Unit 3: Cell Structure and Function: practice

Question 1

Which of these is NOT a role of the mesosome in a bacterial cell?

Question 2

Read the following statements about the endomembrane system. (a) The endoplasmic reticulum divides the space inside the cell into a luminal and an extra-luminal compartment. (b) The Golgi cisternae are flat, disc-shaped sacs 0.5 to 1.0 micrometre across, stacked parallel to each other. (c) The Golgi apparatus is an important site of formation of glycoproteins and glycolipids. (d) Lysosomes are formed by a process of packaging in the Golgi apparatus. (e) The tonoplast moves ions into the vacuole down their concentration gradient, so ions are less concentrated in the vacuole than in the cytoplasm. (f) Proteins made on the rough ER enter the Golgi at its convex face and are released from its concave face. How many of the above statements are correct?

Question 3

Read the following statements about the nucleus and ribosomes. (a) The outer membrane of the nuclear envelope is usually continuous with the endoplasmic reticulum and bears ribosomes. (b) The perinuclear space between the two membranes of the nuclear envelope is 10 to 50 nm wide. (c) Nuclear pores are gaps in the outer membrane only; the inner membrane runs unbroken beneath them. (d) Each nucleolus is enclosed by its own membrane, which separates it from the nucleoplasm. (e) Chromatin contains DNA, basic proteins called histones, some non-histone proteins and RNA. (f) The 80S ribosome in the cytoplasm of a eukaryotic cell is built of a 50S and a 30S subunit. How many of the above statements are correct?

Question 4

Given below are two statements. Statement I: The cis face of the Golgi apparatus is its forming face, and the trans face is its maturing face. Statement II: Proteins from the rough endoplasmic reticulum enter the Golgi at its trans face and leave from its cis face. In the light of the above statements, choose the correct answer.

Question 5

A gland cell that secretes a digestive enzyme is given a radioactive amino acid for a few minutes. In what order does the label pass through the cell as the enzyme is made and secreted?

Question 6

Match the chromosome in List I with its centromere position in List II.

List I	List II
A. Metacentric	i. Centromere at one end of the chromosome
B. Submetacentric	ii. Centromere close to one end, giving one extremely short arm
C. Acrocentric	iii. Centromere at the middle, giving two equal arms
D. Telocentric	iv. Centromere slightly away from the middle, giving arms a little unequal

Choose the correct answer from the options given below.

Question 7

Given below are two statements: one is labelled Assertion A and the other is labelled Reason R. Assertion A: Rough endoplasmic reticulum is extensive in cells that actively make and secrete proteins. Reason R: The rough endoplasmic reticulum is continuous with the outer membrane of the nucleus. In the light of the above statements, choose the correct answer.

Question 8

An antibiotic blocks protein synthesis on 70S ribosomes only. A leaf mesophyll cell is treated with it. Where in the cell does protein synthesis stop?

Question 9

Given below are two statements. Statement I: The cristae of a mitochondrion are infoldings of its outer membrane. Statement II: The mitochondrial matrix contains a single circular DNA molecule, a few RNA molecules and 70S ribosomes. In the light of the above statements, choose the correct answer.

Question 10

Which processes depend on the quasi-fluid nature of the plasma membrane, as the fluid mosaic model describes it?

Question 11

Without an enzyme, about 200 molecules of carbonic acid form from carbon dioxide and water in an hour. With carbonic anhydrase, about 600 000 form in a second. By what factor does the enzyme speed up the reaction?

Question 12

Match the class of enzyme in List I with the reaction it catalyses in List II.

List I	List II
A. Oxidoreductases	i. Removal of groups by means other than hydrolysis, leaving double bonds
B. Transferases	ii. Transfer of a group other than hydrogen between two substrates
C. Hydrolases	iii. Oxidation and reduction between two substrates
D. Lyases	iv. Breaking of ester, ether, peptide or glycosidic bonds with water

Choose the correct answer from the options given below.

Question 13

Given below are two statements: one is labelled Assertion A and the other is labelled Reason R. Assertion A: Adding malonate slows the action of succinic dehydrogenase on succinate. Reason R: Malonate closely resembles succinate in structure and competes with it for the active site of the enzyme. In the light of the above statements, choose the correct answer.

Question 14

Which enzyme is correctly matched with its cofactor and the type of that cofactor?

Question 15

Read the following statements about biomolecules. (a) The R group of glycine is a hydrogen atom. (b) Inulin is a polymer of fructose. (c) Cellulose holds iodine in helices and turns blue with it. (d) Chitin is a complex polysaccharide that contains amino sugars. (e) Palmitic acid has 16 carbon atoms, counting the carboxyl carbon. (f) Lecithin is a phospholipid. How many of the above statements are correct?

Question 16

The rate of an enzyme reaction (as a percentage of its maximum) is measured at rising substrate concentrations, with and without a substance X.

Substrate concentration (arbitrary units)	Rate without X	Rate with X
1	33	11
4	67	33
16	89	67
64	97	89
256	99	97

Which explanation of the effect of X fits these data?

Question 17

A living tissue is ground in trichloroacetic acid and the slurry is filtered. Which set of compounds would all be found in the acid-insoluble fraction?

Question 18

Read the following statements about amino acids and proteins. (a) Amino acids are substituted methanes, with four substituent groups on the alpha carbon. (b) A protein is a heteropolymer of amino acids. (c) The first amino acid of a polypeptide chain is called the N-terminal amino acid. (d) Adult human haemoglobin is made of four subunits, two of the alpha type and two of the beta type. (e) RuBisCO, a plant enzyme, is the most abundant protein in the whole of the biosphere. (f) In the secondary structure of proteins, the polypeptide chain forms left-handed helices. How many of the above statements are correct?

Question 19

Read the following statements about enzymes. (a) The protein part of an enzyme that needs a cofactor is called the apoenzyme. (b) Coenzymes are bound tightly to the apoenzyme throughout its life. (c) Haem is the prosthetic group of peroxidase and catalase. (d) Removing the cofactor leaves the enzyme fully active. (e) Lyases remove groups from their substrates by hydrolysis, leaving double bonds. (f) Ligases link two compounds together, for example by joining C-O, C-S, C-N or P-O bonds. How many of the above statements are correct?

Question 20

A meiocyte of a plant with 2n = 16 has 2C of DNA in G1. What are the chromosome number and the DNA content of each cell at the end of meiosis I?

Question 21

An animal has 2n = 18. How many bivalents and how many chromatids are present in one of its meiocytes at pachytene?

Question 22

A single cell divides repeatedly by mitosis until there are 128 cells. How many rounds of division took place, and how many separate cell divisions occurred in all?

Question 23

In an animal with 2n = 8, a dividing cell is seen with 4 chromosomes, each made of two chromatids, lined up singly at the equator with spindle fibres attached to them. Given below are two statements. Statement I: This cell holds the same amount of DNA as a cell of the same animal in G1. Statement II: A cell of the same animal at metaphase of mitosis holds twice as many chromatids as this cell. In the light of the above statements, choose the correct answer.

Question 24

Match the stage of prophase I in List I with the event in List II.

List I	List II
A. Zygotene	i. Terminalisation of chiasmata
B. Pachytene	ii. Synaptonemal complex forms as homologues pair
C. Diplotene	iii. Synaptonemal complex dissolves and chiasmata become visible
D. Diakinesis	iv. Recombination nodules appear and crossing over occurs

Choose the correct answer from the options given below.

Question 25

In a culture of human cells, the cell cycle lasts 24 hours: G1 11 hours, S 8 hours, G2 4 hours and M 1 hour. The cells are spread evenly through the cycle. Of 1200 cells, how many are expected to hold the 4C amount of DNA? (A cell in M phase counts as one cell until cytokinesis.)

Question 26

Given below are two statements: one is labelled Assertion A and the other is labelled Reason R. Assertion A: The two chromatids of each chromosome separate at anaphase I of meiosis. Reason R: Homologous chromosomes separate at anaphase I of meiosis. In the light of the above statements, choose the correct answer.

Question 27

In a palm whose body cells have 2n = 32, the primary endosperm nucleus divides repeatedly by karyokinesis without cytokinesis; in each round every nucleus divides once. When the liquid endosperm holds 256 free nuclei, how many rounds have taken place, and how many chromosomes does each nucleus hold?

Question 28

Read the following statements about meiosis. (a) Crossing over occurs between non-sister chromatids of homologous chromosomes. (b) Crossing over is enzyme-mediated, and the enzyme is called recombinase. (c) Diplotene can last for months or years in the oocytes of some vertebrates. (d) DNA replicates again during interkinesis. (e) Meiosis II resembles a normal mitosis. How many of the above statements are correct?

Question 29

Given below are two statements. Statement I: Cells in the G0 phase are metabolically inactive. Statement II: Mitosis takes place only in diploid cells. In the light of the above statements, choose the correct answer.

Question 30

Match the cell in List I with the set of features it has in List II.

List I	List II
A. Mycoplasma	i. Cell wall; no nuclear envelope; 70S ribosomes only
B. Escherichia coli	ii. No cell wall; no nuclear envelope; 70S ribosomes only
C. A mesophyll cell of a leaf	iii. No cell wall; nuclear envelope; 70S ribosomes in one kind of organelle
D. A liver cell of a mammal	iv. Cell wall; nuclear envelope; 70S ribosomes in two kinds of organelle

Choose the correct answer from the options given below.

Question 31

Read the following statements about mitochondria and chloroplasts. (a) Both mitochondria and chloroplasts contain circular DNA and 70S ribosomes. (b) The inner membrane of a chloroplast is relatively less permeable than its outer membrane. (c) The stroma of a chloroplast holds the enzymes needed to make carbohydrates and proteins. (d) Mitochondria divide by fission. (e) A mesophyll cell of a leaf usually holds a single chloroplast, as Chlamydomonas does. (f) The number of mitochondria in a cell is fixed and does not depend on the cell's activity. How many of the above statements are correct?

Question 32

An animal has 2n = 8. Match the cell in List I with the number of chromosomes and chromatids it contains in List II.

List I	List II
A. A meiocyte at metaphase I	i. 4 chromosomes, 4 chromatids
B. A daughter cell of mitosis, in G1	ii. 8 chromosomes, 16 chromatids
C. A cell at metaphase II	iii. 4 chromosomes, 8 chromatids
D. A cell formed at the end of meiosis II	iv. 8 chromosomes, 8 chromatids

Choose the correct answer from the options given below.

Question 33

Given below are two statements: one is labelled Assertion A and the other is labelled Reason R. Assertion A: Once an enzyme reaction has reached its maximum velocity, adding more substrate does not speed it up, but adding more enzyme does. Reason R: At that point every enzyme molecule is bound to substrate, so no free enzyme molecules are left to bind the extra substrate. In the light of the above statements, choose the correct answer.

Question 34

A drug that prevents the assembly of microtubules is added to a culture of dividing animal cells. Given below are two statements. Statement I: Cells in the culture can still replicate their DNA in S phase and condense their chromosomes in prophase. Statement II: The sister chromatids of each chromosome still move to opposite poles at anaphase. In the light of the above statements, choose the correct answer.

Unit 3: Cell Structure and Function

NEET-style questions