Download A facultative phototroph can rely on photosynthesis and

A facultative phototroph can rely on photosynthesis and alternative
energy sources to survive and grow.
LEARNING OBJECTIVE [ edit ]
Recognize the traits associated with the classification of facultative phototrophy
KEY POINTS [ edit ]
Phototrophs can obtain cellular energy from light as well as using light to fix carbon to make
complex macromolecules on which to survive.
Chlamydomonas reinhardtii is an organism that can rely on photosynthetic and chemical energy
sources, depending on conditions.
Facultative means optional, in terms of biology it refers to an organism that can switch energy
sources for survival.
TERMS [ edit ]
autotroph
Any organism that can synthesize its food from inorganic substances, using heat or light as a
source of energy.
pyrenoid
any of several transparent structures found in the chloroplast of certain algae etc.; they are
responsible for the fixation of carbon dioxide and the formation of starch
Give us feedback on this content: FULL TEXT [edit ]
An autotrophor "producer", is an organism that produces complexorganiccompounds (such
as carbohydrates, fats, and proteins) from simple substances present in its surroundings,
generally using energy from light (photosynthesis)
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or inorganic chemical reactions(chemosynthesis). They are the producers in a food chain,
such as plants on land or algae in water. They are able to make their own food, and do not
need a living energy or carbon source. Autotrophs can reduce carbon dioxide to make organic
compounds, creating a store of chemical energy. Phototrophs, a type of autotroph, convert
physical energy from sunlight (in case of green plants) into chemical energy in the form of
reduced carbon.
In terms of biology facultative means "optional" or "discretionary" the antonym of which
is obligate meaning "by necessity". Thus facultative phototrophy means an organism that can
switch between phototrophy to make organix compounds and other means of getting cellular
energy. Probably the best studied example of a facultative phototrophy is Chlamydomonas
reinhardtii.
Chlamydomonas reinhardtii is a single celled green alga about 10 micrometres in diameter
that swims with two flagella . It has a cell wall made of hydroxyproline-rich glycoproteins, a
large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light. Although
widely distributed worldwide in soil and fresh water, C. reinhardtii is primarily used as a
model organism in biology in a wide range of subfields. When illuminated, C. reinhardtii can
grow in media lacking organic carbon and chemical energy sources, and can also grow in the
dark when supplied with these. C. reinhardtii is also of interest in the biofuel field, as a source
of hydrogen. As one can imagine switching energy sources under varying conditions allows
facultative microbes to live in different conditions, in the case of a facultative phototroph it
can rely of light other energy sources.
Chlamydomanas reinhardtii
Scanning electron microscope image, showing an example of green algae (Chlorophyta).