The Chemical Basis of Life PDF

**THE CHEMICAL BASIS OF LIFE** Life requires chemical elements (25) - About 25 elements are essential for life - Four elements make up 96% of living matter carbon ( C ) hydrogen (H) oxygen (O) nitrogen (N) - Four elements make up most of the remaining 4% phosphorus (P) calcium (Ca)...

**THE CHEMICAL BASIS OF LIFE** Life requires chemical elements (25) - About 25 elements are essential for life - Four elements make up 96% of living matter carbon ( C ) hydrogen (H) oxygen (O) nitrogen (N) - Four elements make up most of the remaining 4% phosphorus (P) calcium (Ca) sulfur (S) potassium (k) - everything is made of matter matter is made of atoms **BONDING PROPERTIES CONTINUED** Filling the Shell - Atoms will fill the outermost shell in order to become stable-matching negative electron to positive protons **BONDING PROPERTIES** Effects of electrons - electrons determine the chemical behavior of atoms - depends on the number of electrons in atoms outermost shell, the valence shell - Each shell fill from the inside out 1st shell =l 2 electrons 2nd shell =8 electrons 3rd shell = 8 electrons - The chemical behavior of an atom depends on number of electrons in the outermost shell **ELEMENTS AND THEIR VALENCE SHELLS** - Elements in the same row have the same number of shells - Elements in the same column have the same valence & similar chemical properties **CHEMICAL REACTIVITY** Atoms tend to - complete a partially filled valence shell - empty partially filled valence shell **BONDS IN BIOLOGY** Strong bonds - covalent bonds Weak bonds - hydrogen bonds - hydrophobic & hydrophilic interactions - ionic transfer of electron **COVALENT BONDS** - two atoms share a pair of electrons - both atoms holding onto the electrons - forms of molecules **MULTIPLE COVALENT BONDS** - Pairs of electrons shared unequally by 2 atoms - water O+H - oxygen has stronger \"attraction\" for the electrons than hydrogen - oxygen has higher electronegativity - water is a polar molecule - \+ vs. - poles - leads to many interesting properties of water **HYDROGEN BONDING** - polar water creates molecular attractions - positive H atom in one H₂O molecule attracted to negative O in another H₂O - can occur wherever an-OH exists in a larger molecule **LIFE NEEDS WATER** All life occurs in water - inside & outside the cell **SPECIAL PROPERTIES OF WATER** - Cohesion & adhesion - surface tension, capillary action - good solvent - many molecules dissolve in H20 - hydrophilic vs. hydrophobic lower density as a solid - ice floats - high specific heat - water stores heat. - high heat of vaporization - heats &cools slowly **COHESIONS ADHESION** - H bonding between H20 is cohesion - water is \"sticky\", sticks to itself - surface tension - drinking straw - H bonding between H2O & other substances is adhesion - capillary action - water climbs up paper towel or cloth **HYDROPHILIC** - substances that have attraction to H2O - polar **HYDROPHOBIC** - substances that don\'t have an attraction to H20 - non-polar **IONIZATION OF WATER & PH** - water ionizers - H+ splits from H2O leaving, OH - If(H+ )= (- OH) water is neutral - If(H+ )\> (- OH) water is acidic if - (H+ )\< (- OH) water is basic pH Scale how acid or basic a solution is 1-\>7-\>14 **BUFFERS & CELLULAR REGULATION** - photocells must be kept 7 - pH affects the shape of molecules - shape of molecules affects function - pH affects cellular function **ACIDS, BASES, AND BUFFERS** **ACID** - A molecule capable of releasing (donating) a hydrogen ion ❑ combination with a water molecule to form a hydronium ion (𝐻3𝑂+). ❑ combination with a hydroxyl ion to form a molecule of water. ❑ combination with an amino group in a protein to form a charged amine. **BASE** - A molecule that can accept a proton. - The acidity of a solution is measured by the hydrogen ions and is expressed in term of pH. pH= -log (𝐻+) Example: What is the pH solution of the 𝐻3𝑂+ concentration is 2.5 × 10−8? - pH= -log \[𝐻3𝑂+\] - pH= -log \[2.5 × 10−8\] - pH= 3.6 Buffer **BUFFER** - A solution that can resist changes in pH. Example: 𝐶𝐻3𝐶00𝐻 → 𝐶𝐻3− +𝐻+ many biological fluids are buffer solution because they must maintain a steady pH to avoid loss of critical biological function. **THE NATURE OF BIOLOGICAL MOLECULES** - Biological molecules, or biomolecules - are essential for life. Four Main Types: ***Carbohydrates*** - Provide energy and structural support. ***Proteins*** - Perform functions like enzyme activity, structure, and immune responses. ***Lipids*** - Store energy, form cell membranes, and act as signaling molecules. ***Nucleic Acids*** - Store and transmit genetic information (DNA and RNA). These molecules are carbon-based, often polymers, and interact with water, with many reactions catalyzed by enzymes. They support vital life processes like metabolism and reproduction. **FUNCTIONAL GROUPS** **Hydrocarbon** ✓ are organic molecules primarily made up of carbon and hydrogen. ✓ chemically inactive unless they contain functional groups. **Functional Groups** ✓ are small groups of atoms within molecules that have specific chemical properties. ✓ they make hydrocarbons soluble and more reactive. **TWO OF THE MOST COMMON LINKAGES** **Esters bonds** - which form between carboxylic acids and alcohols. **Amide bonds** - which form between carboxylic acids and amines. **COMMON TYPES OF FUNCTIONAL GROUP** Most of the groups in **Table 2.2** below contain electronegative atoms (N, P, O, S), making organic molecules more polar, water-soluble, and reactive. **CLASSIFICATION OF BIOLOGICAL MOLECULES BY FUNCTION** **1. MACROMOLECULES** - Large, complex molecules essential for cell structure and function. - Made up of dozens to millions of carbon atoms. - Polymers are large molecules built from smaller units called monomers through a process called polymerization. **2. THE BUILDING BLOCKS OF MACROMOLECULES** - Cells maintain a pool of the following low-molecular-weight precursors to build new macromolecules: **3. METABOLIC INTERMEDIATES (METABOLITES)** - Cellular molecules are synthesized through metabolic pathways. **4. MOLECULES OF MISCELLANEOUS FUNCTION** - Although diverse, molecules with miscellaneous functions comprise a smaller portion of the cell\'s dry weight, as most of it consists of macromolecules and their precursors. **THE FOUR TYPES OF BIOLOGICAL MOLECULES** **1. CARBOHYDRATES** - are organic molecules composed of carbon, hydrogen, and oxygen. These molecules are crucial energy sources and structural components of all living organisms. Among the most abundant biomolecules on Earth, carbohydrates are produced by plants during photosynthesis, where carbon dioxide and water are converted into energy-storing sugars. Carbohydrates are classified based on the number of sugar units they contain: **Monosaccharides** - are the simplest carbohydrates, consisting of a single sugar unit. Common examples include: Glucose Fructose Galactose **Disaccharides** \- consist of two monosaccharide units linked together. Examples include: Sucrose (glucose + fructose) Lactose (glucose + galactose) Maltose (glucose + glucose) **Oligosaccharides** \- are composed of 3 to 10 monosaccharide units. Examples include: Raffinose Stachyose **Polysaccharides** \- are complex carbohydrates consisting of many monosaccharide units. Examples include: Starch (energy storage in plants) Glycogen (energy storage in animals) Cellulose (structural component of plant cell walls) **2. LIPIDS** \- are hydrophobic molecules that play a variety of roles in living organisms, from energy storage to serving as chemical messengers. Unlike carbohydrates, lipids do not mix with water, making them critical components of cell membranes and long-term energy storage. Lipids are classified into four major types: **1. Fatty Acids** \- are simple lipid molecules composed of a long hydrocarbon chain with a carboxyl group at one end. Examples include: Palmitic acid (saturated) Oleic acid (unsaturated) **2. Triglycerides** \- are composed of three fatty acids attached to a glycerol molecule. These molecules store energy in animals and plants. Fats (solid at room temperature, found in butter) Oils (liquid at room temperature, found in olive oil) **3. Phospholipids** \- contain two fatty acids and a phosphate group attached to a glycerol backbone. These molecules are essential components of the cell membrane, forming the lipid bilayer that controls the entry and exit of substances in and out of the cell. Example: Phosphatidylcholine **4. Steroids** \- have a structure consisting of four fused carbon rings. They play a role in signaling (hormones), membrane structure, and metabolism. Examples: Cholesterol, Testosterone, Estrogen **3. NUCLEIC ACID** \- are the primary information carriers in cells and direct the synthesis of proteins. These molecules are composed of long chains of nucleotides, each made up of a sugar, a phosphate group, and an organic base. There are two main classes of nucleic acids: - **Deoxyribonucleic Acid (DNA)** DNA serves as the genetic blueprint for all living organisms and most viruses. It contains the bases adenine (A), cytosine (C), guanine (G), and thymine (T). - **Ribonucleic Acid (RNA)** RNA is the genetic material for certain viruses and plays an essential role in protein synthesis in all living cells. In RNA, the base uracil (U) replaces thymine. Both DNA and RNA are critical for storing and transmitting genetic information across generations. **4. PROTEIN** \- are complex molecules present in all living organisms. These molecules are vital to the chemical processes that sustain life and hold immense nutritional value. -Proteins are made of long chains of **α-amino acids.** The term α refers to the position of the amino group (-NH2) on the carbon atom adjacent to the carboxyl group (-COOH). Proteins are species-specific, with each species having unique protein structures that differ from others. \- Proteins carry out diverse functions in the body, from acting as enzymes that speed up chemical reactions to providing structural support in cells and tissues. The term \"protein\" was coined in 1838 by Swedish chemist Jöns Jacob Berzelius, derived from the Greek word prōteios, meaning \"holding first place,\" emphasizing the essential role of proteins in biology.