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Introduction to Metabolism - Coggle Diagram
Introduction to Metabolism
Organic Metabolism
Metabolic Pathways
A specific molecule is altered in a series of steps to produce a product. Every step is catalyzed by a specific enzyme, a macromolecule that speeds up a specific reaction
Catabolic pathway
s: it releases energy by breaking down molecules into more simple compounds
Anabolic Pathways
: consumes energy to build molecules from simpler ones. EX: synthesis of proteins from amino acids an anabolic pathways
Bioenergetics
: study of how energy flows through living organisms
Form of Energy
The capacity to cause change, can be used to do work. Move matter up against opposing forces such as gravity and friction
Kinetic Energy
: associated with motion
Thermal Energy
: is kinetic energy associated with random movement of atoms or molecules. It's transfer from one object to another is called
heat
Potential Energy
: energy that matter possesses because of its location or structure. EX: water behind a dam possesses energy bc of its altitude above sea level
Chemical Energy
: potential energy available for release in a chemical reaction
Energy Transformation
Thermodynamics: the study of energy transformation is a collection of matter
isolated system, like the liquid in a thermos bottle is unable to exchange energy or matter with its surrounding
First and Second Law of Thermodynamics
First Law: the energy of the universe of constant
Seconded Law: every energy transfer or transformation increases to entropy of the universe
Order and Disorder
cells create ordered structures from less organized starting materials. EX: simple molecules are ordered into amino acids, which are assembled into ordered polypeptides
Increase in order within living systems is balanced by the catabolic breakdown or organized forms of matter, and releasing heat and small molecules
Free-Energy
Metabolism
The concept of free energy can be applied to the chemistry of life's processes
Exergonic and Endergonic Reactions
Endergonic reaction
: absorbs free energy from the surrounding
Exergonic reaction
: proceeds with a net release or free energy to the surrounding
Equilibrium and Metabolism
the reactions in a closed system, such as an isolated hydroelectric system, eventually reach equilibrium and can then do no work
chemical reaction of metabolism are reversible but never reach equilibrium in a living cell
the flow of materials prevents metabolic equilibrium
Coupling Exergonic and Endergonic Reaction
Structure and Hydrolysis of ATP
ATP: is composed of ribose (sugar), adenine (nitrogenous base), and three phosphate group. They also function as one of the nucleoside triphosphates used to make RNA
ATP Provides Energy to Work
cellular work is powered by ATP hydrolysis. Inside the cell energy from the exergonic hydrolysis of ATP is used to drive endergonic reactions.
Phosphorylated Intermediate: is more reactive that the original molecule. Phosphorylation transfer of a phosphate group from ATP to another molecule is typically used to power endergonic reaction
Transport and mechanical work in the cell are also nearly always powered by ATP hydrolysis. ATP hydrolysis causes a change in protein shape and binding ability
Regeneration of ATP
ATP is regenerated by addition of a phosphate group to adenosine diphosphate (ADP).
Free energy needed to phosphorylate ADP comes from exergonic breakdown reaction (catabolism)
A cell does three main kinds of work.
Chemical work:
pushing endergonic reaction
Transport Work
: pumping substance across membrane against the direction of spontaneous movement
Mechanical Work
: such as beating cilia or contracting muscle cells
Energy coupling
, the use of an exergonic process to drive an endergonic
Metabolic Reactions by Lowering Energy Barriers
Activation Energy Barrier
every chemical reaction between molecules involves bond breaking and bond forming. Molecules must be contorted into a highly unstable state before bond can break to start the reaction
Activation Energy
: initial energy needed to break the bonds of the reactants
Catalyst
: a chemical agent that speeds up a reaction without being consumed by the reaction
Enzyme
: a macromolecule that acts as a catalyst to speed up a specific reaction EX: adding the enzyme sucrase to a sucrose solution at room temperature will catalyze the complete hydrolysis of sucrose within seconds
Enzyme Speed up Reactions
Heat is also impractical because it would speed up all reaction, not just those that are needed. adding heat is not a useful way to speed reactions in cells because it can cause proteins to denature
Catalysis
: the process by which a catalyst selectively speeds up a reaction without itself being consumed
Substrate Specificity of Enzyme
Substrate
: the reactant that an enzyme acts
the enzyme binds to its substrate, forming an
enzyme-substrate complex
. While bound, the catalytic activity of the enzyme convert substrate to product
Catalysis in Enzyme Active Site
substrate is typically held in the enzyme's active site by weak bonds, such as hydrogen bonds. The conversion of substance to product happens rapidly, and product is released from the active site
Effects of Local Conditions and Temperature
Local Conditions
: Enzyme activity can be affected by general environmental factors, such as temperature and pH. It can also be affected by chemicals that specifically influence the enzyme
Temperature and pH
: Each enzyme has an optimal temperature at which it catalyzes its reaction at the maximum possible rate. This point, the reaction rate increases with increasing temperature; beyond this point the rate of reaction begins to drop
spontaneous reaction do not need added energy, but they can be slow enough to be imperceptible.
EX
: hydrolysis of sucrose to glucose and fructose is spontaneous
Cofactors
they are nonprotein helpers that bind to the enzyme permanently, or reversibly with the substrate. inorganic cofactors include metal atoms such as zinc, iron, and copper in ionic form
Coenzymes
: organic cofactors
Regulation of Enzyme Activity
Allosteric Regulation
this occurs when a regulatory molecule binds to a protein at one site and affects the protein's function at another site. This type of regulation may either inhibit or stimulate enzyme activity
Allosteric Activation and Inhibition
MOST allosterically regulated enzyme are made from polypeptide subunits, each with its own active site. complex oscillates between two shapes, one catalytically active and the other inactive
the binding of an activator stabilizes the shape that has functional active sites, whereas the binding of an inhibitor stabilizes the inactive from of the enzyme
Feedback Inhibition
the end product of a metabolic pathway shuts down the pathway. It prevents a cell from wasting chemical resources by synthesizing product than is needed
Localization of Enzyme in Cell
compartmentalization of the cell helps to bring order to metabolic pathways. Enzyme for several steps in a metabolic pathway form a multienzyme complex. Some enzyme have fixed location and acts as structural components of particular membranes
Eukaryotic cells, come enzyme reside within specific organelles. EX: enzyme for the second and third stage of cellular respiration are located within mitochondria