Essential Questions. Cell Discovery and Theory. Copyright McGraw-Hill Education

Transcription

1 Essential Questions How are the advances in microscope technology related to discoveries about cells? What are the similarities and differences between compound light microscopes and electron microscopes? What are the principles of the cell theory? What are the differences between a prokaryotic cell and a eukaryotic cell? Cell Discovery and Theory

2 Vocabulary Review organization New cell cell theory plasma membrane organelle eukaryotic cell nucleus prokaryotic cell Cell Discovery and Theory

3 History of the Cell Theory A cell is the basic structural and functional unit of all living organisms. Cells are so small that their existence was unknown before the invention of microscopes. Cell Discovery and Theory

4 History of the Cell Theory The cell theory The cell theory is one of the fundamental ideas of modern biology, and includes the following three principles: All living organisms are composed of one of more cells. Cells are the basic unit of structure and organization of all living organisms. Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells. Cell Discovery and Theory

5 Microscope Technology Compound light microscopes Use a series of glass lenses and visible light to magnify images Magnify images up to ~1000 actual size Electron microscopes Create an image by illuminating a sample with a beam of electrons and collecting the electrons that are reflected back from the sample Magnify images up to 500,000 actual size Cell Discovery and Theory

6 Basic Cell Types All cells have at least one physical trait in common: a plasma membrane. A plasma membrane is a special boundary that helps control what enters and leaves the cell. Most cells contain genetic material in some form. Most cells break down molecules to generate energy. There are two basic kinds of cells: eukaryotic and prokaryotic. Cell Discovery and Theory

7 Basic Cell Types Eukaryotic cells contain a nucleus and other organelles. Organelles are specialized structures that perform specific cell functions. The nucleus is the distinct central organelle that contains the cell s genetic material. Eukaryotic cells are generally much larger than prokaryotic cells. Cell Discovery and Theory

8 Basic Cell Types Prokaryotic cells are cells without a nucleus or other membrane-bound organelles. Smaller and simpler than eukaryotes Probably similar to first organisms that lived on earth Cell Discovery and Theory

9 Basic Cell Types Origin of cell diversity Eukaryotic cells may have evolved from prokaryotic cells. The endosymbiont theory proposes that a symbiotic relationship formed between two prokaryotic cells, one of which lived inside the other. Eventually the symbiotic relationship led to the two cells becoming one. Because eukaryotic cells are larger and more complex, they developed specific functions. These specific functions led to cell diversity, and thus organismal diversity. Cell Discovery and Theory

10 Review Essential Questions How are the advances in microscope technology related to discoveries about cells? What are the similarities and differences between compound light microscopes and electron microscopes? What are the principles of the cell theory? What are the differences between a prokaryotic cell and a eukaryotic cell? Vocabulary cell cell theory plasma membrane organelle eukaryotic cell nucleus prokaryotic cell Cell Discovery and Theory

11 Essential Questions How does a cell s plasma membrane function? What are the roles of proteins, carbohydrates, and cholesterol in the plasma membrane? The Plasma Membrane

12 Vocabulary Review ion New selective permeability phospholipid bilayer transport protein fluid mosaic model The Plasma Membrane

13 Function of the Plasma Membrane The process of maintaining balance in an organism s internal environment is called homeostasis. One of the structures responsible for homeostasis is the plasma membrane. The plasma membrane forms a thin, flexible boundary between a cell and its environment. The Plasma Membrane

14 Function of the Plasma Membrane Plasma membranes have selective permeability, meaning they allow some substances to pass through while keeping others out. Control of how, when, and how much of various substances enter and leave a cell depends on the structure of the plasma membrane. The Plasma Membrane

15 Structure of the Plasma Membrane The phospholipid bilayer The plasma membrane is composed of phospholipid bilayer two layers of phospholipids are arranged to allow the membrane to exist in a watery environment. The phospholipid bilayer has polar heads facing outside and nonpolar tails facing inside the cell, allowing the membrane to keep the internal and external environments separate. The Plasma Membrane

16 Structure of the Plasma Membrane Other components of the plasma membrane The plasma membrane also contains cholesterol, proteins, and carbohydrates. Some proteins called receptors transmit signals to the inside of the cell. Some proteins serve as support structures for the membrane. Transport proteins move needed substances and wastes through the membrane. The Plasma Membrane

17 Structure of the Plasma Membrane Other components of the plasma membrane Cholesterol prevents the fatty acid tails of the phospholipid bilayer from sticking together. Cholesterol contributes to the fluidity of the membrane. The Plasma Membrane

18 Structure of the Plasma Membrane Other components of the plasma membrane Carbohydrates define the cell s characteristics Help cells identify chemical signals The Plasma Membrane

19 Structure of the Plasma Membrane Other components of the plasma membrane The fluid mosaic model describes the phospholipids in the bilayer as a sea in which other components can float and move around. The different substances in the plasma membrane create a pattern or mosaic on the surface of the cell. The Plasma Membrane

20 Review Essential Questions How does a cell s plasma membrane function? What are the roles of proteins, carbohydrates, and cholesterol in the plasma membrane? Vocabulary selective permeability phospholipid bilayer transport protein fluid mosaic model The Plasma Membrane