The Complexity of Human Organs---Stomach

Your organs are composed of the four tissue types; epithelial, connective, muscle, and nervous tissues. Organs are wondrous things, each one with a different function vital to the homeostasis of your body. While it is easy for us to view a particular organ as a single item, it is in fact comprised of many different types of cells and structures, each one unique and yet each one working together to perform the functions of the organ.

• A general description of your assigned organ in the introduction. In the general description, you will include the following: a brief description of the primary functions of this organ, its general shape, and the location of this organ in the human body.
• Describe in detail the importance of this organ to the function of the body as a whole. What are the functions of this organ and how is it critical for survival?
• Identify and describe which of the four tissue types (epithelial, connective, muscle, and/or nervous tissues) are present in the organ.
• Describe any organ-specific cell types that are present and if these cell types have any special structures (e.g., presence of microvilli and/or abundance of particular organelle such as mitochondria).
• Discuss in detail how these different cell-types work together to provide the overall function of the organ.
• Include a discussion of why each organ requires the different tissue types as well as unique cell types to function. Why can the organs not be comprised of just one cell type? What is the advantage of having so many different types of cells?

Protein Structure1Protein StructureWhat are the levels of protein structure and what role do functional groups play?Why?Proteins accomplish many cellular tasks such as facilitating chemical reactions, providing structure, andcarrying information from one cell to another. How a protein chain coils up and folds determines itsthree-dimensional shape. Its shape will, in turn, determine how it interacts with other molecules and thusperforms its function in the cell.Model 1 – Formation of a Peptide BondAmino acid 1Amino acid 2DipeptideNCCOOHHHHNCCHHHNCCOOHHHONCCOOHHHCH3R1R2CH2OHH2O+H+1. Examine the amino acids in Model 1.a.Circle an amine group in the diagram.b.Draw a triangle around a carboxylic acid (carboxyl) group.2. How are the amino acids similar to one another?3. How are the amino acids different from one another?

 

2POGIL™Activities for AP* Biology4. How many amino acids are involved in the reaction to make a dipeptide?5. In Model 1 the original amino acids are combined through acondensation reactionto make thedipeptide.a.What does R1represent in the dipeptide?b.What does R2represent in the dipeptide?6. Put a box around the atoms in the amino acids that become the H2O molecule produced by thereaction in Model 1.7. A peptide bond is a covalent bond linking two amino acids together in a peptide.a.Circle the peptide bond in Model 1.b.Between which two atoms in the dipeptide is the peptide bond located?c.Between what two functional groups is the peptide bond located?8. There are 22 different amino acids found in nature. Two were shown in Model 1. Additionalexamples are shown below. With your group, write one or two grammatically correct sentencesto describe how these amino acids are similar and how they are different. Use the terms R-group,amine group, and carboxyl group in your description.H2NCHCOOHHH2NCCH2SHCOOHHH2NCCOOHHH2CCONH2H2NCH2CCOOHHGlycineCysteineAsparaginePhenylalanine(Gly)(Cys)(Asn)(Phe)

 

Protein Structure3Model 2 – Protein Structure (Part A)Primary StructureAmino acid sequence: Ser – Tyr – Ala – Phe – Val – Cys – Tyr – Asp – Cys – GlyPeptide structure:H2N CCNCHOCH2OHHCNCOCH3HHCNCOCH2HHCNOHCH2HOHCCNCHOCH2SHCHHHCNCOCH2HHCNCOCH2HHCH3CH3OHCONCCH2SHCONCH2CO2HHCO2H–Secondary StructureCCHNHCNHCOCHCH2NH2NCCNCHOCH2OHHCNCOCH3HHCNCOCH2HCNOHCH2OHCCHCHCH3CH3ONHCHCH2SHCOOHHCH2CCO2–OCH2SHOHHHHydrogen bondNCH2HO2CH9. Locate theprimary structureof the polypeptide in Model 2.a.Draw an arrow to two different peptide bonds in the diagram.b.Circle three separate amino acids that were joined together to make the polypeptide.

 

4POGIL™Activities for AP* Biology10. The first five amino acids in thispol

are serine, tyrosine, alanine, phenylalanine, andypeptidevaline, in that order (Ser-Tyr-Ala-Phe-Val). If the amino acids were changed or rearranged (i.e.,to Val-Phe-Ala-Ser-Tyr), the polypeptide would have a different name and identity. With yourgroup, use this information to write a definition of the primary structure of a protein.11. Locate thesecondary protein structurein Model 2.a.What types of bonds are holding the secondary structure in place?b.What groups on the amino acids are always involved in these bonds?12. Draw a rectangle around two different R groups on the amino acids in the secondary structure inModel 2.13. Is there any interaction between R groups in the secondary structure in Model 2?14. Secondary protein structure can take the form of an alpha(α)-helix or a beta(β)-pleated sheet, asillustrated below.a.Which drawing represents anα-helix, Molecule 1 or Molecule 2? Explain your reasoning.b.Which drawing represents aβ-pleated sheet? Explain your reasoning.Molecule 1Molecule 2RRRRRHydrogenbondsAminoacidsRRRRRR15. With your group, write a grammatically correct sentence that summarizes how the secondaryprotein structure is formed from the primary structure.

 

Protein Structure5Model 3 – Protein Structure (Part B)Tertiary StructureHCH2CH3CH3CH3CH3CHCH(CH2)4NH3+CH2OCH2CO–OOCH2CH2SSHQuaternary StructureThree polypeptide chainsCH2CH3CH3CH3CH2(CH2)4NH3+CH3CH2SCHCHSCOO–

 

6POGIL™Activities for AP* Biology16. Examine thetertiary structurein Model 3 and note the interactions that hold this level of struc-ture in place.a.Four types of bonds or interactions are shown. Label them with the following terms.Disulfide bridgeHydrogen bondHydrophobic interactionsIonic bondb.Describe the part of the amino acid that participates in these interactions.c.How does your answer in partbdiffer from the bonds that stabilize the secondary structure?17. What type of functional groups or atoms would need to be present in the R-groups for hydrogenbonding to occur between two amino acids in a protein chain?18. What type of functional groups or atoms would need to be present in the R-groups for hydro-phobic interactions to occur between two amino acids in a protein chain?19. How many polypeptide chains are shown in the tertiary protein structure in Model 3?20. Many proteins, but not all, have a fourth level of structure termedquaternary structure.a.How many polypeptide chains are shown in the quaternary structure of the protein inModel 3?b.What types of bonds and interactions hold the quaternary structure in place?

 

Protein Structure721. With your group, using grammatically correct sentences, define the following.a.Tertiary protein structure.b.Quaternary protein structure.22. Imagine a protein chain that includes the following amino acids among several others.H2NCCOOHHH2NCCH2SHCH2OHCOOHHH2NCCOOHHH2CCONH2H2NCH2CCOOHHSerineCysteineAsparaginePhenylalaninea.Which of the amino acids could form a hydrogen bond with another amino acid in the chainto stabilize the secondary structure of aβ-pleated sheet?b.Which of the amino acids could form disulfide bonds with another amino acid in the chainto stabilize the tertiary structure of the protein?c.Which of the amino acids could participate in hydrophobic interactions with another aminoacid in the chain to stabilize the tertiary structure of the protein?d.What types of bonds or interactions could asparagine form with another amino acid in thechain in order to form a quaternary structure with another protein chain?

 

8POGIL™Activities for AP* Biology23. Fill in the following chart using what you’ve learned from Models 1–3.StructureBond(s) or interactionsholding the structuretogetherShort descriptionNumber ofpolypeptidechains involvedPrimary1Secondary1Tertiary1Quaternary2 or moreRead This!Heating and changing pH levels are two ways to disrupt the shape of a protein. High temperatures orpH levels that vary from the natural environment of the protein will break hydrogen bonds, ionic bonds,disulfide bridges, and hydrophobic interactions. Covalent bonds will usually remain undisturbed. Thisprocess of destroying the shape of a protein is calleddenaturing.24. Which of the four levels of protein structure is maintained after denaturing? Explain youranswer.

 

Protein Structure925. Proteins carry out a variety of functions, and their function is critically dependent upon theirstructure and shape. Enzymes are proteins. What would happen to the structure and function ofan enzyme that was exposed to heat or a drastic change in pH?26. When people get their hair chemically straightened, one chemical is put on the hair to break thedisulfide bonds that give the hair strands their shape (curled) and a second chemical is used toreform the disulfide bonds to hold the hair in a new position (straight).a.What level(s) of protein structure is/are affected by these processes?b.Why doesn’t the hair stay straight forever after this treatment?

 

10POGIL™Activities for AP* BiologyExtension Questions27. If a mutation in the DNA of an organism results in the replacement of an amino acid containinga polar R-group with another amino acid containing a nonpolar R-group, how might the struc-ture of the protein be affected? Address the impact on all levels of the protein structure in youranswer.28. Egg whites are primarily composed of the protein albumin. One familiar example of the denatur-ing of proteins is the difference between the albumin structure in a raw egg versus a cooked egg.Using what you know about the levels of structure in proteins, propose an explanation of chang-es in albumin (and other proteins) that occur during cooking.29. Predict what would happen to the egg white if a raw egg were placed in vinegar. Explain yourthinking.