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8 Cards in this Set

  • Front
  • Back
What are the four levels of protein structure?
Primary
Secondary
Tertiary
Quaternary
Explain a protein's signficance at the primary structure.
Primary structure is teh number and sequence of amino acids in a polypeptide. The primary structure is determined by the base sequence of the gene that codes for the polypeptide.
Explain a protein's significance at the secondary structure.
-Secondary structures are regular repeating structures, inluding beta pleated sheets and alpha helices stabilized by hydrogen bonds between groups in the main chain of the polypeptide.
Explain a protein's significance at the tertiary structure.
-Tertiary structure is the three-dimensional conformation of a polypeptide.
-It is formed when the polypeptide folds up after being produced by translation.
-The conformation is stablized by intramolecular bonds that form between amino acids in the polypeptide, especially between R groups.
-ionic bonds, hydrogen bonds, hydrophobic interactions and disulfide bridges are bonds that form.
-Intramolecular bonds are often formed betweeen amino acids that are widely separated in the primary structure, but brought together in the folding process.
Explain a protein's significance at the quaternary structure.
Quaternary structure is the linking together of two or more polypeptides to form a signle protein.
-In some cases proteins also contain a non-polypeptide structure called a prosthetic group.
-Each of the four polypeptides in hemoglobin is linked to a heme group, not made of amino acids.
-Congugated proteins are proteins that have a prosthetic group.
What is the difference between fibrous and globular proteins? Make reference to 2 examples of each protein type.
Proteins can be divided into 2 types according to their shape: globular or fibrous.
globular proteins have a rounded shape and are mostly soluble in water.
fibrous proteins have a long and narrow shape and are mostly insoluble in water.
Examples: globular proteins-catalase, hemoglobin, insulin, immunoglobin. Fibrous proteins-collagen, myosin.
What is the significance of polar and non-polar amino acids?
Polar amino acids- have hydrophilic R groups. POlar amino acids on the surface of proteins make them water soluble. They create channels through which hydrophllic substances can diffuse. positively charged R groups allow negatively charged ions to pass and vice versa. Polar amino acids also cause parts of the membrane proteins to protude from the membrane.
-Nonpolar amino acids: hydrophibic R groups. They are in the center of water soluble proteins and stabilize their structure. They cause proteins to remaine embedded in membranes.
- positive and negatively charged R groups of amino acids can help direct substrates to an enzyme's active site.
-Non polar R groups bind non polar substances, attracting substrates to active sites.
What are the six functions of proteins? (Give an example of each)
1. Enzymes-catalase-to catalyse the conversion of hydrogen peroxide, a toxic waste product of metabolism, into water and oxygen.
2. Structural-collagen-to strengthen bone, tendon, and skin. These tissues produce tough collagen fibers in the spaces between their cells
3. Transport-Hemoglobin-The function of hemoglobin is to bind oxygen in the lungs and to transport it to respiring tissues.
4. Movement-Myosin-with another protein called actin, myosin causes contractions in muscle fibers and as a result cause movement in animals.
5. Hormones-insulin-binds to receptors in the plasma membrane of target cells and stimulate them to remove glucose from the blood
6. Defence-immunoglobin-acts as antibodies. Part of the immunoglobin molecule can be varied so almost an endless variety of different antibodies can be produced.