10/1/2014. Chapter Explain why the cell is considered to be the basic unit of life.

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1 Chapter 4 PSAT $ by October by October 11 Test 3- Tuesday October 14 over Chapter 4 and 5 DFA- Monday October 20 over everything covered so far (Chapters 1-5) Review on Thursday and Friday before 1. Explain why the cell is considered to be the basic unit of life. 2. Name the scientists who first observed living and nonliving cells. 3. State the principles of the cell theory. 4. Summarize the research that led to the development of the cell theory. 5. Explain the relationship between cell shape and cell function. 6. Identify the factor that limits cell size. 7. Describe the 3 basic parts of a cell 8. Compare and contrast prokaryotic and eukaryotic cells. 9. Analyze the relationship among cells, tissues, organs, organ systems, and organisms 10. Describe the structure and function of a cell s plasma membrane 11. Summarize the role of the nucleus. 12. Identify the characteristics of the mitochondria. 13. Describe the structure and function of the cytoskeleton. 14. List 3 structures that are present in plants cells but not in animal cells. 15. Compare the plasma membrane, the primary cell wall, and the secondary cell wall. 16. Explain the role of the central vacuole. 17. Describe the role of plastids in the life of a plant. 18. Identify features that distinguish prokaryotes, eukaryotes, plant cells, and animal cells Cells were 1 st discovered in 1665 by Robert Hooke DEAD cork cells Leeuwenhoek- 1 st observed live cells, referred to them as animalcules. Early studies of cells were conducted by Schleiden (1838) and Schwann (1839) Together they proposed the cell theory Cell theory 1.) All organisms are composed of cells 2.) Cells are the smallest living things 3.) Cells arise only from pre-existing cells 1

2 Chapter 4 Introduction to Cells Cellular Organization n multicellular eukaryotes, cells organize into tissues, rgans, organ systems, and finally organisms. Cell size is limited As cell size increases, it takes longer for material to diffuse from the cell membrane to the interior of the cell. Surface area-to-volume ratio: as a cell increases in size, the volume increases 10 times faster than the surface area For example: If the cell radius increases by 10 times, the surface area increases by 100 times, but the volume increases by 1000 times. Types of microscopes Light microscopes- compound light microscopes Can r esolve str uctur es 200 nm apar t Electron microscopes Can r esolve str uctur es 0.2 nm apar t 2 types SEM (scanning electr on micr oscope) Forms 3-D images by beaming electrons onto the surface of the specimen TEM (transmission electron microscope) Also uses a beam of electrons that are transmitted through an ultra thin specimen, interacting with the specimen as it passes through it The use of stains aids in viewing cell structure Chapter 4 Cell Organelles and Features 1.) The genetic material is located in a centrally located nucleus or nucleoid. 2.) A semi fluid matrix called cytoplasm fills the inside of the cell. 3.) The plasma membrane encloses the cell and separates its contents from its surrounding. 2

3 Chapter 4 Cell Organelles and Features Plasma Membrane- Fluid Mosaic Model Membrane Proteins Cell membranes often contain proteins embedded within the phospholipid bilayer. 2 types of Prokaryotes: Eubacteria and Archaea Lack a membrane-bound nucleus Instead genetic material is located in nucleoid Prokaryotic cells possess Cytoplasm Plasma membrane Cell wall Ribosomes However, they lack membrane-bound organelles. Flagella are present in some prokaryotic cells Used for locomotion Rotary motion propels the cell Function to protect the cell and maintain shape Bacterial cell (Eubacteria) walls consist of peptidoglycan May be gram + or gram Detected by gram-staining procedure Gram +: thick, single layer peptidoglycan cell wall that retains the crystal violet stain (purple) Gram -: more complex, multilayered cell wall that does not retain the crystal violet stain; stain with counterstain,safarin (pink) Archaea lack peptiodoglycan Possess a membrane-bound nucleus More complex than prokaryotic cells Compartmentalize cellular functions within organelles and endomembrane system Organelles: membrane-bound structures that form compartments Endomembrane system: system of connected membrane compartments Have a cytoskeleton for support and to maintain cellular structure 3

4 Stores the genetic material of the cell in multiple, linear chromosomes DNA is organized with protein to form chromatin Surrounded by a nuclear envelope Composed of 2 phospholipid bilayers Nuclear pores: opening in the nuclear envelope, allows proteins and nucleic acids in and out of the nucleus Nucleolus (nucleoli): site of rrna (ribosomal RNA) synthesis Site of protein synthesis in the cell Composed of ribosomal RNA (rrna) and proteins Found within cytosol of the cytoplasm and attached to internal membranes Each ribosome is composed of 2 subunits Large and small subunit Types of RNA rrna (ribosomal): provide a mechanism for decoding mrna into amino acids and to interact with the trnas during translation mrna (messenger): carries coding information from DNA trna (transfer): carries amino acids Series of membranes throughout the cytoplasm Divides the cell into compartments where different cellular functions occur Endoplasmic reticulum (ER) SER RER Golgi apparatus Lysosomes 4

5 Membranes that create a network of channels throughout the cytoplasm Attachment of ribosomes to the membrane gives a rough appearance Synthesis of proteins to be secreted, sent to lysosomes or plasma membrane Relatively few ribosomes attached Functions: Synthesis of membrane lipids Calcium storage Detoxification of foreign materials Flattened stacks (golgi bodies) of interconnected membranes Packaging and distribution of materials to different parts of the cell Synthesis of cell wall components Membrane bound vesicles containing digestive enzymes to break down macromolecules Destroy cells or foreign matter that the cell has engulfed by phagocytosis 5

6 Membrane bound vesicles Contain enzymes Not part of the endomembrane system Types: Glyoxysomes in plants contain enzymes for converting fats to carbohydrates Peroxisomes contain oxidative enzymes and catalase Membrane-bound structures with various functions depending on the cell type There are different types of vacuoles: Central vacuole in plant cells Contractile vacuole of some protists Storage vacuoles Organelles present in all types of eukaryotic cells Contain oxidative metabolism enzymes for transferring the energy within macromolecules to ATP Powerhouse of the cell Surrounded by 2 membranes Smooth outer membrane Folded inner membrane with layers called cristae matrix is within the inner membrane Intermembrane space is located between the two membranes Contain their own DNA Organelles like mitochondria found in plants that have a double membrane and contain own DNA Examples: chloroplasts, chromoplasts, amyloplasts 6

7 Organelles present in cells of plants and some other eukaryotes Contain chlorophyll for photosynthesis Surrounded by 2 membranes Inner and Outer membrane Thylakoids are membranous sacs within the inner membrane Grana are stacks of thylakoids Proposal that eukaryotic organelles evolved through a symbiotic relationship One cell engulfed a 2 nd cell and a symbiotic relationship developed Mitochondria and chloroplasts are thought to have evolved this way Evidence that supports Mitochondria and chloroplasts: Have 2 membranes Possess DNA and ribosomes Are about the size of a prokaryotic cell Divide by a process similar to bacteria Barrels of microtubules used in cell division Network of protein fibers found in all eukaryotic cells Support the shape of the cell Keep organelles in fixed location Helps in moving materials within the cell Cytoskeleton fibers include Actin filaments: responsible for cellular contractions, crawling, pinching Microtubules: provide organization to the cell and move materials within the cell Intermediate filaments: provide structural stability 7

8 Cell movement takes different forms. Crawling is accomplished via actin filaments and the protein myosin. Flagella: undulate to propel the cell Cilia: can be arranged in rows on the surface of a eukaryotic cell to propel the cell forward Cilia and flagella have similar structure 9-2 structure: 9 pairs of microtubules surrounded by a 2 central microtubules Cilia are usually more numerous than flagella on a cell. Includes Cell walls in plants, fungi, some protists Extracellular matrix surrounding animal cells Cell walls present surrounding the cells of plants, fungi, and some protists the carbohydrates present in the cell wall vary depending on the cell type plant and protist cell walls cellulose fungal cell walls - chitin ECM surrounds animal cells composed of glycoproteins and fibrous proteins such as collagen may be connected to the cytoplasm via integrin proteins present in the plasma membrane 8

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