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Chapter 2

Chapter 2. Are We Alone in the Universe? What is life? The Chemistry of Life Water and Biochemistry. Are We Alone in the Universe?. Martian rock found on Earth Is there evidence of life? What is life?. Chapter 2. Section 2.1 What Does Life Require?. 2.1 What Does Life Require?.

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Chapter 2

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  1. Chapter 2 • Are We Alone in the Universe? • What is life? • The Chemistry of Life • Water and Biochemistry

  2. Are We Alone in the Universe? • Martian rock found on Earth • Is there evidence of life? • What is life?

  3. Chapter 2 Section 2.1 What Does Life Require?

  4. 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

  5. 2.1 What Does Life Require? Additional Characteristics of Life • Cellular organization • Growth and metabolism  • Reproduction • Heredity

  6. 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

  7. 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. Figure 2.3

  8. Chapter 2 Section 2.1 Part 1 The Chemistry of Water

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 2.1 What Does Life Require? The Properties of Water PLAY Animation—Chemistry and Water

  15. 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

  16. 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

  17. Chapter 2 Section 2.1 Part 2 Organic Chemistry = The Chemistry of Carbon

  18. 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?

  19. 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

  20. 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).

  21. 2.1 What Does Life Require? Structure and Function of Macromolecules Types of Macromolecules • Carbohydrates • Proteins • Lipids • Nucleic Acis Figure 2.12

  22. 2.1 What Does Life Require? Structure and Function of Macromolecules • Carbohydrates: molecules of carbon, oxygen, and hydrogen • Major source of energy for cells Figure 2.12

  23. 2.1 What Does Life Require? Structure and Function of Macromolecules Proteins: polymers of amino acids; joined by peptide bonds Figure 2.13

  24. 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.

  25. 2.1 What Does Life Require? Structure and Function of Macromolecules • Lipids: hydrophobic; composed mostly of carbon and hydrogen • Three important types: Figure 2.14

  26. 2.1 What Does Life Require? Structure and Function of Macromolecules • Nucleic acids = polymers of nucleotides • Nucleotide = a phosphate + sugar + a nitrogenous base Figure 2.15c

  27. 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.

  28. 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. Figure 2.15a

  29. 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 Figure 2.15b

  30. 2.1 What Does Life Require? Structure and Function of Macromolecules PLAY Animation—Nucelic Acids

  31. Chapter 2 End of Section 2.1 What Does Life Require?

  32. Chapter 2 Section 2.2 Life on Earth Part 1 Cells

  33. 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.

  34. 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

  35. 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

  36. 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

  37. 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

  38. 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

  39. 2.2 Life on Earth Prokaryotic and Eukaryotic Cells PLAY Animation—A Comparison of Prokaryotic and Eukaryotic Cells

  40. 2.2 Life on Earth Animal versus Plant Cells Figure 2.18

  41. 2.2 Life on Earth Suggested Media Enhancements: Tour of a Plant Cell Tour of an Animal Cell

  42. Chapter 2 Section 2.2 Life on Earth End of Part 1 Cells

  43. Chapter 2 Section 2.2 Life on Earth Part 2 Tree of Life

  44. 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.

  45. 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

  46. Chapter 2 Section 2.2 Life on Earth End of Part 2: Tree of Life

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

  48. 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

  49. Response No heat produced Heater turned off Room temperature decreases Set point Too hot Set point Set point Too cold Control center: thermostat LE 40-11 Room temperature increases Heater turned on Response Heat produced

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