Test Guide Unit 1 Biochemistry

Unit 1: Biochemistry Structure of Atoms ❖ Atoms are made of: ➢ protons: positive charge, mass = 1 amu, located in nucleus ➢ neutrons: neutral charge, mass = 1 amu, located in nucleus ➢ electrons: negative charge, mass = 0 amu, located outside nucleus ❖ Electrons can move from lower level of energy to higher level of energy (or excited state) by absorbing energy ➢ ground state - lowest level of energy ❖ isotopes - atoms of same element that have different # of neutrons ➢ radioisotopes - radioactive isotopes that decay with a half-life; used for medical diagnosis (tracer), research, and carbon dating Types of Bonds ❖ bond - when the same electron (or electrons) is attracted by the nuclei of 2 atoms to become stable ➢ To break one, energy is absorbed. To create one, energy is released. ❖ ionic bonds: electrons transferred; one atom (anion) gains electron(s) and the other (cation) loses electron(s) ➢ Examples: anion: Cl- , F-; cations: Na+, Ca2+ ❖ covalent bonds: electrons shared and a molecule is formed ➢ 2 types of covalent bonds: ■ nonpolar covalent bond - electrons are shared equally between 2 alike atoms (ex. H2 and O2) ■ polar covalent bond - electrons are shared unequally between 2 different atoms (ex. CO and H2O) ❖ intermolecular attractions: occur between molecules; Some are: ➢ polar-polar attraction - occur between polar molecules, which have stronger attractions towards each other ■ − end of polar molecule attracts + end of other polar molecule (ex. H2O) ➢ hydrogen bonding - important to life because: ■ attaches 2 strands of DNA double helix together ■ causes water molecules to stick to each other, allowing for a variety of special characteristics ■ HF4 is an example ➢ nonpolar molecules - weakest attractions (van der Waals), CO2 is an example Hydrophobic & Hydrophilic ❖ hydrophobic - “water hating” ❖ hydrophilic - “water loving” ❖ Polar substances dissolve in water, nonpolar substances do not ➢ Ex. Plasma membrane is nonpolar so it only lets nonpolar substances diffuse easily, not large polar molecules Special Properties of Water ❖ High specific heat: lots of heat needed to change water temperature, which creates stable ocean + coastal temperatures ❖ High heat of vaporization: lots of heat needed to evaporate water (ex. Sweat cools body efficiently) ❖ Adhesion: water sticks to other substances; allows for capillary action (water goes from roots → leaves) in plants ❖ Cohesion tension: water molecules stick to each other; allows for surface tension + transpirational-pull cohesion tension (water goes from roots → leaves of tree without energy) ❖ Universal solvent: water is very polar so it can dissolve other polar/ionic substances ❖ Ice = less dense than water: floating ice insulates water in winter and brings nutrients to surface in spring when ice melts pH ❖ pH: used to measure how acidic or alkaline/basic a solution is; pH < 7 is acidic, pH > 7 is alkaline, pH = 7 is neutral ➢ *is negative logarithm of H+ ions in moles/liter ➢ As H+ concentration increases, pH decreases. ❖ Living cells maintain homeostasis; pH of ~7 ➢ They use buffers to regulate pH (ex. bicarbonate ion in human blood) Organic Compounds ❖ Compounds that contain carbon; the types of organic compounds are: ❖ Carbohydrates ➢ Made of C, H, O (carbon, hydrogen, oxygen) ➢ Used for quick energy ➢ 1 gram of carb = 4 calories of heat ➢ 3 types of carbs: ■ monosaccharides (CnH2nOn) - glucose, galactose, fructose, etc. ■ disaccharides (C12H22O12) - made of 2 monosaccharides that are bonded through dehydration synthesis/condensation; can be broken down through hydrolysis ● dehydration synthesis produces water; hydrolysis requires water ● Disaccharide examples: sucrose, lactose, maltose ■ polysaccharides - polymer made of many monosaccharides ● Plant polysaccharides: ◆ Cellulose - makes up cell walls in plants ◆ Starch - how plants store carbs ● Animal polysaccharides: ◆ Chitin - makes up exoskeletons/mushroom cell walls ◆ Glycogen - animal starch (stored in liver + skeletal muscle for humans) ❖ Lipids ➢ Examples: fats, oils, waxes ➢ Usually made up of 1 glycerol (an alcohol) + 3 fatty acids ➢ Fats: hydrocarbon chain + carboxyl group at one end ■ Saturated fats ● Usually from animals & solid at room temp (ex. butter) ● Only have single bonds between carbons ■ Unsaturated fats ● From plants & liquid at room temp (ex. oil) ● Have ≥1 double bond between carbons, meaning less hydrogens ➢ Some functions of lipids are: ■ Storing energy - 1 gram of lipid = 9 calories of heat ■ Structure - phospholipids make up cell membrane ■ Endocrine system - certain lipids act as hormones ❖ Proteins ➢ Polymers (polypeptides) made of amino acids joined by peptide bonds ■ Ex. enzymes ➢ Amino acids - carboxyl group, amine group, and variable (R) all bonded to one carbon in the center ■ There are 20 different types of amino acids; each amino acid is unique due to its R group ➢ Necessary for growth + repair ➢ Made of sulfur, phosphorus, carbon, oxygen, hydrogen, nitrogen (CHNOPS) ➢ 1 gram of protein = 4 calories of heat ➢ 2 amino acids make up a dipeptide ➢ Protein structure ■ Protein function depends on its shape/structure ■ primary structure - amino acid sequence ■ secondary structure - double helix or beta sheets that happen due to hydrogen bonding ■ tertiary structure - directly influences specific 3D shape and function of a protein ■ quaternary structure - more than 1 polypeptide chain present ➢ Enzymes ■ Large proteins that lower the energy of activation (Ea), which speeds up reactions ■ Only react with specific chemicals (substrates) and can be reused ■ Change shape a bit to let the substrate bind (induced-fit model) ■ Can become more/less efficient due to pH or temperature ➢ Prions ■ Misfolded proteins are infectious and make other proteins to misfold, causing brain diseases (ex. mad cow disease) ❖ Nucleic acids ➢ Polymers that contain genetic information that is inherited ➢ DNA and RNA ➢ Made up of nucleotides, which are made of a phosphate group, 5-carbon sugar (deoxyribose/ribose), and nitrogenous base ➢ DNA bases: adenine, cytosine, guanine, thymine ➢ RNA bases: adenine, cytosine, guanine, uracil ➢ Adenine {RNA+DNA} & guanine {RNA+DNA} = purines ➢ Cytosine {RNA+DNA}, thymine {only found in DNA}, uracil {only found in RNA} = pyrimidines