AP Chapter 8

Chapter 8

An Introduction to Metabolism

Overview: The Energy of Life

•          The living cell is a miniature chemical factory where thousands of reactions occur

•          The cell extracts energy and applies energy to perform work

•          Some organisms even convert energy to light, as in bioluminescence

Concept 8.3: ATP powers cellular work by coupling _______________________ reactions to _______________________reactions

•          A cell does three main kinds of work:

•          ________________________________

•          ________________________________

•          ________________________________

•          To do work, cells manage energy resources by __________________________________, the use of an exergonic process to drive an endergonic one

•          Most energy coupling in cells is mediated by ATP

The Structure and Hydrolysis of ATP

•          ATP (__________________________________________) is the cell’s energy shuttle

•          ATP is composed of _________________ (a sugar), _______________________ (a nitrogenous base), and _______________ phosphate groups

•          The bonds between the phosphate groups of ATP’s tail can be broken by ___________________

•          Energy is released from ATP when the _________________________ phosphate bond is broken

•          This release of energy comes from the chemical change to a state of lower _____________________________________, not from the phosphate bonds themselves

How ATP Performs Work

•          The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP

•          In the cell, the energy from the ________________________ reaction of ATP hydrolysis can be used to drive an  ___________________________ reaction

•          Overall, the coupled reactions are ___________________________

•          ATP drives endergonic reactions by __________________________________, transferring a phosphate group to some other molecule, such as a reactant

•          The recipient molecule is now ___________________________________________

The Regeneration of ATP

•          ATP is a renewable resource that is regenerated by addition of a phosphate group to __________________________________________ (ADP)

•          The energy to phosphorylate ADP comes from ______________________________________ in the cell

•          The chemical potential energy temporarily stored in ATP drives most _______________________________________

Concept 8.4: Enzymes speed up metabolic reactions by ________________________ energy barriers

•          A _____________________________ is a chemical agent that speeds up a reaction without being consumed by the reaction

•          An _________________________________ is a catalytic protein

•          Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction

The Activation Energy Barrier

•          Every chemical reaction between molecules involves bond _______________________ and bond ____________________________

•          The initial energy needed to start a chemical reaction is called the free energy of activation, or ____________________________________ (____________)

•          Activation energy is often supplied in the form of _____________________ from the surroundings

How Enzymes Lower the E_A Barrier

•          Enzymes catalyze reactions by _____________________________________________________

•          Enzymes do not affect the change in free energy (?G); instead, they ______________________ reactions that would occur eventually

Substrate Specificity of Enzymes

•          The reactant that an enzyme acts on is called the enzyme’s ______________________________

•          The enzyme binds to its substrate, forming an _________________________________________

•          The ______________________________ is the region on the enzyme where the substrate binds

•          __________________________________ of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction

Catalysis in the Enzyme’s Active Site

•          In an enzymatic reaction, the _______________________________ binds to the active site of the __________________________________

•          The active site can lower an E_A barrier by

•          ________________________________________________________________________

•          ________________________________________________________________________

•          ________________________________________________________________________

•          ________________________________________________________________________

Effects of Temperature and pH

•          Each enzyme has an optimal ___________________________________ in which it can function

•          Each enzyme has an optimal __________________ in which it can function

Cofactors

•          ______________________________ are nonprotein enzyme helpers

•          Cofactors may be inorganic (such as a metal in ionic form) or organic

•          An organic cofactor is called a _________________________________

•          Coenzymes include _____________________________

Enzyme Inhibitors

•          _________________________________________________ bind to the active site of an enzyme, competing with the substrate

•          _________________________________________________ bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

•          Examples of inhibitors include _____________, ________________, __________________, and _____________________________

Concept 8.5: Regulation of enzyme activity helps control __________________________________

•          Chemical chaos would result if a cell’s metabolic pathways were not tightly _____________________________

•          A cell does this by switching on or off the __________________ that encode specific enzymes or by regulating the ___________________________ of enzymes

Allosteric Regulation of Enzymes

•          _____________________________________ may either inhibit or stimulate an enzyme’s activity

•          Allosteric regulation occurs when a regulatory molecule binds to a ___________________ at one site and affects the protein’s ____________________________ at another site

Allosteric Activation and Inhibition

•          Most allosterically regulated enzymes are made from ___________________________ subunits

•          Each enzyme has active and _______________________ forms

•          The binding of an _______________________________ stabilizes the active form of the enzyme

•          The binding of an _______________________________ stabilizes the inactive form of the enzyme

•          ____________________________________ is a form of allosteric regulation that can amplify enzyme activity

•          In cooperativity, binding by a substrate to one active site stabilizes favorable _____________________________ changes at all other subunits

Identification of Allosteric Regulators

•          Allosteric regulators are attractive _____________________ candidates for enzyme regulation

•          Inhibition of proteolytic enzymes called ___________________________ may help management of inappropriate inflammatory responses

Feedback Inhibition

•          In ________________________________________________, the end product of a metabolic pathway shuts down the pathway

•          Feedback inhibition __________________________ a cell from wasting chemical resources by synthesizing more product than is needed

Specific Localization of Enzymes Within the Cell

•          Structures within the cell help bring ___________________ to metabolic pathways

•          Some enzymes act as structural components of _______________________________

•          In eukaryotic cells, some enzymes reside in specific __________________________; for example, enzymes for cellular respiration are located in ______________________________