MBBS Biology



control: Something that is not tested during the investigation.

controlled experiment: Two identical experiments are carried out side-by-side; in one of the experiments the independent variable being tested isused, in the other experiment, the control, or the independent variable is not used.

controlled variables: Variables that are kept constant to prevent influencing the effect of the independent variable on the dependent variable.

deduction: Involves determining a single fact from a general statement.
dependent variable: Changes in response to the independent variable.
experiment: A test that is used to eliminate one or more of the possible hypotheses until one hypothesis remains.

hypothesis: A suggested explanation based on evidence that can be tested by observation or experimentation.
independent variable: Factor(s) whose values are controlled by the experimenter to determine its relationship to an observed phenomenon (the dependent variable).
induction: Involves determining a general statement that is very likely to be true, from several facts.
observation: The act of noting or detecting phenomenon through the senses. For example, noting that a room is dark is an observation made through sight.
Occam’s razor: States that the explanation for a phenomenon should make as few assumptions as possible.
phenomenon: Is any occurrence that is observable.
scientific methods: Based on gathering observable, empirical (produced by experimentor observation) and measurable evidence that is critically evaluated.
scientific skepticism: Questions claims based on their scientific verifiability rather than accepting claims based on faith or anecdotes.
variable: A factor that can change over the course of an experiment.

animal cloning: The ability and usefulness of scientists cloning animals for various needs, such as vaccine development, tissues for transplant into humans such as heart valve, and increased food production.
bioethicists: People concerned with the ethical questions that arise in the relationships among biology, biotechnology, medicine, politics, law, and philosophy.
bioinformatics: An interdisciplinary field which helps solve biological problems using computers; may also be called computational biology.
bioremediation: The use of microorganisms to clean up contaminated sites, such as an oil spill.
biotechnology: Technology based on biology; it involves the use of organisms or biological processes and can be especially used in agriculture, food science, and medicine.
conflict of interest: A situation in which a researcher has professional or personal interests that are at odds with each other.
euthanasia: The choice by a terminally ill person to have medical assistance in dying.
ethics The discipline concerned with what is morally good and bad, right and wrong.
reproducibility: The ability to repeat experiments and get the same results.
research scientist: A person that does scientific investigations and makes discoveries.
science magazine: A publication with news, opinions and reports about science; written for a non-expert audience.
scientific article: A scientific article discussing new research and findings; usually published in a scientific journal.

scientific consensus: The collective judgment, position, and opinion of a community of scientists in a particular field of science, at a particular time.
scientific journal: A publication that communicate and document the results of research carried out in universities and various other research institutions.
scientific misconduct: The violation of standard codes of scholarly conduct and ethical behavior in professional scientific research.
stem cell research: Research involving stem cells, usually harvested from human embryos.
systematic bias: A bias that is introduced from a flaw in measurements.

aseptic technique: Laboratory procedures that are carried out under sterile conditions.
compound microscope: An optical microscopes that has a series of lenses, and have uses in many fields of science, particularly biology and geology.
electron microscope: A microscope that uses electrons instead of light; allow a researcher to see things at very high magnification, far higher than an optical microscope can possibly magnify.
International System of Units (SI): The measurements that scientists use; a form of the metric system.
lab coat: A knee-length overcoat that is usually worn while working in the lab; helps to protect the researcher’s clothes from splashes or contamination.
laboratory: A place that has controlled conditions in which scientific research, experiments, and measurement may be carried out.
lab techniques: The procedures used in science to carry out an experiment.
magnification: Enlarging an image of an object so that it appears much bigger than its actual size; also refers to the number of times an object is magnified.
microscopes: Instruments used to view objects that are too small to be seen by the naked eye.
model: A physical, mathematical, or logical representation of a system, phenomenon, or process; allow scientists to investigate a phenomenon in a controlled way.
optical microscope: A microscope that uses visible light and lenses to magnify objects.
resolution: A measure of the clarity of an image; it is the minimum distance two points can be separated and still be distinguished as two separate points.

scanning electron microscope (SEM): Electron microscope that scans an electron beam over the surface of an object and measures how many electrons are scattered back.
scientific modeling: The process of making abstract models of natural phenomena.
simulation: A model that runs overtime; brings a model to life and shows how a particular object or phenomenon will behave.
stereo microscope: A light microscope with two ocular lenses.
transmission electron microscope (TEM): Electron microscope that shoots electrons through the sample and measures how the electron beam changes because it is scattered in the sample.


adaptation Refers to the process of becoming adjusted to an environment; may include structural, physiological, or behavioral traits that improve an organism’s likelihood of survival and reproduction.
biochemistry The study of the chemicals that make up life.
biological interactions The interactions between different organisms in an environment.
biology The study of life.
biosphere Every place that life occurs, from the upper reaches of the atmosphere to the top few meters of soil, to the bottoms of the oceans.
botany The study of plants.
cell The smallest unit of structure and function of living organisms.
cell biology The study of life at the level of the cell.
community Composed of the relationships between groups of different species.
competition An interaction between organisms or species, for the same resources such as water, food, or hunting grounds in an environment.

ecology The study of how organisms interact with their environment and each other.
ecosystem Made up of the relationships among smaller groups of organisms with each other, and their environment.
evolution The process by which populations of organisms change over time by acquiring and passing on new traits from generation to generation.
evolutionary biology The study of how populations and species change over time.
genetics The study of how organisms pass traits to their offspring (heredity).
homeostasis The ability to keep an internal environment within a certain range, despite changes in the external environment.
immunology The study of an organism’s resistance to disease.
metabolism The sum of the chemical reactions in a cell.
microbiology The study of microscopic organisms.
natural selection A process that causes heritable traits that are helpful for survival and reproductiontobecomemorecommon,andharmfultraits,ortraitsthatarenothelpful or advantageous for survival to become more rare in a population of organisms.
organism An individual living creature.
physiology The study of how the human body works.
symbiosis Various types of close relationships between organisms of different species; comes from a Greek word that means ”living together.”
zoology The study of animals.


chemical compound Unique substance with a fixed composition that forms when atoms of two or more elements react. element Pure substance made up of just one type of atom. energy Property of matter that is defined as the ability to do work. gas State of matter in which atoms or molecules have enough energy to move freely. kinetic energy Form of energy that an object has when it is moving. liquid State of matter in which atoms or molecules are constantly in contact but have enough energy to keep changing positions relative to one another. matter All the substances of which things are made. mixture Combination of chemical substances that does not have a fixed composition and does not result from a chemical reaction. organic compound Type of chemical compound that contains carbon and hydrogen and is found mainly in organisms. potential energy Form of energy that is stored in an object due to its position. solid State of matter in which atoms or molecules do not have enough energy to move. state of matter Condition that matter is in, depending on how much energy its atoms or molecules have.


amino acid Small organic molecule that is a building block of proteins.
carbohydrate Typeoforganiccompoundthatconsistsofoneormoresmallerunitscalled monosaccharides.
cholesterol Type of steroid that is an important part of cell membranes and plays other vital roles.
complementary bases Nucleic acid bases that form bonds with each other and help hold together two nucleotide chains.
complex carbohydrate Another term for a polysaccharide.
deoxyribonucleic acid (DNA) Double-stranded nucleic acid that contains the genetic instructions for proteins.
disaccharide Small carbohydrate, such as sucrose, that consists of two monosaccharides.
double helix Normal shape of a DNA molecule in which two chains of nucleotides are intertwined.
essential amino acids Amino acids that the human body needs but cannot make and must consume in food.
essential fatty acids Fatty acids that the human body needs but cannot make and must consume in food.
fatty acid OrganiccompoundfoundinlipidsthathasthegeneralformulaCH3(CH2)nCOOH.
functional group Small group of elements within an organic compound that determines the nature and function of the organic compound.

lipid Type of organic compound that consists of one or more fatty acids with or without additional molecules.
monosaccharide Small carbohydrate, such as glucose, with the general formula (CH2O)n.
nucleic acid Type of organic compound that consists of smaller units called nucleotides.
nucleotide Small organic molecule that is a building block of nucleic acids.
peptide Short chain of amino acids.
phospholipid Type of lipid that is a major component of cell membranes.
polypeptide Long chain of amino acids.
polysaccharide Large carbohydrate that consists of more than two monosaccharides.
protein Type of organic compound that consists of smaller units called amino acids.
ribonucleic acid (RNA) Single-stranded nucleic acid that uses information contained in DNA to assemble amino acids and make proteins.
saturated fatty acid Type of fatty acid in which all the carbon atoms are bonded to as many hydrogen atoms as possible.
simple sugar Another term for a monosaccharide or disaccharide.
steroid Typeoflipidthathasseveralfunctions,suchasformingcellmembranesandacting as sex hormones.
trans fatty acid Artificial, unsaturatedfattyacidthathaspropertiessimilartosaturated fatty acids.
triglyceride Type of lipid that is the main form of stored energy in animals.
unsaturated fatty acid Type of fatty acid in which some carbon atoms are not bonded to as many hydrogen atoms as possible.


activation energy Energy needed for a chemical reaction to get started.
anabolic reaction Endothermic reaction that occurs in organisms.
catabolic reaction Exothermic reaction that occurs in organisms.
chemical reaction Process that changes some chemical substances into other chemical substances.
combustion reaction Type of chemical reaction in which a compound or element burns in oxygen.
decomposition reaction Typeofchemicalreactioninwhichacompoundisbrokendown into smaller compounds or elements.
endothermic reaction Any chemical reaction that consumes energy.
enzyme Chemical that speeds up chemical reactions in organisms.
exothermic reaction Any chemical reaction that releases energy.
product Substance that forms as a result of a chemical reaction.
reactant Substance involved in a chemical reaction that is present at the beginning of the reaction.
substitution reaction Type of chemical reaction in which one element replaces another element in a compound.
synthesis reaction Type of chemical reaction in which elements or compounds unite to form a more complex product.


acid Solution with a higher hydronium ion concentration than pure water and a pH lower than 7.
acidity Hydronium ion concentration of a solution.
base Solution with a lower hydronium ion concentration than pure water and a pH higher than 7.

condensation Process in which water vapor changes to water droplets, forming clouds or fog.
evaporation Process in which liquid water changes into water vapor.
hydrogen bond Bondthatformsbetweenahydrogenatominonemoleculeandadifferent atom in another molecule.
ion Electrically charged atom or molecule.
metabolism Sum total of all body reactions, including those that build up molecules (anabolic reactions) and those that break down molecules (catabolic reactions).
neutralization Chemical reaction in which an acid and a base react to form a neutral solution of water and a salt.
pH Measure of the acidity, or hydronium ion concentration, of a solution.
polarity Difference in electrical charge between different parts of a molecule.
precipitation Rain, snow, sleet, or other type of moisture that falls from clouds.
solubility Ability of a solute to dissolve in a particular solvent.
solute Substance in a solution that is dissolved by the other substance (the solvent).
solution Homogeneous mixture in which one substance is dissolved in another.
solvent Substance in a solution that dissolves the other substance (the solute).
sublimation Process in which snow or ice changes directly into water vapor.
transpiration Process in which plants give off water, most of which evaporates.


cell The smallest unit that can carry out the processes of life; the basic unit of all living things.
cell membrane The physical boundary between the inside of the cell (intracellular) and its outside environment (extracellular).
cytoplasm The general term for all of the material inside the cell, between the cell membrane and the nucleus.
cytosol A watery fluid that contains dissolved particles and organelles; makes up cytoplasm.
DNA Deoxyribonucleicacid,thegeneticmaterial; containsthegeneticinformationneeded for building structures such as proteins.
eukaryote An organism whose cells are organized into complex structures by internal membranes and a cytoskeleton.
eukaryotic cells Typicalofmulti-celledorganisms;havemembraneboundorganelles;usually larger than prokaryotic cells.
nucleus The membrane bound organelle that contains DNA; found in eukaryotic cells.
organelle Structure that carries out specific functions inside the cell.
prokaryotic cells Typical of simple, single-celled organisms, such as bacteria; lack a nucleus and other membrane bound organelles.
resolution A measure of the clarity of an image; the minimum distance that two points can be separated by and still be distinguished as two separate points.
ribosomes The organelles on which proteins are made (synthesized).


chloroplast The organelle of photosynthesis; captures light energy from the sun and uses it with water and carbon dioxide to make food (sugar) for the plant.
cilia (cilium) Made up of extensions of the cell membrane that contain microtubules; involved in movement.
cell wall A rigid layer that is found outside the cell membrane and surrounds the cell; provides structural support and protection.
cytoplasm The gel-like material within the cell that holds the organelles.
cytoskeleton A cellular ”scaffolding” or ”skeleton” that crisscrosses the cytoplasm; helps to maintain cell shape, it holds organelles in place, and for some cells, it enables cell movement.
endoplasmic reticulum (ER) A network of phospholipid membranes that form hollow tubes, flattened sheets, and round sacs; involved in transport of molecules, such as proteins, and the synthesis of proteins and lipids.
flagella (flagellum) Long, thin structures that stick out from the cell membrane; help single-celled organisms move or swim towards food.
Fluid Mosaic Model Model of the structure of cell membranes; proposes that integral membrane proteins are embedded in the phospholipid bilayer; some of these proteins extendall thewaythroughthe bilayer, and someonly partiallyacross it; alsoproposes that the membrane behaves like a fluid, rather than a solid.
gene A short segment of DNA that contains information to encode an RNA molecule or a protein strand.
gene expression The process by which the information in a gene is ”decoded” by various cell molecules to produce a functional gene product, such as a protein molecule or an RNA molecule.
Golgi apparatus A large organelle that is usually made up of five to eight cup-shaped, membrane-covered discs called cisternae; modifies, sorts, and packages different substances for secretion out of the cell, or for use within the cell.

integral membrane proteins Proteinsthatarepermanentlyembeddedwithintheplasma membrane; involved in channeling or transporting molecules across the membrane or acting as cell receptors.
intermediate filaments Filamentsthatorganizetheinsidestructureofthecellbyholding organelles and providing strength.
lipid bilayer A double layer of closely-packed lipid molecules; the cell membrane is a phospholipid bilayer.
lysosome A vesicle that contains powerful digestive enzymes.
membrane protein A protein molecule that is attached to, or associated with the membrane of a cell or an organelle.
microfilament Filament made of two thin actin chains that are twisted around one another; organizes cell shape; positions organelles in cytoplasm; involved in cell-to-cell and cell-to-matrix junctions.
microtubules Hollow cylinders that make up the thickest of the cytoskeleton structures; made of the protein tubulin, with two subunits, alpha and beta tubulin; involved in organelle and vesicle movement; form mitotic spindles during cell division; involved in cell motility (in cilia and flagella).
mitochondria (mitochondrion) Membrane-enclosed organelles that are found in most eukaryotic cells; called the ”power plants” of the cell because they use energy from organic compounds to make ATP.
multicellular organisms Organismsthataremadeupofmorethanonetypeofcell; have specialized cells that are grouped together to carry out specialized functions.
nucleus The membrane-enclosed organelle found in most eukaryotic cells; contains the genetic material (DNA).
organ A group of tissues that has a specific function or group of functions.
organ system Agroupoforgansthatactstogethertocarryoutcomplexrelatedfunctions, with each organ focusing on a part of the task.

peripheral membrane proteins Proteins that are only temporarily associated with the membrane; can be easily removed, which allows them to be involved in cell signaling.
peroxisomes Vesicles that use oxygen to break down toxic substances in the cell.
phospholipid Alipidmadeupofupofapolar, phosphorus-containinghead, andtwolong fatty acid, non-polar ”tails.” The head of the molecule is hydrophilic (water-loving), and the tail is hydrophobic (water-fearing).
plasma membrane Phospholipid bilayer that separates the internal environment of the cell from the outside environment.
ribosomes Organelles made of protein and ribosomal RNA (rRNA); where protein synthesis occurs.
selective permeability The ability to allow only certain molecules in or out of the cell; characteristic of the cell membrane; also called the cell membrane.
spontaneous generation The belief that living organisms grow directly from decaying organic substances.
tissue A group of connected cells that has a similar function within an organism.
transport vesicle A vesicle that is able to move molecules between locations inside the cell.
vacuole Membrane-bound organelles that can have secretory, excretory, and storage functions; plant cells have a large central vacuole.
vesicle A small, spherical compartment that is separated from the cytosol by at least one lipid bilayer.


active transport The energy-requiring process of pumping molecules and ions across membranes against a concentration gradient.
carrier protein A transport protein that is specific for an ion, molecule, or group of substances; carries the ion or molecule across the membrane by changing shape after the binding of the ion or molecule.
channel protein Atransportproteinthatactslikeaporeinthemembranethatletswater molecules or small ions through quickly.
contractile vacuole A type of vacuole that removes excess water from a cell.

diffusion The movement of molecules from an area of high concentration of the molecules to an area with a lower concentration. endocytosis The process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane. exocytosis The process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. facilitated diffusion The diffusion of solutes through transport proteins in the plasma membrane. gated channel protein A transport protein that opens a ”gate,” allowing a molecule to flow through the membrane. ion channel A protein that transports ions across the membrane by facilitated diffusion. ligand A small molecule that binds to a larger molecule. osmosis The diffusion of water molecules across a selectively permeable membrane from an area of higher concentration to an area of lower concentration. passive transport A way that small molecules or ions move across the cell membrane without input of energy by the cell. second messenger A small molecule that starts a change inside a cell in response to the binding of a specific signal to a receptor protein. selectively permeable Thecharacteristicofthecellmembranethatallowscertainmolecules to pass through the membrane, but not others. signal-transduction pathway The signaling mechanism by which a cell changes a signal on it surface into a specific response inside the cell; most often involves an ordered sequence of chemical reactions inside the cell which is carried out by enzymes and other molecules. sodium-potassium pump Acarrierproteinthatmovessodiumandpotassiumionsagainst large concentration gradients, moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid. transport protein A protein that completely spans the membrane, and allows certain molecules or ions to diffuse across the membrane; channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion.

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