autotroph
an organism capable of producing its own food
An autotroph is an organism that can produce its own food.
chlorophyll
the green pigment that captures the light energy that drives the reactions of photosynthesis
Embedded in the thylakoid membrane are molecules of chlorophyll, a pigment (a molecule that absorbs light) through which the entire process of photosynthesis begins.
chloroplast
the organelle where photosynthesis takes place
In all autotrophic eukaryotes, photosynthesis takes place inside an organelle called a chloroplast.
granum
a stack of thylakoids located inside a chloroplast
As shown in Figure 5.7, a stack of thylakoids is called a granum, and the space surrounding the granum is called stroma (not to be confused with stomata, the openings on the leaves).
heterotroph
an organism that consumes other organisms for food
Heterotrophs are organisms incapable of photosynthesis that must therefore obtain energy and carbon from food by consuming other organisms.
light-dependent reaction
the first stage of photosynthesis where visible light is absorbed to form two energy-carrying molecules (ATP and NADPH)
The overall purpose of the light-dependent reactions is to convert light energy into chemical energy.
mesophyll
the middle layer of cells in a leaf
The process of photosynthesis occurs not on the surface layers of the leaf, but rather in a middle layer called the mesophyll (Figure 5.7).
photoautotroph
an organism capable of synthesizing its own food molecules (storing energy), using the energy of light
Plants are also photoautotrophs, a type of autotroph that uses sunlight and carbon from carbon dioxide to synthesize chemical energy in the form of carbohydrates.
pigment
a molecule that is capable of absorbing light energy
Embedded in the thylakoid membrane are molecules of chlorophyll, a pigment (a molecule that absorbs light) through which the entire process of photosynthesis begins.
stoma
the opening that regulates gas exchange and water regulation between leaves and the environment; plural: stomata
The gas exchange of carbon dioxide and oxygen occurs through small, regulated openings called stomata.
stroma
the fluid-filled space surrounding the grana inside a chloroplast where the Calvin cycle reactions of photosynthesis take place
As shown in Figure 5.7, a stack of thylakoids is called a granum, and the space surrounding the granum is called stroma (not to be confused with stomata, the openings on the leaves).
thylakoid
a disc-shaped membranous structure inside a chloroplast where the light-dependent reactions of photosynthesis take place using chlorophyll embedded in the membranes
Within the chloroplast is a third membrane that forms stacked, disc-shaped structures called thylakoids.
absorption spectrum
the specific pattern of absorption for a substance that absorbs electromagnetic radiation
Each type of pigment can be identified by the specific pattern of wavelengths it absorbs from visible light, which is its absorption spectrum.
chlorophyll a
the form of chlorophyll that absorbs violet-blue and red light
All photosynthetic organisms contain a pigment called chlorophyll a, which humans see as the common green color associated with plants.
chlorophyll b
the form of chlorophyll that absorbs blue and red-orange light
Other pigment types include chlorophyll b (which absorbs blue and red-orange light) and the carotenoids.
electromagnetic spectrum
the range of all possible frequencies of radiation
The electromagnetic spectrum is the range of all possible wavelengths of radiation (Figure 5.10).
photon
a distinct quantity or “packet” of light energy
A pigment molecule in the photosystem absorbs one photon, a quantity or “packet” of light energy, at a time.
photosystem
a group of proteins, chlorophyll, and other pigments that are used in the light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy
The light-dependent reactions begin in a grouping of pigment molecules and proteins called a photosystem.
wavelength
the distance between consecutive points of a wave
The electromagnetic spectrum is the range of all possible wavelengths of radiation (Figure 5.10).
Calvin cycle
the reactions of photosynthesis that use the energy stored by the light-dependent reactions to form glucose and other carbohydrate molecules
This chemical energy will be used by the Calvin cycle to fuel the assembly of sugar molecules.
carbon fixation
the process of converting inorganic CO2 gas into organic compounds
This process is called carbon fixation, because CO2 is “fixed” from its inorganic form into organic molecules.
These terms were extracted from Concepts of Biology – 1st Canadian Edition by Charles Molnar and Jane Gair, eCampusOntario (originally published by BCcampus) which is licensed under a Creative Commons Attribution 4.0 International License. Chapter content adapted from Concepts of Biology by OpenStax (© Rice University), licensed under CC BY 4.0.