Lecture 2: Chemistry of Life Flashcards
When are the earliest chemical signatures of life on Earth?
About 4 billion years old.
What was critical in making conditions suitable for life on Earth?
The presence of water, possibly brought by comets.
What is the basic unit of matter?
Atom.
What are the primary components of an atom?
-Proton
-Electron
-Neutron
What is the atomic number of an element?
The number of protons in that atom.
What is the atomic mass of an atom?
The sum of protons and neutrons.
What are isotopes?
Atoms of the same element that have different atomic weights.
What is an electron’s orbital?
The region in which an electron travels.
How many electrons can occupy the first orbital?
2 electrons at most.
How many electrons can occupy every other orbital?
8 electrons at most.
What is a molecule?
Two or more atoms bonded together.
What is a chemical bond?
An attractive force that links two atoms together.
What is a covalent bond?
A bond formed by sharing a pair of electrons between two atoms.
What are compounds?
Molecules made up of more than one type of atom.
What does molecular weight represent?
The sum of all atoms in the molecule.
What type of bond is the strongest?
Covalent bond.
What is electronegativity?
The attractive force that an atom exerts on electrons.
What causes a polar covalent bond?
Unequal sharing of electrons between atoms with different electronegativities.
What are polar molecules?
Molecules that have polar covalent bonds.
What are hydrogen bonds?
Weak attractions that may form within or between molecules with polar covalent bonds.
What are ionic bonds?
Bonds formed by complete transfer of one or more electrons.
What are cations?
Positively charged ions.
What are anions?
Negatively charged ions.
What happens to ionic bonds when salt is introduced into water?
The partial charges of water molecules interfere with the ionic bonds.
What does hydrophilic mean?
Polar molecules that tend to dissolve in water.
What are hydrophobic molecules?
Nonpolar molecules that tend to aggregate with other nonpolar molecules.
What are van der Waals forces?
Weak attractions between nonpolar molecules.
What unusual property does water have when it freezes?
Ice is less dense than liquid water.
What is cohesive strength in water?
The resistance of water molecules to come apart from one another.
What is surface tension?
The difficulty of puncturing the surface of liquid water due to cohesive strength.
What is a solution?
A substance (solute) dissolved in a liquid (solvent).
What are acids?
Substances that dissolve in water and release hydrogen ions (H+).
What are bases?
Substances that dissolve in water and release hydroxide ions (OH–).
What is the pH scale?
A measure of hydrogen ion concentration ranging from 0 to 14.
What is the significance of a pH of 7?
It means the concentration of hydrogen ions is 1 x 10–7 moles per liter of water.
What are functional groups?
Specific groups of atoms that give particular properties to molecules.
What are isomers?
Molecules with the same chemical formula but different structural formulas.
What are structural isomers?
Isomers that differ in how atoms are joined together.
What are optical isomers?
Structural isomers that are mirror images of each other.
What are the properties of a Carboxyl Group?
Acidic ionizes in living tissues to form COO- and H+ . Enters in dehydration synthesis by giving up -OH.
What are the properties of an Amino group?
Basic. Accepts H+ in living tissues to form -NH3+. Enters in dehydration synthesis by giving up H+.
What are the properties of a Sulfhydryl group?
By giving up H, two -SH groups can react to form a disulphide bridge, thus stabilizing protein structure.
