Chapter 4: Cell Structure and Function

Transcription

1 Chapter 4: Cell Structure and Function This vital chapter about the components of cells spans Big Idea 1, Big Idea 2, and Big Idea 4. Big Idea 1 indicates that organism share lines of descent from a common ancestry. The cell theory states that all organisms are composed of one or more cells. All cells are derived from existing cells. The type of structures contained in cells is evidence of shared core processes and thus evolution. This chapter explains in detail the differences and similarities between eukaryotes and prokaryotes. The theory of endosymbiosis is the most widely accepted theory of how eukaryotes developed from prokaryotes. Big Idea 2 explains that organisms must use energy and building blocks to grow. One important aspects of cells is that their size is limited due to their need to exchange materials with the environment (transporting substances across their membrane). Internal membranes of eukaryotes enable those cells to be more efficient in their use of energy because chemical reactions can occur within the boundaries of specific organelles. This is important to the large eukaryotic cell and is not necessary in the smaller prokaryotic cell. Big Idea 4 concerns itself with interactions of biological systems. The specific organelles that must interact in eukaryotic biological systems and their importance are listed here. Students need to know the structure and function of the ribosomes, endoplasmic reticulum, mitochondria, chloroplasts, and vacuoles. ALIGNMENT OF CONTENT TO THE CURRICULUM FRAMEWORK Big Idea 1: The process of evolution drives the diversity and unity of life. Enduring understanding (EU) 1.B: Organisms are linked by lines of descent from common ancestry. Essential knowledge (EK) 1.B.1: Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. b. Structural evidence supports the relatedness of all eukaryotes. Cytoskeleton (a network of structural proteins that facilitate cell movement, morphological integrity and organelle transport) Membrane-bound organelles (mitochondria and/or chloroplasts) Linear chromosomes Endomembrane systems, including the nuclear envelope Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring understanding (EU) 2.A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential knowledge (EK) 2.A.3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization. b. Surface area-to-volume ratios affect a biological system s ability to obtain necessary resources or eliminate waste products. Mader, Biology, 12 th Edition, Chapter 4 53

2 1. As cells increase in volume, the relative surface area decreases and demand for material resources increases; more cellular structures are necessary to adequately exchange materials and energy with the environment. These limitations restrict cell size. To foster student understanding of this concept, instructors can choose an illustrative example such as: Root hairs Cells of the alveoli Cells of the villi Microvilli 2. The surface area of the plasma membrane must be large enough to adequately exchange materials; smaller cells have a more favorable surface area-to-volume ratio for exchange of materials with the environment. Enduring understanding (EU) 2.B: Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Essential knowledge (EK) 2.B.3: Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. a. Internal membranes facilitate cellular processes by minimizing competing interactions and by increasing surface area where reactions can occur. b. Membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions. To foster student understanding of this concept, instructors can choose an illustrative example, such as: Endoplasmic reticulum Mitochondria Chloroplasts Golgi Nuclear envelope c. Archaea and Bacteria generally lack internal membranes and organelles and have a cell wall. Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties. Enduring understanding 4.A: Interactions within biological systems lead to complex properties. Essential knowledge 4.A.2: The structure and function of subcellular components, and their interactions, provide essential cellular processes. a. Ribosomes are small, universal structures comprised of two interacting parts: ribosomal RNA and protein. In a sequential manner, these cellular components interact to become the site of protein synthesis where the translation of the genetic instructions yields specific polypeptides. b. Endoplasmic reticulum (ER) occurs in two forms: smooth and rough 1. Rough endoplasmic reticulum functions to compartmentalize the cell, serves as 54 Mader, Biology, 12 th Edition Chapter 4

3 mechanical support, provides site-specific protein synthesis with membranebound ribosomes and plays a role in intracellular transport. 2. In most cases, smooth ER synthesizes lipids. Specific functions of smooth ER in specialized cells are beyond the scope of the course and the AP Exam. c. The Golgi complex is a membrane-bound structure that consists of a series of flattened membrane sacs (cisternae). 1. Functions of the Golgi include synthesis and packaging of materials (small molecules) for transport (in vesicles), and production of lysosomes. The role of this organelle in specific phospholipid synthesis and the packaging of enzymatic contents of lysosomes, peroxisomes and secretory vesicles are beyond the scope of the course and the AP Exam. d. Mitochondria specialize in energy capture and transformation. 1. Mitochondria have a double membrane that allows compartmentalization within the mitochondria and is important to its function. 2. The outer membrane is smooth, but the inner membrane is highly convoluted, forming folds called cristae. 3. Cristae contain enzymes important to ATP production; cristae also increase the surface area for ATP production. e. Lysosomes are membrane-enclosed sacs that contain hydrolytic enzymes, which are important in intracellular digestion, the recycling of a cell s organic materials and programmed cell death (apoptosis). Lysosomes carry out intracellular digestion in a variety of ways. Specific examples of how lysosomes carry out intracellular digestion are beyond the scope of the course and the AP Exam. f. A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. In plants, a large vacuole serves many functions, from storage of pigments or poisonous substances to a role in cell growth. In addition, a large central vacuole allows for a large surface area to volume ratio. g. Chloroplasts are specialized organelles found in algae and higher plants that capture energy through photosynthesis. 1. The structure and function relationship in the chloroplast allows cells to capture the energy available in sunlight and convert it to chemical bond energy via photosynthesis. 2. Chloroplasts contain chlorophylls, which are responsible for the green color of a plant and are the key light-trapping molecules in photosynthesis. There are several types of chlorophyll, but the predominant form in plants is chlorophyll a. The molecular structure of chlorophyll a is beyond the scope of the course and the AP Exam. 3. Chloroplasts have a double outer membrane that creates a compartmentalized structure, which supports its function. Within the chloroplasts are membranebound structures called thylakoids. Energy-capturing reactions housed in the thylakoids are organized in stacks, called grana, to produce ATP and Mader, Biology, 12 th Edition, Chapter 4 55

4 NADPH2, which fuel carbon-fixing reactions in the Calvin-Benson cycle. Carbon fixation occurs in the stroma, where molecules of CO2 are converted to carbohydrates. Enduring understanding (EU) 4.B: Competition and cooperation are important aspects of biological systems. Essential knowledge (EK) 4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter. a. Organisms have areas or compartments that perform a subset of related to energy and matter, and these parts contribute to the whole. 1. At the cellular level, the plasma membrane, cytoplasm and, for eukaryotes, the organelles contribute to the overall specialization and functioning of the cell. Concepts covered in Chapter 4 also align to the learning objectives that provide a foundation for the course, an inquiry-based laboratory experience, class activities, and AP exam questions. Each learning objective (LO) merges required content with one or more of the seven science practices (SP), and one activity or lab can encompass several learning objectives. The learning objectives and science practices from the Curriculum Framework that pertain to organic chemistry are shown in the table below. Note that other learning objectives may apply as well. The specific Learning Objectives that apply to Chapter 4 are listed below. The structure and function of the cell membrane are included in Chapter 5. LO 1.15 The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. LO 1.16 The student is able to justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. LO 2.6 The student is able to use calculated surface area-to-volume ratios to predict which cell(s) might eliminate wastes or procure nutrients faster by diffusion. LO 2.7 Students will be able to explain how cell size and shape affect the overall rate of nutrient intake and the rate of waste elimination. LO 2.13 The student is able to explain how internal membranes and organelles contribute to cell functions. LO 2.14 The student is able to use representations and models to describe differences in prokaryotic and eukaryotic cells. LO 4.4 The student is able to make a prediction about the interactions of subcellular organelles. LO 4.5 The student is able to construct explanations based on scientific evidence as to how interactions of subcellular structures provide essential functions. LO 4.6 The student is able to use representations and models to analyze situations qualitatively to describe how interactions of subcellular structures, which possess 56 Mader, Biology, 12 th Edition Chapter 4

5 specialized functions, provide essential functions. LO 4.18 The student is able to use representations and models to analyze how cooperative interactions within organisms promote efficiency in the use of energy and matter. Key Concepts Summary Cell theory The cell theory states that all organisms consist of one or more cells and that cells come from existing cells Cells are limited in size by their surface-to-volume ratio Prokaryotic vs. eukaryotic cells Prokaryotic cells evolved first and are smaller that eukaryotic cells Prokaryotic cell membranes do enfold to provide surface area for enzyme attachment The theory of endosymbiosis explains the origin of many organelles Eukaryotic organelles The nucleus of the eukaryotic cells evolved from enfolding of the cell membrane to surround the chromatin material Ribosomes are the site of protein synthesis and are compose of rrna and proteins The endomembrane system moves and modifies proteins and in some cases synthesizes lipids Vacuoles and microbodies can store material for use or export and in some cases contain enzymatic reactions Chloroplasts are the site of carbohydrate production in photosynthetic eukaryotic cells Mitochondria are the site of conversion of molecules to ATP in eukaryotic cells Cytoskeleton consists of actin filament, intermediate filaments and microtubules and functions to support the nucleus and plasma membrane and to move organelles as needed Mader, Biology, 12 th Edition, Chapter 4 57

6 Key Terms capsule cell wall chloroplast cytoplasm endomembrane system endosymbiotic theory eukaryotic cells glycocalyx mitochondrion nucleoid region nucleus organelles plasma membrane prokaryotic cells ribosome surface-area-to-volume ratio vacuoles Teaching Strategies This will probably not be the first time that your students have heard about organelles. The evolutionary connection between the first cells on Earth, the prokaryotes, and the theory of endosymbiosis will probably be new to them. I would start with organelles and the differences between prokaryotes and eukaryotes and then move to endosymbiosis. This chapter also contains information about the restrictions on cell size. Chapter 5 concentrates on cell membranes and transport but Procedure 1 in Investigation 4 of the College Board Manual involves a cell size activity. I would have students conduct this investigation now. Class time: Allow three days consisting of 45 minute periods to cover the information on cells. Day 1: 20 minute lecture on prokaryotes, eukaryotes and endosymbiosis. Demonstration of endosymbiosis Day 2: Have students work in groups to review cellular organelles with the attached worksheet. Day 3: Have students conduct Procedure 1 in Investigation 4 of the College Board Manual. Attached is a worksheet to accompany this investigation. 58 Mader, Biology, 12 th Edition Chapter 4

7 Suggested Approaches One alternative approach to cells is to assign a cell project like the one detailed in the activities section. The project is intended for group work and involves cell communication which is described in Chapter 5. Student Misconceptions and Pitfalls One common misconception about cells that many students have is that ribosomes have a double membrane because they are organelles. Ribosomes do not have a membrane. Most students get the function of the nucleolus, production of rrna, confused with the function of the nucleus, housing DNA and site of mrna production. Suggested Activities Attached are worksheets/directions for the following activities: 1. Endosymbiosis demonstration 2. Review of cellular organelles worksheet 3. Worksheet to accompany Procedure 1 of Investigation 4 4. Cell group project Endosymbiosis demonstration Allow five minutes for a short demonstration on endosymbiosis. Prior to class, place a small balloon inside of a larger balloon. Blow both balloons up together to represent one prokaryote becoming trapped inside of another cell. Explain that the trapped cell evolved into the mitochondria and ask students to provide evidence that this occurred. They should be able to tell you that the mitochondrion today has its own DNA, its own ribosomes, is about the same size as a prokaryotic cell and has an inner membrane structure similar to the enfolding of a prokaryotic cell membrane. Mader, Biology, 12 th Edition, Chapter 4 59

8 Work in groups to review the characteristics of different cellular organelles. Sketch the basic structure of the organelle, describe its function, and identify if it is found in prokaryotes and/or eukaryotes, or if it is specific to animals or plants. CELL ORGANELLES Cell Part Structure Function Prokaryotes Eukaryote Animal Plant Plasma membrane Cell wall Ribosomes Chromatin Nucleus and nuclear envelope Cytoplasm Cytoskeleton Nucleolus 60 Mader, Biology, 12 th Edition Chapter 4

9 CELL ORGANELLES Cell Part Structure Function Prokaryotes Eukaryote Animal Plant Endoplasmic reticulum Golgi apparatus Mitochondria Chloroplast Vacuole Lysosomes, peroxisomes, and secretory vesicles Cilia Flagella Mader, Biology, 12 th Edition, Chapter 4 61

10 CELL ORGANELLES Cell Part Structure Function Prokaryotes Eukaryote Animal Plant Centriole Plastid 62 Mader, Biology, 12 th Edition Chapter 4

11 Limits to Cell Size a worksheet to accompany Procedure 1, Investigation 4 Surface Area to Volume Ratio Activity Cube: The surface area and volume of a cube can be found with the following equations: and and where S = surface area (in units squared), V = volume (in units cubed), and l = the length of one side of the cube. 1. From the baking dish, cut blocks of specific sizes: 1cm x 1cm x 1cm 2cm x 2cm x 2cm 3cm x 3cm x 3cm2. Calculate volume, surface area, SA:V ratio for each block. 2. Immerse each block in white vinegar. Time and record how long it takes for the blue to completely disappear. Create a data table for your results- time and SA:V ratios for each cube. Prepare a Data Table 1 and place this information into that data table. 3. Then take an ice cube block of the agar and design and make your own cell to maximize volume mass, but minimize diffusion time. No donut-like holes through the agar cell. No poking, prodding, touching beaker containing agar cell in vinegar. Teacher determines when 100% diffusion takes place. Students mass agar at conclusion of race...cell must not break when handled. Disqualification if cell breaks upon massing. Winner = highest ratio of mass divided by time. Mader, Biology, 12 th Edition, Chapter 4 63

12 Analysis Questions 1. Describe the results from the comparative diffusion trials in Table Explain the results from the comparative diffusion trials in Table In general, what is the relationship between cell volume and diffusion time? 4. In general, what is the relationship between surface area and diffusion time? 5. Explain why cells can't get very, very big. 6. Explain how cell shape can be modified so that diffusion can support life processes. 7. Which team's cell won the race? Offer a hypothesis as to why. 64 Mader, Biology, 12 th Edition Chapter 4

13 Cell Project This project helps students understand in detail how homeostasis is maintained by organisms. This includes the structure and interactions that occur between various cells, tissues, and organs. You will produce a model of a specialized cell that will emphasize how structure fits function. Your project will center around one of the specialized cells that are found in the immune, endocrine, or lymphatic system. 1. Students will need to research the shape and components that are found in your specialized cell. They will construct a 3-D model of a specialized cell, labeling organelles and other important structures that are found in your cell. 2. The student will research and provide detailed information about cell signaling that occurs in this system. What is the significance of signals that are received by this cell(s) and where do these signals originate? What types of signals are initiated by your one of cell(s) and what is their target? What is the specific signal transduction pathway and what is the desired response? 3. Make connections between normal cell functioning and a disease state. The disease cannot be cancer. Communicate with a support group or health care provider that works with this disease. Proof of this connection includes printed s or printed material from the organization. Describe a day in high school for a teenage with this disease. 4. Describe your cell s contribution to maintaining homeostasis for the human body. 5. Explain one example of an evolutionary trend for the system that your cell represents. Grades will reflect organization, technical accuracy, and a clear, engaging, creative presentation. Remember to: use visual aids be organized in your presentation provide an outline summary with works cited page for your fellow classmates. Outlines should not exceed front and back of a page, no smaller than 11 font write important vocabulary on the board practice your presentation out loud prior to the classroom presentation Mader, Biology, 12 th Edition, Chapter 4 65

14 take time to coordinate your presentation among group members if you need to use notes during your presentation, make them in an outline form at no time should you be reading to your classmates cite all images you borrow for you visual presentation citation should be with/on the image itself cite all sources you use to gain information Organ System Specialized Cells System Function Immune and Lymphatic Endocrine Nervous Bone marrow, lymph nodes, thymus, spleen, lymph vessels, white blood cells, B-Cells Pituitary, thyroid, pancreas, other hormonesecreting glands Brain, spinal cord, nerves, sensory organs Body defense (fighting infections and cancer) Coordination of body activities (e.g., digestion, metabolism) Coordination of body activities; detection of stimuli and formulation of responses to them Suggested Groups: 1: Non-specific immune response in plants, vertebrates, and invertebrates 2: Specific Immunity (cell mediated response): Helper T-cells, cytotoxic T-cells, MHC 3: Humoral Response: B- cells, plasma cells, antibodies, helper T-cells 4: Active and Passive Immunity: memory cells and 2 nd exposure 5: Structure of Neuron: glial cells, neuron, astrocytes: action potential & neurotransmitters 6: Hearing and Vision: sensory receptors, integration of sensory input 7. Endocrine: insulin: feedback mechanisms: pancreatic cell 8. HGH in conjunction with Insulin like growth factor: liver cell 9. Anterior Pituitary: neurosecretory cell 10. Testosterone/estrogen: oocyte or spermatocyte 66 Mader, Biology, 12 th Edition Chapter 4

15 Student Edition Chapter Review Answers Answers to Assess Questions 1. c; 2. d; 3. d; 4. a; 5. a; 6. c; 7. d; 8. a; 9. c; 10. a; 11. c; 12. c; 13. b; 14. d; 15. c; 16. a; 17. c; 18. c; 19. d; 20. d Answers to Applying the Big Ideas Questions 1. Cells, the smallest units of living matter, make life possible. a) Draw one generalized prokaryotic cell AND one generalized eukaryotic cell. b) Label the cellular components. c) Answer the question: What are two major differences a between prokaryotic and eukaryotic cells? Make sure that these differences are evident in your drawings. Essential Knowledge Science Practice Learning Objective 2.B.3: Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. 1.4: The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. 2.14: The student is able to use representations and models to describe differences in prokaryotic and eukaryotic cells. 4 points maximum. Labeled diagrams and descriptions of differences may include: Drawings and labels (1 point each) Prokaryotic cell (should include at least 3 of the following for full credit): Cell envelope (plasma membrane, cell wall and glycocalyx) Cytoplasm Nucleoid region Ribosomes Descriptions of differences (1 point each) Nucleus: Prokaryotic cells lack a nucleus and nucleolus and instead have a nucleoid region where their DNA is located. Endomembrane system: Membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions, as seen with the Mader, Biology, 12 th Edition, Chapter 4 67

16 Cilia, Flagella, Fimbriae and/or Pili Eukaryotic cell (should include at least 3 of the following for full credit): Plasma membrane Cell wall, chloroplasts and/or vacuole only if diagram is clearly representing a plant cell Nucleus Cytoplasm Organelles (Rough and Smooth ER, Golgi) Mitochondria Peroxisomes, Lysosomes, Vesicles, and/or Ribosomes ER and Golgi. Eukaryotic cells may also contain organelles not found in prokaryotic cells, such as: mitochondria, chloroplasts (plants), peroxisomes, and lysosomes (animals). Eukaryotic cells are composed of a cytoskeleton. Take note: While prokaryotic cells usually have a cell wall, plant cells (eukaryotic) do as well. Additionally, while animal cells often have centrioles, prokaryotic cells and plant cells do not. Animal cells often have flagella or cilia as well, though in different numbers from prokaryotic cells. 2. The subcellular components of eukaryotic cells increase cell efficiency. a) Describe two scenarios where scientists have found subcellular structures interact. b) Explain how these interactions provide essential functions for the cell. Essential Knowledge Science Practice Learning Objective 4.A.2: The structure and function of subcellular components, and their interactions, provide essential cellular processes. 6.2: The student can construct explanations of phenomena based on evidence produced through scientific practices. 4.5: The student is able to construct explanations based on scientific evidence as to how interactions of subcellular structures provide essential functions. 68 Mader, Biology, 12 th Edition Chapter 4

17 4 points maximum. Description of the subcellular structures and the appropriately linked explanation their contributions to essential functions may include: Descriptions of interactions (1 point each) Ribosomal RNA and protein interact to form ribosomes. Membrane-bound ribosomes and the endoplasmic reticulum work together as the rough ER. The endomembrane system includes the ER, the Golgi apparatus, the lysosomes, and transport vesicles. Mitochondria have a double membrane that allows compartmentalization within the mitochondria. The outer membrane is smooth, but the inner is highly convoluted, forming folds call cristae. Cristae contain enzymes important to ATP production; cristae also increase the surface area for ATP production. The matrix contains DNA and ribosomes. For cellular respiration, the cytoplasm of the cell is also involved. Explanations of functions (1 point each) Ribosomal RNA and protein interact to become the site of protein synthesis where the translation of genetic instructions yields specific polypeptides. Rough endoplasmic reticulum provides site-specific protein synthesis and plays a role in intracellular transport. Through their interactions, newly produced proteins and lipids are modified, packaged and transported throughout the cell. Lysosomes are produced by the Golgi and contain digestive enzymes. Cellular respiration: Mitochondria specialize in energy capture and transformation. Liver cells need a great concentration of mitochondria due to their high metabolic needs. Mader, Biology, 12 th Edition, Chapter 4 69

18 The cytoskeleton interacts with many organelles. Intermediate filaments support the nuclear and plasma membranes and interact with other cells. Microtubules radiate out from the centrosome and are the system along which vesicles and other organelles move. Ribosomes and the nucleus with its structures (and possibly cytoplasm and rough ER) function together in protein synthesis. These interactions provide cell structure, support, internal transport, interactions between cells (such as forming tissues), and mediate the occurrence of cell division. These interactions are involved in protein synthesis from DNA. 3. Organisms share many conserved features that evolved and are widely distributed among organisms today. Describe THREE specific examples of evidence from cells and their structures that support the concept of common ancestry for all organisms. Essential Knowledge Science Practice Learning Objective 1.B.1: Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. 1.15: The student is able to describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. 70 Mader, Biology, 12 th Edition Chapter 4

19 3 points maximum. Student descriptions include the following connections: Cell Theory: The work of Brown, Schleiden, and Schwann contributed to the idea that all organisms are composed of cells, the basic units of structure and function in organisms. Cell Theory: The work of Virchow showed that cells self-reproduce and that every cell comes from a preexisting cell. Fossil Record: Suggests the first cells ere prokaryotes. Endomembrane System: Organelles (nucleus, Golgi, and ER) are believed to have evolved due to the invagination of the plasma membrane. Endosymbiotic Theory: Mitochondria and chloroplasts were independent prokaryotes that took up residence in a eukaryotic cell. Both organelles are similar to bacteria in size and structure and are surrounded by a double membrane. They also contain genetic material (DNA) that is a circular loop like in prokaryotes, and they produce some proteins. Their ribosomes resemble those of prokaryotes. Answers to Applying the Science Practices Questions Think Critically 1. The two complexes are targeting complex and unknown targeting complex. 2. Vesicle transport might be directed through the cytoplasm by microtubules. Mader, Biology, 12 th Edition, Chapter 4 71

20 Additional Questions for AP Practice 1. Explain the theory of endosymbiosis and justify its role in evolution. 2. Describe the components of the endomembrane system and explain their importance. 3. Choose the best prediction of the fate of a protein that is produced on a ribosome that is embedded in the rough endoplasmic reticulum. A) The protein will be added to new rrna and become part of a new ribosome. B) The protein will be released immediately via exocytosis and act as a signal protein. C) The protein will definitely have a carbohydrate attached to it in the lumen of the ER. D) The protein may be delivered to the golgi for further processing. 4. Determine the surface are to volume ration of a cell with a roughly cube shape of 3.25 μm. 5. Describe the features of a cell that organisms in all Domains share. 72 Mader, Biology, 12 th Edition Chapter 4

21 Grid-In Questions 1. The green alga Volvox forms spherical colonies. Determine the surface area to volume ratio of a colony that is 2 mm in diameter. 2. The table below gives the dimensions of four different sized cubes. What is the height of the cube that has a 3:1 surface area to volume ratio? Height (cm) Surface Area (cm 2 ) Volume (cm 3 ) A chloroplast is 1 µm in size, whereas a frog egg is around 1 mm. How many factors smaller is the chloroplast compared to the frog egg? Mader, Biology, 12 th Edition, Chapter 4 73

22 Answers to Additional Questions for AP Practice 1. The endosymbiotic theory states mitochondria and chloroplasts were independent prokaryotes that took up residence in a eukaryotic cell. The functions within a\the cell became specialized with the mitochondria becoming specialized to produce ATP. Endosymbiosis was a beginning step toward the origin of the eukaryotic 2. The endomembrane system consists of the nuclear envelope, the membranes of the endoplasmic reticulum, the Golgi apparatus, and several types of vesicles. This system compartmentalizes the cell so that particular enzymatic reactions are restricted to specific regions and overall cell efficiency is increased. The vesicles transport molecules from one part of the system to another. 3. D is the best answer. Most proteins are added to the rrna in the nucleolus. Most proteins have some sort of refinement before they are released from the cell. While many proteins have carbohydrates added to them in the lumen of the ER, not all of them are processed in this way. 4. SA: 3.25 x 3.25 x 6 = μm. Volume = 3.25 x 3.25 x 3.25 = SA: Volume = : or reduced to 1.8: 1 5. All cells have a cell membrane, DNA and RNA, ribosomes, and cytoplasm. All cells practice the central dogma of biology; DNA carries the code for protein production that is passed onto mrna. mrna is used as instructions for making a protein by attaching to a ribosome and providing the code for which amino acids should be delivered to the ribosome by the trna. 74 Mader, Biology, 12 th Edition Chapter 4

23 Answers to Grid-In Questions 1. Chapter: 4 Cell Structure and Function Topic: surface area-to-volume ratio Answer: 12.6/4.2 A = 4 π r 2 V = 4/3 π r 3 A = 4 π (1) 2 = 12.6, V = 4/3 π (1) 3 = 4.2 A:V = 12.6/ Chapter: 4 Cell Structure and Function Answer: Chapter: 4 Cell Structure and Function Answer: 1000 µm = 10-6 mm = /10-6 = 10 3 =1000 Mader, Biology, 12 th Edition, Chapter 4 75