Chapter 2: The Molecules of Life Flashcards
elements
a pure substance, such as oxygen, copper, gold, and sodium, that cannot be broken down by the methods of chemistry
atom
the basic unit of matter
nucleus (of an atom)
the dense central part of an atom containing protons and neutrons
protons
positively charged particles
neutron
electrically neutral particles
electron
negatively charged particles that move around the atomic nucleus
the # of protons determines the _____ which specifics the atom as a particular _______
atomic number; element
atomic mass
the mass of the atom, determined by the protons and neutrons (electrons have negligible mass)
isotopes
atoms of the same element that have different numbers of neutrons (different mass)
ions
electrically charged atoms (# of protons and electrons not balanced)
orbital
a region of space where an electron is present most of the time
shell
energy levels of various orbitals (electrons in orbit close to the nucleus have less energy than electrons in orbitals farther away)
what is the max number of electrons in one orbital?
2
periodic table of elements
tabular form of the arranged chemical elements
molecules
groups of two or more atoms attached together that act as a single unit
chemical bond
a form of attraction between atoms that holds them together (what holds a molecule together)
valence electrons
electrons in the outermost orbitals of an atom, at the highest energy level (determines atom’s ability to combine with other atoms)
molecular orbital
a merged orbital traversed by a pari of shared electrons
covalent bond
a chemical bond formed by a shared pair of electrons holding two different atoms together
double bond
when two adjacent atoms share two pairs of electrons
electronegativity
the ability of atoms to attract electrons
polar covalent bond
a bond between two atoms where the electrons are shared unequally
nonpolar covalent bond
a covalent bond between atoms that have the same or nearly the same electronegativity (electrons shared almost equally)
ionic bond
a bond between two oppositely charged atoms in which the atom with higher electronegativity “steals” the electron
chemical reaction
the process by which molecules are transformed into different molecules
reactants
any of the starting molecules in a chemical reaction
products
any one of the transformed molecules that result from a chemical reaction
polar (molecule)
a molecule with regions of positive and negative charge
hydrophilic
“water loving”
hydrophobic
“water fearing”
solvent
a liquid capable of dissolving a substance
aqueous
water-solution in water
nonpolar
does not have regions of positive and negative charge; associate with HYDROPHOBIC
hydrophobic effect
the exclusion of non polar molecules by polar molecules, which drives biological processes such as the formation of cell membranes and the folding of proteins
hydrogen bond
interaction between a hydrogen atom with a slight positive charge and an electronegative atom of another molecule (depicted by a dotted line, much weaker than covalent bonds)
cohesion
attraction between molecules; one consequence of cohesion is high surface tension
acidic
describes a solution in which the concentration of protons is higher than that of hydroxide ions (the pH is lower than 7)
basic
describes a solution in which the concentration of protons is lower than that of hydroxide ions (the pH is higher than 7)
organic molecules
a carbon-containing molecule
isomers
molecules that have the same chemical formula but different structures
proteins
the key, structural, and functional molecules that do the work of the cell, providing structural support and catalyzing chemical reactions. the term “protein” is often used as a synonym for “polypeptide.”
nucleic acids
a polymer of nucleotides that encodes and transmits genetic information
carbohydrates
an organic molecule containing C, H, and O atoms that provides a source of energy for metabolism and that forms the starting point for the synthesis of all other organic molecules. makes up the cell wall in bacteria, plants, and algae
lipids
an organic molecule that stores energy, acts as a signalling molecule and is a component of cell membranes
polymer
complex molecules made up of repeated simpler units connected by covalent bonds
proteins are polymers of:
amino acids
nucleic acids are polymers of:
nucleotides
carbohydrates are polymers of:
simple sugars
instead of being defined by chemical structure, lipids are defined by:
property
the lipid membranes that define cell boundaries consist of:
fatty acids bonded to other organic molecules
functional groups
groups of one or more atoms that have particular chemical properties of their own, regardless of what they are attached to
enzymes
catalysts that accelerates the rates of chemical reactions
each amino acid consists of:
alpha carbon, amino group (-NH2), carboxyl group (-COOH), a hydrogen atom, R group of side chain
at pH in a cell (7.4), what happens to the amino acid?
amino and carboxyl groups are ionized or charged (-NH3+) and (-COO-)
peptide bond
covalent bond where carbon atom in the carboxyl group of one amino acid is joined to the nitrogen atom in the amino group of the next, link amino acids in a chain to form a protein (a water molecule is lost for each bond)
deoxyribonucleic acid (DNA)
genetic material in all organisms. transmitted from parents to offspring. contains information needed to specify the amino acid sequence of all proteins synthesized in an organism.
ribonucleic acid (RNA)
key player in protein synthesis and regulation of gene expression
nucleotides consist of:
5-carbon sugar, nitrogen containing base, one or more phosphate groups
bases built from nitrogen containing two types of rings:
pyrimidine (single ring structure) or purines (double ring structure)
what are the pyrimidines?
cytosine (C), thymine (T) - DNA, uracil (U) - RNA
what are the purine?
guanine (G), adenine (A)
phosphodiester bond
bond between nucleotides, forms when a phosphate group in one nucleotide is covalently joined to the sugar unit in another nucleotide-forms the backbone of the DNA strand - involves a loss of a water molecule
double helix
structure of DNA, two strands of nucleotides twisted around each other
what are the complementary base pairs of purine-pyrimidine pairs?
A-T, G-C
complementary base pairs results from…?
hydrogen bonds between bases
carbohydrates
distinctive molecules composed of C, H, O atoms usually in a ratio of 1:2:1, provides principal source of energy for metabolism
simplest carbohydrates are sugars (AKA saccharides), examples are:
glucose (product of photosynthesis), galactose (dairy products), and fructose (commercial sweeteners)
monosaccharide
simple sugar
disaccharide
two simple sugars linked together by a covalent bond
polysaccharides
polymers of simple sugars that provide long-term energy storage (starch or glycogen) or structural support (cellulose in plant walls)
complex carbohydrates
long, branched chains of monosaccharides
monosaccharides with aldehyde group (HC=O) are called
aldoses (ex. glucose, galactose)
monosaccharides with ketone group (C=O) are called
ketoses (ex. fructose)
glycosidic bonds
covalent bonds attaching monosaccharides; involves loss of a water molecule. formed between carbon one of one monosaccharide and a hydroxyl group carried by an atom in a different monosaccharide molecule
ALL LIPIDS ARE….
HYDROPHOBIC, but they are chemically diverse
triacylglyceral
lipids used for energy storage, major component of animal fat and vegetable oil
what is a fatty acid?
a long chain of carbon atoms attached to a carboxyl group (-COOH) at one end
glycerol
3-carbon molecule with OH groups attached to each carbon
phospholipid
a type of lipid and an important component of cell membranes
fatty acids differ in….
length of their hydrocarbon chain
saturated fatty acids are:
fatty acids that do not contain double bonds (all atoms “saturated” with hydrogen atoms) ex. animal oils
unsaturated fatty acids are:
fatty acids that contain carbon-carbon double bonds (“kink” occurs in chain where double bond occurs, weaker bonds, lower melting/boiling points) ex. plant oils
fatty acid molecules are:
unpolar, uncharged, and HYDROPHOBIC (although motion of electrons can lead to a slight charge)
van der Waals force
attraction of opposite charges (weak), atom must be close, an intermolecular force
melting point of fatty acids depend on :
their length and saturation
steroid
a type of lipid (ex. cholesterol) that is involved in the synthesis of steroid hormones and is a component of animal cell membranes
