Download An anabolic pathway requires energy and builds

An anabolic pathway requires energy and builds molecules while a
catabolic pathway produces energy and degrades molecules.
LEARNING OBJECTIVE [ edit ]
Describe the two major types of metabolic pathways
KEY POINTS [ edit ]
A metabolic pathway is a series of chemical reactions in a cellwith each reaction in a pathway being
catalyzed by an enzyme.
The metabolic pathway that requires energy and synthesizesmolecules is referred to as anabolic.
The metabolic pathway that produces energy and breaks down molecules is referred to as
catabolic.
Examples of anabolic pathways include the synthesis of sugar from CO2, the synthesis of
large proteins from amino acidbuilding blocks, and the synthesis of new DNA strands from
nucleic acid building blocks.
Catabolic pathways involve breaking down complexmolecules into simpler ones such as
where glucose is broken down into 36­38 molecules of ATP.
TERMS [ edit ]
enzyme
a globular protein that catalyses a biological chemical reaction
catabolism
destructive metabolism, usually including the release of energy and breakdown of materials
anabolism
the constructive metabolism of the body, as distinguished from catabolism
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Metabolic Pathways
The processes of making and breaking
down sugar molecules illustrate two types
of metabolic pathways. A metabolic
pathway is a step­by­step series of
interconnected biochemical reactions that
convert a substrate molecule or molecules
through a series of metabolic
intermediates, eventually yielding a final
product or products. In the case of sugar
metabolism, the first metabolic pathway
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synthesizes sugar from smaller molecules; the other pathway breaks sugar down into smaller
molecules. The first of these processes requires energy and is referred to as anabolic. The
second process produces energy and is referred to as catabolic. Consequently, metabolism is
composed of these two opposite pathways: building (anabolism) and degradation
(catabolism).
Anabolic and Catabolic Pathways
Anabolic pathways require an input of energy to synthesize complex molecules from simpler
ones. One example of an anabolic pathway is the synthesis of sugar from CO2. Other
examples include the synthesis of large proteins from amino acid building blocks and the
synthesis of new DNA strands from nucleic acid building blocks. These processes are critical
to the life of the cell, take place constantly, and demand energy provided by ATP and other
high­energy molecules likeNADH (nicotinamide adenine dinucleotide) and NADPH .
Anabolic and catabolic pathways
Anabolic pathways are those that require energy to synthesize larger molecules. Catabolic pathways are
those that generate energy by breaking down larger molecules. Both types of pathways are required for
maintaining the cell's energy balance.
ATP is an important molecule for cells to have in sufficient supply at all times. The
breakdown of sugars illustrates how a single molecule of glucose can store enough energy to
make a great deal of ATP, which is around 36 to 38 molecules. This is a catabolic pathway.
Catabolic pathways involve the degradation of complex molecules into simpler ones.
Molecular energy stored in the bonds of complex molecules is released in catabolic pathways
and harvested in such a way that it can be used to produce ATP. Other energy­storing
molecules, such as fats, are also broken down through similar catabolic reactions to release
energy and make ATP.
It is important to know that the chemical reactions of metabolic pathways don't take place
spontaneously. Each reaction step is facilitated, or catalyzed, by a protein called an enzyme.
Enzymes are important for catalyzing all types of biological reactions: those that require
energy as well as those that release energy.