Free Cell Structure and Function MCQs with Answers

• A. requires energy from ATP
• B. uses specific carrier or channel proteins in the membrane
• C. moves substances against their concentration gradient
• D. occurs only through the lipid portion of the membrane

Explanation: Facilitated diffusion still follows the concentration gradient and costs no energy, but polar molecules and ions pass through specific…

• A. cytoplasm
• B. a nuclear envelope
• C. ribosomes
• D. a plasma membrane

Explanation: The defining absence in a prokaryote is a membrane-bound nucleus; its DNA lies free in the nucleoid.

• A. a linear molecule wrapped around histones
• B. distributed over many chromosomes
• C. enclosed inside a nuclear envelope
• D. a single circular DNA molecule lying in the nucleoid

Explanation: The bacterial chromosome is one circular DNA molecule condensed into a nucleoid region, with no membrane around it and no histone…

• A. Plasmid
• B. Plasma membrane
• C. Ribosomes
• D. Cytoplasm

Explanation: Plasmids are small circular DNA molecules that carry extra genes, often for antibiotic resistance, and are widely used as vectors in…

• A. contains no DNA
• B. possesses 80S ribosomes
• C. lacks a cell wall
• D. is multicellular

Explanation: Mycoplasma is the smallest known self-living organism and has no cell wall, which is why antibiotics that attack wall synthesis, such as…

• A. cell theory
• B. germ theory
• C. theory of biogenesis
• D. endosymbiotic theory

Explanation: The endosymbiotic theory is supported by the double membranes, circular DNA and 70S ribosomes of both organelles.

• A. block transcription in the human nucleus
• B. dissolve the plasma membrane of bacteria only
• C. bind to 70S ribosomes and stop bacterial protein synthesis
• D. prevent DNA replication in both cell types equally

Explanation: Human cytoplasmic ribosomes are the larger 80S type, so drugs aimed at the bacterial 70S ribosome interfere selectively with the…

• A. Amoeba
• B. Cyanobacterium
• C. Yeast
• D. Paramecium

Explanation: Cyanobacteria, once called blue green algae, are photosynthetic bacteria with no membrane-bound organelles.

• A. detoxification of drugs and poisons
• B. synthesis of proteins for export
• C. production of most of the cell's ATP
• D. digestion of worn out organelles

Explanation: The smooth ER carries the enzymes that break down drugs, alcohol and metabolic poisons, which is why liver cells are rich in it.

• A. Golgi apparatus
• B. ribosome
• C. mitochondrion
• D. smooth endoplasmic reticulum

Explanation: During sperm maturation, vesicles from the Golgi collect hydrolytic enzymes and fuse at the tip of the nucleus to form the acrosome.

• A. actin
• B. tubulin
• C. myosin
• D. keratin

Explanation: Tubulin dimers polymerise into hollow tubes that form the cytoskeleton, spindle fibres, cilia and flagella.

• A. centrioles
• B. bacterial flagella
• C. microvilli of the intestine
• D. cilia and eukaryotic flagella

Explanation: Cilia and eukaryotic flagella contain nine doublet microtubules around a central pair, an arrangement visible only by electron microscopy.

• A. Golgi apparatus
• B. Lysosome
• C. Mitochondrion
• D. Peroxisome

Explanation: Mitochondria carry a small circular genome and 70S ribosomes and make some of their own proteins, evidence of their endosymbiotic origin.

• A. the reactions of glycolysis
• B. the reactions of the electron transport chain
• C. the storage of fat
• D. the synthesis of ribosomal RNA

Explanation: The electron carriers and ATP synthase are embedded in the inner membrane, so its folding into cristae multiplies the space for oxidative…

• A. stacks of flattened thylakoid sacs
• B. free ribosomes and DNA
• C. grains of stored starch
• D. infoldings of the outer membrane

Explanation: Thylakoids pile into grana, and their membranes carry chlorophyll and the photosynthetic electron chain, while the surrounding stroma…

• A. metacentric
• B. submetacentric
• C. acrocentric
• D. telocentric

Explanation: Centromere position names the chromosome: metacentric gives equal arms, submetacentric unequal ones, acrocentric a very short arm, and…

• A. are found only in gametes
• B. consist of a single chromatid each throughout the cell cycle
• C. carry genes for the same characteristics and come one from each parent
• D. are present in prokaryotic cells

Explanation: One member of each homologous pair is maternal and the other paternal, matching in size, centromere position and gene positions though…

• A. homologues
• B. sister chromatids
• C. bivalents
• D. telomeres

Explanation: DNA replication produces two identical sister chromatids joined at the centromere, which separate at anaphase into different daughter…

• A. allow chromosomes to be identified in a karyotype
• B. change from one cell division to the next
• C. by themselves determine the sex of the individual
• D. are identical for every chromosome in the cell

Explanation: Since each chromosome type has a characteristic length and centromere position, these features let cytogeneticists arrange a karyotype in…

• A. are absent from every gamete
• B. carry no genes at all
• C. determine the sex of the individual
• D. are present in four pairs

Explanation: The 23rd pair, XX in females and XY in males, determines sex, while the 22 pairs of autosomes govern the rest of the body.