Question
1.Which cellular structure is present in eukaryotic cells but absent in prokaryotic cells?
A. Mitochondria for respiration
B. DNA containing genetic information
C. Ribosomes for protein synthesis
D. Cell wall to maintain shape
▶️Answer/Explanation
Ans : A
Mitochondria are membrane-bound organelles found in eukaryotic cells that play a crucial role in cellular respiration, producing energy in the form of ATP. Prokaryotic cells, such as those of bacteria, lack membrane-bound organelles, including mitochondria. Instead, prokaryotes carry out their cellular processes in the cytoplasm without specialized compartments like mitochondria. Options B, C, and D (DNA, ribosomes, and cell wall) are present in both eukaryotic and prokaryotic cells.
Question
2. For what reason is the Singer–Nicolson model considered a better representation of the cell membrane than the Davson–Danielli model?
A. It has extrinsic proteins.
B. It shows how the phospholipid bilayer is arranged.
C. It helps in the understanding of the fluidity of the cell membrane.
D. It shows how oxygen can diffuse into the cell.
▶️Answer/Explanation
Ans : C
Question
3.Describe the passive movement of a substance into the cell across the cell membrane, as depicted in the diagram.
A. Energy of ATP is used to transport substances into the cell.
B. Substances can move from areas of low to areas of high concentration.
C. The proteins ensure that movement of substances is only in one direction.
D. Net movement occurs until the concentrations in and out of the cell are equal.
▶️Answer/Explanation
Ans : D
The scenario described, where substances move passively across the cell membrane through protein channels, is indicative of facilitated diffusion. In facilitated diffusion, substances move down their concentration gradient, and the process continues until equilibrium is reached, resulting in equal concentrations inside and outside the cell. This aligns with option D. Options A, B, and C are not characteristic of passive movement through protein channels; they are more related to active transport or specific directional control, which is not the case here.
Question
4.What provides support for the endosymbiotic theory?
A. Eukaryote mitochondria contain DNA.
B. Prokaryotes evolved before eukaryotes.
C. Unicellular organisms exist as both prokaryotes and eukaryotes.
D. Prokaryote cells have no double membranes.
▶️Answer/Explanation
Ans : A
The endosymbiotic theory proposes that eukaryotic cells evolved through a symbiotic relationship between different types of prokaryotic cells. One piece of evidence supporting this theory is that mitochondria, which are organelles in eukaryotic cells responsible for energy production, have their own DNA. This is similar to the DNA found in prokaryotic cells. The presence of DNA in mitochondria supports the idea that mitochondria were once free-living prokaryotic cells that were engulfed by a host cell. Options B, C, and D are not direct evidence for the endosymbiotic theory.
Question
5. In the late prophase of mitosis in the root tip of an onion (Allium cepa) with a chromosome number of 2n = 16, what is the count of chromatids in the cell?
A. 8
B. 16
C. 32
D. 64
▶️Answer/Explanation
Ans : C
In late prophase of mitosis, each chromosome consists of two sister chromatids. Since the cell is in mitosis, and the chromosome number is given as 2n = 16 (where n is the number of chromosomes), the total number of chromatids would be twice the number of chromosomes. Therefore, 2n * 2 = 16 * 2 = 32 chromatids are present in the cell.