Tour of an Animal Cell Structures and Functions

ch 7, 8 and 9 14 of 51 Tour of an Animal Cell: Structures and Functions The cell is the basic structural and functional unit of all organisms. To understand how an organism works, you must first understand how its cells are structured and the roles that each structure performs in the cell. Before beginning this tutorial, watch the Tour of an Animal Cell animation to learn about the general structure of an animal cell. Although animals are made up of many different cell types (for example, nerve cells, blood cells, muscle cells), all of the cells share many basic similarities with the cell shown in the animation. Part A - Animal cell structures and functions To understand how cells function as the fundamental unit of life, you must first become familiar with the individual roles of the cellular structures and organelles. Drag the labels on the left onto the diagram of the animal cell to correctly identify the function performed by each cellular structure. Hint 1. Structure and function of cell organelles The structure of each organelle in a eukaryotic cell makes it very well-suited for the task it performs. Some examples are described here. Rough endoplasmic reticulum: This organelle plays an important role in the synthesis of secretory proteins. The outer surfaces of rough ER are studded with ribosomes, the sites where proteins are made. As a protein chain grows from a bound ribosome, it is threaded through a pore in the ER membrane. Once inside, protein folding occurs. Golgi apparatus: The Golgi is composed of a series of flattened membranous discs called cisternae. Each cisterna forms an enclosed space that houses a distinct set of enzymes used to process proteins in a sequential manner as they are prepared for transport to different sites. Mitochondria: The inner membrane of a mitochondrion has extensive infoldings, which greatly increase the surface area available for key reactions in the energy-producing processes of cellular respiration. Hint 2. Which organelles are involved in protein secretion? A key feature of cells is their ability to synthesize proteins. Although proteins are constructed in the cytoplasm, many must be transported outside of the cell to perform their role. For example, the docking stations and protein components of the extracellular matrix (shown in the animation) are all synthesized inside the cell, but function outside. Through which pathway do proteins move out of the cell to the extracellular matrix? ANSWER: smooth ER → lysosome → plasma membrane rough ER → Golgi → plasma membrane nucleus → Golgi → plasma membrane Golgi → smooth ER → plasma membrane Hint 3. Can you identify the parts of the nucleus? The nucleus is the defining characteristic of eukaryotic cells. This structure is best known for its role in housing the cell’s genetic information, but there is more to this organelle than simply storing DNA. 6/13/2019, 11:24 AM ch 7, 8 and 9 15 of 51 Drag the terms from the left to the appropriate blanks on the right to complete the sentences. Terms can be used once or not at all. ANSWER: Reset Help 1. The genetic information housed within the nucleus is associated with protein and is called nucleoid chromatin . 2. The nuclear envelope is a double membrane that separates the nucleus from the cytoplasm. 3. The synthesis and assembly of ribosomal components occurs in the nucleolus . 4. The shape of the nucleus is maintained by a network of protein filaments called the nuclear lamina . 5. Before RNA can be translated into protein, it first must be exported from the nucleus through a nuclear pore . ANSWER: 6/13/2019, 11:24 AM ch 7, 8 and 9 16 of 51 Reset Help Part B - Comparing eukaryotic and prokaryotic cells Two fundamental types of cells are known to exist in nature: prokaryotic cells and eukaryotic cells (like the one shown in the Tour of an Animal Cell animation). Both prokaryotic and eukaryotic cells carry out all of the processes necessary for life, but they differ in some important ways. In this activity, you will identify which cell structures are found only in prokaryotic cells, only in eukaryotic cells, or in both types of cells. Drag each cell structure to the appropriate bin. Hint 1. Origins of eukaryotic organelles According to the serial endosymbiosis theory, mitochondria were originally free-living prokaryotes that were taken up by an ancestor of the modern eukaryotic cell. It is estimated that this event occurred approximately 3 billion years ago. Evidence that supports this theory includes the ways in which mitochondria differ from other organelles in eukaryotic cells. Unlike the organelles of the endomembrane system, mitochondria replicate independently and cannot be regenerated if they are lost. Mitochondria contain their own small, circular genome and ribosomes that are used to synthesize some of their own proteins. The mitochondrial ribosomes are similar in size and structure to prokaryotic ribosomes. The metabolic pathways housed in the inner membrane of mitochondria are similar to those found in bacterial plasma membranes (e.g., the respiratory chain). The serial endosymbiosis theory also explains how certain eukaryotic cells acquired chloroplasts, organelles with many of the same distinguishing characteristics as mitochondria. Hint 2. Which cell structures are enclosed by membranes? Eukaryotic cells contain many membrane-enclosed structures not found in prokaryotic cells. Which cell structures are enclosed by membranes? Select all that apply. ANSWER: 6/13/2019, 11:24 AM ch 7, 8 and 9 17 of 51 ribosome mitochondrion nucleoid nucleus bacterial flagellum lysosome ANSWER: Reset Help Part C - Role of the eukaryotic cytoskeleton The cytoskeleton of a eukaryotic cell plays a major role in organizing the structures and activities of the cell. The cytoskeleton consists of three main types of fibers: microfilaments, intermediate filaments, and microtubules. The three types of fiber differ in size, composition, and the functions they perform in the cell. 6/13/2019, 11:24 AM ch 7, 8 and 9 18 of 51 Drag the terms on the left to the appropriate blanks in the sentences on the right. Terms can be used once, more than once, or not at all. Hint 1. The role of cytoskeletal fibers in cell division Replication of an animal cell requires the participation and coordination of microtubules, intermediate filaments, and microfilaments. Breakdown of the nuclear envelope: Before mitosis begins, the nuclear envelope is broken down by disassembling the lamins, a type of intermediate filament that supports the structure of the envelope. Mitotic spindle formation: Once the nuclear contents become continuous with the cytoplasm, the microtubules of the spindle grow out from the centrosomes at the two poles. The microtubules are captured by motors associated with the chromosomes. Formation of the nuclear envelope: Once the chromosomes have been separated, marking the end of anaphase, a nuclear envelope begins to form around each set of chromosomes through the assembly of new lamins and vesicles. Cytokinesis: Like a drawstring, a belt of microfilaments and their associated myosin motor proteins pull in the membrane between the two newly formed nuclei, constricting the cytoplasm and creating a furrow that eventually divides the cell. Hint 2. Which cytoskeleton fibers enable directional movement? Directional movement (as opposed to random movement, as is the case with diffusion) is required for a number of processes within the cell. For example, the targeted movement of vesicles in the cytoplasm occurs in a specific directional manner. To ensure that movement occurs in only one direction, the fibers that control the movement must have polarity, so that one end of the fiber differs from the other. Which of the three cytoskeletal fibers have polarity? Select all that apply. ANSWER: intermediate filaments microtubules microfilaments ANSWER: 6/13/2019, 11:24 AM ch 7, 8 and 9 19 of 51 Reset microfilaments intermediate filaments microtubules Help 1. In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules . 2. Many cell organelles, most notably the nucleus, are anchored by intermediate filaments which are assembled from a diverse class of proteins. 3. Centrosomes are sites where protein dimers assemble into microtubules . 4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfilaments . 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments . 6. During muscle contractions, myosin motor proteins move across tracks of microfilaments . 6/13/2019, 11:24 AM