Key Concepts in Biology and Life Sciences

biology

The scientific study of life and living organisms.

organization

The hierarchical arrangement of biological systems from atoms to organisms.

cell

The basic unit of life in all living organisms.

unicellular

Organisms made up of a single cell.

multicellular

Organisms composed of more than one cell.

organ

A group of tissues that work together to perform a specific function.

tissue

A group of similar cells that perform a specific function.

homeostasis

The process by which organisms maintain a stable internal environment.

metabolism

All the chemical reactions that occur within an organism.

cell division

The process by which a cell splits into two new cells.

gene

A segment of DNA that codes for a specific trait or protein.

CHNOPS

The six essential elements of life: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

matter

Anything that has mass and takes up space.

atom

The smallest unit of an element that retains its chemical properties.

element

A pure substance made of only one kind of atom.

compound

A substance formed when two or more elements are chemically bonded.

chemical bond

The force that holds atoms together in a compound.

covalent

A type of bond where atoms share electrons.

ionic

A type of bond where electrons are transferred from one atom to another.

ion

An atom or molecule with a net electric charge due to the loss or gain of electrons.

molecule

Two or more atoms bonded together.

energy

The ability to do work or cause change.

activation energy

The minimum energy needed for a chemical reaction to occur.

polar (polarity)

A molecule with uneven distribution of charge.

hydrogen bonding

A weak bond between slightly positive hydrogen and a more electronegative atom.

solution

A homogeneous mixture of two or more substances.

concentration

The amount of a substance in a defined space.

acidic

A solution with a pH less than 7.

basic

A solution with a pH greater than 7.

pH

A measure of the hydrogen ion concentration in a solution.

monomer

A single molecule that can join with others to form a polymer.

polymer

A large molecule made of repeating monomers.

macromolecule

A very large molecule, such as proteins, nucleic acids, or polysaccharides.

condensation reaction

A chemical reaction where two molecules combine and release water.

hydrolysis

A chemical reaction that breaks bonds using water.

adenosine triphosphate

The main energy-carrying molecule in cells.

carbohydrate

Organic compounds made of carbon, hydrogen, and oxygen; includes sugars and starches.

monosaccharide

The simplest type of carbohydrate, a single sugar molecule.

disaccharide

A sugar formed from two monosaccharides.

polysaccharide

A carbohydrate made of many sugar units linked together.

amino acid

The building blocks of proteins.

peptide bond

The bond formed between two amino acids.

lipid

A group of organic compounds including fats, oils, and waxes.

fatty acid

A long chain of hydrocarbons that makes up lipids.

phospholipid

A lipid containing a phosphate group; forms cell membranes.

wax

A type of lipid that is solid at room temperature.

steroid

A type of lipid with a structure of four fused rings.

nucleic acid

Macromolecules that store genetic information (DNA & RNA).

deoxyribonucleic acid (DNA)

A molecule that carries genetic instructions for living organisms.

ribonucleic acid (RNA)

A molecule that helps in protein synthesis and carries genetic information in some viruses.

nucleotide

The building block of nucleic acids, made of a sugar, phosphate, and base.

reactant

A substance that enters a chemical reaction.

product

A substance formed as a result of a chemical reaction.

enzyme

A protein that speeds up chemical reactions.

catalyst

A substance that speeds up a chemical reaction without being consumed.

substrate

The reactant on which an enzyme acts.

active site

The region on an enzyme where the substrate binds.

bind

To attach or connect to another molecule.

complementary

Two structures that fit together due to matching shapes or chemical properties.

denature

To alter the shape of a protein so it no longer functions properly.

negative feedback

A control mechanism that reduces the output or activity to maintain balance.

positive feedback

A mechanism that increases the change or output in a system.

feedback regulation

A process where the output of a system regulates itself through positive or negative loops.

DNA

The genetic material of the cell.

prokaryotic

Cells that do not have a nucleus or membrane-bound organelles.

eukaryotic

Cells that have a nucleus and membrane-bound organelles.

nucleus

The organelle that contains DNA in eukaryotic cells.

mitochondria

The powerhouse of the cell; site of cellular respiration.

chloroplast

Organelle where photosynthesis occurs in plant cells.

golgi apparatus

Organelle that modifies and packages proteins.

rough endoplasmic reticulum

ER with ribosomes; involved in protein synthesis.

smooth endoplasmic reticulum

ER without ribosomes; involved in lipid synthesis.

vacuole

A storage organelle in cells, especially large in plant cells.

ribosome

A molecular machine in cells that assembles proteins by linking amino acids together.

cell wall

A rigid structure that supports and protects plant cells.

cell membrane

A semi-permeable barrier that surrounds the cell.

semi-permeable

Allows certain substances to pass through while blocking others.

surface area to volume ratio

The amount of surface area per unit volume of an object; affects cell efficiency.

hypotonic

A solution with lower solute concentration compared to the cell.

hypertonic

A solution with higher solute concentration compared to the cell.

isotonic

A solution with equal solute concentration compared to the cell.

active transport

The movement of substances against a concentration gradient using energy.

passive transport

The movement of substances across membranes without energy.

diffusion

The movement of molecules from high to low concentration.

osmosis

The diffusion of water across a membrane.

solute

The substance that is dissolved in a solution.

solvent

The substance that does the dissolving in a solution.

cellular respiration

The process of breaking down glucose to produce ATP.

fermentation

An anaerobic process that generates energy without oxygen.

glycolysis

The first step in cellular respiration; breaks down glucose.

cytosol

The fluid portion of the cytoplasm.

lactic acid fermentation

An anaerobic process where microorganisms like bacteria and yeast convert sugars (like glucose) into lactic acid.

alcoholic fermentation

An anaerobic process where microorganisms, primarily yeast, convert sugars into alcohol and carbon dioxide

photosynthesis

The process by which green plants use sunlight to make food from carbon dioxide and water.

autotroph

An organism that can produce its own food using light, water, carbon dioxide

producer

an organism that can make its own food

pigment

Light-absorbing molecule

chlorophyll

Green pigment in plants that absorbs light energy used to carry out photosynthesis

stomata

Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

cell cycle

The series of events that take place in a cell leading to its division and duplication.