How do the structures of cells and biological membranes enable the functions that are required to sustain life?

Transcription

1 Cells & Membranes How do the structures of cells and biological membranes enable the functions that are required to sustain life? Essential Understandings 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. 2.B.1 Cell membranes are selectively permeable due to their structure. 2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. 2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. 4.A.2 The structure and function of subcellular components, and their interactions, provide essential cellular processes. 4.B.2 Cooperative interactions within organisms promote efficiency in the use of energy and matter. Major Connections: 1.B.1b Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today: Structural evidence supports the relatedness of all eukaryotes. 3.D.1 Cell communication processes share common features that reflect a shared evolutionary history. 3.D.2 Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. Textbook References Chapter 7 and 8 Laboratories Diffusion & Osmosis Lab Investigation Page 1 of 12

2 *Remember to mark the key terms required to understand a statement or question* 2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. b. What factors affect the ability of the cell to obtain necessary resources or eliminate waste products? b.1. For each of the following structures, explain how it functions to meet the need to exchange materials and energy with their environment: Root hairs Cells of the alveoli Cells of the villi Microvilli b.2. Surface area-to-volume ratios affect biological systems. How do surface area-to-volume (SA/V) ratios change as the size and shape of cells and organisms change? To answer this, calculate the SA and V of a cube 1 mm on a side. Then do the same for cubes that are 2 mm and 4 mm on a side and compare their SA/V ratios. In general, how does surface area change as linear dimensions increase twofold? In general, how does volume change as linear dimensions increase twofold? In general, how do SA/V ratios change as linear dimensions increase twofold? Assume a bacterium is 10 µm in linear dimension. Fill in the chart. a. If modeled as a cube, what would its SA, V, and SA/V ratio be? b. If modeled as a sphere, what would its SA, V, and SA/V ratio be? c. What are the SA and V values and the SA/V ratios for a cube-shaped eukaryotic cell that is 100 µm in linear dimension? a. 10-μm bacterium as a cube b. 10-μm bacterium as a sphere c. 100-μm eukaryote cube-shaped SA V SA/V ratio Page 2 of 12

3 Is it possible to change the SA/V ratio of an organism or cell by changing its shape? To prove this to yourself and to help you determine the changes in SA/V ratios that occur, use modeling clay or dough to make a cube that is 1 inch on a side. The cube will obviously have a constant mass or volume. Assume that every cell requires a minimum of 1 unit of oxygen per um3 per second to stay alive. Fill in the chart below. a. How much oxygen must cross each µm2 of surface area per second in the 10- µm bacterium versus the 100-µm eukaryote to keep each alive? b. What effects might this difference have on metabolic rates in these organisms? 10-μm bacterium 100-μm eukaryote a. Oxygen/μm2 of SA/second b. Possible effect(s) on metabolic rate 2.B.1 Cell membranes are selectively permeable due to their structure. a. Cell membranes separate the internal environment of the cell from the external environment. b. Describe the fluid-mosaic model of a plasma membrane and its overall properties. b.1. Review fluid mosaic membrane structure by labeling (and coloring) the diagram below. Start with the cytoplasm and extracellular fluid. In the membrane, color phospholipids gray, embedded protein molecules purple, carbohydrates, glycoprotein and glycolipid molecules green, and cholesterol molecules yellow. Also show the functions of certain proteins by labeling them enzyme, receptor protein, and transport protein. Page 3 of 12

4 Now, draw from memory a labeled diagram of the fluid mosaic membrane! b.2. Diagram an individual phospholipid molecule. What properties do the phospholipids give the membrane? b.3. Which properties of the embedded proteins are similar to that of the phospholipids? b.4. For each of the following types of molecules, explain whether or not it can freely pass through the membrane: small nonpolar molecules large polar molecules ions water For the types of molecules that do not pass freely through the membrane, how do they move across? Include specific examples. c. Some cells have cell walls. What are the two major functions of cell walls? c.1. What types of cells have a cell wall? What kind of molecules are unique to each type. 2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. a./b./c. For each of the types of transport listed below: Describe the transport process and explain how the organization of cell membranes functions in the movement of specific molecules across membranes; and, Explain the significance of each type of transport to a specific cell (you may use different cell types as examples.) passive transport active transport endocytosis exocytosis osmosis (include hypotonic, hypertonic, and isotonic) facilitated diffusion glucose transport Na + /K + transport Add to your diagram of the fluid mosaic membrane. Show the types of transport across the membrane. Page 4 of 12

5 Review diffusion and the function of cell membranes by matching each of the phrases on the right with the appropriate mechanisms from the list on the left. Two questions require more than one answer. A. Diffusion B. Active transport C. Osmosis D. Phagocytosis E. Passive transport F. Facilitated diffusion G. Pinocytosis H. Receptor-mediated endocytosis I. Exocytosis 1. Diffusion across a biological membrane 2. Moves solutes against concentration gradient 3. Any spread of molecules from area of higher concentration to area of lower concentration 4. Diffusion with help of transport protein 5. Three types of endocytosis 6. Engulfing of fluid in membrane vesicles 7. Diffusion of water across selectively permeable membrane, from hypotonic to hypertonic solution 8. Transport molecules need ATP to function 9. Enables cell to engulf bulk quantities of specific large molecules 10. How oxygen and carbon dioxide enter and leave cells 11. Two types of passive transport 12. Engulfing of particle in membrane vesicle 13. Fusion of membrane-bound vesicle with membrane, and dumping of contents outside cell Page 5 of 12

6 Experiment Analysis Graph 1: Percent Change in Mass of Dialysis Tubing in Sucrose Solutions of Different Molarities Answer the following questions, based on Graph 1 above. Explain the relationship between the change in mass and the molarity of sucrose within the dialysis bags. Predict what would happen to the mass of each bag in this experiment if all the bags were placed in a 0.4 M sucrose solution instead of distilled water. Explain your response. Why would you calculate the percent change in mass rather than simply using the change in mass? A dialysis bag is filled with distilled water and then placed in a sucrose solution. The bag s initial mass is 20g, and its final mass is 18g. Calculate the percent change of mass. Page 6 of 12

7 Graph 2: Percent Change in Mass of Potato Cores at Different Molarities of Sucrose Answer the following two questions, based on Graph 2 above. Determine the osmotic molar concentration of the potato core. *Indicate this point on the graph. Molar concentration of sucrose = M What is the osmotic potential of the sucrose solution? The solute potential of this sucrose solution can be calculated using the following formula: ψs = icrt Where, i = ionization constant (for sucrose this is 1 because sucrose does not ionize in water) C = osmotic molar concentration R = pressure constant (handbook value: R = liter bars/mole K) T = temperature in K (take an average of recorded temperatures) If a potato is allowed to dehydrate by sitting in the open air, would the water potential of the potato cells decrease or increase? Why? If a plant cell has a lower water potential than its surrounding environment, and if pressure is equal to zero, is the cell hypertonic or hypotonic to its environment? Will the cell gain water or lose water? Explain your response. What effect does adding solute have on the solute potential component of that solution? Why? Explain what would happen to a red blood cell placed in distilled water in terms of concentration of water molecules and water potential. Page 7 of 12

8 2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. a. Identify the two main functions that internal membranes serve to help facilitate cellular processes. b. Explain how each of the following membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions. endoplasmic reticulum mitochondria chloroplasts lysosomes vacuoles Golgi nuclear envelope Sketch and label the endomembrane system on this diagram. Include rough ER, smooth ER, ribosomes, Golgi apparatus, lysosome, and transport vesicles. (1) Trace the path of a protein from its site of manufacture to the outside of the cell with a red arrow. (2) Trace the path of a protein incorporated into a lysosome in blue. (3) Trace the path of a protein incorporated into the plasma membrane in green. (4) Trace the path of a lipid secreted from the cell in yellow. Page 8 of 12

9 Review the nucleus and the various structures that make up the endomembrane system by matching each phrase on the left with a structure from the list on the right. Answers can be used more than once. 1. Lipids manufactured here 2. Small structure that makes protein 3. Contains chromatin 4. Sac of enzymes that digest things 5. Carries secretions for export from cell 6. Breaks down drugs and toxins in liver 7. Makes cell membranes 8. Cell control center 9. Numerous ribosomes give it its name 10. "Ships" products to plasma membrane, outside, or to other organelles 11. May store water, needed chemicals, wastes, pigments in plant cell 12. Buds off from Golgi apparatus 13. Defective in Pompe's disease and Tay-Sachs disease 14. Proteins made here for secretion from cell 15. Pumps out excess water from some cells 16. Nonmembranous organelle 17. Takes in transport vesicles from ER and modifies their contents 18. Digests food, wastes, foreign substances 19. Surrounded by double layer of membrane with pores A. Nucleus 20. How proteins, other substances get from ER to Golgi apparatus B. Transport vesicle C. Central vacuole D. Smooth ER E. Lysosome F. Golgi apparatus G. Rough ER H. Contractile vacuole I. Ribosome Page 9 of 12

10 c. Examine cell diagrams and then compare the structures of the cells of prokaryotes, plants and animals by checking off their characteristics below. Characteristic Prokaryote Cell Plant Cell Animal Cell Prokaryotic structure Eukaryotic structure Relatively large size Relatively small size Extensive internal memb. Plasma membrane Cell wall Cytoplasm Ribosomes Nucleus Rough ER Smooth ER Golgi apparatus Lysosome Peroxisome Mitochondrion Chloroplast Central vacuole Cytoskeleton Cilia/Flagellum (9+2) Flagellum Centriole Linear chromosomes Circular chromosome Page 10 of 12

11 4.A.2: The structure and function of subcellular components, and their interactions, provide essential cellular processes. Explain how the following organelles work together to perform living functions: 1. Nucleus and ribosomes 2. Endoplasmic reticulum and ribosomes 3. Golgi bodies and lysosomes 4. Nucleus and endoplasmic reticulum 5. Endoplasmic reticulum and Golgi bodies and vesicles 6. Endoplasmic reticulum and Golgi bodies and cell membrane 4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter. a. Explain how organisms, at the cellular level, have areas or compartments that perform a subset of functions related to energy and matter, and how these parts contribute to the whole. Page 11 of 12

12 How do the following topics connect to what you are learning in this unit? 1.B.1b Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today: Structural evidence supports the relatedness of all eukaryotes. 3.D.1 Cell communication processes share common features that reflect a shared evolutionary history. 3.D.2 Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. Enrichment 1. Explain how technology can be used to better understand living processes at the cellular level. 2. Compare the components of the cytoskeleton by indicating with a checkmark which of the following are characteristics of microfilaments or microtubules. Hollow tubes Solid rods Made of tubulin Made of actin Help cell change cell shape Act in muscle cell contraction Move chromosomes Act as tracks for organelles Give cell rigidity, shape In cilia In flagella In centrioles Microfilaments Microtubules 3. Match each cell surface characteristic or structure on the left with a phrase on the right. A. Tight junction B. Plasmodesma C. Anchoring junction D. Cell wall E. Communicating junction F. Extracellular matrix 1. Channel between animal cells 2. Made of cellulose 3. Link animal cells in leakproof sheet 4. Channel between plant cells 5. Connects animal cells, leaving space between them 6. Sticky layer holds animal cells together Page 12 of 12