Biology Vocab

Observation

Gathering information through senses or instruments, which provides the basis for forming questions or hypotheses.

Scientific Question

A question based on observations that can be tested through experiments or further observations.

Hypothesis

A tentative explanation or prediction that can be tested by experiments or observations.

Prediction

A specific outcome expected if the hypothesis is correct.

Theory

A well-substantiated explanation of some aspect of the natural world that is based on a body of evidence.

Controlled Experiment

An experiment in which only one variable is changed while keeping all other variables constant.

Dependent Variable

The variable that is measured or observed in response to changes in the independent variable.

Independent Variable

The variable that is changed or manipulated by the researcher to observe its effect on the dependent variable.

Valence electron

An electron in the outermost shell of an atom that can participate in chemical bonding.

Electronegativity

A measure of an atom's ability to attract electrons in a chemical bond.

Four types of bonds

Covalent, ionic, hydrogen, and Van der Waals bonds.

Covalent bond

A bond where atoms share electrons; polar covalent bonds have unequal sharing, nonpolar bonds have equal sharing.

Ionic bond

A bond formed by the transfer of electrons from one atom to another, resulting in oppositely charged ions.

Hydrogen bond

A weak bond between a hydrogen atom and an electronegative atom like oxygen or nitrogen.

Van der Waals

Weak attractions between molecules due to temporary dipoles created by the movement of electrons.

pH

A measure of how acidic or basic a solution is, based on the concentration of hydrogen ions (H+).

Solute

The substance that is dissolved in a solvent to form a solution.

Solvent

The substance that dissolves the solute to form a solution.

Solution

A homogeneous mixture of solute and solvent.

Hydrophobic

Water-fearing; substances that do not dissolve in water.

Hydrophilic

Water-loving; substances that dissolve or interact well with water.

Biomolecule

A molecule that is essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

Monomer

A small molecule that can bind to others to form a polymer.

Polymer

A large molecule made up of repeating monomer units.

Hydrolysis

A reaction where water breaks a bond in a polymer to separate it into monomers.

Dehydration Synthesis

A reaction where monomers are joined by removing water to form a polymer.

Enzyme

A biological catalyst that speeds up chemical reactions in cells.

Polypeptide

A chain of amino acids linked by peptide bonds.

Protein

A functional molecule made of one or more polypeptides folded into a specific structure.

Amino Acid

The building block of proteins, consisting of an amino group, carboxyl group, and side chain.

Lipids

Hydrophobic molecules, including fats, oils, and phospholipids, that are used for energy storage and membrane structure.

Hydrophobic interaction

The tendency of nonpolar substances to avoid water and group together in aqueous environments.

Fatty acid

A long hydrocarbon chain with a carboxyl group, which is a component of fats.

Saturated fatty acid

A fatty acid with no double bonds, meaning it is fully saturated with hydrogen.

Unsaturated fatty acid

A fatty acid that contains one or more double bonds in its hydrocarbon chain.

Nucleic Acid

A polymer of nucleotides, such as DNA or RNA, that stores and transmits genetic information.

Adenine

A nitrogenous base in DNA and RNA; pairs with thymine in DNA and uracil in RNA.

Purine

A type of nitrogenous base, including adenine and guanine, characterized by a double-ring structure.

Cytosine

A nitrogenous base in DNA and RNA; pairs with guanine.

Uracil

A nitrogenous base found in RNA, replacing thymine.

Thymine

A nitrogenous base in DNA; pairs with adenine.

Guanine

A nitrogenous base in DNA and RNA; pairs with cytosine.

Complementary

Refers to the specific pairing of nitrogenous bases in DNA or RNA (A-T, G-C).

Pyrimidine

A type of nitrogenous base with a single-ring structure, including cytosine, thymine, and uracil.

Ribonucleic Acid (RNA)

A nucleic acid involved in protein synthesis, consisting of a single strand of nucleotides.

Deoxyribonucleic Acid (DNA)

A nucleic acid that carries genetic information, consisting of two strands in a double helix.

Nucleotide

The monomer of nucleic acids, consisting of a sugar, phosphate group, and nitrogenous base.

Polynucleotide

A polymer of nucleotides, forming either DNA or RNA.

Glucose (6C)

A six-carbon sugar that serves as a primary energy source in cells.

Monosaccharide

The simplest type of carbohydrate, consisting of a single sugar molecule.

Polysaccharide

A carbohydrate polymer made of many monosaccharide units.

Starch vs Cellulose

Starch is a polysaccharide used for energy storage in plants; cellulose is a structural polysaccharide in plant cell walls.

Organelle

Specialized structures within a cell that perform specific functions, like the nucleus or mitochondria.

Chromosome

A thread-like structure made of DNA and proteins, carrying genetic information.

Cytoplasm

The fluid inside the cell, excluding the nucleus, that contains organelles and other cell components.

Cytosol

The liquid part of the cytoplasm, where metabolic reactions occur.

Plasma membrane

The semi-permeable membrane that surrounds the cell, controlling the movement of substances in and out.

Nucleus

The organelle that contains the cell’s genetic material (DNA) and controls cell activities.

Nuclear envelope

The double membrane surrounding the nucleus, containing nuclear pores for material exchange.

Nuclear pore

Openings in the nuclear envelope that allow for the transport of molecules between the nucleus and cytoplasm.

Endomembrane system

A group of organelles involved in modifying, packaging, and transporting proteins and lipids, including the ER and Golgi apparatus.

Vesicles

Small membrane-bound sacs that transport materials within or outside the cell.

Endoplasmic reticulum (ER)

A network of membranes involved in protein and lipid synthesis.

Smooth ER

Lacks ribosomes, involved in lipid synthesis and detoxification.

Rough ER

Studded with ribosomes, involved in protein synthesis.

Transport vesicle

A small membrane-bound sac that moves molecules between organelles in the cell.

Golgi apparatus

An organelle that modifies, sorts, and packages proteins and lipids for storage or transport out of the cell.

Vacuole

A large vesicle that stores nutrients, waste products, and helps maintain pressure within the plant cells.

Lysosome

An organelle that contains enzymes to break down and digest waste and cellular debris.

Cell wall

A rigid structure found in plant cells, providing support and protection; made of cellulose.

Ribosomes (bound and free)

Small organelles that synthesize proteins; bound ribosomes are attached to the rough ER, while free ribosomes float in the cytoplasm.

Inner membrane/Outer membrane

Refers to the double membranes found in mitochondria and chloroplasts; the inner membrane often plays a role in energy production.

Intermembrane space

The space between the inner and outer membranes of mitochondria or chloroplasts, important for processes like oxidative phosphorylation.

Mitochondria

The powerhouse of the cell, where cellular respiration and energy (ATP) production occur.

Mitochondrial matrix

The innermost compartment of the mitochondria, where the citric acid cycle takes place.

Chloroplast

An organelle found in plant cells responsible for photosynthesis.

Stomata

Pores in plant leaves and stems that allow gas exchange.

Stroma

The fluid-filled space inside chloroplasts where the Calvin cycle of photosynthesis occurs.

Phospholipid

A lipid with a hydrophilic head and hydrophobic tails, forming the main structure of cell membranes.

Semi-permeability

The ability of a membrane to allow some substances to pass through while blocking others.

Amphipathic

A molecule with both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, like phospholipids.

Fluid mosaic model

A model describing the dynamic, flexible nature of the cell membrane, where proteins float in or on a fluid lipid bilayer.

Integral proteins

Proteins embedded in the lipid bilayer that can span the membrane and facilitate transport.

Peripheral proteins

Proteins attached to the surface of the membrane, involved in signaling and maintaining structure.

Transport protein

Proteins that help move substances across the cell membrane, either by facilitated diffusion or active transport.

Aquaporin

A transport protein specifically for water, allowing water to move through the cell membrane.

Active transport

The movement of substances across a membrane against their concentration gradient, requiring energy (ATP).

Cotransport

The coupled transport of two substances across a membrane, where one substance moves down its concentration gradient and the other moves against it.

Concentration gradient

A difference in the concentration of a substance across a space, driving diffusion.

Diffusion

The passive movement of molecules from a region of high concentration to low concentration.

Dynamic Equilibrium

When the concentration of molecules is the same throughout a space, but molecules continue to move randomly.

Facilitated diffusion

The passive movement of molecules across a membrane via transport proteins.

Exocytosis

The process by which cells expel materials in vesicles by fusing them with the cell membrane.

Endocytosis

The process by which cells take in materials by engulfing them in vesicles.

Hypoosmotic

Lower solute concentration outside the cell.

Hyperosmotic

Higher solute concentration outside the cell.

Isoosmotic

Equal solute concentration inside and outside the cell.

Ion pumps

Transport proteins that use energy to move ions across the membrane against their concentration gradients.

Membrane Potential

The voltage difference across a cell membrane, caused by the distribution of ions.

Osmosis

The passive movement of water molecules across a semi-permeable membrane from an area of lower solute concentration to higher solute concentration.