Chapter 2 The Chemical Level Fall 2024 PDF

9/16/24 1 The Chemical Level of Organization 2 Matter Organisms are composed of matter Matter is anything that takes up space and has mass Rocks Metals Oils Gase...

9/16/24 1 The Chemical Level of Organization 2 Matter Organisms are composed of matter Matter is anything that takes up space and has mass Rocks Metals Oils Gases Matter is made up of Elements… 3 Elements Pure substances with uniform composition and properties Cannot be broken down by simple chemical processes 90 occur naturally on Earth, although some are only present in extremely small quantities. 4 Essential Elements of Life 5 An element’s properties depend on the structure of its atoms Each element consists of unique atoms 6 1 4 5 Each element consists of unique atoms An atom is the smallest unit of matter that still retains the properties of an element 6 Components of an atom Atoms composed of three subatomic particles Neutrons Mass of one atomic mass unit (amu) No charge Protons Mass of one amu Positive charge of one (+1) Electrons 1/1800th of the mass of a proton or neutron Negative charge of one (−1) Located at varying distance from the nucleus in regions called orbitals 7 Elements and the periodic table Chemical symbol Unique to each element Usually identified by first letter, or first letter plus an additional letter, for example, C is carbon Atomic number Number of protons in an atom of the element Located above symbol name Elements arranged by atomic number within rows Average atomic mass Mass of both protons and neutrons Shown below the element’s symbol on the table 8  Mass of both protons and neutrons Shown below the element’s symbol on the table 8 Diagramming atomic structures An atom has “shells” of electrons surrounding the nucleus Most likely region of the electron cloud in which to find electrons Each shell holds a limited number of electrons Innermost shell: two electrons, second shell up to eight Shells close to the nucleus must be filled first 9 Chemical Stability and the Octet Rule Periodic table is organized into columns based on number of electrons in outer shell, referred to as the valence shell Column IA shows hydrogen, lithium, sodium, potassium All with one electron in their valence shell Each consecutive column has one additional electron in valence shell Elements in column VIIA each have a full valence shell Results in chemical stability Helium, neon, etc., chemically inert noble gases 10 Octet Rule Elements tend to lose, gain, or share electrons to obtain complete outer shells with eight electrons Known as the octet rule 11 From atoms to molecules… As atoms come together to form molecules, chemical bonds bind them togetherà due to sharing or exchanging electrons between the atoms 12 13 11 12 13 Chemical Constituents of Cells Inorganic usually lack carbon & are structurally simple water, oxygen, carbon dioxide, salts, acids and bases Organic contain carbon and hydrogen as primary elements linked by covalent bonds Often large, complex 14 Inorganic Compounds: Water Oxygen is more electronegative than hydrogen Electrons spend more time near the oxygen nucleus than the hydrogen nucleus 15 Hydrogen Bonds forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom Do NOT form new molecules Only link-up existing molecules Affects the properties of those molecules 16 Inorganic Molecules: Water Most important inorganic molecule in living systems water properties: Water is liquid at room temp 16 water properties: Water is liquid at room temp water molecules are cohesive: fills vessels water retains temperature stable: thermal inertia water has high heat capacity: carries heat away w/ vapor Water is a universal solvent for electrically charged/ or polar molecules >>Hydrophilic, hydrophobic 17 Organic Molecules Large and complexà Macromolecules Made up of smaller subunits: monomers Monomers can be linked together to make larger polymers 4 classes: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids 18 19 1. Carbohydrates Diverse group of substances formed from C, H, and O 1:2:1 ratio glucose is C6H12O6 Main function is source of energy Can also function as energy storage and structural molecules 20 2. Lipids Formed from C, H and O 20 2. Lipids Formed from C, H and O 1:2: less than 1. Less oxygen atoms per molecule includes triglycerides, phospholipids, steroids… Different lipids have different structures and different functions Unifying theme: Hydrophobicity! 21 Diversity of Lipids: Triglycerides Triglycerides are composed of glycerol attached to three fatty acids Triglycerides are great source of energy as dietary fats or oils 22 Fatty Acid Shapes The level of saturation of a fatty acid affects its shape. (a)Saturated fatty acid chains are straight. (b)Unsaturated fatty acid chains are kinked. 23 Fats and Health A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits Atherosclerosis Impedes blood circulation 24 What are trans fats and why are they bad for us? 25 Hydrogenation the process of converting unsaturated fats to saturated fats by adding hydrogen Partial Hydrogenation also creates unsaturated fats with trans double bonds These trans fats may contribute more than saturated fats to cardiovascular disease 26 25 These trans fats may contribute more than saturated fats to cardiovascular disease 26 3. Proteins Contain carbon, hydrogen, oxygen, and nitrogen Can perform multiple activities in the cell! Constructed from combinations of 20 amino acids. amino acids joined by a covalent bond called a peptide bond 27 28 Functions of Proteins 29 4. Nucleic Acids Huge molecules containing C, H, O, N and phosphorus Made of monomers called Nucleotides Primary function is “Information” 30 A molecule of DNA is two chains of nucleotidesà “Double Helix” two strands attach via hydrogen bonds between the bases of the complimentary nucleotides. 31 DNA: Genetic Code 32 DNA Code DNA Code is a triplet code 3 nucleotidesà code for 1 amino acid Each gene of our genetic material is a piece of DNA that controls the synthesis of a specific protein 33  33 RNA Structure Differs from DNA single stranded ribose sugar not deoxyribose sugar uracil nitrogenous base replaces thymine Types of RNA within the cell, each with a specific function messenger RNA ribosomal RNA transfer RNA 34 RNA functions DNA has the code RNA copies the code and translates the code 35 Genetic Code is Universal