Biologically Important Molecules Flashcards
what are the four biologically important classes of molecules?
protein, carbohydrate, fat, nucleic acid
what makes the polypeptide chain unique and functional?
the sequence and composition of amino acids
what does the structure of an amino acid consist of?
variable R group, carboxyl group (COOH), tetrahedral alpha carbon (central carbon), amino group (NH2)
side chain (variable R group)
the unique feature of each amino acid that provides distinct physical and chemical properties
peptide bond
covalent bond that links amino acids together into polypeptide chains
disulfide bridges
covalent bond between cysteine R groups
how are peptide bonds formed?
reaction between carboxyl group of one amino acid with amino group of another amino acid, loss of water
backbone of amino acid
NCCNCC
what is the beginning functional group in a polypeptide chain?
amino group
what is the terminal functional group in a polypeptide chain?
the carboxyl group
residue
an individual amino acid that is part of a polypeptide chain
proteolysis/proteolytic cleavage
hydrolysis of a protein by another protein
proteolytic cleavage is a specific means of:
cleaving specific peptide bonds
proteolytic enzyme/protease
the enzyme that does the cutting in proteolysis/proteolytic cleavage
what is the R group in the amino acid cysteine?
a thiol group (SH) - can form disulfide bond
a cysteine residue in a disulfide bond is called:
cystine
denatured
improperly folded proteins, generally nonfunctional
denaturation
the disruption of a protein’s shape without breaking peptide bonds
how can proteins be denatured?
urea (disrupts hydrogen bonding interactions), extreme pH, extreme temperatures, changes in salt concentration (tonicity)
what is the primary structure of amino acids?
the order of amino acids bonded to each other in the polypeptide chain
primary structure of proteins is the same thing as:
the sequence
what is the bond that determines primary structure?
peptide bond (this is the bond that links one amino acid to the next in the polypeptide)
what is the secondary structure of amino acids?
the initial folding of a polypeptide chain into shapes stabilized by noncovalent interactions
what is the bond that determines secondary structure?
hydrogen bonds between the backbone (also disulfide bonds)
what are the two most common secondary structures?
alpha helix and beta sheets
parallel beta-pleated sheets
adjacent polypeptide strands run in the same direction
antiparallel beta-pleated sheets
adjacent polypeptide strands run in the opposite direction
what is the tertiary structure of amino acids?
the interactions between amino acid residues located more distantly from each other in the polypeptide chain
what are the bonds/interactions that determines tertiary structure?
interactions of R groups with each other and the solvent (water), determined by hydrophobicity/hydrophilicity of R group: non-covalent interactions, van der Waals forces, hydrogen bonds, disulfide bonds, and electrostatic interactions (between distant amino acids on the SAME polypeptide chain)
what distinguishes tertiary and quaternary disulfide bonds?
tertiary disulfide bonds and bonds between residues located far apart on the SAME polypeptide chain, quaternary disulfide bonds are between different polypeptide chains
what is the quaternary structure of amino acids?
interactions between polypeptide subunits
subunit
a single polypeptide chain that is part of a large complex containing many subunits
multisubunit complex
a large complex containing many subunits
what is the bonds that determine quaternary structure?
non-covalent interactions, van der Waals forces, hydrogen bonds, disulfide bonds, electrostatic interactions (between DIFFERENT polypeptide chains)
oxidation
also known as combustion, the process of breaking down carbohydrates to form carbon dioxide, releases large amounts of energy
monosaccharide
a single carbohydrate molecule, also known as a simple sugar
glycosidic linkage
the covalent bond between two sugar molecules
how is the glycosidic bond formed?
by a dehydration reaction that requires enzymatic catalysis
what are the tree physiological roles played by lipids?
1) in adipose cells, triglycerides store energy
2) in cellular membranes, phospholipids form the barrier between intracellular and extracellular environments
3) cholesterol serves as a building block for steroid hormones
hydrophobicity
degree of “water fearing”
what is the cardinal characteristic of lipids?
ALL WATER FEARING/HYDROPHOBIC
hydrophilic
water loving
what is another term for hydrophobic
lipophilic
what is another term for hydrophilic
lipophobic
saturated
a fatty acid with no carbon-carbon bond
unsaturated
fatty acid with one or more Z/cis double bonds that form kinks in the structure
describe the structure of a fatty acid
consists of a hydrophilic head (COO-) and hydrophobic tail, chain has an even number of carbons
in aqueous solution, free fatty acids automatically form:
a micelle structure
hydrophobic interaction
the force that drives the tails into the centre of the micelle (hydrophobicity)
triacylglycerol/triglyceride
the storage form of fatty acids as fat
what is triglyceride composed of?
three fatty acids esterified to a glycerol molecule
lipases
enzymes that hydrolyze fats
why are fats more efficient energy storage molecules than carbohydrates?
1) packing-hydrobicity allows for closer packing while carbohydrates are generally solvated
2) energy content-fact molecules store more energy than carbohydrates
phospholipids
membrane lipids derived from diacylglycerol phosphate (DG-P)
how do phospholipids minimalize their interactions with water?
by forming a lipid bilayer
what interactions drives the formation of the lipid bilayer?
hydrophobic interactions
what interactions stabilize the lipid bilayer once formed?
van der Waals forces between the long hydrophobic tails
double bonds (unsaturation) in phospholipid fatty acids result in:
increased membrane fluidity by prevent orderly packing of hydrophobid lipid tails
what is another way of increasing fluidity of fatty acid?
by decreasing the length of fatty acid tails (reduced van der Waals interactions)
how does cholesterol act as a modulator of membrane fluidity?
at low temperatures, it increases fluidity; at high temperatures, it decreases fluidity; constantly maintains fluidity at an optimum level
what are the three structural determinants of membrane fluidity?
degree of saturation, tail length, and amount of cholesterol
how are steroids similar to fats?
hydrophobic
how are steroids unique from fats?
have basic tetracyclic ring system (similar to cholesterol) but otherwise distinct
lipoproteins
structure formed when steroid cholesterol is carried in the blood in a package with fats and proteins
what is the state of phosphoric acid as it exists in the human body?
in anionic form due to its potential to donate three hydrogens
phosphate is also known as:
orthophosphate
anhydride linkage
the bond between two orthophosphates to form pyrophosphate
the bond in pyrophosphate is:
POP
is the pyrophosphate bond high or low energy:
it is a HIGH-ENERGY PHOSPHATE BOND because: the negative charges repel each other, more favourable than linked phosphates due to resonance forms and favourable interactions with water
what is the universal short-term energy storage molecule
ATP (a nucleic acid)
what are nucleotides composed of?
a phosphate group, nitrogenous base, a deoxyribose or ribose sugar group
