Unit 1: The Chemical Basis of Life
- Page ID
- 3735
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The following pages examine some of the principles of chemistry upon which an understanding of modern biology depends.
- 1.1: Mixtures and Compounds
- This page explains the differences between mixtures and compounds, highlighting that mixtures are heterogeneous and can be separated easily, while compounds are homogeneous with fixed element proportions that do not retain individual properties. Techniques like dialysis and chromatography separate mixture components, with pure substances being elements or compounds that cannot be broken down.
- 1.2: Elements and Atoms
- This page explains that elements are pure substances composed of one type of atom, crucial for life, with only around 25 of Earth's 90 elements being essential. It details atomic structure, focusing on the nucleus and outer electrons, which dictate chemical behavior, valence, and electronegativity. Elements with similar outer electron configurations share chemical properties and react to achieve stability.
- 1.3: Electronegativity and types of Chemical Bonds
- This page explains electronegativity as an atom's affinity for electrons, highlighting fluorine as the most electronegative element. It describes three bond types: ionic (large electronegativity differences), covalent (minor differences), and polar covalent (moderate differences). Examples include NaCl for ionic bonds, carbon and hydrogen for covalent bonds, and water for polar covalent bonds. It notes that polar molecules can form hydrogen bonds and are good solvents for polar substances.
- 1.4: Noncovalent Bonding
- This page discusses noncovalent bonding's importance in biological systems, highlighting its role in stabilizing DNA and protein structures and enabling key interactions like enzyme-substrate binding and antibody-antigen recognition. The main types of noncovalent forces include ionic interactions (which depend on pH and salt concentration), hydrophobic interactions (favoring nonpolar residues), and hydrogen bonds (involving electronegative atoms and hydrogen).
- 1.5: Hydrogen Bonds
- This page discusses hydrogen bonds, which are weak attractions between polar molecules like water. Each water molecule can form bonds with four others, leading to unique properties such as a wide liquid temperature range and high heat of vaporization. These characteristics support cooling via sweat evaporation and stabilize temperatures near water bodies.
- 1.6: Acids and Bases
- This page explains that acids donate protons (H+) to bases, while bases accept them. For instance, hydrochloric acid (HCl) ionizes in water, producing chloride and hydronium ions. Ammonia (NH3) acts as a base by accepting a proton from HCl, forming ammonium and water. It also highlights the role of biological acids, particularly those with carboxyl groups like acetic acid, and notes that biological bases often contain amino groups, with bicarbonate ions being significant bases.
- 1.7: Molecular Weight and the Mole
- This page explains molecular weight (MW) as the total weight of atoms in a molecule, measured in daltons, and its significance in experiments, such as studying honeybee sugar solution responses. It highlights that a 35% glucose solution has nearly twice the molecule count as a 35% sucrose solution due to different MWs. Additionally, it defines a mole as the weight in grams equal to the MW, approximately 6 x 10^23 molecules, known as Avogadro's number, applicable to all substances.
- 1.8: pH
- This page explains pH as a measure of hydrogen ion concentration, noting that pure water has a pH of 7. It describes how acidic solutions (pH < 7) have higher H+ concentrations and basic solutions (pH > 7) have lower. The impact of pH on protein properties and amino acid interactions is highlighted. Additionally, it mentions that the typical cytosolic pH in human cells is 7.4, with variations in organelles like lysosomes and mitochondria, which are essential for enzyme activity and ATP synthesis.