Proteins Flashcards
What elements do proteins contain?
Carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
What are the sub-units from which proteins are formed?
Amino acids.
What is the generalized structure of an amino acid?
H2N, COOH, and a carbon-containing side group R.
How many different commonly occurring amino acids are there in living organisms?
20.
What groups do all amino acids have?
- Amine group (NH2)
- Carboxylic acid group (COOH)
What type of bond joins amino acids together?
Peptide bonds (-CONH-).
What reaction forms a dipeptide?
Condensation reaction between two amino acids.
What do many amino acids joined together form?
A polypeptide.
What may a protein consist of?
One or more polypeptides.
What process can hydrolyze proteins?
Heating with acid or using enzymes (proteases).
Fill in the blank: Amino acids are joined together by _______.
Peptide bonds.
True or False: Proteins can only be hydrolyzed by heating with acid.
False.
What determines the primary structure of proteins?
The sequence of amino acids in the polypeptide chain
The primary structure is crucial as it dictates the protein’s shape and function.
What are the two main types of secondary structures in proteins?
Alpha helix and beta-pleated sheet
These structures arise from hydrogen bonding between amino acids.
What type of bonds contribute to the tertiary structure of proteins?
Hydrogen bonds, ionic bonds, and disulfide bonds
The tertiary structure is influenced by the sequence of amino acids in the primary structure.
How does the tertiary structure of an enzyme affect its function?
It determines the shape of its active site
The active site shape is critical for enzyme-substrate interactions.
What characterizes globular proteins?
They are soluble and consist of a highly folded and coiled polypeptide chain
Examples include enzymes and antibodies.
What is the quaternary structure of proteins?
When proteins consist of more than one polypeptide chain
These chains are held together by ionic bonds, hydrogen bonds, and sometimes disulfide bonds.
Fill in the blank: The _______ structure refers to the sequence of amino acids in the polypeptide chain.
primary
The primary structure is foundational for protein formation.
True or False: The secondary structure of proteins is solely determined by the primary structure.
True
The folding and coiling in secondary structure arise from interactions dictated by the primary structure.
What is the significance of the R groups of amino acids in protein structure?
They determine the formation of tertiary structure through bonding
The unique interactions between R groups lead to the specific shape and function of proteins.
List the types of bonds involved in stabilizing tertiary structure.
- Hydrogen bonds
- Ionic bonds
- Disulfide bonds
These bonds contribute to the protein’s overall stability and functionality.
What type of protein structure is characterized by more than one polypeptide chain?
Quaternary structure
This structure is important for the function of many multi-subunit proteins.
What is denaturation of proteins?
An alteration in the tertiary structure of a protein, leading to a loss of its three-dimensional shape and functionality.
Denaturation is often irreversible.
What usually causes denaturation of proteins?
Breaking of hydrogen and ionic bonds, high temperatures above the optimum, extreme changes in pH, and heavy metals.
Heavy metals can also contribute to denaturation.
Are disulfide bonds broken during protein denaturation at typical temperatures?
No, disulfide bonds are not broken at the temperatures that break hydrogen and ionic bonds.
Some proteins can have disulfide bonds remain unbroken at 70 °C.
What is the Biuret test used for?
To test a sample for the presence of protein.
A specific reagent is used in this test.
What indicates the presence of protein in the Biuret test?
A purple or lilac color indicates protein is present.
If the solution remains blue, no protein is present.
Fill in the blank: Denaturation is often _______.
irreversible
What happens to the functionality of a protein after denaturation?
The protein is no longer functional.
This is a key consequence of denaturation.
True or False: Denaturation can be caused by extreme changes in pH.
True
List three factors that can lead to protein denaturation.
- High temperatures above the optimum
- Extreme changes in pH
- Heavy metals
