1.
Two amino acids can join together to form a _________.
Correct Answer
D. Dipeptide
Explanation
Two amino acids can join together through a process called dehydration synthesis to form a dipeptide. During dehydration synthesis, the carboxyl group of one amino acid reacts with the amino group of another amino acid, resulting in the formation of a peptide bond. This bond links the two amino acids together, forming a dipeptide.
2.
How do amino acids join together?
Correct Answer
C. By condensation reactions
Explanation
Amino acids join together by condensation reactions. In this process, the carboxyl group of one amino acid reacts with the amino group of another amino acid, resulting in the formation of a peptide bond. This reaction involves the removal of a water molecule, hence the term "condensation." This process continues as more amino acids are added, forming a chain called a polypeptide. Eventually, these polypeptides fold and interact to form proteins, which are essential for various biological functions in living organisms.
3.
When two amino acids join together, what bond is formed?
Correct Answer
A. Peptide
Explanation
When two amino acids join together, a peptide bond is formed. A peptide bond is a covalent bond that connects the carboxyl group of one amino acid to the amino group of another amino acid. This bond is formed through a dehydration synthesis reaction, where a water molecule is eliminated. Peptide bonds are essential for the formation of proteins, as they link amino acids together in a specific sequence to create a polypeptide chain.
4.
What is the primary structure of a protein?
Correct Answer
B. The sequence of amino acids
Explanation
The primary structure of a protein refers to the sequence of amino acids that make up the protein. This sequence determines the overall structure and function of the protein. The arrangement of amino acids into alpha helixes and beta pleated sheets is part of the secondary structure, while the 3D arrangement held together by bonds and bridges is part of the tertiary structure. Multiple polypeptide chains in a protein are part of the quaternary structure. Therefore, the correct answer is the sequence of amino acids.
5.
What is the secondary structure of a protein?
Correct Answer
D. The sequence of amino acids form alpha helix's and beta pleated sheets
Explanation
The secondary structure of a protein refers to the 3D arrangement of the amino acid sequence, specifically the formation of alpha helices and beta pleated sheets. This arrangement is stabilized by hydrogen bonds between the backbone atoms of the amino acids. Ionic bonds and disulphide bridges are involved in the tertiary structure, which is the overall 3D shape of the protein. The answer choice that states "the sequence of amino acids form alpha helix's and beta pleated sheets" accurately describes the secondary structure of a protein.
6.
What is the tertiary structure of a protein?
Correct Answer
B. 3D arrangement held together by ionic bonds, hydrogen bonds and disulphide bridges
Explanation
The tertiary structure of a protein refers to its 3D arrangement, which is held together by various types of chemical bonds such as ionic bonds, hydrogen bonds, and disulphide bridges. These bonds play a crucial role in stabilizing the protein structure and determining its overall shape. The sequence of amino acids alone (option 3) does not fully describe the tertiary structure, as it only represents the primary structure of the protein. The presence of more than one polypeptide chain (option 4) describes the quaternary structure of a protein, not its tertiary structure.
7.
What is the quaternary structure of a protein?
Correct Answer
B. More than one polypeptide chain in the protein
Explanation
The quaternary structure of a protein refers to the arrangement of multiple polypeptide chains in a protein. This means that the protein is made up of more than one chain, with each chain contributing to the overall structure and function of the protein. The interaction between these chains is typically held together by various types of bonds such as ionic bonds, hydrogen bonds, and disulfide bridges. The other options mentioned, such as the sequence of amino acids and the formation of alpha helices and beta pleated sheets, are related to the primary and secondary structures of a protein, respectively.
8.
Some proteins are ______ proteins. In this protein, the polypeptides join together to form long fibers or sheets. The proteins are strong and _______ in water, for example, ______, which makes up human hair.
Correct Answer
fibrous, insoluble, keratin
Explanation
Fibrous proteins are characterized by the joining of polypeptides to form long fibers or sheets. These proteins are strong and do not dissolve in water. An example of a fibrous protein is keratin, which is the main component of human hair.
9.
Hemoglobin on the other hand, is a ________ protein. These proteins are roughly spherical, or globular in shape. They are usually ______ in water.
Correct Answer
globular soluble
Explanation
Hemoglobin is a type of protein that is described as "globular" because it has a roughly spherical shape. These types of proteins are usually "soluble" in water, meaning they can dissolve or mix well with water.
10.
What temperature do proteins usually denature at? (degrees Celcius)
Correct Answer
D. 45
Explanation
Proteins usually denature at a temperature of 45 degrees Celsius. Denaturation refers to the process in which proteins lose their structure and function due to external factors like heat. At temperatures higher than the protein's optimal range, the thermal energy disrupts the weak bonds (hydrogen bonds, disulfide bonds, etc.) that maintain the protein's shape, leading to denaturation. Therefore, 45 degrees Celsius is the temperature at which proteins are most likely to denature.
11.
A hemoglobin molecule is made up of four polypeptide chains, each with a _____ group attached to it. In the middle of this group, there is an ____ ion, which can associate with one oxygen molecule.
Correct Answer
haem iron
Explanation
A hemoglobin molecule is composed of four polypeptide chains, and each chain has a haem group attached to it. The haem group contains an iron ion in its center, which has the ability to bind with one oxygen molecule. This binding of oxygen to the iron ion is crucial for the transport of oxygen throughout the body by hemoglobin.