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: Neutron: Electron: positive, 1 mass unit 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 atoms joined by strong bonds Compounds: atoms joined by strong or weak bonds

States of Matter Solid: Liquid: Gas: constant volume and shape 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 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 imbalance seriously 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: Alkalosis: 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) 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: DNA: Single strand 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): Adenosine triphosphate (ATP): 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