Cell Structure and Cell Division
All cells share a plasma membrane, cytoplasm and genetic material. Prokaryotes (bacteria) lack a true nucleus and membrane-bound organelles; their DNA lies in the nucleoid. Eukaryotes (plants, fungi, animals) have a nucleus and organelles. Plant cells additionally have a cell wall of cellulose, chloroplasts and a large central vacuole; fungal walls contain chitin; animal cells have neither wall nor chloroplasts and store carbohydrate as glycogen.
Organelles and their functions must be matched precisely: nucleus (stores DNA, controls activity), mitochondria (aerobic respiration, ATP), chloroplasts (photosynthesis), ribosomes (protein synthesis), endoplasmic reticulum (transport and synthesis), Golgi apparatus (packaging and secretion), lysosomes (digestion), vacuole (storage, turgor).
Cell division: mitosis produces two genetically identical diploid cells and underlies growth, repair and asexual reproduction. Meiosis halves the chromosome number and produces four genetically varied haploid cells, the basis of gamete formation. The cell cycle includes interphase (DNA replication) before division. A common trap is confusing mitosis with meiosis and forgetting that chromosome number doubles during replication but the ploidy of daughter cells depends on division type.
Rule of thumb
Mitosis = same (2n → 2n, identical); meiosis = half (2n → n, varied).
Worked example
"A somatic cell of an organism has 24 chromosomes. How many will each daughter cell have after mitosis?" Mitosis preserves number, so 24. After meiosis each gamete would have 12.