Download NAME: IDU DOREEN MATRIC NUMBER: 14/SCI03/011 COURSE

NAME: IDU DOREEN
MATRIC NUMBER: 14/SCI03/011
COURSE CODE: BCH 413
DATE: 11/12/16
ASSIGNMENT: Explain the following terms: Autotrophs, Saprotrophs and Heterotrophs
AUTOTROPHS: An autotroph is an organism that produces complex organic compounds
(such as carbohydrates, fats, and proteins) from simple substances present in its surroundings,
generally using energy from light (photosynthesis) or inorganic chemical reactions
(chemosynthesis). They are the producers in a food chain, such as plants on land or algae in
water (in contrast to heterotrophs as consumers of autotrophs). They do not need a living
source of energy or organic carbon. Autotrophs can reduce carbon dioxide to make organic
compounds for biosynthesis and also create a store of chemical energy. Most autotrophs use
water as the reducing agent, but some can use other hydrogen compounds such as hydrogen
sulphide. Some autotrophs, like green plants and algae, are phototrophs, meaning that they
convert electromagnetic energy from sunlight into chemical energy in the form of reduced
carbon.
Autotrophs can be photoautotrophs or chemoautotrophs. Phototrophs use light as an energy
source, while chemotrophs utilize electron donors as a source of energy, whether from
organic or inorganic sources; however in the case of autotrophs, these electron donors come
from inorganic chemical sources. Such chemotrophs are lithotrophs. Lithotrophs use
inorganic compounds, such as hydrogen sulfide, elemental sulfur, ammonium and ferrous
iron, as reducing agents for biosynthesis and chemical energy storage. Photoautotrophs and
lithoautotrophs use a portion of the ATP produced during photosynthesis or the oxidation of
inorganic compounds to reduce NADP+ to NADPH to form organic compounds.
HETEROTROPHS: A heterotroph is an organism that cannot fix carbon from inorganic
sources (such as carbon dioxide) but uses organic carbon for growth. Heterotrophs can be
further divided based on how they obtain energy; if the heterotroph uses light for energy, then
it is considered a photoheterotroph, while if the heterotroph uses chemical energy, it is
considered a chemoheterotroph.
Heterotrophs contrast with autotrophs, such as plants and algae, which can use energy from
sunlight (photoautotrophs) or inorganic compounds (lithoautotrophs) to produce organic
compounds such as carbohydrates, fats, and proteins from inorganic carbon dioxide. These
reduced carbon compounds can be used as an energy source by the autotroph and provide the
energy in food consumed by heterotrophs. Ninety-five percent or more of all types of living
organisms are heterotrophic, including all animals and fungi and most bacteria and protists.
SAPROTROPHS: Organisms that feeds on the excrement or the dead bodies or tissues of
others. They include most fungi (the rest being parasites); many bacteria and protozoa;
animals such as dung beetles and vultures; and a few unusual plants, including several
orchids. Saprotrophs cannot make food for themselves, so they are a type of heterotroph.
They are useful scavengers, and in sewage farms and refuse dumps break down organic
matter into nutrients easily assimilable by green plants.