Chemical Composition of the Body PDF

Chemical Composition of the Body Humans are large collections of tissues and organ systems. Organ systems are large collections of extracellular matrixes and cells. Cells are large collections of organelles and molecules. Molecules are small to large collections of...

Chemical Composition of the Body Humans are large collections of tissues and organ systems. Organ systems are large collections of extracellular matrixes and cells. Cells are large collections of organelles and molecules. Molecules are small to large collections of elements whose atoms are held together by chemical bonds. Atoms are made up of subatomic particles: an atomic nucleus with neutrons and protons and a surrounding “cloud” of electrons.  Ions An ion results when an atom What is an ion? gains or loses one or more electrons. Ions are mismatched in the number of protons and electrons, and are therefore electrically charged. The origin of an ion’s proton-electron mismatch is indicated by the sign (plus or minus) and number of signs: Cl- represents a chlorine atom that has gained an electron. Ca++ represents a calcium atom that has lost two electrons.  There are several ways to express the structure of molecules. Structure helps us understand function. Two dimensions Three dimensions Space filling models Fig. 2.3 Strength and Type of Chemical Bonds and Interactions Covalent bonds (share electrons) STRONG e.g., methane, CH4 (Figure 2.3) Ionic bonds (opposite charges attract) e.g., sodium chloride, Na+Cl- Hydrogen bonds (attraction of H to O or N) e.g., (Figure 2.7) van der Waals forces (local forces) e.g., between compound molecules WEAK Fig 2.7 In each water molecule, the shared electrons spend more time close to the larger oxygen atom, making that area slightly electronegative compared to the area near the hydrogen atoms. Covalent O-H bonds (solid lines). The dotted lines between water molecules represent the “hydrogen bonds” resulting from the weak electrical attractions.  Solvent + Solute(s) = A Chemical Solution To describe the number of dissolved solutes in a solution, we refer to the “chemical concentration” of the solute, which is the amount of solute present in a given volume of solvent. The molecular weight (MW) of a solute is the number of grams of that solute you would need to add to one liter (L) of solvent to produce a 1-molar (M) solution. 1 molar = 1 M = 1 mole compound in 1 L water C6H12O6 (glucose) has a MW of 180 (180 g = 1 mol), so to make a 1 M glucose solution, add 180 g of glucose to 1 L of water. Examples of non-polar and polar bonds, and ionized chemical groups Compounds: Polar compounds (atoms at each end of bond have opposite charge, e.g. O-H), including water molecules, readily associate with each other, whereas Non-polar compounds (atoms at each end of bond have same charge, e.g. C-H) readily associate with each other, including such compounds in cell membranes. Hydrophilic, or “water loving,” compounds, e.g., NaCl, dissolve readily in water; they are water soluble. Hydrophobic, or “water fearing,” compounds, e.g., fats, do not dissolve readily in water, but will dissolve readily into non-polar solvents, even (fatty) cell membranes.  Fig 2.6 NaCl dissolves in water. Positive sodium ions (Na+) Water, because of its regions are attracted to negative of polarity, is a solvent that chloride ions (Cl-) to form readily dissolves Na+Cl-. ionic bonds. Na+ & Cl- are the solutes and water is the solvent. Here, the non-polar regions associate with each other and the polar regions form hydrogen bonds with the surrounding (polar) water molecules. Fig 2.23  Organic Molecules Contain Carbon (C) and Hydrogen (H) 4 types: carbohydrates, lipids, proteins, and nucleic acids  Carbohydrates Structure ▪ Sugars and starches ▪ C, H, O ▪ Usually hydroxyl (OH) group linked to C ▪ CnH2nOn ▪ Covalent bonds Function ▪ Energy storage and production  Carbohydrates Both representations of glucose, C6H12O6, show the many covalent bonds that make this monosaccharide an energy-rich molecule. Fig 2.14a Carbohydrates A difference in the position of the–OH group is the structural difference between the monosaccharides glucose and galactose; both are C6H12O6. Fig 2.14a & b  Carbohydrates The disaccharide sucrose (table sugar) and a water molecule result from the linkage of the monosaccharides glucose and fructose (energy input is required and intermediate stages are not shown here). Fig 2.16b  Carbohydrates Fig 2.15 Glycogen is a polysaccharide that serves as a high-energy storage polymer made up of glucose units. When needed, these glucose units are released into the blood for energy-transfer reactions.  Lipids Structure ▪ Based on fatty acid monomers (single, long molecules that can bind to others) ▪ Fatty acids, triglycerides, phospholipids, steroids (ring structures) ▪ H, C ▪ Nonpolar covalent bonds (low solubility in water) Function ▪ Best energy source ▪ Membranes, hormones ▪ Insulation (adipose tissue)  Lipids Fatty acids may be (a) saturated (all C linked by single covalent bonds) or (b) unsaturated (fewer C-H bonds than saturated) Fig 2.18  Lipids Glycerol and fatty acids are subunits for the formation of: triglycerides (among the body’s fats), and phospholipids (membrane components). Fig 2.20  Lipids Phospholipids are formed from glycerol, two fatty acids, and one or more charged groups. Fig 2.22  Lipids Fig 2.23 Micelles (aggregates of molecules) form when phospholipids, which are amphipathic, mix in water. They group together so that their polar, hydrophilic regions face the surrounding water molecules. Steroids Cholesterol molecules (steroids) promote membrane fluidity and serve as starting materials for the synthesis of steroid hormones. Fig 2.24  Proteins Structure ▪ Based on amino acid (AA) monomers ▪ Macromolecules with 1000s of atoms ▪ Levels of structure ▪ C, H, O, N, sulfur + other elements in small amounts ▪ Various bonds, created via dehydration Function ▪ Many!!! ▪ Enzymes, cell attachment, cytoskeleton, locomotion, hormones Fig 2.26 Proteins All amino acids have: an amino group, a carboxyl group, and a varying side chain [R] that determines the amino acid Side chains can be: ▪ nonpolar groups or ▪ polar groups or ▪ ionized groups  Proteins Fig 2.27 Peptide bonds are covalent bonds that connect neighboring amino acids together to form a polypeptide  Nucleotides/Nucleic Acids Structure ▪ Sugar + Base + Phosphate ▪ Various types of bonds ▪ Repeating subunits in a chain Function ▪ Information storage (DNA and RNAs) ▪ Energy storage (ATP) ▪ High energy e-transfer molecules (coenzymes) NADH and FADH2  Nucleotides/Nucleic Acids Fig 2.32 DNA is made up of a chain of deoxyribonucleotides and RNA is made up of a chain of ribonucleotides.  Nucleotides/Nucleic Acids The sequence of bases in DNA and in RNA is held together by phosphate-sugar bonds. You will learn later how this sequence is an information code. Fig 2.31  Deoxyribonucleic Acid (DNA) Hydrogen bonds between complementary bases hold together the DNA double helix. Fig 2.33  Nucleotides/Nucleic Acids RNA has uracil instead of thymine, and only a single (not double) chain of nucleotides. Fig 2.34 Comparison of DNA & RNA Structure DNA RNA Number of Chains Two One Nucleotide Sugar Deoxyribose Ribose Nucleotide Bases Purines Adenine (A) Adenine (A) Guanine (G) Guanine (G) Pyrimidines Cytosine (C) Cytosine (C) Thymine (T) Uracil (U)