Cell and Cell Structure

The cell is the fundamental unit of life - all living organisms are composed of cells, and cells carry out all life processes. This is a core principle of cell theory. Tissues (A) are groups of cells, organs (B) are groups of tissues, and organ systems (D) are groups of organs - all are built FROM cells, not the basic unit themselves.

Protoplasm is the living, jelly-like material composing all cellular contents, including the cytoplasm and nucleus. Cytoplasm (B) is only the material OUTSIDE the nucleus, missing the nucleoplasm. Endoplasmic reticulum (C) and golgi bodies (D) are specific organelles within the protoplasm, not the entire living matter.

Plant cells characteristically lack both centrosomes AND centrioles, which are present in animal cells and help organize microtubules during cell division. Vacuoles (A), plastids (B), and chlorophyll (D) are all structures that plant cells DO contain - they're defining features of plant cells, not absences.

Plastids are membrane-bound organelles in plant cells that synthesize and store food - chloroplasts make food via photosynthesis, chromoplasts store pigments, and leucoplasts store starch. Plasma (A), polymer (B), and protein (D) are incorrect - plasma refers to membrane or blood fluid, polymers are large molecules, and proteins are synthesized not stored in these organelles.

The plasma membrane (also called cell membrane) forms the outer boundary of the cell, controlling what enters and exits. Endoplasmic reticulum (A) and golgi bodies (B) are internal organelles for protein synthesis and secretion. Cytoplasm (D) is the gel-like substance INSIDE the cell, not the boundary itself.

The largest cell in the human body is nerve cell 

The powerhouse of a cell is mitochondria. 

Lysosomes contain digestive enzymes that break down waste materials, cellular debris, and foreign invaders - hence called digestive bags or suicide bags. Ribosomes (A) synthesize proteins, centrosomes (B) organize microtubules, and protein (C) is what's digested, not the digester - making all distractors incorrect.

Ribosomes are the cellular sites where protein synthesis (translation) occurs - they read mRNA and assemble amino acids into proteins. The question's wording is slightly confusing because ribosomes are organelles, not processes - the process is translation. Centrosomes (A) organize division, chromosomes (C) carry DNA, and cellulose (D) is a structural polysaccharide in cell walls.

Mitochondria are the powerhouses of the cell where cellular respiration occurs, producing ATP through the Krebs cycle and electron transport chain. Ribosomes (A) make proteins, golgi bodies (B) process and package substances, and endoplasmic reticulum (D) synthesizes lipids and proteins - none are the primary respiration site.

Cytology is the branch of biology specifically studying cells - the prefix cyto- means cell, and -ology means study of. Mythology (A) studies myths, ornithology (C) studies birds, and pharmacology (D) studies drugs and medicines - none relate to cellular study.

Golgi bodies (or golgi apparatus) package, process, and secrete cellular products - they modify proteins and lipids from the ER and release them outside the cell. Plastids (A) are plant-specific for food storage, endoplasmic reticulum (B) synthesizes but doesn't secrete, and nucleolus (D) makes ribosomal RNA.

The endoplasmic reticulum (ER) is a network of membranes that extends throughout the cytoplasm of eukaryotic cells. It provides a large surface area for cellular reactions and connects to the nuclear envelope. The nucleus, nucleolus, and chromosomes are all nuclear structures, not cytoplasmic networks.

An animal cell and a plant cell differ in their mode of nutrition. 

The endoplasmic reticulum fits this description perfectly - it's a folded membrane network in the cytoplasm that synthesizes proteins (rough ER) and lipids (smooth ER), then transports materials to the Golgi apparatus. Cytoplasm is the fluid matrix, lysosomes break down waste, and the Golgi apparatus modifies and packages proteins.

Chromosomes are composed of DNA (nucleic acid) tightly coiled around histone proteins. This DNA-protein complex is called chromatin. The other options are enzymes (lypase), carbohydrates (glucose, sucrose) - not structural components of chromosomes.

Mitosis is the division process that occurs in somatic (body) cells to produce identical daughter cells for growth and repair. Ribosomes synthesize proteins, nucleic acids are molecules, and polymer is a general chemical term - not locations where mitosis occurs.

Genes are segments of DNA located on chromosomes within the nucleus. Each chromosome contains hundreds to thousands of genes. The nucleolus produces ribosomes, plasma membrane regulates transport, and mitochondria produce energy - none of these house genes.

The centrosome, which contains centrioles, is located in the cytoplasm near the nucleus. It organizes microtubules and plays a crucial role in cell division. Golgi bodies and plastids are other organelles, while the nucleus houses genetic material.

Cytokinesis is the division of the cytoplasm that completes cell division, occurring after nuclear division. Karyokinesis is nuclear division, plasmolysis is water loss in plant cells, and osmosis is water movement across membranes.

The four phases of mitosis are prophase (chromatin condenses), metaphase (chromosomes align), anaphase (sister chromatids separate), and telophase (nuclear membranes reform). Plastid, tonoplast, and leucoplast are not mitotic phases.

Karyokinesis specifically refers to the division of the nucleus during cell division, involving chromosome separation. Cytokinesis is cytoplasmic division, plasmolysis is water loss, and osmosis is water diffusion.

Meiosis occurs in reproductive cells (germ cells) to produce gametes (sperm and egg) with half the chromosome number. Enzymes catalyze reactions, exocytosis releases substances, and vacuoles store materials - none undergo meiosis.

The cytoplasm acts as a reservoir for vital chemicals including amino acids, glucose, vitamins, ions, and other metabolites needed for cellular reactions. Protoplasm is the entire living content, golgi bodies modify proteins, and nucleolus makes ribosomes.

Robert Hooke coined the term 'cell' in 1665 when observing cork under a microscope, noting box-like structures resembling monks' cells. Flemming studied mitosis, Robert Brown discovered the nucleus, and Darwin proposed evolution by natural selection.