Chapter 4 Lecture.pptx

Because learning changes everything. Chapter 04 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. ® 4.1 Metabolic Reactions Metabolism: Sum of all chemical reactions in the body Cellular Metabolism: Sum of all...

Because learning changes everything. Chapter 04 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. ® 4.1 Metabolic Reactions Metabolism: Sum of all chemical reactions in the body Cellular Metabolism: Sum of all chemical reactions occurring in a cell; metabolic reactions usually occur in pathways or cycles. There are 2 types of metabolic reactions: Anabolism: Small molecules are built into larger ones; requires energy Catabolism: Larger molecules are broken down into smaller ones; releases energy Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 2 Anabolism and Catabolism Anabolism: Provides materials for maintenance, cellular growth and repair; requires A T P made during catabolism; example: Dehydration synthesis: Smaller molecules are bound together to form larger ones H2O produced in the process Used to produce polysaccharides, proteins, triglycerides Catabolism: Breaks down larger molecules into smaller ones; A T P is produced; Example: Hydrolysis: Used to decompose carbohydrates, proteins, lipids Uses H2O to split the substances Reverse of dehydration synthesis Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 3 Enzyme Action Enzymes (protein catalysts): Globular proteins that catalyze specific reactions Increase rates of chemical reactions Lower the activation energy necessary to start reactions Not consumed in the reaction, so are used repeatedly Each enzyme is specific to a particular substrate Ability to recognize substrate depends on shape of active site of enzyme Many enzymes are named after substrate, with “-ase” as suffix; example: “lipase” breaks down lipids Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 4 Figure 4.6 Enzyme Action Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 5 Enzymes and Metabolic Pathways Metabolic Pathways: Series of enzyme-controlled reactions leading to formation of a product Each new substrate is the product of the previous reaction Each step of a pathway is catalyzed by a different enzyme In some pathways, end product inhibits rate-limiting enzyme; this is example of negative feedback Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 6 Factors That Alter Enzymes Cofactor: Non-protein substance that combines with the enzyme to activate it Some help fold active site into proper conformation Some help bind enzyme to substrate Can be ion, element, or small organic molecule (coenzyme) Coenzyme: Organic molecule that acts as cofactor Most are vitamins, which are essential organic molecules that humans must get from their diet Denaturation: Inactivation of an enzyme (or any other protein), due to an irreversible change in its conformation Results in enzyme being unable to bind to substrate Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 7 4.3 Energy for Metabolic Reactions Energy: Capacity to change something, or the ability to do work Common forms of energy: Heat, light, sound, electrical energy, mechanical energy, chemical energy Energy cannot be created or destroyed, but can be changed from one form to another Cellular respiration: Process that transfers energy from molecules, and makes it available for cellular use Most metabolic reactions use chemical energy Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 8 Release of Chemical Energy Many metabolic processes require chemical energy, which is stored in ATP Energy is held in chemical bonds, and released when bonds are broken Oxidation releases energy from glucose and other molecules, via loss of hydrogen atoms and their electrons In cells, enzymes lower activation energy needed for oxidation in reactions of cellular respiration Energy is transferred to ATP: 40% is released as chemical energy 60% is released as heat; maintains body temperature Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 9 ATP Molecules 1 ATP (Adenosine Triphosphate): Molecule that carries energy in a form the cell can use Main energy-carrying molecule in the cell; energy from ATP breakdown is used for cellular work Consists of 3 portions: Adenine Ribose (a sugar) 3 phosphates in a chain Second and third phosphates are attached by high-energy bonds; energy can be quickly transferred to other molecules Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 10 Figures 4.8 and 4.9 ATP Molecules Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 11 4.4 Cellular Respiration 1 Cellular Respiration of glucose occurs in 3 interconnected reaction sequences: Glycolysis (anaerobic) 2ATP Citric acid cycle (aerobic) 2ATP Electron transport chain/oxidative phosphorylation (aerobic) 32 – 34 ATP Glycolysis and the Electron Transport Chain are stepwise reaction sequences Citric Acid Cycle occurs in a metabolic cycle in which the final product reacts to replenish original substrate Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 12 Process of Cellular Respiration Cellular respiration of glucose requires a supply of glucose and O2. Final products of cellular respiration: Carbon dioxide Water ATP (chemical energy, 40%) Heat (60%) Includes 2 types of reactions: Anaerobic reactions: do not require O2, and make little ATP Lactic acid production Aerobic reactions: require O2, and make most of A TP Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 13 4.5 DNA (Deoxyribonucleic Acid) Deoxyribonucleic acid (DNA): The genetic material Molecule that stores information on its sequence of nucleotides, that instructs a cell to how synthesize certain proteins The proteins coded for on DNA function as: Enzymes Blood proteins Structural proteins of muscle and connective tissue Antibodies Cell membrane components Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 14 Structure of DNA Double helix: Double-stranded molecule, consisting of 2 chains of nucleotides DNA resembles ladder twisted into a spiral Backbone of each strand is a sugar-phosphate chain Bases from the 2 complementary strands are linked together by hydrogen bonds: C ̶ G, A ̶ T Nucleotides are building blocks of DNA, and consist of: 5-carbon sugar, deoxyribose A phosphate group A nitrogenous base (adenine, cytosine, guanine, or thymine) Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 15 Figures 4.18 and 4.19 The Structure of DNA Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 16 DNA and Chromosome Structure 2 nucleotide chains of the double helix are antiparallel: point in opposite directions Complementary Base Pairing: Bases pair only with specific (A ̶ T and C ̶ G) A and G are purines, and C and T are pyrimidines A purine only binds to a specific pyrimidine DNA wraps around histone proteins to give double helix a compact form in chromatin and chromosomes Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 17 Figure 4.20 DNA and Chromosome Structure Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 18 4.6 Protein Synthesis A sequence of 3 nucleotides provides template for complementary RNA Each unit of 3 RNA nucleotides represents genetic code Sequence of bases in a gene determines the amino acid sequence in a polypeptide Each sequence of 3 nucleotides either represents an amino acid or signals to start or stop protein synthesis Protein synthesis involves processes of transcription and translation Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 19 Figure 4.23 Transcription of mRNA Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 20 Translation 1 Each amino acid is specified by a sequence of 3 bases in DNA, called codons Protein synthesis occurs in cytoplasm mRNA leaves nucleus and binds to ribosome, to act as template for protein synthesis At the ribosome, the genetic code, carried by mRNA, is used to synthesize a protein Translation: Process of converting the genetic code, carried by mRNA, into a sequence of amino acids that becomes a protein Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 21 Figure of Table 4.2 Codons (mRNA Three-Base Sequence) Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 22 4.7 Changes in Genetic Information 99.9% of human genome sequences are the same among all people 0.1% of the genome that varies among people includes: DNA sequences that affect health DNA sequences that affect appearance DNA base variations that have no observable effects Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 23 Nature of Mutations 1 Mutations: Changes in the DNA sequence Mutations occur when bases are changed, added, or deleted Mutations can be: Spontaneous: due to insertion of unstable base into DNA sequence Induced: due to exposure to mutagens, chemicals, or radiation that cause mutation Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 24 Figure 4.26 The Mutation That Causes Sickle Cell Disease Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 25 Nature of Mutations 2 Some mutations are not harmful, and do not affect health. Many mutations affect health, by changing the amino acid sequence, resulting in a nonfunctional or missing protein. Example: Sickle cell disease is caused by a single nucleotide substitution; this causes production of abnormal hemoglobin, which causes change in shape of red blood cells, in low-oxygen conditions, and extreme pain Rarely, a mutation provides an advantage to health. Example: A mutation protects some people against HIV; the receptor to which the virus binds is incomplete Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 26