Module 1B - Biomolecules and Enzymes Flashcards
What is the shape and structure of proteins
structurally complex and
functionally sophisticated
molecules
The Shape of a Protein Is Specified by Its ____ ___Sequence
Amino Acid
How many types of amino acids in proteins
20 amino acids
Proteins are made of long ____ ___of amino acids
unbranched chain
Proteins are also known as?
polypeptides
-repeating sequence of atoms along the core of the polypeptide chains
polypeptide backbone
give amino acids its unique properties
Side chains
Polar amino acids
Aspartic acid (Asp)
Glutamic acid (Glu)
Arginine (Arg)
Lysine (Lys)
Histidine (His)
Asparagine (Asn)
Glutamine (Gln)
Serine (Ser)
Threonine (Thr)
Tyrosine (Tyr)
Non-polar amino acids
alanine (Ala)
Glycine (Gly)
Valine (Val)
Leucine (Leu)
Isoleucine (Ile)
Proline (Pro)
Phenylalanine (Phe)
Methionine (Met)
Tryptophan (Trp)
Cysteine (Cys)
2 polar amino acids that have negative side chain
Aspartic acid and Glutamic acid
3 polar amino acids that have positive side chain
Arginine
Lysine
Histidine
5 polar amino acid that has uncharged polar
Asparagine
Glutamine
Serine
Threonine
Tyrosine
Has weak noncovalent bonds
Protein folding
3 weak noncovalent bonds
- hydrogen bonds
-electrostatic attractions
-van der Waals
hydrophobic molecules, including the nonpolar side chains of amino acids, tend to be forced together in an aqueous environment to minimize their disruptive effect on the hydrogen bonded network of water
hydrophobic clustering forces
_____ ____, including the _____ ___ ___tend to be forced together in an aqueous environment to minimize their disruptive
effect on the hydrogen-bonded network of water molecules
hydrophobic molecules, including the nonpolar side chains of amino acids
In the folded confirmation in aqueous environment of protein, it can form hydrogen bonds to water
Polar side chain on the outside of the molecule
the folded confirmation in aqueous environment of protein has hydrophobic core region which contains _____ __ __
nonpolar side chains
an important factor governing the folding of any protein is the distribution of its ___ and ___ ___
hydrophobic (nonpolar) and polar groups
determined by the order of the amino acids in its chain
three-dimensional structure of protein
reversible changes in a protein’s structure
denatures ↔ renatures
contain all the information needed for specifying the three-dimensional shape of a protein
Amino acids
A protein can be unfolded, or ____, by treatment with certain solvents, which disrupt the noncovalent interactions holding the folded chain together. This treatment converts the protein into a flexible polypeptide chain that has lost its natural shape
denatured
When the denaturing solvent is removed, the protein often refolds spontaneously, or _____, into its original conformation, indicating that all the information needed for specifying the three-dimensional shape of a protein is contained in its amino acid sequence.
renatures
Assist in the protein folding
Molecular chaperones
2 regular folding patterns
The α Helix and the β sheet
α helix and β sheet are particularly common because they result from hydrogen-bonding between ___-__ and __=__ in the polypeptide group
N-H and C=O groups
- The first folding pattern to be discovered
- was found in the protein α-keratin, which is abundant in skin and its derivatives—such as hair, nails, and horns.
α helix
found in the protein fibroin, the major constituent of silk.
β sheet
β sheets can form either from ____ ___ or ______ __
parallel chains or antiparallel chains
form from neighboring segments of the polypeptide backbone that run in the same orientation
Parallel chains
from a polypeptide backbone that folds
back and forth upon itself, with each section of the chain running in the direction opposite of that of its immediate neighbors
antiparallel chains
generated when a single
polypeptide chain twists around on itself to form a rigid cylinder
a helix
A hydrogen bond is made between every ___ peptide – linking C=O of one peptide bond to N-H of another
4th
wrap around each other to form a particularly stable structure, known as a coiled-coil.
α helices
formed from two or more have most of their nonpolar (hydrophobic)
side chains on one side
coiled-coil
Modular units from
which larger proteins are built
Protein domains
- a substructure produced by any part of a polypeptide chain that can fold independently into a compact, stable structure
-contains between 40 and 350 amino acids
Protein domains
four levels of organization in the structure of a protein
- Primary structure
- Secondary structure
- Tertiary structure
- Quaternary structure
Primary structure of protein
Amino acid sequence
Secondary structure of protein
hydrogen bonding of the peptide backbone; helices and β sheets
tertiary structure of protein
full 3D organization of a polypeptide chain
Quaternary structure of protein
protein molecule formed as a complex of more than one polypeptide chain
many present-day
proteins can be grouped
into protein ____
families
each protein family member has an ___ ___ ___ and a __-____conformation that resemble those of the other family members.
amino acid sequence and a three-dimensional conformation
a large family of protein-cleaving (proteolytic) enzymes that includes the digestive enzymes chymotrypsin, trypsin, and elastase, and several proteases involved in blood clotting
serine proteases
has been more highly conserved than the amino acid sequence
the structure of the
different members of a
protein family
- both gene regulatory proteins in the homeodomain family4
- identical in only 17 of 60 aa residues
yeast α2 protein and the
Drosophila engrailed
protein
protein families are readily recognized when the ___ of any organism is
sequenced
genome
human genome = ____ protein-coding genes
21,000
40% of our protein-coding genes to known protein structures, ___ diff
families
500
are the most powerful and predominant techniques used to experimentally determine the three-dimensional structures of biological macromolecules at near atomic resolution
x-ray crystallography and nuclear
magnetic resonance (NMR)
the basic units of proteins that can fold, function, and evolve independently
Protein domains
process of creating new combination of gene functional domains
Domain shuffling
– subset of protein domains, mobile
during evolution
protein modules
The three-dimensional structures of some protein modules
- Immunoglobulin module
- Fibronectin type 3 module
- Kringle module
easily integrated into other proteins
Protein domains
can be readily linked in
series to form extended
structures
Domains
Major Histocompatibility Complex (MHC) has ____-___ ___ that bind to and present fragments of pathogens (antigens) to immune cells.
antigen-recognition domain (only in humans)
Human genome encodes
how many protein-coding genes
21,000 protein-coding genes
genome sequences also reveal that _____
have inherited
nearly all of their protein
domains from invertebrates with only 7% identified human domains being vertebrate-specifics
Vertebrate
has given rise to many novel combinations of protein domains
domain shuffling during
vertebrate evolution
allow proteins to bind to each other to produce
structures in the cell
weak noncovalent bonds
any region of a protein’s
surface that can interact with another
molecule
binding site
forming a symmetric complex of two protein
subunits (dimer)
“head-to-head” arrangement
Contains two identical α-globin subunits and two identical β-globin subunits, symmetrically arranged
hemoglobin
a long chain of identical
protein molecules can be
constructed if each molecular
has a ___ __
complementary to another
region of the surface of the
same molecule
binding site
long helical structure produced from many
molecules of the protein actin
actin filament
why is a helix a common
structure in biology?
all subunits are identical, they can only fit together in one way – rarely straight line –resulting in a helix (resembles
a staircase
Elongated, fibrous shapes protein molecules
-fibrous protein
- keratin filaments
- a-keratin
- intermediate filaments
elongated three-dimensional
structure
Fibrous protein
main component in long
lived structures
Keratin filaments
a dimer of two identical subunits
a-keratin
rope-like structures; important component of the cytoskeleto
intermediate filaments
- abundant outside the cell
- main component of the
gel-like extracellular
matrix
Fibrous protein
consists of three long polypeptide chains,
each containing
that nonpolar
amino acid glycine
at every 3rd position
collagen
collagen consists
of three long
polypeptide chains,
each containing
that nonpolar
amino acid ____
at every ___ position
glycine
3rd
another abundant
protein in ecm; highly
disordered polypeptide
elastin
Ep1 PHD PHD Ep2
Yeast
Ep1 PHD PHD Ep2 Br
Worm
Znf Ep1 PHD PHD Ep2 Br BMB
Human
Elastin molecules are formed from relatively ___ and ___ polypeptide chains that are covalently cross-linked into a rubberlike elastic meshwork
loose and unstructured