FT LEC: Proteins and Enzymes Flashcards
All _________ contain the elements carbon, hydrogen, oxygen, and nitrogen; most also contain sulfur
PROTEINS
the main protein of milk, contains phosphorus
Casein
Other elements, such as phosphorus and iron, are essential constituents of certain specialized proteins
- Casein
- Hemoglobin
The presence of nitrogen sets them apart from carbohydrates and lipids, which most often do not contain nitrogen.
PROTEINS
the oxygen-transporting protein of blood, contains iron
Hemoglobin
Casein, the main protein of milk, contains ________
phosphorus
Hemoglobin, the oxygen-transporting protein of blood, contains _______
iron
Proteins are naturally occurring polymers in which the monomer units are ________
amino acids
The Building Blocks for Proteins
AMINO ACIDS
an organic compound that contains both an amino (-NH2) group and a carboxyl (-COOH) group
AMINO ACIDS
Amino acids found in proteins
α-amino acid
the amino group and the carboxyl group are attached to the α-carbon atom
α-amino acid
distinguishes α-amino acids from each other
R group
amino acid side chain
R group
STANDARD AMINO ACIDS
- Nonpolar Amino Acid
- Polar Amino Acid
has nonpolar side chain
Nonpolar Amino Acid
hydrophobic (water-fearing)
Nonpolar Amino Acid
Found in the interior of proteins, where there is limited contact with water
Nonpolar Amino Acid
R group – hydrocarbons (aliphatic or aromatic)
Nonpolar Amino Acid
has polar side chain
Polar Amino Acid
hydrophilic (water-loving)
Polar Amino Acid
Found on the surfaces of proteins
Polar Amino Acid
Subcategorized to: Polar neutral, polar acidic, and polar basic
Polar Amino Acid
Side chain of Polar neutral
has groups containing heteroatoms
TYPES OF POLAR AMINO ACIDS
- Polar Neutral
- Polar Acidic
- Polar Basic
contain polar but neutral side chain (R group)
Polar neutral
contain a carboxyl group as part of the side chains
Polar acidic
Side chain of polar acidic:
carboxylic acid
contain an amino group as part of the side chain
Polar basic
Side chain of polar basic
amine, imine
The ________ of one amino acid interacts with the amino group of the other amino acid.
carboxyl group
Amino acids are linked together by an _______
amide (peptide) bond via a condensation reaction
The four levels of protein structure are
Primary (1o)
Secondary (2o)
Tertiary (3o)
Quaternary (4o)
Amino acid sequence
Primary (1o)
Overall 3D shape of folded protein
Tertiary (3o)
H-bonds on protein backbone
Secondary (2o)
Subunit organization
Quaternary (4o)
is the order/sequence in which amino acids are linked together in a protein
PRIMARY STUCTURE (1o)
Amino acids are linked to each other by ____________
peptide bonds
Arrangement in space adopted by the hydrogen-bonded arrangement of the backbone portion of a protein
SECONDARY STRUCTURE (2o)
Common types of secondary structures
- α helix
- β pleated sheet (β-sheet)
Folding is stabilized by noncovalent interactions
SECONDARY STRUCTURE (2o)
Composed of 1 polypeptide chain
α helix
H bonds are within a single polypeptide chain (backbone only)
α helix
R-groups are outside
α helix
Right-handed or clockwise, spiral
α helix
Composed of two or more polypeptide chains
β pleated sheet (β-sheet)
H-bonds are between adjacent strands
β pleated sheet (β-sheet)
H-bonds are between adjacent strands
β pleated sheet (β-sheet)
A single protein chain adopts a shape that resembles a coiled spring (helix)
ALPHA-HELIX STRUCTURE
Coil configuration maintained by
hydrogen bonds
Two fully extended protein chain segments in the same or different molecules
BETA-PLEATED SHEET STRUCTURE
Twist of the helix forms a
right-handed, or clockwise, spiral
Hydrogen bonds between C=O and N—H entities are orientated ________ to the axis of the helix
parallel
Overall three-dimensional shape of a protein
TERTIARY STRUCTURE (3o)
chains (R groups) that are widely separated from each other
TERTIARY STRUCTURE (3o)
There are two main factors for folding of a protein:
- hydrophobic residues
- polar residues
Covalent, strong, and involve two cysteine units
Covalent disulfide bonds
Can occur between amino acids with polar R groups
Hydrogen bonds
Involve the interaction between charged side chains of acidic and basic amino acids
Electrostatic attractions (salt bridges)
Occur when two nonpolar side chains are close to each other
Hydrophobic attractions
Highest level of protein organization
QUATERNARY STRUCTURE (4o)
Organization among the various peptide subunits in a multimeric protein
QUATERNARY STRUCTURE (4o)
found in proteins that have two or more polypeptide chains (subunits)
QUATERNARY STRUCTURE (4o)
Subunits are independent of each other and not covalently bonded to each other
QUATERNARY STRUCTURE (4o)
Contain even number of subunits
QUATERNARY STRUCTURE (4o)
Reverse of peptide bond formation
PROTEIN HYDROLYSIS
Results in the regeneration of an amine and carboxylic acid functional groups
PROTEIN HYDROLYSIS
is when all peptide bonds are broken, and the only products are amino acids
Complete hydrolysis
is when some but not all peptide bonds are broken, and the product is a mixture of amino acids and small peptides
Partial hydrolysis
Partial or complete disorganization of a protein’s characteristic three-dimensional shape
PROTEIN DENATURATION
Filamentous or elongated shape
FIBROUS PROTEIN
PROTEIN CLASSIFICATION BASED ON SHAPE
- FIBROUS PROTEIN
- GLOBULAR PROTEIN
Function is mostly structural (strength/support)
FIBROUS PROTEIN
Repetitive AA sequence
FIBROUS PROTEIN
Usually water-insoluble
FIBROUS PROTEIN
Provide protective coating for organisms
α-Keratin
Major protein constituent of hair, feather, nails, horns, and turtle shells
α-Keratin
Mainly made of hydrophobic amino acid residues
α-Keratin
Most abundant protein in humans
COLLAGEN
Organic component of bones and teeth
COLLAGEN
Major structural material in tendons, ligaments, blood vessels, and skin
COLLAGEN
help maintain the structure of the triple-helix
Glycine and proline
Spherical or globular shape
GLOBULAR PROTEIN
Function is mostly as catalyst, transport, etc.
GLOBULAR PROTEIN
irregular AA sequence
GLOBULAR PROTEIN
Usually, water-soluble
GLOBULAR PROTEIN
Oxygen-storage molecule in muscles
MYOGLOBIN
Consists of a single peptide chain and one heme unit
Monomer
An oxygen-carrier molecule in blood
HEMOGLOBIN
Each subunit contains a heme group (four polypeptide chains)
Tetramer
A compound, usually a PROTEIN, that acts as a CATALYST for a biochemical reaction.
ENZYME
Most enzymes are __________
GLOBULAR PROTEINS
enzyme composed only of protein (amino acid chains)
Simple enzyme
enzyme that has a nonprotein and protein parts
Conjugated enzyme
Redox reactions
Oxidoreductase
CLASSES OF ENZYME
Ligase
Isomerase
Lyase
Hydrolase
Oxidoreductase
Transferase
Transfer of functional groups
Transferase
Isomerization
Isomerase
Hydrolysis reactions
Hydrolase
Addition of groups to double bonds or removal of groups to form double bonds
Lyase
Joining of two molecules (hydrolysis of ATP as energy source)
Ligase
an enzyme that catalyzes an oxidation-reduction reaction
OXIDOREDUCTASE
an enzyme that catalyzes the transfer of a functional group from one molecule to another
TRANSFERASE
help disposal of nitrogen during the metabolism of amino acids for energy production or for synthesis of bioactive compounds from amino acids
Aminotransferases
an enzyme that catalyzes a hydrolysis reaction in which the addition of a water molecule to a bond causes the bond to break
HYDROLASE
effect the breaking of glycosidic bonds in oligo- and polysaccharides
Carbohydrases
effect the breaking of peptide linkages in proteins
Proteases
effect the breaking of ester linkages in triacylglycerols
Lipases
an enzyme that catalyzes addition or removal of atoms across a double bond
LYASE
adds water across the double bond in trans-Enoyl CoA during the oxidation of fatty acids for biochemical energy production
Enoyl CoA hydratase
small part of an enzyme’s structure that is involved in catalysis; it is where the substrate binds to the enzyme
ACTIVE SITE
formed due to folding and bending of the protein
ACTIVE SITE
“CREVICE-LIKE” location in the enzyme
ACTIVE SITE
contains catalytic amino acid residues or groups
ACTIVE SITE
FACTORS AFFECTING ENZYME ACTIVITY
- Temperature
- pH
- Substrate Concentration
- Enzyme Concentration
is the maximum amount of substrate molecules that an enzyme can convert to products
Turnover number