Chapter 4: Protein Function
Chapter 7, Voet, Voet & Pratt * Link between protein structure and physiological function * Focus on myoglobin and hemoglobin * Both proteins reversibly bind to O2 * Extremely well-studied examples of structure/function relationships * Behavior is a model for many other proteins, especially metabolic enzymes
Learning Objectives * Compare myoglobin and hemoglobin * Structures * Properties * O2 binding characteristics * Understand structural basis for hemoglobin’s O2 binding characteristics * Relate these characteristics to physiological role of hemoglobin * Understand biochemical basis of diseases/adaptations involving hemoglobin
O2 Binding
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1. Binding of O2causes the Fe(II) to move into the plane of the porphyrin. 2. Movement of the Fe(II) and flattening of the porphyrin forces Helix F to shift (~1Å)
3. The shift of the Helix F causes the 3° structure of the subunit to change, which in turn affects how the protomers interact * Specifically at the α1 – β2 interface during the T R transition
4. The subunit structural changes reduce the number of salt-pair interactions at their C-terminals
Their conformational change caused by oxygen binding tears these ionic interactions apart.
The Bohr Effect Enhances O2 Transport * Decreases the pH induces Hb to bind less O2 at lower oxygen pressures * Conformational changes that occur on O2 binding alter the pKa’s of several groups: * N-terminal α-subunit * C-terminal Histidine of β-subunit
In the T-state, these units participate in ion bridges; raising their pKa’s
In the R-state, they are not in ion-pairs; pKa’s decrease and become more acidic * Hb releases ~0.6 protons per O2 bound
When we increase the pH, the concentration of protons increase and there is an increase of Hb and the t-state
We decided to do the McMush Lab. The lab was designed to see the biomolecules inside an average McDonald’s Happy Meal. We decided to use a meal we have all had and to see what we were eating. Our results showed certain biomolecules.
Figure 1.b shows the ‘Lock and Key’ model where two individual substrates meet the active site where
Biomolecules are present in every living organism. Larger biomolecules (macromolecules) consists of proteins, lipids, and carbohydrates. In layman’s terms, proteins are long chains of amino acids that have many functions such as, providing structural support and regulating many body processes. Lipids are the scientific term used for fats. There are many different types of fats, but they all share one common characteristic: They are not soluble in water. Lipids provide protection and insulation to organs and also act as an energy source. Carbohydrates are made up of carbon, hydrogen,
1. Carbohydrates: Are Molecule composed of carbon, hydrogen, and oxygen, and they include sugars and starches.
. The 3-D tertiary structure of polypeptide proteins globular and is the result of interactions that occur between R groups. Tertiary structure is a result of the bonds between sidechains of amino acids, the R groups. The structure and bonds involve alpha helices, beta pleated sheets, and also regions unique to each protein. Tertiary proteins are held together by four different types of forces; hydrogen bonds, hydrophobic interactions (including Van der Waals interactions), ionic bonding (electrostatic interactions), and disulfide bridges (strong covalent bonds). Hydrogen bonds occur within and between polypeptide chains and the aqueous environment. Hydrogen bonding forms between a highly electronegative oxygen atom or a nitrogen atom and a hydrogen atom attached to another oxygen atom or a nitrogen atom. This links the amino acid
Dehydration-synthesis is a reaction that occurs to form different types of macromolecules. It is a reaction that leaves a macromolecule structure along the lines of developing its own specific function in a living organism. The 4 most common ones are carbohydrates which includes monosaccharides and polysaccharides, lipids, proteins and nucleic acids (Mack 2012). Scientists identify different types of macromolecules to achieve a better understanding on how they function in our bodies. This can be achieved by studying their chemical properties and structure.
zipper, enabling these residues to interact with the water in the surrounding. This arrangement reduces the free-energy of protein folding by burying the hydrophobic residues in the interior of the protein, while exposing the hydrophilic residues to the water containing environment and thereby, stabilizing the coiled-coil structure.
Introduction: In this lab, we studied biomolecules. Biomolecules are molecules that are existent in all living organisms. The four biomolecules, we are learning in class are proteins, carbohydrates, lipids, and nucleic acid. The three biomolecules being addressed in the lab are proteins, carbohydrates, and lipids.
Proteins are made of amino acids, which are compounds built around a central carbon atom. Amino acids then join together through dehydration reactions. These are called peptide bonds. Many amino acids joined together are called polypeptides. A polypeptide becomes a protein when it folds into a three dimensional structure. This is the primary structure of a protein. The next structure in the hierarchy is the secondary structure. Secondary structures can either form alpha helixes, where an amino acid sequence forces the polypeptide to twist into a helical shape; or beta sheets, where an amino acid sequence forces the polypeptide into a zigzag shape. In the tertiary structure, the polypeptide folds several times on itself to form a more complex three dimensional shape. A quaternary structure is when two tertiary structures interact with each other. This is when a protein becomes a functional
The position of some of these hydrogen atoms formed change when the pH of a solution changes.
There are four basic macromolecules that contribe to healthy eating, Carbohydrates, proteins, fats and lipids. Each one of these needs to maintant a balance in your diet despit the diets that promote elimating them all together from your meals.
The active site of an enzyme and substrate are extremely shape-specific
There may also be sections where the secondary structure is neither helix nor sheet. Then the structure is called a random structure, indicating that it folds in random directions. The amino acids in an alpha helix are arranged in a right-handed helical structure resembling a spring. The alpha helix is the most common form of regular secondary structure in proteins. The beta-sheet is the second form of regular secondary structure in proteins consisting of beta strands connected laterally by three or more hydrogen bonds, forming a generally twisted, pleated sheet. The beta-sheet is sometimes called the beta pleated sheet since sequential neighboring atoms are alternately above and below the plane of the sheet giving a pleated appearance. Turns are the third of the three "classical" secondary structures that serve to reverse the direction of the polypeptide chain. They are located primarily on the protein surface and accordingly contain polar and charged residues. However, they are not very common in discussions of protein structure today.
Bettelheim, Brown, Campbell and Farrell assert that polypeptide chains do not extend in straight lines but rather they fold in various ways and give rise to a large number of three-dimensional structures (594). This folding or conformation of amino acids in the localized regions of the polypeptide chains defines the secondary structure of proteins. The main force responsible for the secondary structure is the non-covalent
The structure is a phospholipid bilayer that is embedded with proteins. Phospholipid molecules are arranged in an opposing manner with the hydrophobic tails facing inward, and their hydrophilic tails facing out away from the other.