IB Biology B2.3 Definitions
This page contains our IB Biology definitions for B2.3. By learning each one of these definitions, you will fully cover the content for IB Biology 'Further cell specialisation'.
Acrosome
An enzyme-filled sac in sperm cells responsible for digesting the outer layer of the egg cell
action potential
The depolarization, repolarization, and hyperpolarization of a neuron
Desmosomes
Structures that fuse cardiac cells together to provide structural integrity
diffusion
The net passive movement of particles from areas of high concentration to areas of low concentration, requiring no energy
Erythrocytes
Red blood cells that have a flattened disc shape with invaginations to increase surface area for oxygen diffusion and binding to haemoglobin
gamete
Sex cell
haploid
A cell that contains one chromosome of the homologous pair
meiosis
The process by which one diploid nucleus divides to form four haploid nuclei
Microvilli
Hair-like structures that increase the surface area of a cell for absorption and diffusion
mitosis
The division of the nucleus into two genetically identical daughter nuclei
Myofibrils
Long contractile fibers within a muscle cell
Sarcolemma
The plasma membrane of a muscle fiber
Sarcoplasmic Reticulum
A network of tubules in muscle fibers that stores calcium ions and coordinates muscle contraction
Surfactant
A substance secreted by Type II pneumocytes that reduces surface tension in the alveoli, preventing collapse and aiding in gas exchange
Zona Pellucida
A gelatinous layer around the egg cell that prevents sperm entry before and after fertilization
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