IB Biology Sub-topic B2.3 Definitions

An enzyme-filled sac in sperm cells responsible for digesting the outer layer of the egg cell

The depolarization, repolarization, and hyperpolarization of a neuron

Structures that fuse cardiac cells together to provide structural integrity

The net passive movement of particles from areas of high concentration to areas of low concentration, requiring no energy

Red blood cells that have a flattened disc shape with invaginations to increase surface area for oxygen diffusion and binding to haemoglobin

Sex cell

A cell that contains one chromosome of the homologous pair

The process by which one diploid nucleus divides to form four haploid nuclei

Hair-like structures that increase the surface area of a cell for absorption and diffusion

The division of the nucleus into two genetically identical daughter nuclei

Long contractile fibers within a muscle cell

The plasma membrane of a muscle fiber

A network of tubules in muscle fibers that stores calcium ions and coordinates muscle contraction

A substance secreted by Type II pneumocytes that reduces surface tension in the alveoli, preventing collapse and aiding in gas exchange

A gelatinous layer around the egg cell that prevents sperm entry before and after fertilization