PDA

View Full Version : Metabolic Pathways



Pushtoday
08-28-2015, 09:15 AM
An anabolic pathway requires energy and builds molecules while a catabolic pathway produces energy and breaks down molecules.



LEARNING OBJECTIVE



Describe the two major types of metabolic pathways


KEY POINTS





A metabolic pathway is a series of chemical reactions (https://www.boundless.com/biology/definition/reaction) in a cell (https://www.boundless.com/biology/definition/cell) that build and breakdown molecules (https://www.boundless.com/biology/definition/molecule) for cellular processes.
Anabolic pathways synthesize molecules and require energy (https://www.boundless.com/biology/definition/energy).
Catabolic pathways break down molecules and produce energy.
Because almost all metabolic reactions take place non-spontaneously, proteins (https://www.boundless.com/biology/definition/protein) called enzymes (https://www.boundless.com/biology/definition/enzyme) help facilitate those chemical reactions.



TERMS



enzyme (https://www.boundless.com/definition/enzyme/)a globular protein that catalyses a biological chemical reaction
anabolism (https://www.boundless.com/definition/anabolism/)the constructive metabolism of the body, as distinguished from catabolism
catabolism (https://www.boundless.com/definition/catabolism/)destructive metabolism, usually including the release of energy and breakdown of materials






https://figures.boundless.com/18650/large/figure-06-01-03.jpeAnabolic and catabolic pathways

(https://www.boundless.com/biology/textbooks/boundless-biology-textbook/metabolism-6/energy-and-metabolism-68/metabolic-pathways-343-11480/images/fig-ch06_01_04/)


(https://www.boundless.com/biology/textbooks/boundless-biology-textbook/metabolism-6/energy-and-metabolism-68/metabolic-pathways-343-11480/images/fig-ch06_01_04/)Anabolic Pathways

Anabolic pathways require an input of energy to synthesize complex (https://www.boundless.com/biology/definition/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 (https://www.boundless.com/biology/definition/amino-acid) building blocks and the synthesis of new DNA (https://www.boundless.com/biology/definition/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 (https://www.boundless.com/biology/definition/atp) and other high-energy molecules like NADH (https://www.boundless.com/biology/definition/nadh) (nicotinamide adenine dinucleotide) and NADPH .
https://figures.boundless.com/18650/large/figure-06-01-03.jpeAnabolic and catabolic pathways




(https://www.boundless.com/biology/textbooks/boundless-biology-textbook/metabolism-6/energy-and-metabolism-68/metabolic-pathways-343-11480/images/fig-ch06_01_04/)
Anabolic Pathways

Anabolic pathways require an input of energy to synthesize complex molecules from simpler ones. For example, synthesizing proteins from amino acid building blocks is an anabolic pathway. Replicating new DNA is also an anabolic process. These processes are critical to the life of the cell, take place constantly, and demand energy provided by ATP and other high-energy molecules.
Catabolic Pathways

Catabolic pathways involve the degradation of complex molecules into simpler ones, releasing the chemical energy (https://www.boundless.com/biology/definition/chemical-energy) stored in the bonds of those molecules. Some catabolic pathways can capture that energy to produce ATP, the molecule used to power all cellular processes. Other energy-storing molecules, such as lipids (https://www.boundless.com/biology/definition/lipid), are also broken down through similar catabolic reactions to release energy and make ATP.
Importance of Enzymes

Chemical reactions in metabolic pathways rarely 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.



[/COLOR]