BIO U5:L3 Proteins PDF

Lesson 5.3 Proteins General Biology 11/2 Science, Technology, Engineering, and Mathematics Having a source of protein in our diet is very important. Proteins help us grow faster and stronger. 2 Athletes utilize proteins more frequently because their muscles are prone t...

Lesson 5.3 Proteins General Biology 11/2 Science, Technology, Engineering, and Mathematics Having a source of protein in our diet is very important. Proteins help us grow faster and stronger. 2 Athletes utilize proteins more frequently because their muscles are prone to tear during their training regimen. 3 How would you describe the structure and functions of proteins? 4  Learning Competencies At the end of the lesson, you should be able to do the following: Categorize the biological molecules (proteins) according to their structure and function (STEM_BIO11/12-Ii-j-15). Explain the role of each biological molecule in specific metabolic processes (STEM_BIO11/12-Ii-j-16). 5  Learning Objectives At the end of the lesson, you should be able to do the following: Describe the structure and functions of proteins. Describe the different classes of proteins. Explain the metabolic processes that involve proteins. 6  Protein Structure Amino acid structure Amino acids have: ○ Central carbon ○ Amino group ○ Carboxyl group ○ Hydrogen atom ○ R group The basic structure of an amino acid. 7  Protein Structure Non-polar and Nonpolar and aliphatic R group aromatic R group R Groups of Amino Acids Polar and Negatively Positively uncharged R charged R charged R groups groups groups 8  Protein Structure The twenty amino acids in living organisms have different R groups (highlighted in blue), which give them varying chemical properties in the cell's physiological conditions. 9  Protein Structure The twenty amino acids in living organisms have different R groups (highlighted in blue), which give them varying chemical properties in the cell's physiological conditions. 10  Protein Structure The twenty amino acids in living organisms have different R groups (highlighted in blue), which give them varying chemical properties in the cell's physiological conditions. 11  Protein Structure The Classification of Amino Acids Based on their Chemical Nature Hydrophobic Hydrophilic Nonpolar Polar Acidic Basic Glycine Phenylalanine Serine Alanine Tryptophan Cysteine Aspartic acid Lysine Valine Methionine Tyrosine Glutamic acid Arginine Leucine Proline Threonine Histidine Isoleucine Asparagine Glutamine 12  Protein Structure Peptide Bond Formation Cells link amino acid monomers together by dehydration reactions. The bond between adjacent amino acids is In the process of a dehydration called a peptide bond. reaction, one amino acid releases an H+, and the other releases OH–. Thus, a water molecule is produced. 13 Levels of Protein Structure Primary Secondary Levels of Protein Structure Tertiary Quaternary 14 Levels of Protein Structure The primary protein structure refers to the unique sequence of amino acids. 15  Levels of Protein Structure Secondary protein structures include the alpha-helices and beta-sheets, which resulted from amino acid chain coiling or folding. 16  Levels of Protein Structure Tertiary structures of proteins are formed and maintained by hydrophobic, hydrophilic, and ionic interactions, as well as by disulfide bridges. 17  Levels of Protein Structure Hemoglobin is an example of a protein that can attain a quaternary structure. It has four polypeptides, wherein each has primary, secondary and tertiary structures. 18  Protein Structure Protein Denaturation Some conditions can cause a protein to unravel and lose its normal shape. ○ Examples of these conditions include The change in the appearance and pH and chemical composition of an egg once temperature. cooked is primarily because of protein denaturation. 19 Why can denatured proteins no longer perform their normal functions? 20 Functional Classification of Proteins Structural Storage Enzymes Functional Classifications of Proteins Transport Messengers Contractile 21  Functional Classification of Proteins Structural Proteins The keratin in hair and silk in spider webs are examples of structural proteins. Keratin can also be found in the horns, claws, hooves, and outer skin of vertebrates. 22  Functional Classification of Proteins Enzymes Enzymes are mostly globular proteins that catalyze reactions. They are very specific to the substrate molecule or reactants, the reactions of which are catalyzed. 23  Functional Classification of Proteins Transport Proteins Channel and carrier proteins allow the movement of different molecules across the cell membrane. 24  Functional Classification of Proteins Immune Proteins Interactions between antigens and antibodies help trigger immune responses. 25  Functional Classification of Proteins Chemical Messengers Insulin consists of two amino acid chains connected by disulfide bridges (in yellow color) between cysteine residues. 26  Functional Classification of Proteins Contractile Proteins Contractile proteins are present in muscle cells, which helps the body to initiate various forms of movements. 27  Functional Classification of Proteins Storage Proteins Storage proteins provide amino acids for growing organisms, such as germinating seeds and developing embryos in eggs. 28 How are proteins involved in the different metabolic processes? 29  Metabolic Activities Involving Proteins The essential and non essential amino acids in humans. Essential amino acids Non essential amino acids Isoleucine Alanine Glutamine Leucine Arginine Glycine Valine Asparagine Proline Lysine Aspartic acid Serine Methionine Cysteine Tyrosine Phenylalanine Glutamic acid Threonine Tryptophan Histidine 30  Metabolic Activities Involving Proteins Protein Digestion and Absorption Proteins are digested by proteases, and amino acids are absorbed actively.31  Metabolic Activities Involving Proteins Urea Cycle The urea cycle happens in the liver, which produces urea from the ammonium ions to avoid toxicity in the body. Then, urea is excreted in the urine through kidneys. 32  Metabolic Activities Involving Proteins Pyruvate Dehydrogenase Complex Deficiency and Phenylketonuria Many countries, including the Philippines, can already perform the early genetic testing of newborns for possible cases of phenylketonuria. 33  Check Your Understanding Write true if the statement is correct and false if it is otherwise. 1. The twenty 20 amino acids can be grouped according to whether their R group is hydrophobic or hydrophilic. 2. Tertiary protein structure consists of more than one polypeptide. 3. An unfavorable change in the condition of the environment cannot affect the shape of proteins. 34  Check Your Understanding Briefly explain the possible consequences should the following events take place. 1. All amino acids have the same side groups. 2. Some gene mutations resulted in an impaired urea cycle. 3. The body does not produce ammonium ions. 35  Let’s Sum It Up! Proteins are biological compounds composed of chains of amino acid monomers. Proteins, given the variety of their structures, have diverse functions in living organisms. 36  Let’s Sum It Up! Each amino acid consists of a central carbon that is bonded to four covalent groups. Three of these four attachments are common to all 20 amino acids—an amino group (—NH2), a carboxyl group (—COOH), and a hydrogen atom. The variable component of amino acids, the R group (radical group), is attached via the fourth bond of the central carbon. 37  Let’s Sum It Up! A peptide consists of two or more amino acids bonded together, and the resulting longer chain of amino acids joined by peptide bonds is called a polypeptide. A protein is a polymer consisting of one or more polypeptides. 38  Let’s Sum It Up! The overall shape of a protein has at least three levels of structure, which are primary, secondary, and tertiary structures. Proteins with more than one polypeptide chain have a fourth level called the quaternary structure. 39  Let’s Sum It Up! Protein shape is sensitive to the surrounding environment. Any unfavorable change in temperature, pH, salt, or some other cellular conditions may result in denaturation or loss of normal protein function. 40  Let’s Sum It Up! Proteins are, in many ways, important to living organisms. Proteins may function to provide structure, storage, catalysis, transport, chemical signaling, motility, and immunity. 41  Let’s Sum It Up! Protein digestion involves various enzymes produced by the stomach, pancreas, and small intestine. After absorption, amino acids are transported to the liver and other body tissues for further metabolism. 42  Let’s Sum It Up! One byproduct of amino acid metabolism is ammonium. The urea cycle in the liver allows the processing of ammonium ions so that they can be excreted in the urine. 43 Let’s Sum It Up! Graphical representation of structure, functions, and metabolic activities involving proteins 44 Challenge Yourself How do the 20 sets of amino acids have different properties when they have the same basic structures? 45 Photo Credit Slide 19: This photo, Protein Denaturation by RMADLA, is licensed under CC-BY SA 3.0 via Wikimedia Commons. 46 Bibliography Hoefnagels, Marielle. Biology: The Essentials. 2nd ed. McGraw-Hill Education. 2016. Mader, Sylvia S., and Michael Windelspecht. Biology. 11th ed. McGraw-Hill Education. 2014. “Protein Metabolism.” BC Campus. Accessed April 17, 2020. https://opentextbc.ca/anatomyandphysiology/chapter/24-4-protein-metabolism/. Reece, Jane B, Martha R. Taylor, Eric J. Simon, Jean L. Dickey, and Kelly Hogan. Biology Concepts and Connections. 8th ed. Pearson Education South Asia, Pte Ltd., 2016. Simon, Eric J., and Jane B. Reece. Campbell Essential Biology. 5th ed. Pearson Education Inc., 2013. 47 Bibliography Starr, Cecie, Christine A. Evers, and Lisa Starr. Biology Applications and Concepts. 8th ed. Cengage Learning Asia Pte. Ltd., 2012. Starr, Cecie, Christine A. Evers, and Lisa Starr. Biology: Today and Tomorrow. 4th ed. Cengage Learning Asia Pte. Ltd., 2014. 48