Chapter 2 - The Molecules of Life Flashcards
(28 cards)
What is the structure of an atom?
An atom is made up of neutrons, protons, and electrons. The neutrons and protons form a nucleus.
Distinguish between an element and a compound.
An element is a pure substance that cannot be broken down further.
A compound is a substance formed when two or more elements mare chemically bonded together.
What are the six elements that make up 96-98% of living matter?
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur.
Define trace element and give examples.
Trace elements are elements that an organism needs very small quantities of to survive. Examples are zinc, manganese, and iodine.
What are the bonds formed within molecules?
Covalent bonds and ionic bonds.
What are the bonds formed between molecules?
Hydrogen bonds, hydrophobic interactions, and van der Waals interactions.
What is a covalent bond?
A covalent bond is a chemical bond formed by a shared pair of electrons holding two different atoms together.
What is a polar covalent bond?
A polar covalent bond is a chemical bond formed by unequal sharing of electrons between two atoms.
What is an ionic bond?
An ionic bond is the bonding of two atoms resulting from the attraction of opposite charges.
Explain why strong covalent bonds and weak bonds are essential in living organisms.
Covalent bonds link atoms to form a cell’s molecules while weak bonds can be broken down and put together easily. An example is DNA: the phosphodiester bonds form the backbones of the strands and the hydrogen bonds hold the two strands together. However, the hydrogen bonds can be unzipped easily for duplication.
What is a hydrogen bond?
A hydrogen bond is when a hydrogen atom covalently bound to an electronegative atom interacts with an electronegative atom of another molecule. An example is hydrogen bonding in water.
What is a hydrophobic interaction?
A hydrophobic interaction is an interaction of nonpolar substances and polar substances. An example is oil and water.
What is a van der Waals interaction?
A van der Waals interaction is the interaction of electrons of nonpolar substances.
Give an example that illustrates how a molecule’s shape can determine its biological function.
A phospholipid is made up of a phosphate head and a fatty acid tail. The phosphate head is hydrophillic while the fatty acid tail is hydrophobic. The phospholipid bilayer makes up the cell membrane and helps to control what goes in and out of a cell. Another example is DNA.
Why are water molecules (a) polar and (b) capable of hydrogen bonds?
Water molecules are formed by a covalent bond. Oxygen is much larger than hydrogen, so the electrons are more attracted to them. This results in a positive charge on the oxygen end and a negative charge on the hydrogen end, making the molecule polar. This is also why water molecules are capable of hydrogen bonds since hydrogen is positively charged.
List 5 properties of water that are emergent properties resulting from hydrogen bonding.
- Cohesion and adhesion
- Moderation of temperature
- Insulation
- Excellent solvent
- Weak acid
Distinguish among a solute, a solvent, and a solution.
A solute is the dissolved substance in a solution.
A solvent is the major component in a solution.
A solution is a homogeneous mixture containing particles the size of a typical ion or covalent molecule.
Distinguish between hydrophobic and hydrophilic substances.
A hydrophobic substance is a nonpolar substance that is insoluble in water and is “water fearing” or “water repelling”. A hydrophilic substance is “water loving” and is soluble in water (can be dissolved into ions).
Define acid, base, and pH.
An acid is a substance that provides H+ ions in water.
A base is a substance that provides OH- ions in water.
pH is the concentration of H+ ions in water.
–> pH = -log[H+], where [H+] is the concentration of protons
Explain how carbon’s electron configuration accounts for its ability to form large, complex, and diverse organic molecules.
Carbon has four valence electrons, which allow the formation of 4 covalent bonds with a variety of atoms to stabilize it. This versatility leads to the diversity of organic molecules.
Name the major functional groups found in organic molecules.
- Hydroxyl group (OH)
- Carbonyl group (CO)
- Carboxyl group (COOH)
- Amino group (NH2)
- Sulfhydryl group (SH)
- Phosphate group (OPO3)2-
- Methyl group (CH3)
List the four major classes of macromolecules.
Proteins, nucleic acids, carbohydrates, and lipids.
Identify the monomers for proteins, nucleic acids, and carbohydrates.
Proteins – amino acids
Nucleic acids – nucleotides
Carbohydrates – monosaccharides
Why are lipids not considered true polymers like the other macromolecules?
Their monomer units, fatty acids, are not linked by covalent bonds.
