IB Biology Sub-topic C2.1 Definitions

This page contains our IB Biology definitions for sub-topic C2.1. By learning each one of these definitions, you will fully cover the content for IB Biology 'Chemical signalling'.
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action potential

The depolarization, repolarization, and hyperpolarization of a neuron

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Cytokines

A large group of peptides and small proteins that coordinate immune responses over short and long distances, including interferons (IFs), interleukins (ILs), and tumor necrosis factors (TNFs)

differentiation

The growth and development of cells into specialized cell types

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exocytosis

Release of substances into the extra-cellular matrix through fusion of vesicles with the plasma membrane

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gene expression

The conversion of genes to proteins to express the gene's coded characteristic

hydrophilic

Attracted to water (water-loving)

hydrophobic

Repelled to water (water-fearing)

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ligand

Neutral molecule or anion with a non-bonding pair of electrons (commonly water)

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negative feedback

The process whereby substances decrease each other's levels

neuron

A nervous system cell that carries electrical impulses from the brain to the body or vice versa

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Neurotransmitters

Chemical messengers released in synapses to carry signals to another neuron, gland, or muscle cell

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positive feedback

The process whereby substances increase each other's levels

synapse

The junction between two neurons or between a neuron and receptor or effector cell

synaptic cleft

The space between two neurons or between a neuron and receptor or effector cell

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