Cell: The Building Block of Life MCQs for UPSC Prelims
120 practice questions covering Cell: The Building Block of Life, organised into 0 topics.
120 questions include a written explanation.
Pick a topic below, or try the samples first.
Sample questions
Q1
easy
Osmosis is the movement of water molecules across a selectively permeable membrane
Afrom the more concentrated solution towards the more dilute solution
Bfrom the warmer side of the membrane towards the cooler side
Cin whatever direction gravity happens to pull the water
Dfrom the more dilute solution towards the more concentrated solution
Show answer and explanation
Correct answer: D - from the more dilute solution towards the more concentrated solution
In osmosis water moves from where the solution is more dilute, and therefore richer in water, towards where the solution is more concentrated. Stating the opposite direction reverses the whole idea. Temperature changes how fast osmosis goes but does not set its direction, and osmosis works upward or sideways just as well as downward.
Q2
medium
Cells taken from a potato tuber growing under the soil are found to contain plastids, yet these cells are not green at all. The best explanation is that
Athe plastids there really are green, but the soil around them hides the colour
Bpotato cells contain mitochondria in place of plastids
Cpotato cells lose their plastids because they grow buried in the soil
Dthe plastids in those cells are colourless ones that store starch, not green ones that make food
Show answer and explanation
Correct answer: D - the plastids in those cells are colourless ones that store starch, not green ones that make food
Plastids are a family of structures: some are green and make food, while others are colourless and store food such as starch, and a potato tuber is packed with the storing kind. The cells clearly still have plastids, so they have not lost them. Colour is a property of the plastid itself and is not hidden by surrounding soil, and mitochondria are present as well as plastids, not instead of them.
Q3
medium
Assertion (A): A bacterial cell is a prokaryotic cell. Reason (R): A bacterial cell has a cell wall lying outside its cell membrane.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true, but R is false
DA is false, but R is true
Show answer and explanation
Correct answer: B - Both A and R are true, but R is not the correct explanation of A
(A) is true, since bacteria are the best known prokaryotes. (R) is also true, because bacterial cells are surrounded by a wall outside the membrane. But (R) does not explain (A): plant cells also have a wall outside the membrane and are firmly eukaryotic. What makes a cell prokaryotic is the absence of a membrane-bounded nucleus, not the presence of a wall.
Q4
medium
A wilted spinach leaf is stood in a bowl of plain water and after an hour it is crisp and firm again. The best explanation is that
Athe leaf took in dissolved minerals from the water and these minerals stiffened the walls
Bwater entered the cells by osmosis and the swollen contents now press firmly against the rigid cell walls
Cwater entered the cells and dissolved the cell walls, leaving the leaf softer inside and firmer outside
Dwater left the cells, which allowed the bent cell walls to straighten out again
Show answer and explanation
Correct answer: B - water entered the cells by osmosis and the swollen contents now press firmly against the rigid cell walls
Plain water is more dilute than the cell sap, so water moves in, the contents swell and push on the walls, and the whole leaf stiffens. Water does not dissolve cellulose walls; if it did, the leaf would collapse. A cell losing water goes limp rather than crisp, and plain water carries no minerals to add.
Q5
medium
Assertion (A): Meiosis produces cells that have half the chromosome number of the parent cell. Reason (R): Chromosomes are located inside the nucleus of a cell.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true, but R is false
DA is false, but R is true
Show answer and explanation
Correct answer: B - Both A and R are true, but R is not the correct explanation of A
(A) is true, since halving the chromosome number is what marks meiosis out from mitosis. (R) is also true, because chromosome material is held inside the nuclear membrane. But (R) only says where chromosomes sit; mitosis takes place in the same nucleus and does not halve anything, so the location cannot explain the halving.
Q6
medium
When a cell is badly damaged, the membranes around its lysosomes may break open, and the cell is then digested from within. This happens because
Athe cell loses its chromosomes the moment the lysosomes burst
Bthe digestive substances held inside the lysosomes are released into the cytoplasm and act on the cell's own material
Cthe lysosomes stop supplying the cell with energy as soon as they break open
Dthe broken lysosomes let all the water in the cell escape at once
Show answer and explanation
Correct answer: B - the digestive substances held inside the lysosomes are released into the cytoplasm and act on the cell's own material
Lysosomes keep strong digestive substances shut safely inside a membrane; once that membrane gives way, those substances spill out and break down the cell's own parts. Lysosomes never supplied energy, which comes from mitochondria. Water loss is controlled by the cell membrane, and chromosomes stay in the nucleus whatever happens to lysosomes.
Practice the full Cell: The Building Block of Life bank free
All 120 questions with timed practice, instant scoring, and explanations. Free forever.