Loading...
Loading...
Master essential biology terms and concepts for NEET 2026-27. Comprehensive definitions with examples, key points, and NEET relevance ratings.
Select a category to jump to those definitions
7 definitions
Mitosis is a type of cell division in which a single cell divides to produce two genetically identical daughter cells. It is the process by which the body grows and repairs damaged tissues. During mitosis, the chromosomes in the nucleus are separated into two identical sets, each going to one of the two daughter cells.
Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four haploid daughter cells from one diploid parent cell. It occurs in germ cells and is essential for sexual reproduction, introducing genetic variation through crossing over and independent assortment.
An enzyme is a biological catalyst, typically a protein, that speeds up chemical reactions in living organisms without being consumed in the process. Enzymes lower the activation energy required for reactions and are highly specific, each acting on a particular substrate. They are essential for metabolism and virtually all cellular processes.
Osmosis is the movement of water molecules from a region of lower solute concentration to a region of higher solute concentration through a semipermeable membrane. It is a special type of diffusion that only involves water and continues until equilibrium is reached or opposed by other forces.
Cellular respiration is the metabolic process by which cells break down glucose and other organic molecules to produce ATP (energy). It occurs in three stages: glycolysis, the Krebs cycle, and oxidative phosphorylation. The overall process uses oxygen and produces carbon dioxide and water as byproducts.
ATP (Adenosine Triphosphate) is the primary energy currency of all living cells. It consists of adenine, ribose sugar, and three phosphate groups. Energy is released when ATP is hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate. ATP is continuously recycled in cells.
The Krebs cycle (citric acid cycle or TCA cycle) is a series of chemical reactions in the mitochondrial matrix that completely oxidizes acetyl-CoA derived from carbohydrates, fats, and proteins. It produces CO₂, NADH, FADH₂, and ATP, connecting glycolysis to oxidative phosphorylation.
6 definitions
DNA replication is the biological process by which a DNA molecule makes an identical copy of itself. This semiconservative process ensures that genetic information is accurately transmitted from parent to daughter cells during cell division. Key enzymes include DNA polymerase, helicase, and ligase.
Transcription is the first step of gene expression, where a segment of DNA is copied into RNA (specifically mRNA) by the enzyme RNA polymerase. This process occurs in the nucleus in eukaryotes and transfers genetic information from DNA to messenger RNA, which then carries the code to ribosomes for protein synthesis.
Translation is the process by which ribosomes decode the mRNA sequence into a polypeptide chain (protein). It involves transfer RNA (tRNA) molecules that bring specific amino acids to the ribosome, where they are joined together in the order specified by the mRNA codons. This occurs in the cytoplasm.
A chromosome is a thread-like structure of DNA and protein found in the nucleus of cells that carries genetic information. Humans have 46 chromosomes (23 pairs). During cell division, chromosomes condense and become visible under a microscope. They contain genes that determine an organism's traits.
A mutation is a permanent change in the DNA sequence of an organism. Mutations can occur spontaneously or be induced by mutagens (radiation, chemicals). They can be beneficial, harmful, or neutral. Mutations are the ultimate source of genetic variation and drive evolution.
Mendelian inheritance refers to the patterns of inheritance discovered by Gregor Mendel through his pea plant experiments. It includes the Law of Segregation (alleles separate during gamete formation) and the Law of Independent Assortment (genes for different traits are inherited independently).
3 definitions
An ecosystem is a community of living organisms (biotic factors) interacting with each other and their physical environment (abiotic factors) as a system. It includes energy flow through trophic levels and nutrient cycling. Ecosystems can range from a small pond to an entire forest or ocean.
Biodiversity refers to the variety of life on Earth at all levels, from genes to ecosystems. It includes species diversity (number and variety of species), genetic diversity (variation within species), and ecosystem diversity (variety of habitats). Biodiversity is crucial for ecosystem stability and human welfare.
Nitrogen fixation is the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) or other usable nitrogen compounds. This can occur biologically (by bacteria like Rhizobium) or abiotically (lightning, industrial processes). It is essential for making nitrogen available to plants.
5 definitions
Homeostasis is the ability of an organism or cell to maintain internal stability by adjusting its physiological processes. It involves feedback mechanisms that detect changes and trigger responses to restore optimal conditions. Examples include temperature regulation, blood sugar control, and water balance.
An antibody (immunoglobulin) is a Y-shaped protein produced by B cells of the immune system in response to foreign substances (antigens). Antibodies specifically recognize and bind to antigens, marking them for destruction by other immune cells. There are five classes: IgG, IgA, IgM, IgE, and IgD.
A hormone is a chemical messenger produced by endocrine glands and transported through the bloodstream to target organs where it regulates physiological processes. Hormones can be proteins, steroids, or amino acid derivatives. They are essential for growth, metabolism, reproduction, and homeostasis.
A neuron is a specialized cell that transmits nerve impulses (electrical signals) in the nervous system. It consists of a cell body (soma), dendrites (receive signals), and an axon (transmits signals). Neurons communicate with each other at synapses using neurotransmitters.
A vaccine is a biological preparation that provides active acquired immunity against a specific infectious disease. It contains weakened, killed, or parts of the pathogen that stimulate the immune system to produce antibodies and memory cells without causing the disease itself.
4 definitions
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy (usually from the sun) into chemical energy stored in glucose. This process uses carbon dioxide and water as raw materials and releases oxygen as a byproduct. It occurs in chloroplasts and involves light-dependent and light-independent reactions.
Chlorophyll is the green pigment found in chloroplasts that is essential for photosynthesis. It absorbs light energy, particularly from red and blue wavelengths, and reflects green light (making plants appear green). Chlorophyll a is the primary pigment, while chlorophyll b is an accessory pigment.
Xylem is the vascular tissue in plants that conducts water and dissolved minerals from roots to stems and leaves. It consists of tracheids, vessel elements, xylem fibers, and xylem parenchyma. The movement of water through xylem is driven by transpiration pull and root pressure.
Phloem is the vascular tissue that transports organic nutrients (mainly sucrose) from leaves to other parts of the plant. It consists of sieve tubes, companion cells, phloem fibers, and phloem parenchyma. Unlike xylem, phloem can transport in both directions (bidirectional).
2 definitions
Natural selection is the process by which organisms with favorable traits are more likely to survive and reproduce, passing these traits to the next generation. First proposed by Charles Darwin, it is the primary mechanism of evolution. Over time, beneficial traits become more common in a population while harmful traits decrease.
Genetic drift is the random change in allele frequencies in a population due to chance events, not natural selection. It has a stronger effect in small populations. Two types are founder effect (new population from few individuals) and bottleneck effect (population size drastically reduced).
2 definitions
A plasmid is a small, circular, double-stranded DNA molecule found in bacteria and some eukaryotes. It replicates independently of chromosomal DNA. Plasmids are commonly used in genetic engineering as vectors to introduce foreign DNA into host cells and produce recombinant proteins.
PCR (Polymerase Chain Reaction) is a laboratory technique used to amplify specific DNA segments, creating millions of copies from a small sample. Invented by Kary Mullis in 1983, PCR uses thermal cycling with a heat-stable DNA polymerase (Taq polymerase) and specific primers.
Join Cerebrum Biology Academy for complete NEET Biology preparation with live classes, personalized guidance, and proven strategies by Dr. Shekhar C Singh