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Chapter 2: The Nature of Life

Chapter 2: The Nature of Life. What makes something alive, or “living”?. Characteristics of Living Things. Composition (made of cells) Structure (cell wall) Growth (increase in mass and number of cells) Reproduction Response to stimuli

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Chapter 2: The Nature of Life

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  1. Chapter 2: The Nature of Life

  2. What makes something alive, or “living”?

  3. Characteristics of Living Things • Composition (made of cells) • Structure (cell wall) • Growth (increase in mass and number of cells) • Reproduction • Response to stimuli • Metabolism (all chemical reactions within cells: respiration, photosynthesis, digestion, etc.) • Movement • Organization (molecules  cells  tissues  organs, etc) • Evolution

  4. Chemical and Physical Bases of Life • Matter: anything that takes up space • Made of elements • Atom: smallest stable unit of an element • Molecules: two or more atoms held together by chemical bonds • Chemical reactions are controlled by enzymes • 3 types of Chemical bonds: • Hydrogen • Covalent • Ionic

  5. Polarity of Molecules • Uneven distribution of electrons (charges) on a molecule • Affects the way molecules interact with each other • Capillarity of water • Cohesion of water molecules • Adhesive properties of water

  6. Acids, Bases, and Salts • Due to polarity of water molecules • Acids: pH <7, excess hydrogen (H+) ions • Bases: pH>7, excess hydroxide (OH-) ions • pH scale is used to measure # H+ in a solution • **pH of soil can drastically affect the growth of a plant

  7. Energy • The ability to do work • *We will discuss with photosynthesis

  8. Chemical Components of Cells • Organic: molecules make up 96% of cytoplasm • Carbon, hydrogen, oxygen, and nitrogen • Inorganic: molecules with no carbon

  9. Can you name the 4 main groups of organic molecules?

  10. Monomers and Polymers • Polymer: macromolecule “large molecules” • Monomer: smaller molecules that build polymers • Carbohydrates: main source of energy • Monosaccharides, disaccharides, polysaccharides • Cellulose: makes up cell walls of plants

  11. Monomers and Polymers • Lipids: insoluble in water; store energy • Fats, oils, waxes, phospholipids • Proteins: regulate chemical reactions, chains of amino acids • Plants use storage proteins in some cases • ex: legumes, gluten • Enzymes: organic catalysts, names end in –ase • Nucleic Acids: made of nucleotides, store genetic information; ex: DNA and RNA

  12. Chapter 3: Cells

  13. History • Robert Hooke: named cells; looked at cork cells • Cell Theory • All organisms are made of cells • Cells are the basic unit of life • New cells come from pre-existing cells

  14. What are the two main classifications of cells?

  15. Cell Classification • Prokaryotic: no nuclei and lack membrane-bound organelles • Ex: bacteria • Eukaryotic: have nuclei and other organelles • Ex: protists, plants, fungi, and animals • Cells are very small and can be various shapes • Bacteria < Animal <Plant (Usually)

  16. Plant Cells • Have cell wall outside cell membrane • Mostly cellulose in bundles called microfibrils • Also contains pectins and lignins for strength • Some plant cells have thicker cell walls depending on their function • Cells are connected by structures called plasmodesmata: used for communication and movement

  17. Cell Components • Cytoplasm: jellylike fluid holding organelles in place • Plasma or Cell Membrane: semipermeable, allows materials in and out, made of phospholipids and proteins • Nucleus: control center of the cell, contains the DNA • Nuclear envelope, nucleolus, chromatin

  18. Cell Components • Endoplasmic Reticulum: cell communication and transport of materials • Rough and Smooth ER • Ribosomes: site of protein synthesis, made of RNA and proteins • Golgi apparatus: synthesize and package

  19. Cell Components • Mitochondria: powerhouse of the cell, site of cellular respiration • Vacuoles: maintain pressures inside cell and hold cell sap: mostly water with dissolved salts, sugars, proteins, etc. • Cytoskeleton: movement and structure of cell • Microtubules and microfilaments

  20. Plastids • Chloroplast: site of photosynthesis • Contains pigment chlorophyll • Chromoplast: similar to chloroplast but have carotenoids: yellow, orange, and red pigments; abundant in carrots, tomatoes, and red peppers • Leucoplast: colorless, synthesize starches and oils; can develop into chloroplasts

  21. How do existing cells make new cells?

  22. The Cell Cycle • Cell division • Interphase: mostly growth and DNA replication • Mitosis: division of the cell nucleus • Prophase, Metaphase, Anaphase, and Telophase • Cytokinesis: division of the cytoplasm, formation of the cell plate • Results in two identical daughter cells

  23. Plant cells vs. Animal cells • Structures unique to plant cells: • Cell wall • Plasmodesmata • Cell plate • Minor differences: • No centrioles in plant cells • Plant cells contain plastids • Vacuoles small or absent in animal cells

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