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Chemistry Of Cells Chemistry • Science that studies the elements, their compounds, the chemical reactions that occur between them and the molecular structure of all matter Matter • Anything that takes up space and has mass • Everything we touch is matter • Three forms – Solid – Liquid – Gas Elements • Substances that can’t be broken down into another substance by ordinary chemical means • All matter, living and non-living composed of elements • 92% naturally occurring elements – Differ by properties Our Elements • Six elements special to us – C- carbon – H- hydrogen – N- nitrogen – O- oxygen – P- phosphorus – S- sulfur • Make up 98% of our body weight Atomic Theory • Elements consist of tiny particles called atoms- smallest particle of an element that displays the properties of the element Atomic Structure • Three types of subatomic particles – Neutrons- no electrical charge – Protons- positive charge – Electrons- negatively charge • Nucleus- center of the atom – Protons and neutrons located within – Electrons (e-) move about nucleus Periodic Table • Developed as a way to display elements according to their characteristics Understanding Chemical Bonds • Atoms most stable when outer shell is full • Octet rule- outer shell containing 8 electrons Compounds • Substance composed of atoms of two or more elements that are chemically combined – Example: NaCl (table salt) • Compounds form when elements try to comply to the octet rule Types of Bonds • Ionic- forms when 2 atoms are held together by attraction between opposite charges – Ions- charged atoms – Often form salts • Example: Na+ Cl- Types of Bonds • Covalent- two atoms share electrons in order to have completed outer shell – Example: oxygen gas (O2) • Molecule- group of atoms held together by covalent bonds Bonds • Single bond- when two atoms share a single electron • Double bond- when each atom shares two electrons • Triple bond- when each atom shares three electrons Chemical Reactions • Occur when bonds are formed or broken causing substances to recombine into different substances • Metabolism- all chemical reactions occurring in the cells of organisms • Written as follows: Mixtures and solutions • Mixture- combination of substances in which individual components retain their own properties – Example: mixing sand and sugar • Solution- mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent) – Example: adding sugar to ice tea Acids and Bases • Acids- substances that dissociate in water – Release hydrogen ions (H+) – Example: HCl-hydrochloric acid (stomach) • Base- substances that take up hydrogen (H+) ions or release hydroxide (OH-) ions – Example: NaOH- sodium hydroxide pH and Its Scale • pH- way of indicating the number of hydrogen ions in solutions • pH scale- used to indicate acidity or basicity of solutions – Ranges from 0 to 14 – 7 is neutral – pH < 7= acid – pH > 7= base • Buffer- chemical that keeps pH within normal limits (example- Tums and Rolaids) Water’s Importance to Life • Life began in water • Single most important molecule on Earth • Cells are 60-80% water • Polar molecule- molecule with an unequal distribution of charge – Each molecule has a positive end and negative end • Unique properties Another Type of Bond • Hydrogen (H)- weak bond, arises between slightly positive hydrogen atom of one molecule and slightly negative atoms of another molecule – Example: H2O – Water molecules attract other water molecules Properties of Water • Because of H-bonds – Can engage in 4 H-bonds • Properties – Solvency – Cohesion and adhesion – High surface tension – High heat capacity – High heat of vaporization Life Substances • Carbon has 4 electrons available for bonding – To be stable it forms 4 covalent bonds – Can bond with other carbons or with many other elements – Form straight chains, branched chains, or rings – Can have almost any number of carbons – Can form different structure (shapes) • Isomer- compounds with same chemical formula but different 3-d structures Carbohydrates • Biomolecule composed of carbon, hydrogen and oxygen (1:2:1 ratio) • Monosaccharide- simplest type of carb (sugar) – Glucose and fructose • Disaccharide- combining of two monosaccharides – Glucose and fructose link together to form sucrose Carbohydrate cont’d • Polysaccharide- largest, composed of many monosaccharides – Starch- branched, energy storage – Glycogen- highly branched, stores energy in liver – Cellulose- long chains (like chain link fenece), forms cell walls of plants and gives them support Carbohydrates cont’d • Five- and six-carbon simple sugars are smallest – Five-carbon: deoxyribose and ribose – Six-carbon: glucose and fructose • Functions: energy storage and cell structure Lipids • Insoluble in water • 95% of fats in body are triacylglycerols • Saturated fat: fatty acids have single covalent bonds • Unsaturated fat: fatty acids have one or more double covalent bonds • Functions: energy, insulation and protection Proteins • Contain carbon, oxygen, hydrogen, nitrogen and sulfur • Amino acids are building blocks of proteins • Functions: energy and structure • Enzymes: protein catalysts for chemical reactions Proteins • Structure – Primary: amino acid sequence – Secondary: determined by hydrogen bonds – Tertiary: folding caused by interactions within peptide bonds and sulfur atoms – Quaternary: determined by spatial relationships between units Nucleic Acids • Deoxyribonucleic acid: genetic material of the cell (DNA) • Ribonucleic acid: protein synthesis – Messenger RNA – Transfer RNA • Structure – DNA: double helical chain – RNA: single chain Nucleic Acids • Nucleic acids are made up of chains of nucleotides – Nucleotide: nitrogen base, sugar and phosphate group – Nitrogen bases: purines (two) and pyrimidines (three) Adenosine Triphosphate • ATP • Fuel for cell function and maintenance • Molecule consists of sugar, adenine, and three phosphates – Energy is stored in the second and third phosphates • Breakdown of glucose provides energy to make ATP Enzyme • Protein that changes rate of chemical reactions • Involved in nearly all metabolic processes – Speed reactions in digestion of food • Activities of enzymes depend on temp, ionic conditions, and pH of surroundings