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. Figure What Does Life Require?  Protons (positive charge) + neutrons form atomic nucleus  Electrons (negative charge) are outside the nucleus. Atoms are composed of protons, neutrons, and electrons

Copyright © 2010 Pearson Education, Inc. 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 Figure 2.4

Copyright © 2010 Pearson Education, Inc. 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. Figure 2.6

Copyright © 2010 Pearson Education, Inc. 2.1 What Does Life Require? The Properties of Water Animation—Chemistry and Water PLAY

Copyright © 2010 Pearson Education, Inc. 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. 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? Types of Macromolecules 1.Carbohydrates 2.Proteins 3.Lipids 4.Nucleic Acis Figure 2.12 Structure and Function of Macromolecules

Copyright © 2010 Pearson Education, Inc. 2.1 What Does Life Require?  Carbohydrates: molecules of carbon, oxygen, and hydrogen  Major source of energy for cells Figure 2.12 Structure and Function of Macromolecules

Copyright © 2010 Pearson Education, Inc. 2.1 What Does Life Require? Proteins: polymers of amino acids; joined by peptide bonds Figure 2.13 Structure and Function of Macromolecules

Copyright © 2010 Pearson Education, Inc. 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. Figure 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 2.15c 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. 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?  The structure of a DNA molecule is a double helix made up of nucleotides. Figure 2.15a Structure and Function of Macromolecules

Copyright © 2010 Pearson Education, Inc. 2.1 What Does Life Require?  Bonding between bases on opposite strands follows strict base-pairing rules:  A with T  G with C Figure 2.15b Structure and Function of Macromolecules

Copyright © 2010 Pearson Education, Inc. 2.1 What Does Life Require? Structure and Function of Macromolecules Animation—Nucelic Acids PLAY

Copyright © 2010 Pearson Education, Inc. Chapter 2 End of Section 2.1 What Does Life Require?

Copyright © 2010 Pearson Education, Inc. 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 Figure 2.17b

Copyright © 2010 Pearson Education, Inc. 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 Prokaryotic and Eukaryotic Cells Animation—A Comparison of Prokaryotic and Eukaryotic Cells PLAY

Copyright © 2010 Pearson Education, Inc. 2.2 Life on Earth Animal versus Plant Cells Figure 2.18

Copyright © 2010 Pearson Education, Inc. 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 End of Part 1 Cells

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. Figure 2.19

Copyright © 2010 Pearson Education, Inc. Chapter 2 Section 2.2 Life on Earth End of Part 2: Tree of Life

Copyright © 2010 Pearson Education, Inc. 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

Steve McCommas Southern Illinois State University PowerPoint lecture prepared by Copyright © 2010 Pearson Education, Inc. LE Response No heat produced Room temperature decreases Room temperature increases Set point Too hot Set point Heater turned off Too cold Set point Control center: thermostat Heater turned on Response Heat produced

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. Chapter 2 Section 2.2 Life on Earth End of Part 3: Homeostasis End of Chapter 2