Chapter 2: The Chemical Level of Organization
KEY CONCEPT • All Matter is made up of atoms • Atoms join together to form chemicals with different characteristics • Chemical characteristics determine physiology at the molecular and cellular level
Atomic Particles • Proton: • positive, 1 mass unit • Neutron: • neutral, 1 mass unit • Electron: • negative, low mass
Isotopes • 2 or more elements with equal numbers of protons but different numbers of neutrons
Elements in the Human Body Table 2–1
Molecules and Compounds • Molecules: • atoms joined by strong bonds • Compounds: • atoms joined by strong or weak bonds
States of Matter • Solid: • constant volume and shape • Liquid: • constant volume but change shape • Gas: • change volume and shape
Chemical reactions & Physiology? • Energy: • the power to do work • Work: • a change in mass or distance
Forms of Energy • Kinetic energy - energy of motion • Potential energy - stored energy • Chemical energy - potential energy stored in chemical bonds
KEY CONCEPT • When energy is exchanged, heat is produced, but cells cannot capture it or use it for work
Break Down, Build Up • Decomposition reaction (catabolism): AB A + B • Synthesis reaction (anabolism): A + B AB • Exchange reaction (reversible): AB A + B
KEY CONCEPT • Reversible reactions seek equilibrium, balancing opposing reaction rates • Add or remove reactants: • reaction rates adjust to reach a new equilibrium
How do enzymes control metabolism?
Activation Energy • Chemical reactions in cells cannot start without help • Activation energy gets a reaction started Figure 2–7
How Enzymes Work Figure 2–21
KEY CONCEPT • Most chemical reactions that sustain life cannot occur unless the right enzymes are present
Organic and Inorganic Molecules • Organic: • molecules based on carbon and hydrogen • Inorganic: • molecules not based on carbon and hydrogen
Why is water so important to life?
Properties of Water (1 of 2) • Solubility: • water’s ability to dissolve a solute to make a solution • Reactivity: • most body chemistry uses or occurs in water
Properties of Water (2 of 2) • High heat capacity: • water’s ability to absorb and retain heat • Lubrication: • to moisten and reduce friction
KEY CONCEPT • Most of our body weight is water • Water is the key structural and functional component of cells and their control mechanisms, the nucleic acids
Electrolytes • Inorganic ions conduct electricity in solution • Electrolyte imbalanceseriously disturbs vital body functions • Fluid balance • Blood pressure • Muscular contractions
pH • pH: • the concentration of hydrogen ions (H+) in a solution • Neutral pH: • a balance of H+ and OH— • pure water = 7.0
Acids and Bases • Acid (acidic):pH lower than 7.0 • high H+ concentration, low OH— concentration • Base (basic):pH higher than 7.0 • low H+ concentration, high OH— concentration
pH Scale • Has an inverse relationship with H+ concentration: • more H+ ions mean lower pH, less H+ ions mean higher pH Figure 2–9
KEY CONCEPT • pH of body fluids measures free H+ ions in solution • Excess H+ ions (low pH): • damages cells and tissues, alters proteins • interferes with normal functions • Excess OH— ions (high pH) also problem • Normal blood pH – 7.35 to 7.45 • Incompatibile with life – 6.8 to 7.8
Acid and Alkaline • Acidosis: • excess H+ in body fluid (low pH) • Loss of bicarbonate • Blood level < 7.2 • Alkalosis: • excess OH— in body fluid (high pH) • Blood level > 7.5
Nucleic Acids • Large organic molecules, found in the nucleus, which store and process information at the molecular level • DNA and RNA
Deoxyribonucleic Acid (DNA) • Deoxyribonucleic Acid (DNA) • Determines inherited characteristics • Directs protein synthesis • Controls enzyme production • Controls metabolism • Ribonucleic Acid (RNA) • Codes intermediate steps in protein synthesis
KEY CONCEPT • DNA in the cell nucleus contains the information needed to construct all of the proteins in the body
Nucleotides • Building blocks of DNA • Have 3 molecular parts: • sugar (deoxyribose) • phosphate group • nitrogenous base (A, G, T, C)
DNA Bases Figure 2–22b, c
Complementary Bases • Complementary base pairs: • purines pair with pyrimidines: • DNA: • adenine (A) and thymine (T) • cytosine (C) and guanine (G) • RNA: • uracil (U) replaces thymine (T)
Nucleic Acids • Long chains of nucleotides form RNA and DNA • RNA and DNA Figure 2–23
RNA and DNA • RNA: • Single strand • DNA: • Double helix • Joined at bases by hydrogen bonds
Forms of RNA • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)
ADP and ATP • Adenosine diphosphate (ADP): • 2 phosphate groups • di = 2 • Adenosine triphosphate (ATP): • 3 phosphate groups • tri = 3 • Energy for muscular contractions
KEY CONCEPT • Body recycles/renews all chemical components at intervals ranging from minutes to years • Metabolic turnover lets your body: • Grow • Change • Adapt
SUMMARY (1 of 2) • Atoms, molecules, and chemical bonds control cellular physiology • Metabolism and energy work within the cell • Importance of organic and inorganic nutrients and metabolites
SUMMARY (2 of 2) • Role of water and solubility in metabolism and cell structure • Chemistry of acids and bases, pH and buffers • Structure and function of carbohydrates, lipids, proteins, and nucleic acids
