F214 definitions

Question	Answer
Negative feedback	Process that reverses any change in the internal environment, to ensure that an optimum steady state can be maintained. Homeostasis is negative feedback system.
Positive feedback	Process that increases any change detected by the receptors. Tends to be harmful and does not lead to homeostasis.
Homeostasis	The MAINTENANCE of the INTERNAL ENVIRONMENT in a CONSTANT state DESPITE external CHANGES.
Endocrine gland	Ductless gland that secretes hormones directly into the blood.
Exocrine gland	Gland that secretes molecules into a duct that carries the molecules to where they are used.
Hormone	A molecule released into the blood (by an endocrine gland) that acts as a chemical messenger.
Target tissue	A tissue whose cells have receptors for a particular hormone. This is the tissue where the hormone has its effects.
Excretion	The removal of metabolic waste from the body
Autotroph	Organism that uses light energy or chemical energy, and inorganic molecules to synthesise complex organic molecules (food).
Photosynthetic pigment	Substance that absorbs light energy. Found in thylakoid membranes, in photosystems. Each pigment absorbs energy associated with light of a specific wavelength. Examples include chlorophyll a and chlorophyll b.
Respiratory substrate	An organic substrate that can be used for respiration.
Heterotroph	Organism that ingests and digests complex organic molecules, releasing the chemical potential energy stored in them.

Resource summary

	Created by lucy.wright73 about 10 years ago