Week 1 (1.3 and 1.4) Flashcards
What is a molecule?
Group of 2 or more atoms attached together that act as a single unit; in forming a molecule, individual atoms interact through a “chemical bond”
What is a valence electron?
Electrons that are farthest from the nucleus (those in the outermost orbitals of an atom, highest energy level of an atom)
- These are the ones being shared in chemical bonds
What is a polar covalent bond?
Unequal sharing of electrons
→ Results from a difference in the ability of atoms to attract electrons → “electronegativity”
Electronegativity: increase across a row in the periodic table, as the # protons increases (negative e are held more tightly to the nucleus)
What is a nonpolar covalent bond?
Covalent bond where the atoms have the same electronegativity → atoms share the bonding electron pair almost equally
→ gaseous H, O, C-C, and C-H
→ non water soluble
What is an ionic bond?
→ When an atom of very high electronegativity is paired with another with a very low electronegativity, due to the difference in electronegativity the atom with higher electronegativity steals electron from the less electronegative
Result: atom with extra electron has a negative charge → negative ion (anion); atom that lost an electron has a positive charge → positive ion (cation)
Ions are NOT covalently bound, but opposite charges attract so they associate
Ex. sodium chloride and water (NaCl separates and the corresponding charged portions of a water molecule will be attracted to the corresponding ion)
What is a chemical reaction?
Chemical reactions: process by which atoms or molecules (reactants) are transformed into different molecules (products)
→ In a chemical reaction atoms keep their identity but change which atoms they are bonded to
Ex. 2 molecules of H gas (2H2) and one molecule of O gas (O2) can react to form 2 water molecules (2H2O) → number of each type of atoms are conserved, but their arrangement is different in the reactants and products
H-H bonds and O=O bonds are broken
Each O atom forms are covalent bonds with 2 H atoms
→ Provide a way to build and break down molecules + way to harness energy (held in chemical bonds)
What is the difference between hydrophilic and hydrophobic?
Hydrophilic (polar; water-loving or water soluble) and hydrophobic (nonpolar; water-fearing or non water soluble)
Hydrophilic compounds can be broken down into a solution in an aqueous environment
Hydrophobic compounds are nonpolar arrange themselves to minimize their contact with water (drives folding of proteins and formation of cell membranes)
→ Polar molecules are broken down into by water (negative side of water attracted to positive charge and vice versa), while non polar molecules can’t interact with a charged molecule like water since they have no charge for water to be attracted to
What are some properties of water?
- Density
Ice: most water molecules bond to 4 other water molecules through H bonds → form a crystalline structure
Liquid water: as temperature increases some H bonds are destabilized and break, allow water molecules to pack more closely, causing it to be more dense - Cohesion: tend to stick to one another
Consequence is high surface tension
What is pH and what are the 3 conditions it creates?
→ In any solution of water: small proportion exists as protons (H+) and hydroxide ions (OH-). pH measures for the concentration of H+
pH influences many chemical reactions and biological processes → pH=-log(H+)
Range from 0-14 → since it is logarithmic one pH unit corresponds to a tenfold difference in H concentration
Neutral: pH is 7 when the concentration of protons (H+) and hydroxide ions (OH-) are equal
Acidic: pH lower than 7 and the concentration of protons is higher than hydroxide ions
Molecule that releases protons
Basic: pH higher than 7 and the concentration of protons is higher than that of hydroxide ions
Molecule that accepts a proton in aqueous solution
What are the 4 main macromolecules essential for life?
Protein, nucleic acid, lipids, and carbohydrates
How does the physiological pH inside a cell affect the chemical structure of an amino acid?
In a cell about 7.4 → amino and carboxyl groups are ionized due to interaction with the medium
Amino group gains a proton and carboxyl loses a proton
What are the monomers of the 4 macromolecules of interest? What are they composed of? What kind of bond forms the polymers of each macromolecule?
What are the 2 types of fatty acids?
Saturated: fatty acids that don’t contain double bonds
No double bonds = max. number of H atoms is attached to each C so all of them are saturated with H atoms
Straight
Unsaturated: contain C-C double bonds → have a kink at each double bond
How are hydrocarbon chains held together and what does melting point is dependent on?
Due to VDW melting point depend on their length and level of saturation
Increase length of hydrocarbon → VDW increases as well = melting is higher
Kinks (due to double bonds) reduce tightness of molecular packing → reduce intermolecular interactions as well = melting is lower
What is different about lipids?
→ Don’t follow usual monomer-to-polymer type of synthesis
→ All are hydrophobic (non-polar) and tend to almost lack completely of functional groups
→ Cells don’t look at lipids by their directionality and polarity
