Proteins Flashcards
are by far the most important of all biological compounds.
Proteins
The main structural material for plants is cellulose.
For animals, it is structural proteins, which are the chief constituents of skin, bones, hair, and nails.
Structure
Two important structural proteins are
collagen and keratin
Virtually all the reactions that take place in living organisms
Catalysis
Every time we crook a finger, climb stairs, or blink an eye, we use our muscles.
Movement
A large number of proteins perform transportation duties.
Transport
Many hormones are proteins, including insulin, erythropoletin, and human growth hormone.
Hormones
are fat-soluble molecules made from cholesterol.
Steroid hormones
these are the three major sex hormones groups:
estrogens, androgens and progesterones.
Some proteins store materials in the way that starch and glycogen store energy.
Storage
Some proteins not only control the expression of genes, thereby regulating the kind of proteins synthesized in a particular cell, but also dictate when such manufacture takes place.
Regulation
which are insoluble in water and are used mainly for structural purposes
fibrous proteins
which are more or less soluble in water and are used mainly for nonstructural purposes.
globular proteins
is an organic compound containing an amino group and a carboxyl group.
amino acid
A pH at which a sample of amino acids or protein has an equal number of positive and negative charges.
Isoelectric point (pl)
Compounds that have a positive charge on one atom and a negative charge on another are called
zwitterions
zwitterions, from the German word
zwitter
zwitterions, from the German word zwitter, meaning?
hybrid
The very word “protein” is derived from the Greek
proteios
The very word “protein” is derived from the Greek proteios, meaning?
of first importance
the amino acid is still an lon, so it is still soluble in water. There is no pH at which an amino acid has no lonic character at all. If the amino acid is a positive ion at low pH and a negative lon at high pH, there must be some pH at which all the molecules have equal positive and negative charges. This pH is called the
isoelectric point (pt)
can in turn be fairly easily reduced to give two molecules of cysteine.
cystine
the presence of cystine has important consequences for the chemical structure and shape of the protein molecules of which it is part. The bond is also called a
disulfide bond
Tryptophan is converted to serotonin, more properly called
5-hydroxytryptamine
can be managed by controlling the levels of serotonin and Its further metabolites.
bipolar disorder
Itself normally derived from phenylalanine, is converted to the neurotransmitter class called catecholamines
Tyrosine
which includes epinephrine, commonly known by its proprietary name, adrenalin.
catecholamines
is an intermediate in the conversion of tyrosine.
L-Dihydroxyphenylalanine (L-dopa)
L-dopa are involved in
Parkinson’s disease
an amino acid that cannot be synthesized (from scratch) by the organism, and thus must be supplied in Its diet.
Essential amino acid
uncommon amino acids are derived from the common amino acids and are produced by modification of the parent amino acid after the protein is synthesized by the organism in a process called
post-translational modification
is unique among the proteinogenic amino acids. It is the only amino acid containing an essential dietary micronutrient (selenium) as a constitutive component, the only amino acid encoded by a UGA codon and the only one synthesized on its TRNA in all domains of life.
Selenocysteine
is an a-amino acid that is used in the biosynthesis of proteins In some methanogenic archaea and bacteria
Pyrolysine
an amide bond that links two amino acids.
Peptide bond
The amino acids in a chain are often called
residues
is the residue with the free a-COO^-group
C-terminal amino acid
is the residue with the free a-NH3^+ group
N-terminal amino acid
The amino acid at the end of a peptide that has a free a-carboxyl group.
C-terminus
The amino acid at the end of a peptide that has a free a-amino group.
N-terminus
consists of the sequence of amino acids that makes up the chain.
primary structure
This change affects only two positions in a molecule containing 574 amino acid residues, yet it is enough to produce a very serious disease
sickle cell anemia
differs from the normal type only in the beta chains and only in one position on these two chains: The glutamic acid in the sixth position of normal Hb Is replaced with a valine residue in HbS.
hemoglobin (called Hbs)
a repetitive conformation of the protein backbone.
Secondary structure
the orderly alignment of protein chains is maintained by intermolecular or intramolecular hydrogen bonds.
B-pleated sheet.
a secondary structure where the protein folds into a coil held together by hydrogen bonds parallel to the axis of the coil.
Alpha (a)-helix
a secondary protein structure in which the backbone of two protein chains in the same or different molecules is held together by hydrogen bonds
Beta (B) pleated sheet
It is quite different from the a-helix.
Collagen is the structural protein of connective tissues (bone, cartilage, tendon, blood vessels, skin), where it provides strength and elasticity.
extended helix of collagen
of a protein is the three-dimensional arrangement of every atom in the molecule.
tertiary structure
most often involved in stabilization of the tertiary structure of proteins is the disulfide bond.
Covalent Bonds
We saw earlier that secondary structures are stabilized by hydrogen bonding between backbone - C=0 and —N-H groups.
Hydrogen Bonding
also called electrostatic attractions, occur between two amino acids with lonized side chains-that is, between an acidic amino acid (—COO^-) and a basic amino acid (-NH,^+ or =NH,^*) side chain.
Salt Bridges
in aqueous solution, globular proteins usually turn their polar groups outward, toward the aqueous solvent, and their nonpolar groups inward, from
molecules.
Hydrophobie Interactions
Two side chains with the same charge would normally repel each other, but they can also be linked via a metal ion.
Metal Ion Coordination
a protein that helps other proteins to fold into the biologically active conformation and enables partially denatured proteins to regain their biologically active conformation.
Chaperone
the spatial relationship and interactions between subunits in a protein that has more than one polypeptide chain.
quaternary structure
in adult humans is made of four chains (called globins): two identical a chains of 141 amino acid residues each and two identical B chains of 146
residues each.
hemoglobin
another example of quaternary structure and higher organizations of subunits can be seen In?
collagen
partly or completely traverse a membrane bilayer.
Integral membrane proteins
the loss of the secondary, tertiary, and quaternary structures of a protein by a chemical or physical agent that leaves the primary structure intact.
Denaturation -
The main structural material for plants is
cellulose
