Fungal cell walls are rigid with less flexibility due to a combination of more sugar (more chitin) and protein flexibility.

Transcription

1 Cell Structure Assignment Score. Name Sec.. Date. Working by yourself or in a group, answer the following questions about the Cell Structure material. This assignment is worth 40 points with the possible points for each question in parenthesis. Maybe these web sites will help you grasp and learn the material (6) Draw and label a diagram of the arrangement of molecules found in the construction of a cell wall found surrounding bacterial cells versus fungal cells versus plant cells. Bacterial cell walls are rigid but flexible due to a combination of rigidity due to sugar (chitin) and flexibility due to protein moieties (components). Fungal cell walls are rigid with less flexibility due to a combination of more sugar (more chitin) and protein flexibility. 1

2 Plant cell walls are rigid with the least flexibility due to a combination of sugars called cellulose, hemicellulose, and lignin webbing giving some flexibility and pectin glue (rigid). 2. (18) (18) Design a table on a separate sheet of paper to show the relationship between all the eukaryotic membrane bound organelles (Nucleus (nuclear membrane with pores, nucleolus, and chromatin), Endoplasmic reticulum (rough and smooth) Golgi Body (or apparatus), Mitochondria, Chloroplast, Lysosome, Peroxisome, and Vacuoles) to reveal their individual structure and functional relationship. Organelle Description of Structure Description of Function Nucleus This organelle has a dual bi-layered covering membrane (envelope) that contains a permanent webbing of protein covered pores to move material from the nucleus to the cytoplasm. Nucleolus (inside kernel where protein is combined with rrna to make ribosomes)? Chromatin (two types Euchromatin (open sequences for cell to read and use) and Heterochromatin (closed to the cell due to chemically bound to prevent access)? This organelle is basically a safe deposit box for the DNA (chromatin (eu. vs. hetero.)) and a site where the various RNA molecules are constructed. The pores are needed to move the large RNA molecules to the cytoplasm without losing the integrity of the envelope. The chromatin (DNA) is found embedded in a gel like substance called the nucleoplasm. A substructure called the nucleolus seems to be the site where ribosomes are organized. Rough E.R. Smooth E.R. Golgi Body (or Golgi Apparatus) A tubular system that courses from being close to the nuclear pores and ending as a blind tube in the cytoplasm. It has an rrna and protein structure attached to the cytoplasmic side of the tube called a ribosome. Another tubular system (Maybe just one long tube divided into sections?) but has no ribosomes attached to its cytoplasmic side. A stack of tubular structures (like a stack of pancakes) usually associated with the blind (or exit) end of the rer. The arrival side of the Golgi is called the Cis face while the exit side is called the Trans face. Because of the ribosomes the organelle seems to be the primary site of protein synthesis for the cell. The proteins constructed here usually end up being shipped to the Golgi Body (or Golgi Apparatus) in a membrane bound vacuole that has budded off from the rer. The ser seems to function differently in different cells. The functions vary from lipid synthesis, detoxifying chemicals (think drugs), to storing ions (mainly calcium). Proteins arriving (Cis face) from the rer are modified, cut to the proper lengths, concentrated, and packaged for shipment (Trans face) (usually out of the cell) as the protein moves from pancake to pancake but can form lysosomes or peroxisomes. 2

3 Mitochondria Chloroplast Lysosome Peroxisome Vacuoles Another dual bi-layered organelle with the inner layer thrown into folds called cristae that houses a gelatinous mass called matrix. This organelle is tri-layered with the outer two layers forming an oval structure and the inner layer (called the thylakoid membrane) thrown into disc shaped structures called grana. An oval shaped organelle whose membrane is constructed with less fluidity (change the polar head of the phospholipid) that is significantly less permeable than other membranes to contain the various powerful digestive enzymes. Similarly structured to the lysosome they just contain different enzymes. Membrane bound storage chests for whatever the cell wants to store. These little guys are designed to dismantle molecules (think carb s) to release energy and transfer the energy to a molecule called ATP and giving off CO 2 and H 2O as waste. This is the site of photosynthesis or the conversion of random sunlight energy, CO 2, and H 2O into glucose or any other organic molecule the organism needs. What is the Endosymbiotic Theory? ( ) Their role is to unite with organelles that must be destroyed (like vacuoles containing bacteria or other organelles that are damaged) to let their contained enzymes loose to dismantle the molecular contents. So these guys remove large waste material (beyond the molecular or atomic level). These organelles remove waste that is at the molecular or atomic level. Duh, they store stuff like water, food, pigments or etc. depending on the cell type. 3. (6) Complete this table to show the relationship between the following identified eukaryotic nonmembrane bound organelles by describing their structural versus functional relationship. Organelle Description of Structure Description of Function Ribosome These are tiny little structures that look like grains of sand either roaming free in the cytoplasm or attached to the rer, and consist of a short sequence of rrna and protein. They are sites of protein construction. Those that are attached to the rer make proteins that are usually sent outside of the cell via transport vacuoles while those proteins made on free ribosomes usually stay in the cytoplasm for cellular function. Cytoskeleton Centriole These are protein fibers embedded into the cytoplasm that forms a sort of meshwork like organization. The cytoskeleton consists of three types of fibers actin microfilaments, microtubules, and intermediate fibers. These are paired little barrel shaped structures made of tubulin (same as microtubules) protein. The actin is contractile and is used to change the shape of the cell, the microtubules are used as a sort of railroad network to move the organelles around inside the cell, and the intermediate fibers are more rigid to primarily hold the cell shape. Their function is to build something called a spindle tubular apparatus that is used during cell division to move copied chromatin material to opposite ends of the cell. 3

4 4. (6) Complete this table to show the relationship between the identified cellular structures by describing their structural versus functional relationship. Structure Description of Structure Description of Function Microvillus These are relatively short membrane Cells use these to fold their membranes to extensions that are filled with protein increase their overall surface area without microfilaments. drastically increasing their total volume. Cilium These structures arise from a structure of inside the cell membrane called a basal body. As the cilium grows from the basal body it pushes towards the outside of the cell but never penetrating the membrane. This prevents a weakening of the membrane even when these structures extend 4 to 10µm s from the cell. These usually move with a sort of waving motion to move material across the cell s surface or beat in unison to establish micro currents in water to move material toward the cell. Flagellum Similarly structured like the cilia (made of tubulin) only extremely longer they can be 15 to 20µm in length with the cell being 10µm in length. Both cilia and flagella consist of a arrangement of tubulin (central doublet surrounded by 9 doublets in a circle around the 2) joined together by dyein arms and radial spokes. As the dyein arms contract via ATP they pull on the radial spokes to get the cilia or flagella to sway by pulling on the tubulin doublets. They move the entire cell through the environment in a similar motion to that of a cilium. The only human cell with a flagellum is the spermatozoa, but many other species use this means of motility to get around. 5. (4) Describe the structural and functional differences between intercellular junctions found between animal versus plant cells. Animal cells are held together by three types of junctions. The tight junction (also called annealing junctions) holds neighboring cells tightly together at the tops (apical surface) of the cells (think neighboring blocks). They are almost like folding neighboring membrane together into one membrane. The adhesion (also called desmosomes or anchoring) junction holds the membranes between the cells together or sort of on the side to reduce the stress on the tight junctions. Finally gap junctions (also called communication) are between cells but have teeny tiny protein tubes running between the cells for intercellular communication. 4

5 Plant cells are primarily held to each other through the construction of their cell walls that is a meshwork of cellulose and hemicellulose molecules glued together by the carbohydrate based pectin molecules, but due to the structure and rigidity of the cell wall small channels called plasmodesmata are left in the cell wall to allow for cell to cell communication. 5