CELL METABOLISM

• Metabolism


  Total cellular chemical changes
• Anabolism


  Process of building up
• Catabolism


  Process of breaking down
• Calorie


  Measure of energy contained in food
• ATP


  Energy source available to the cell
• Glycolysis


  1. Breakdown of glucose

  2. Anaerobic or aerobic process

  3. Final outcome: 2 pyruvic acid molecules, 2 ATP molecules (anaerobic), 8 ATP molecules (aerobic)
• The Krebs Citric Acid Cycle

  1. Pyruvic Acid > Acetic Acid > Acetyl-CoA

  2. Acetyl-CoA enters Krebs cycle in mitochondria

  3. Final outcome: 6 CO2, 8 NADH2, 2 FADH2, 2 ATP (GTP)
• The Electron Transport (Transfer) System

  1. Series of reduction/oxidation reactions

  2. Requires O2

  3. Electron carriers

  4. Number of ATP molecules dependent on electron carrier

  5. Water is a waste product
• Fermentation


  1. Yeast breaks down glucose anaerobically

  2. Pyruvic acid is broken down by decarboxylase to form carbon dioxide and acetaldehyde

  3. Final products: 2 ATP, CO2, ethyl alcohol
• Anaerobic Production of ATP by Muscles

  1. Pyruvic acid converted to lactic acid

  2. Accumulation of lactic acid causes fatigue in muscles

  3. When oxygen is supplied, lactic acid turns back into pyruvic acid

  4. 2 ATP produced per glucose molecule
• Carbohydrates


  Fit into cellular furnace at same level as glucose, can be stored in liver or as fat
• Fats


  Digested into fatty acids and glycerol, glycerol enters at PGA stage of glycolysis, fatty acids enter Krebs citric acid cycle
• Proteins


  Digested into amino acids, enter into Krebs cycle at different stages dependent on chemical structure
• Cellular Reproduction


  Process of cell duplication, Mitosis: duplication of genetic material, Cytokinesis: duplication of organelles, Meiosis: reduction division only in gonads
• DNA Molecule


  Double helical chain of nucleotides, Phosphate group, Five-carbon sugars (deoxyribose), Nitrogen-containing base (Pyrimidines and Purines), Pyrimidines pair with purines, Chains held together by hydrogen bonds
• Gene


  Sequence of base pairs that codes for polypeptide or protein
• Human Genome Project: 3 billion base pairs that code for 30,000 genes
• Duplication of DNA Molecule

  Helicase separates at hydrogen bonds, DNA polymerase adds new nucleotides
• Interphase


  Time between divisions, G1: Primary growth phase, S: DNA duplication, G2: Centrioles complete duplication, mitochondria replicate, chromosomes condense and coil
• Mitosis


  1. Prophase: Chromosomes become visible as chromatids are joined by centromere, Two kinetochores at the centromere, Centrioles move to opposite poles, Nuclear membrane breaks down, Microtubules attach kinetochores to spindle

  2. Metaphase: Chromatids align at equator of cell, Centromere divides

  3. Anaphase: Divided centromere pulls chromatids to opposite pole, Cytokinesis begins

  4. Telophase: Chromosomes uncoil and decondense, Spindle apparatus breaks down, New nuclear membrane forms, Cytokinesis nearly complete
• Cytokinesis


  1. Animal cells: Cleavage furrow forms, Cell is pinched into daughter cells

  2. Plant cells: Cell plate forms at equator, Cell plate becomes new cell wall
• Meiosis


  Reduction division only in gonads, Reduces genetic material from diploid to haploid, Two divisions resulting in four cells
• Stages of Meiosis


  1. Prophase I: homologous chromosomes pair and cross over

  2. Metaphase I: chromosomes align along equator

  3. Anaphase I: centromeres pulled to poles, One member to each pole

  4. Telophase I: one of each pair is at each pole

  5. Prophase II: spindle forms; centrioles move to poles

  6. Metaphase II: chromosomes line up at equator

  7. Anaphase II: centromeres divide

  8. Telophase II: chromatids at each pole; new nuclear membrane forms
• Spermatogenesis


  Four cells produced, Develop into sperm
• Oogenesis


  Four cells produced, Only one becomes functional egg
• Mitosis - duplication of genetic material
• Cytokinesis - duplication of organelles
• Meiosis - reduction division only in gonads
• Friedrich Miescher, 1869 - first discovery
• Rosalind Franklin - helical structure
• P.A. Levene, 1920s - composition
• Watson and Crick - three-dimensional

  structure
• Double helical chain of nucleotides

  – Phosphate group

  – Five-carbon sugars (deoxyribose)

  – Nitrogen-containing base

  • Pyrimidines (thymine and cytosine)

  • Purines (adenine and guanine)

  – Pyrimidines pair with purines

  – Chains held together by hydrogen bonds
• Interphase - Previously called resting stage
• Final outcome of Glycolysis

  – 2 pyruvic acid molecules, 2 ATP molecules

  (anaerobic), 8 ATP molecules (aerobic)
• The Electron Transport (Transfer) System

  • Series of reduction/oxidation reactions

  • Requires O2

  • Electron carriers

  • Number of ATP molecules dependent on

  electron carrier

  • Water is a waste product
• ATP Production

  • During glycolysis, the citric acid cycle, and

  electron transport

  • Glycolysis: 8 ATP (aerobic)

  • Krebs cycle and electron transport

  – 28 ATP + 2 GTP or

  – 30 ATP

  • 1 glucose molecule yields 38 ATP
• Fermentation - Yeast breaks down glucose anaerobically
• Pyruvic acid is broken down by

  decarboxylase – Forms carbon dioxide and acetaldehyde

  Final products: 2 ATP, CO2, ethyl alcohol
• 2 ATP produced per glucose molecule