CHAPTER 6 AN INTRODUCTION TO METABOLISM Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section B: Enzymes 1.Enzymes speed up.

Slides:



Advertisements
Similar presentations
Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that speeds up a reaction without being consumed.
Advertisements

Enzymes and Substrates Presenter: Mrs. Knopke FUHS Science Dept.
Introduction to Metabolism Chapter 6. Metabolism - sum of organism’s chemical processes. Enzymes start processes. Catabolic pathways release energy (breaks.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 8.
CHAPTER 8 AN INTRODUCTION TO METABOLISM The totality of an organism’s chemical reactions is called _______________. A cell’s ______________ is an elaborate.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 5 The Working Cell.
ENZYMES.
A cell does three main kinds of work: Chemical Transport Mechanical
Enzymes Chapter 8 (sections 4 & 5) Biology – Campbell Reece.
Enzymes!!!.
CHAPTER 6 AN INTRODUCTION TO METABOLISM
Enzymes An introduction to metabolism. The purpose of an enzyme in a cell is to allow the cell to carry out chemical reactions very quickly. These reactions.
CHAPTER 6 AN INTRODUCTION TO METABOLISM Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section B: Enzymes 1.Enzymes speed up.
ENZYMES - Spesificity Aulanni’am Biochemistry Laboratory Brawijaya University.
A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction. An enzyme is a protein. 1. Enzymes speed up.
Enzymes AP Biology Mrs. Kiefer Chapter 6. Spontaneous chemical rxns will occur on their own, but that could take a very long time. A catalyst is a chemical.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 8 An Introduction to Metabolism.
Forms of Energy Energy is the capacity to cause change Energy exists in various forms, some of which can perform work Kinetic energy is energy associated.
Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that speeds up a reaction without being consumed.
Enzymes. A. Are Proteins (usually) that speed up metabolic reactions by lowering the activation energy. A. Some chemical reactions will occur spontaneously,
Metabolism and Enzymes. Metabolism- the total of all chemical reactions done in an organism to store or release energy. (the number of molecules built.
Enzymes Concepts
Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that changes the rate of a reaction without being consumed.
ENZYMES. Enzymes are Catalysts  Catalytic proteins: change the rate of reactions w/o being consumed  Enzymes speed up reactions by lowering the activation.
AN INTRODUCTION TO METABOLISM
1 CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES Pages CHAPTER 6 AN INTRODUCTION TO METABOLISM Section B: Enzymes 1.Enzymes speed up metabolic.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings For a chemical reaction to begin, reactants must absorb some energy –This energy.
Enzymes and Feedback Inhibition
Enzymes Enzymes speed up the cell’s chemical reactions The cell uses catalysis to drive (speed up) biological reactions –Catalysis is accomplished by enzymes,
Enzymes Essential knowledge 4.B.1: Interactions between molecules affect their structure and function.
 Spontaneous chemical reactions occur without a need for outside energy but may be very slow  Free energy: Δ G  Catalyst : a chemical agent that speeds.
Enzymes An introduction to metabolism. The purpose of an enzyme in a cell is to allow the cell to carry out chemical reactions very quickly. These reactions.
AN INTRODUCTION TO METABOLISM CHAPTER 8 I. Metabolism, Energy, and Life.
ENZYMES AND HOMEOSTASIS Enzymes. LEARNING GOALS I CAN … …explain how enzymes speed up the rate of a chemical reaction …discuss the properties of enzymes.
1 CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES Pages CHAPTER 6 AN INTRODUCTION TO METABOLISM Section B: Enzymes 1.Enzymes speed up metabolic.
1. 2 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers.
Enzymes!. Enzymes speed up the rate of metabolic reactions by lowering energy barriers A catalyst is a chemical agent that speeds up a reaction without.
Proteins Importance: instrumental in nearly everything organisms do; 50% dry weight of cells; most structurally sophisticated molecules known Monomer:
Chapter 8 Part B METABOLISM.
Enzymes 8.4.
Metabolism Lecture 5, part 2 Fall 2008
AN INTRODUCTION TO METABOLISM
Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that speeds up a reaction without being consumed.
8 An Introduction to Metabolism.
Enzymes.
CHAPTER 6 AN INTRODUCTION TO METABOLISM
Enzymes Enzymes speed up metabolic reactions by lowering energy barriers A catalyst Is a chemical agent that speeds up a reaction without being consumed.
AN INTRODUCTION TO METABOLISM
The Regeneration of ATP
Chapter 5 The Working Cell.
CHAPTER 6 AN INTRODUCTION TO METABOLISM
Enzymes.
Enzymes and Chemical Reactions
ENZYMES.
AN INTRODUCTION TO METABOLISM
Enzymes.
Enzymes.
AN INTRODUCTION TO METABOLISM
CHAPTER 5 The Working Cell
Enzymes and Feedback Inhibition
CONCEPT 3: ANALYZING CELL METABOLISM AND ENZYME FUNCTION (CH 8, AP LAB 2) Holtzclaw: “Metabolism” pg Campbell: Read pg , Look.
AN INTRODUCTION TO METABOLISM
Chapter 6: Metabolism Energy and enzymes.
General Animal Biology
CHAPTER 6 AN INTRODUCTION TO METABOLISM
AN INTRODUCTION TO METABOLISM
AN INTRODUCTION TO METABOLISM
General Animal Biology
General Animal Biology
Presentation transcript:

CHAPTER 6 AN INTRODUCTION TO METABOLISM Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section B: Enzymes 1.Enzymes speed up metabolic reactions by lowering energy barriers 2.Enzymes are substrate specific 3. The active site in an enzyme’s catalytic center 4. A cell’s physical and chemical environment affects enzyme activity

A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction. An enzyme is a catalytic protein. Enzymes regulate the movement of molecules through metabolic pathways. 1. Enzymes speed up metabolic reactions by lowering energy barriers Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Even in an exergonic reaction, the reactants must absorb energy from their surroundings, the free energy of activation or activation energy (E A ), to break the bonds. This energy makes the reactants unstable, increases the speed of the reactant molecules, and creates more powerful collisions. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Activation energy is the amount of energy necessary to push the reactants over an energy barrier. At the summit the molecules are at an unstable point, the transition state. The difference between free energy of the products and the free energy of the reactants is the delta G. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.12

Enzyme speed reactions by lowering E A. The transition state can then be reached even at moderate temperatures. Enzymes do not change delta G. Because enzymes are so selective, they determine which chemical processes will occur at any time. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.13

A substrate is a reactant that binds to an enzyme. When a substrate, or substrates, binds to an enzyme, the enzyme catalyzes the conversion of the substrate to the product. Sucrase is an enzyme that binds to sucrose and breaks the disaccharide into fructose and glucose. 2. Enzymes are substrate specific Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The active site of an enzyme is typically a pocket or groove on the surface of the protein into which the substrate fits. The specificity of an enzyme is due to the fit between the active site and that of the substrate. As the substrate binds, the enzyme changes shape leading to a tighter induced fit, bringing chemical groups in position to catalyze the reaction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.14

In most cases substrates are held in the active site by weak interactions, such as hydrogen bonds and ionic bonds. 3. The active site is an enzyme’s catalytic center Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 6.15

A single enzyme molecule can catalyze thousands or more reactions a second. Enzymes are unaffected by the reaction and are reusable. Most metabolic enzymes can catalyze a reaction in both the forward and reverse direction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The three-dimensional structures of enzymes (almost all proteins) depend on environmental conditions. Changes in shape influence the reaction rate. Some conditions lead to the most active conformation and lead to optimal rate of reaction. 4. A cell’s physical and chemical environment affects enzyme activity Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Temperature has a major impact on reaction rate. As temperature increases, collisions between substrates and active sites occur more frequently as molecules move faster. However, at some point thermal agitation begins to disrupt the weak bonds that stabilize the protein’s active conformation and the protein denatures. Each enzyme has an optimal temperature. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.16a

Because pH also influences shape and therefore reaction rate, each enzyme has an optimal pH too. This falls between pH for most enzymes. However, digestive enzymes in the stomach are designed to work best at pH 2 while those in the intestine are optimal at pH 8, both matching their working environments. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.16b

Many enzymes require nonprotein helpers, cofactors, for catalytic activity. They bind permanently or reversibly to the enzyme. Some inorganic cofactors include zinc, iron, and copper. Organic cofactors, coenzymes, include vitamins or molecules derived from vitamins. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Binding by some molecules, inhibitors, prevent enzymes from catalyzing reactions. If binding involves covalent bonds, then inhibition is often irreversible. If binding is weak, inhibition may be reversible. If the inhibitor binds to the same site as the substrate, then it blocks substrate binding via competitive inhibition. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.17a, b

If the inhibitor binds somewhere other than the active site, it blocks substrate binding via noncompetitive inhibition. Binding by the inhibitor causes the enzyme to change shape, rendering the active site unreceptive (at worst) or less effective at catalyzing the reaction. Reversible inhibition of enzymes is a natural part of the regulation of metabolism. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 6.17c