane*.
– A semi-permeable membrane allows solvent molecules to pass through but restricts the passage of solute molecules.

– A fully permeable membrane allows both solute and solvent to pass freely, so osmosis as defined does not occur across such a membrane; diffusion would happen.
– The cell wall of plant cells is generally fully permeable, not semi-permeable. The cell membrane is the semi-permeable barrier.