In a protein, amino acids are connected by (strong) covalent bonds called peptide bonds (Figure 2): Figure 2. Generalized structure of a peptide Based on its unique amino acid sequence, each polypeptide folds into the most stable 3-dimensional shape, and it is this shape that determines the specific function (activity) of the protein. The three-dimensional structure is stabilized by interactions called because they are weaker than covalent ones, but “non-covalent” they are still very important in the aggregate. Some proteins have more than one chain (subunit), and these come together in specific ways that are also stabilized by non-covalent interactions. Hb is an example of one such protein. It is composed of four subunits, two of each of two kinds. Proteins with multiple subunits can be regulated in complex ways. More details of this regulation are discussed below. Additionally, some proteins have additional to them after they are “decoration” synthesized. EPO is an example of such a protein. It has sugar molecules added onto some of its amino acids. Sugars account for approximately 40% of its weight. As we will see in later sections, the pattern of these sugars can tell us about the origins of the EPO. Many proteins also have acid, or groups. One of these is heme, “prosthetic” discussed on page 5, below. Hemoglobin: Examine the binding curves below (Figure 3) for hemoglobin and the related protein myoglobin (Mb). The units for pressure are sometimes expressed as “torr,” “mm Hg.” Typical oxygen pressure in the lungs is ~100 torr and in body tissues is ~40 torr. Note that saturated with oxygen” can also be described as of “Percent “percent subunits that have oxygen bound.” Myoglobin can be considered an oxygen-storage protein in muscle tissue. Recall that hemoglobin circulates in the Answer the questions that follow: Oxygen-binding curves for myoglobin and hemoglobin Figure 3. Questions What is plotted on the x-axis? On the y-axis? How does the percent saturation change with increasing oxygen concentration (O2 pressure) for both Mb and Hb?
In a protein, amino acids are connected by (strong) covalent bonds called peptide bonds (Figure 2): Figure 2. Generalized structure of a peptide Based on its unique amino acid sequence, each polypeptide folds into the most stable 3-dimensional shape, and it is this shape that determines the specific function (activity) of the protein. The three-dimensional structure is stabilized by interactions called “non-covalent” because they are weaker than covalent ones, but they are still very important in the aggregate. Some proteins have more than one chain (subunit), and these come together in specific ways that are also stabilized by non-covalent interactions. Hb is an example of one such protein. It is composed of four subunits, two of each of two kinds. Proteins with multiple subunits can be regulated in complex ways. More details of this regulation are discussed below. Additionally, some proteins have additional “decoration” to them after they are synthesized. EPO is an example of such a protein. It has sugar molecules added onto some of its amino acids. Sugars account for approximately 40% of its weight. As we will see in later sections, the pattern of these sugars can tell us about the origins of the EPO. Many proteins also have acid, or “prosthetic” groups. One of these is heme, discussed on page 5, below. Hemoglobin: Examine the binding curves below (Figure 3) for hemoglobin and the related protein myoglobin (Mb). The units for pressure are “torr,” sometimes expressed as “mm Hg.” Typical oxygen pressure in the lungs is ~100 torr and in body tissues is ~40 torr. Note that “Percent saturated with oxygen” can also be described as “percent of subunits that have oxygen bound.” Myoglobin can be considered an oxygen-storage protein in muscle tissue. Recall that hemoglobin circulates in the Answer the questions that follow: Figure 3. Oxygen-binding curves for myoglobin and hemoglobin Questions What is plotted on the x-axis? On the y-axis? How does the percent saturation change with increasing oxygen concentration (O2 pressure) for both Mb and Hb?