Flashcards in Chapter 2: The Molecules of Life Deck (86)
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elements
a pure substance, such as oxygen, copper, gold, and sodium, that cannot be broken down by the methods of chemistry
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atom
the basic unit of matter
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nucleus (of an atom)
the dense central part of an atom containing protons and neutrons
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protons
positively charged particles
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neutron
electrically neutral particles
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electron
negatively charged particles that move around the atomic nucleus
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the # of protons determines the _____ which specifics the atom as a particular _______
atomic number; element
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atomic mass
the mass of the atom, determined by the protons and neutrons (electrons have negligible mass)
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isotopes
atoms of the same element that have different numbers of neutrons (different mass)
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ions
electrically charged atoms (# of protons and electrons not balanced)
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orbital
a region of space where an electron is present most of the time
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shell
energy levels of various orbitals (electrons in orbit close to the nucleus have less energy than electrons in orbitals farther away)
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what is the max number of electrons in one orbital?
2
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periodic table of elements
tabular form of the arranged chemical elements
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molecules
groups of two or more atoms attached together that act as a single unit
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chemical bond
a form of attraction between atoms that holds them together (what holds a molecule together)
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valence electrons
electrons in the outermost orbitals of an atom, at the highest energy level (determines atom's ability to combine with other atoms)
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molecular orbital
a merged orbital traversed by a pari of shared electrons
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covalent bond
a chemical bond formed by a shared pair of electrons holding two different atoms together
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double bond
when two adjacent atoms share two pairs of electrons
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electronegativity
the ability of atoms to attract electrons
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polar covalent bond
a bond between two atoms where the electrons are shared unequally
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nonpolar covalent bond
a covalent bond between atoms that have the same or nearly the same electronegativity (electrons shared almost equally)
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ionic bond
a bond between two oppositely charged atoms in which the atom with higher electronegativity "steals" the electron
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chemical reaction
the process by which molecules are transformed into different molecules
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reactants
any of the starting molecules in a chemical reaction
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products
any one of the transformed molecules that result from a chemical reaction
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polar (molecule)
a molecule with regions of positive and negative charge
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hydrophilic
"water loving"
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hydrophobic
"water fearing"
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solvent
a liquid capable of dissolving a substance
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aqueous
water-solution in water
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nonpolar
does not have regions of positive and negative charge; associate with HYDROPHOBIC
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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
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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)
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cohesion
attraction between molecules; one consequence of cohesion is high surface tension
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acidic
describes a solution in which the concentration of protons is higher than that of hydroxide ions (the pH is lower than 7)
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basic
describes a solution in which the concentration of protons is lower than that of hydroxide ions (the pH is higher than 7)
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organic molecules
a carbon-containing molecule
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isomers
molecules that have the same chemical formula but different structures
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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."
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nucleic acids
a polymer of nucleotides that encodes and transmits genetic information
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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
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lipids
an organic molecule that stores energy, acts as a signalling molecule and is a component of cell membranes
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polymer
complex molecules made up of repeated simpler units connected by covalent bonds
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proteins are polymers of:
amino acids
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nucleic acids are polymers of:
nucleotides
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carbohydrates are polymers of:
simple sugars
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instead of being defined by chemical structure, lipids are defined by:
property
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the lipid membranes that define cell boundaries consist of:
fatty acids bonded to other organic molecules
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functional groups
groups of one or more atoms that have particular chemical properties of their own, regardless of what they are attached to
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enzymes
catalysts that accelerates the rates of chemical reactions
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each amino acid consists of:
alpha carbon, amino group (-NH2), carboxyl group (-COOH), a hydrogen atom, R group of side chain
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at pH in a cell (7.4), what happens to the amino acid?
amino and carboxyl groups are ionized or charged (-NH3+) and (-COO-)
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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)
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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.
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ribonucleic acid (RNA)
key player in protein synthesis and regulation of gene expression
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nucleotides consist of:
5-carbon sugar, nitrogen containing base, one or more phosphate groups
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bases built from nitrogen containing two types of rings:
pyrimidine (single ring structure) or purines (double ring structure)
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what are the pyrimidines?
cytosine (C), thymine (T) - DNA, uracil (U) - RNA
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what are the purine?
guanine (G), adenine (A)
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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
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double helix
structure of DNA, two strands of nucleotides twisted around each other
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what are the complementary base pairs of purine-pyrimidine pairs?
A-T, G-C
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complementary base pairs results from...?
hydrogen bonds between bases
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carbohydrates
distinctive molecules composed of C, H, O atoms usually in a ratio of 1:2:1, provides principal source of energy for metabolism
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simplest carbohydrates are sugars (AKA saccharides), examples are:
glucose (product of photosynthesis), galactose (dairy products), and fructose (commercial sweeteners)
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monosaccharide
simple sugar
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disaccharide
two simple sugars linked together by a covalent bond
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polysaccharides
polymers of simple sugars that provide long-term energy storage (starch or glycogen) or structural support (cellulose in plant walls)
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complex carbohydrates
long, branched chains of monosaccharides
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monosaccharides with aldehyde group (HC=O) are called
aldoses (ex. glucose, galactose)
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monosaccharides with ketone group (C=O) are called
ketoses (ex. fructose)
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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
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ALL LIPIDS ARE....
HYDROPHOBIC, but they are chemically diverse
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triacylglyceral
lipids used for energy storage, major component of animal fat and vegetable oil
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what is a fatty acid?
a long chain of carbon atoms attached to a carboxyl group (-COOH) at one end
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glycerol
3-carbon molecule with OH groups attached to each carbon
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phospholipid
a type of lipid and an important component of cell membranes
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fatty acids differ in....
length of their hydrocarbon chain
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saturated fatty acids are:
fatty acids that do not contain double bonds (all atoms "saturated" with hydrogen atoms) ex. animal oils
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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
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fatty acid molecules are:
unpolar, uncharged, and HYDROPHOBIC (although motion of electrons can lead to a slight charge)
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van der Waals force
attraction of opposite charges (weak), atom must be close, an intermolecular force
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melting point of fatty acids depend on :
their length and saturation
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