INVESTIGATION C2 C2 LEARN™ Plant Cell Key Question: What organelles and structures make up a generalized plant cell, and what are their functions? In this investigation, students will interact with the Online Resources ™ LEARN app to explore a generalized plant cell model. Available at www.curiosityplace.com A cookie factory analogy will guide students as they identify and consider the structure and function of Student Vocabulary Words organelles. Note: The names and functions of general plant cell organelles and structures can be found in Table 1 of the Learning Goals investigation. Those organelles are not listed again here. ✔ Identify 17 structural features of a generalized plant cell. TEACHER BACKGROUND ✔ Explain the function of 17 plant cell structural features within the context of a factory analogy. amoeba – protist that uses pseudopods for feeding and locomotion ✔ Compare and contrast plant and animal cells. autotrophic – describes organisms that are able to produce their own food GETTING STARTED Euglena – protist genus that has chloroplasts and can be both an autotroph and a heterotroph Time 150 minutes galacturonic acid – oxidized form of D-galactose and the main component of pectin found in the cell wall’s Setup and Materials middle lamellae 1. Make copies of investigation sheets for students. heterotrophic – describes organisms that must consume 2. Have students work in small groups, depending on food for nutrition how many devices are available. middle lamella – part of the cell wall made mostly of 3. Make sure each group has a device with the pectin; helps adjacent cells bind to each other LEARN™ app downloaded and ready to use. primary cell wall – cell wall layer between the middle lamella and the cell membrane that makes the cell wall Materials for each group sturdy; made mostly of cellulose y Device with LEARN™ app y Highlighters y Colored pencils, markers, and sticky notes or flags for customizing App Map NGSS Connection This investigation builds conceptual understanding and skills for the following performance expectation. HS-LS1-1. Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. Science and Engineering Practices Disciplinary Core Ideas Crosscutting Concepts Developing and Using Models LS1.A: Structure and Function Structure and Function Engaging in Argument from Evidence Scale, Porportion, and Quantity LEARN™ Plant Cell 119 LEARN™ PLANT CELL Although many of the organelles found in plant cells are primary cell wall is the layer between the middle lamella similar to those in animal cells, there are some important and the cell membrane, and it contains mostly cellulose differences that allow for the special needs and functions and pectin, as well. This makes the primary cell wall both of these diverse organisms. Students will use the strong and flexible. LEARN™ app to explore a generalized plant cell in this investigation, highlighting the similarities and differences In order to communicate with the other plant cells, between plant and animal cells. the cell wall has openings called plasmodesmata. These channels are membrane-lined, allowing for the Without a strong skeleton to hold them up, plant trafficking of molecules and even proteins from one cell cells need to provide support for their stems, which to another. are sometimes very tall. Thus, in addition to the cell membrane (which animal cells have as well), plant cells Cell wall layers also have a sturdy cell wall. This structure is made primarily of cellulose, a type of polysaccharide containing at least 3,000 glucose molecules. Cellulose is the most abundant naturally occurring polymer on the planet. The cell wall also includes soluble proteins and pectin—another type of polysaccharide. Pectins are a group of polysaccharides that are rich in galacturonic acid and found in non-woody structures of land plants, especially in fruit. There are three main layers to the cell wall: the middle lamella, the primary cell wall, and the cell (or plasma) membrane. The middle lamella, made up of pectin, helps the cell walls of adjacent cells bind to one another. The Plant cell Control nucleus nucleolus Maintenance cytoskeleton ribosomes Fulllment Power central vacuole vesicle lysosome Golgi apparatus chloroplast rough ER mitochondria cell wall cytoplasm smooth ER cell membrane 120 C2 The cell wall can withstand high internal pressure created typically both single-celled and microscopic, protists— by another plant-specific organelle called the central as eukaryotes—still contain a nucleus and membrane- vacuole. The central vacuole fills with water, food, and bound organelles. waste, creating pressure that helps stabilize the cell wall and keeps the plant upright. Evidence of this comes in First proposed in 1886 by Ernst Haeckel, the Kingdom the form of a plant that wilts when water supplies are Protista has changed over time based on new genetic, low. The empty central vacuole cannot produce the morphological, and biochemical information. Previously, pressure necessary to keep the structure supported, a protist was any eukaryote that was not an animal, land causing the plant to wilt. plant, or fungus. Many protists have been reclassified into other groups based on new data. Another important plant organelle is the chloroplast, a membrane-bound organelle that is found in many parts of Two protists will be featured in the games for the plant but is most abundant in the leaves. This structure Investigations 3 and 4—one of which is considered to captures sunlight and, along with water and carbon be animal-like, and one plantlike. Animal-like protists are dioxide, produces glucose and oxygen. If you’d like more heterotrophic (they must consume food for nutrition), information about photosynthesis, Chloroplast Blast— mobile, and unicellular. The animal-like protist is the from CPO Science’s “Energy Quest” Link series—provides a amoeba, which is a term used to describe a single-celled detailed, fun, and interactive look at photosynthesis in the eukaryote that can alter its shape via pseudopods— chloroplast using a cooperative board game. armlike extensions of the plasma membrane. In addition to having some additional organelles, Plantlike protists are autotrophic (able to produce their plant cells are also missing an organelle found in own food); some are mobile, and some are multicellular. the generalized animal cell. This organelle, called a The plantlike protist Euglena contains chloroplasts, so centriole, plays a role in cell division in animal cells. it can carry out photosynthesis. Interestingly, Euglena During mitosis, centrioles organize the mitotic spindles, can also consume its food, like a heterotroph. When which are cytoskeletal structures that will help pull the feeding, a tail-like projection called a flagellum propels chromosomes apart. Instead of relying on these, plant it toward food. cell mitotic spindles organize through a mechanism that There are also fungus-like protists, which include is still not well understood but likely relies on the polar organisms that have cell walls like plants but reproduce nature of the spindles. via spores like fungi. They also have the ability to move— A group of organisms that cannot be classified as plants at least at some point in their life cycle. The two most or animals are the protists—a collection of diverse, often common types of fungus-like protists are slime molds single-celled eukaryotic organisms. Although they are and water molds. Amoeba Euglena LEARN™ Plant Cell 121 LEARN™ PLANT CELL 5E LESSON PLAN through plasmodesmata, as can harmful plant viruses. The nature of the cell-to-cell communication allowed by Engage plasmodesmata is an active area of research. An earthworm has the ability to crawl and move around, Some animal cells also have channels between but a sunflower remains rooted in one spot. Use the neighboring cells, called gap junctions. Although the following discussion questions to help students focus on functions of plasmodesmata and gap junctions are the structures and organelles they will observe with the similar, the structures are very different. Instead of LEARN™ app that are unique to plant cells: the cell wall, membrane-lined channels, gap junctions are protein- chloroplasts, and the central vacuole. lined pores. Cardiac muscle cells use gap junctions for the transmission of electrical signals that control rhythmic y Ask students which organism would benefit the most contractions of the heart muscle. from having its cells surrounded by a thick, strong, rigid wall. Why? Elaborate y Which organism would benefit the most from having the ability to make its own food? Why? Plant Biomechanics y Which organism would benefit the most from having Your students have probably heard of biomechanics— cells with a large water storage organelle? the study of how physics relates to the movement and structure of living things. But do they know that plant biomechanics is an important field of study that dates Explore back to Hooke’s first observations of cork cell structure Have students use the LEARN™ app to complete Investi- in the 1600s? Plant biomechanics shows how plant cells, gation C2, LEARN™ Plant Cell. Students interact with the tissues, and structures can be modeled and studied as LEARN™ app to explore a generalized plant cell model. complex composite materials. An example of a plant A cookie factory analogy will guide students as they biomechanics application is using different types of wood identify and consider the structure and function for musical instruments, depending on the acoustic quality of organelles. you want to achieve. The ability of plants to perceive and respond to gravity, touch, and wind is also a fascinating Explain and active area of plant biomechanics research. Plasmodesmata, often illustrated as holes in a plant The International Plant Biomechanics Conference is held cell wall, are membrane-lined channels that form every three years. The conference is held every three years.