1.5 Proteins & Nucleic acids Flashcards
Protein definition
A large molecule that consists of many amino acid subunits that are joined together by peptide bonds folded into a specific 3D shape
Nucleic acid definition
A blueprint for proteins that are synthesized in cells; stores hereditary information
All proteins are _________ that are composed of amino acid ________.
polymers; monomers
Amino acid definition
A molecule that contains a carboxyl group and an amino group; serves as the monomer subunit of proteins
Attached to the central carbon atom (beside the amino acid) is a variable side group, called an ___ ______, which gives each amino acid its distinct _____________.
R group; characteristics
There are __ different amino acid side groups, or ___ _____, ranging from a single hydrogen atom to complex carbon chains or rings
20; R groups
The one exception to the 20 different amino acid groups is the amino acid ______, which has a ring structure that includes the ______ and central carbon atoms.
proline; nitrogen
Among the polar side groups in amino acids, some carry a positive or negative _______ and
others act as _____ or _____.
charge; acids; bases
Many of the amino acid side groups contain a _______ functional group, such as -NH2, -OH,
-COOH, or -SH, which may interact with atoms located elsewhere in the same protein or with molecules and ions located ______ the protein.
reactive; outside
With few exceptions, all proteins in living things are an assembly of various numbers and
_________ of 20 different amino acids.
combinations
___ of these amino acids are considered
essential for humans because they can only be obtained from our ____. The rest can
be synthesized by the _____.
8; diet; cells
________ proteins provide much of the supportive framework of the cells
Structural
Defensive proteins called _________, which are found in the human body, help to fight off ________.
antibodies; infections
Hormones and other messenger chemicals in the cell are ______ proteins.
signal
Special proteins called ________ are largely responsible for making almost every __________ reaction possible. They _______ up the rate of chemical reactions.
enzymes; biochemical; speed
Structural protein function and example
Framework support
e.g. hair, tendons, and ligaments
Defensive protein function and example
Infection fighters
e.g. antibodies
Signal protein function and example
Messenger
e.g. hormones
Carrier protein function and example
Transport of materials
e.g. hemoglobin
Recognition and receptor protein function and example
Cellular markers
e.g. major histocompatibility complex
Enzyme protein function and example
Catalyst
e.g. amylase
Motile protein function and example
Movement
e.g. actin and myosin
Peptide bond definition
A covalent bond that links many amino acids into chains of subunits that make proteins.
Peptide bonds are formed by a ________ _______ reaction between the -NH2 group of one amino acid and the -COOH group of a second amino acid
dehydration; synthesis
An amino acid chain always has an group
at one end, called the __________, and a -COOH group at the other end, called the ____________
N-terminal end; C-terminal end
In cells, amino acids are added only to the
_____ end of the growing peptide strand.
-COOH
Peptide definition
A chain of amino acid subunits that are connected by peptide bonds
Polypeptide definition
A peptide with more than 50 amino acids
Protein definition
A protein is one or more polypeptides that are folded into a precise 3D shape.
True or false:
A protein can function without folding.
False
Only after folding occurs is the protein able to function.
The primary structure of a protein is the unique _______ sequence of its amino acids in
each __________ chain
linear; polypeptide
Changing even a single amino acid
in the primary structure will _____ the overall structure of the protein to some degree.
A single change can alter or even destroy the __________ function of the protein.
alter; biological
The possible combinations of lengthy primary structures are virtually _________.
limitless
Most polypeptides have portions that repeatedly _____ or fold into patterns and contribute to the overall _____ of a protein.
coil; shape
This secondary structure is the result of __________ bonding between different parts of the same amino acid _________.
hydrogen; backbone
Two common secondary structures are the _____-pleated (or ß-pleated) sheet and the ______-helix (or a-helix)
beta; alpha
A B-pleated sheet forms by a side-by-side _________ of the amino acid chain. B-pleated sheets play an important role in the strength of ______.
alignment; silk
An a-helix is a delicate ____ that is held together by ________ bonds between every _____ amino acid.
coil; hydrogen; fourth
An a-helix is found in ____ proteins and _______________ proteins, and it provides the necessary _________ for their functions.
thin; transmembrane; structure
The secondary structure of a protein is the result of _________ between atoms in the _________.
interactions; backbone
The tertiary structure of a protein is the overall ___ _______ of a protein due to a range of interactions among the amino acid _________
3D shape; R groups
It is in the tertiary structure that the interactions of the R groups determine the 3D _____ of the __________ chain.
shape; polypeptide
Hydrophobic interactions definition
Hydrophobic interactions are the interaction of non-polar side groups that cluster together as a
result of other amino acid R groups interacting with water.
Disulfide bridge definition
A disulfide bridge is the bond that is formed when the -SH groups of two cysteine amino acids line up and react to form an S-S covalent bond.
This is a strong bond that holds 2 parts of the
polypeptide strand together, stabilizing its shape.