A1.1 Water

solvent

A substance that dissolves a solute to form a solution. Water is a common biological solvent.

cohesive

The attraction between molecules of the same substance. Water molecules are cohesive because of hydrogen bonds.

adhesive

The attraction between molecules of different substances. Water can adhere to the walls of plant xylem.

polar

A molecule with an uneven distribution of electrical charge, giving it slightly positive and negative regions.

non polar

A nonpolar substance or moleculehas an even distribution of electrical charge, meaning it lacks distinct positive and negative poles

polarity

The uneven distribution of electrical charge within a molecule.

hydrogen bonds

Weak attractions between a slightly positive hydrogen atom and a slightly negative atom, usually oxygen or nitrogen. They give water cohesion, adhesion, surface tension and a high specific heat capacity, and help hold DNA strands together.

LUCA

Last Universal Common Ancestor; the most recent common ancestor of all organisms living today.

cytoplasm

The jelly

cell

The smallest unit of life capable of carrying out the functions needed for life.

organelles

Specialized structures inside cells that perform specific functions.

plant cell

A eukaryotic cell containing structures such as a cell wall, chloroplasts and a large central vacuole.

animal cell

A eukaryotic cell that lacks a cell wall and chloroplasts and generally has smaller temporary vacuoles.

eukaryote

An organism whose cells contain a nucleus surrounded by a membrane and other membrane

prokaryote

An organism whose cells lack a nucleus and membrane

molecule

Two or more atoms chemically bonded together.

compound

A substance made of two or more different elements chemically bonded together.

element

A pure substance consisting of only one type of atom.

atom

The smallest unit of an element that retains the properties of that element.

intercellular or tissue fluid

Fluid surrounding cells that allows substances such as oxygen, nutrients and waste products to move between cells and the blood.

diatomic

A molecule consisting of two atoms, usually of the same element, such as O₂ or H₂.

electronegativity

The ability of an atom to attract electrons toward itself in a chemical bond.

covalent bond

A strong chemical bond formed when atoms share electrons.

ionic bond

A chemical attraction between oppositely charged ions formed after electrons are transferred from one atom to another.

ions

Atoms or molecules with a net electrical charge because they have gained or lost electrons.

fast molecular motion

The rapid movement of molecules caused by high kinetic energy, usually due to increased temperature.

surface tension

The resistance of a liquid's surface to being broken or stretched, caused by cohesive forces between its molecules.

water column

A continuous column of water within a plant's xylem, allowing water to move from roots toward the leaves.

xylem

Plant tissue that transports water and dissolved minerals from the roots to the rest of the plant.

stomata

Small pores, mainly on leaves, that allow gas exchange and control water loss.

polar substances

Substances whose molecules have an uneven distribution of electrical charge and can interact strongly with other polar substances.

cellulose molecules

Long chains of glucose molecules joined together, forming the main structural component of plant cell walls.

Goldilocks zone

The region around a star where conditions may allow liquid water to exist on a planet's surface.

deuterium

A stable isotope of hydrogen containing one proton and one neutron.

atomic

Relating to atoms.

atomic nuclei

The dense central parts of atoms containing protons and neutrons.

nuclear reactions

Reactions that change an atomic nucleus, releasing or absorbing large amounts of energy.

outgassing

The release of gases from the interior of a planet or other body, often through volcanic activity.

streetlight effect

The tendency to search for something where it is easiest to look rather than where it is most likely to be found.

buoyancy

The upward force exerted by a fluid on an object placed in it.

viscosity

A measure of how strongly a fluid resists flowing.

thermal conductivity

How easily a substance transfers heat through itself.

thermal inertia

The resistance of a material or system to changing temperature.

specific heat capacity

The amount of energy required to raise the temperature of 1 kg of a substance by 1°C.

temperature gradient

A change in temperature over a given distance.

locomotive capabilities

The ability of an organism or cell to move from one place to another.

vestigial limbs

Body structures that have become reduced or lost most or all of their original function through evolution.

propulsion

The force or mechanism that moves an organism or object forward.

piloerection

The raising of hairs on the skin, often in response to cold or emotional stimuli.

subcutaneous

Located beneath the skin.

hydrophilic

Describes a substance that interacts easily with or is attracted to water.

hydrophobic

Describes a substance that does not interact easily with water and tends to avoid it.

carbohydrates

Organic molecules made mainly of carbon, hydrogen and oxygen; they include sugars and starches and are important for energy and structure.

proteins

Large molecules made of amino acid chains that perform many functions, including enzymes, transport and structure.

lipids

A group of mostly water

genetics

The study of genes, heredity and variation.

genes

Sections of DNA that contain information used to produce functional products, such as proteins or functional RNA.

ribosome

A cellular structure that reads mRNA and assembles amino acids into proteins.

phosphate

A chemical group containing phosphorus and oxygen that forms part of the backbone of DNA and RNA.

complementary base pairing

Specific pairing between nitrogenous bases: adenine pairs with thymine in DNA, while cytosine pairs with guanine.

pentose sugar

A sugar containing five carbon atoms. DNA contains deoxyribose and RNA contains ribose.

monomer

A small molecule that can join with other monomers to form a polymer.

amino acid

The monomer that makes up proteins.

glucose

A simple carbohydrate used by cells as an important source of energy.

cell membrane

A selectively permeable barrier surrounding cells that controls what enters and leaves the cell.

chloroplast

The organelle in plant cells where photosynthesis occurs.

mitochondrion

An organelle where most aerobic cellular respiration occurs.

transpiration

The loss of water vapour from a plant, mainly through the stomata of its leaves.

capillary action

The movement of a liquid through narrow spaces or tubes due to adhesion between the liquid and the surface and cohesion between the liquid molecules. In plants, it helps water move upward through the narrow xylem vessels.

transpiration pull

The pulling force created when water evaporates from leaves, helping draw a continuous column of water upward through the xylem.

evaporation

The change of a liquid into a gas at its surface. In plants, water evaporates from moist surfaces inside the leaf during transpiration.