Chapter 2: Leninger's Principles Of Biochemistry PDF

Copyright © 2010 Pearson Education, Inc.  Chapter 2 ▪ Are We Alone in the Universe? ▪ What is life? ▪ The Chemistry of Life ▪ Water and Biochemistry Copyright © 2010 Pear...

Copyright © 2010 Pearson Education, Inc.  Chapter 2 ▪ Are We Alone in the Universe? ▪ What is life? ▪ The Chemistry of Life ▪ Water and Biochemistry Copyright © 2010 Pearson Education, Inc.  Are We Alone in the Universe? ▪ Martian rock found on Earth ▪ Is there evidence of life? ▪ What is life? Copyright © 2010 Pearson Education, Inc.  Chapter 2 Section 2.1 What Does Life Require? Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? A Definition of Life ▪ There is no simple definition of life. ▪ But, all Earth organisms… ▪ require liquid water ▪ have a common set of biological molecules ▪ can maintain homeostasis ▪ can evolve Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Additional Characteristics of Life ▪ Cellular organization ▪ Growth and metabolism ▪ Reproduction ▪ Heredity Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Physical Properties of Chemicals ▪ Elements: fundamental forms of matter ▪ EXP: carbon, hydrogen, oxygen, etc ▪ Atoms: the smallest units of an element Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Atoms are composed of protons, neutrons, and electrons ▪ Protons (positive charge) + neutrons form atomic nucleus ▪ Electrons (negative charge) are outside the nucleus. Copyright © 2010 Pearson Education, Inc. Figure 2.3  Chapter 2 Section 2.1 Part 1 The Chemistry of Water Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Molecule: two or more atoms held together by chemical bonds Example: Water ▪ Water molecule: two hydrogen atoms bonded to one oxygen atom Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? The Properties of Water ▪ Water is a polar molecule: ▪ Oxygen side is slightly negative ▪ Hydrogen side is slightly positive ▪ Electronegativity = how strongly the atoms pull electrons ▪ When molecules have no charges, they are nonpolar Copyright © 2010 Pearson Education, Inc. Figure 2.4  2.1 What Does Life Require? The Properties of Water ▪ Hydrogen bond: the weak attraction between the hydrogen atom of one water molecule and the oxygen atom of another ▪ Water molecules tend to stick together: cohesion Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? The Properties of Water ▪ Due to its polarity, water is a good solvent ▪ Solute: what is being dissolved ▪ Solution: the solute in the solvent Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? The Properties of Water ▪ Water can dissolve salts and hydrophilic (water–loving) molecules because it is polar. Copyright © 2010 Pearson Education, Inc. Figure 2.6  2.1 What Does Life Require? The Properties of Water ▪ Water can dissolve acids and bases. ▪ Acid = a substance that donates H+ ions to solution ▪ Base = a substance that accepts H+ ions Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? ▪ The pH scale is a measure of the relative amounts of acids and bases in a solution. ▪ pH greater than 7 = basic ▪ Pure water pH = 7 = neutral ▪ pH lower than 7 = acidic Copyright © 2010 Pearson Education, Inc.  React on the following: Can alkaline diet stop you from acquiring diseases? Copyright © 2010 Pearson Education, Inc.  Chapter 2 Section 2.1 Part 2 Organic Chemistry = The Chemistry of Carbon Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Organic Chemistry ▪ All life on Earth is based on organic chemistry: the chemistry of the element carbon. ▪ Carbon makes up most of the mass of living organisms. ▪ Why? Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Carbon as a building block ▪ Carbon forms Covalent bonds: strong bonds from sharing electrons ▪ Carbon is like a molecular TinkerToy ▪ Can bond to 4 different atoms at once ▪ Carbon can make macromolecules Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Nonpolar & Hydrophobic Molecules ▪ Nonpolar molecules, such as oil, do not contain charged atoms. ▪ These atoms are called hydrophobic (water–hating). Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Structure and Function of Macromolecules Types of Macromolecules 1. Carbohydrates 2. Proteins 3. Lipids 4. Nucleic Acis Copyright © 2010 Pearson Education, Inc. Figure 2.12  2.1 What Does Life Require? Structure and Function of Macromolecules ▪ Carbohydrates: molecules of carbon, oxygen, and hydrogen ▪ Major source of energy for cells Copyright © 2010 Pearson Education, Inc. Figure 2.12  2.1 What Does Life Require? Structure and Function of Macromolecules Proteins: polymers of amino acids; joined by peptide bonds Copyright © 2010 Pearson Education, Inc. Figure 2.13  2.1 What Does Life Require? Structure and Function of Macromolecules Proteins ▪ There are 20 different common amino acids, with different chemical properties. ▪ Amino Acids are made up of carbon, oxygen, hydrogen, and nitrogen. ▪ Different combinations of amino acids give proteins different properties. Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Structure and Function of Macromolecules ▪ Lipids: hydrophobic; composed mostly of carbon and hydrogen ▪ Three important types: Copyright © 2010 Pearson Education, Inc. Figure 2.14  2.1 What Does Life Require? Structure and Function of Macromolecules ▪ Nucleic acids = polymers of nucleotides ▪ Nucleotide = a phosphate + sugar + a nitrogenous base Copyright © 2010 Pearson Education, Inc. Figure 2.15c  2.1 What Does Life Require? Structure and Function of Macromolecules ▪ Nucleotides are of two types, depending on the sugar ▪ RNA = ribonucleic acid ▪ DNA = deoxyribonucleic acid ▪ DNA is the hereditary material in nearly all organisms. Copyright © 2010 Pearson Education, Inc.  2.1 What Does Life Require? Structure and Function of Macromolecules ▪ The structure of a DNA molecule is a double helix made up of nucleotides. Copyright © 2010 Pearson Education, Inc. Figure 2.15a  2.1 What Does Life Require? Structure and Function of Macromolecules ▪ Bonding between bases on opposite strands follows strict base-pairing rules: ▪ A with T ▪ G with C Copyright © 2010 Pearson Education, Inc. Figure 2.15b  Chapter 2 Section 2.2 Life on Earth Part 1 Cells Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth Cells – the smallest living unit ▪ All cells on Earth are either: ▪ Prokaryotic or Eukaryotic. ▪ Prokaryotic cells are smaller and simpler in structure. ▪ EXP: bacteria ▪ They probably resemble the earliest cells to arise on Earth. ▪ Some structures in the Martian meteorite resemble them. Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth Characteristics of Cells ▪ Cells have a cell membrane (plasmalemma) ▪ a phospholipids bilayer: hydrophobic tails orient inside the membrane, away from water Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth ▪ Plasma membrane (plasmalemma) properties. ▪ Fluid mosaic model: lipids and proteins can move about within the membrane ▪ Semipermeable: some molecules can cross and some can’t Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth Characteristics of Prokaryotic Cells ▪ Prokaryotes are simpler than eukaryotes ▪ Prokaryotes have cell membrane ▪ Prokaryotes do not have a true nucleus Copyright © 2010 Pearson Education, Inc. Figure 2.17b  2.2 Life on Earth Characteristics of Cells ▪ Eukaryotic cells are much more complex. ▪ Have true nuclei surrounded by a membrane ▪ Also have membrane-bound organelles with specialized jobs Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth Eukaryotic Cell Organelles ▪ Mitochondria: provide energy for the cell, using oxygen ▪ Chloroplasts: sites of photosynthesis in plants ▪ Endoplasmic reticulum: involved in protein and lipid synthesis ▪ Golgi apparatus: modifies and sorts proteins Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth Animal versus Plant Cells Copyright © 2010 Pearson Education, Inc. Figure 2.18  2.2 Life on Earth Suggested Media Enhancements: Tour of a Plant Cell Tour of an Animal Cell Copyright © 2010 Pearson Education, Inc.  Chapter 2 Section 2.2 Life on Earth Part 2 Tree of Life Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth The Tree of Life and Evolutionary Theory ▪ All Earth organisms share many similarities: ▪ Same basic biochemistry, with same types of macromolecules ▪ All organisms consist of cells ▪ Cells always have phospholipid bilayer plasma membrane ▪ Eukaryotes share most of the same organelles. Copyright © 2010 Pearson Education, Inc.  2.2 Life on Earth Prokaryotic and Eukaryotic Cells ▪ This unity of life is best explained by a tree of life, with modern species having evolved from common ancestors. Copyright © 2010 Pearson Education, Inc. Figure 2.19  Chapter 2 Section 2.2 Life on Earth Part 3: Homeostasis Copyright © 2010 Pearson Education, Inc.  Homeostasis ▪ Homeostasis – a dynamic state of equilibrium in which internal conditions remain relative stable (Steady State) ▪ homeostasis maintains constant conditions in the internal environment ▪ A homeostatic control system has ▪ a receptor – can sense internal conditions ▪ a set point – what conditions should be maintained at. ▪ a control center – processes information & sends instructions to effectors ▪ an effector – can make changes to internal conditions Copyright © 2010 Pearson Education, Inc. LE 40-11 Response No heat produced Heater turned Room off temperature decreases Set Too point hot Set point Set Too point Control center: cold thermostat Room temperature Heater increases turned on Response PowerPoint lecture prepared by Heat produced Steve McCommas Southern Illinois State University Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc.  Two Types of Regulatory Systems ▪ Negative Feedback – Homeostatic mechanism that stops or reduces a change in internal conditions ▪ Causes a change in the variable in the opposite direction as the initial stimulus ▪ Positive feedback – a physiological mechanism that disrupts homeostasis and causes dramatic swings in physiological parameters ▪ Causes a change in the variable in the same direction as the initial stimulus Copyright © 2010 Pearson Education, Inc.