IB Biology

70S ribosomes are small ribosomes found in prokaryotic cells, as well as in the mitochondria and chloroplasts of eukaryotic cells. They are responsible for protein synthesis, translating messenger RNA (mRNA) into functional proteins.

80S ribosomes are larger ribosomes found in eukaryotic cells that synthesize proteins.

The origin of life from non-living matter, such as simple organic compounds.

Abiotic factors are non-living components like temperature, water availability, salinity, and soil type.

A non-living component of the environment, such as temperature, light, or water availability, that influences the survival and reproduction of organisms.

Absorption is the process by which digested nutrients are transported into the body, primarily occurring in the small intestine.

A graph showing the percentage of light absorbed at each wavelength by a pigment or group of pigments.

Acetylcholine is a neurotransmitter found in many types of synapses, including neuromuscular junctions (where nerves connect to muscles).

The acrosome reaction is the first step in fertilization. It allows a sperm to penetrate the egg's protective glycoprotein layer, called the zona pellucida, to reach the plasma membrane of the egg.

The action potential is the rapid electrical signal generated when the neuron's membrane potential reaches a threshold.

A graph showing the rate of photosynthesis at each wavelength of light.

Activation energy is the minimum amount of energy required to start a chemical reaction.

The active site is a small region on an enzyme where the substrate binds. It is formed by a specific sequence of amino acids within the enzyme's overall three-dimensional structure.

Active transport is the movement of molecules or ions across a membrane against their concentration gradient (from low to high concentration), which requires energy.

Adaptations are traits that increase an organism’s fitness in response to environmental factors.

Adaptive radiation is the evolutionary process by which a single ancestral species rapidly diversifies into many species, each specialized to exploit a different ecological niche.

The attraction between water molecules and other surfaces, enabling water to cling to them and move against gravity.

Small glands located above the kidneys responsible for producing hormones, including epinephrine.

Albedo ($\alpha$) measures the reflectivity of a surface.

An allele is a variation of a gene.

Allele frequency refers to how common a particular allele is within a population. It is expressed as a proportion or percentage of all alleles for a specific gene.

Allelopathy occurs when plants release chemicals, called allelochemicals, into the soil to inhibit the growth of nearby plants.

Allopatric speciation occurs when populations are physically separated by a geographical barrier, such as a river, mountain range, or ocean.

A site on an enzyme other than the active site, where specific molecules can bind to regulate enzyme activity.