Presentation on theme: "Chapter 3 Notes, part 1 “Looking at Cells”"— Presentation transcript:
1 Chapter 3 Notes, part 1 “Looking at Cells” Cells were discovered in the 17th century, when microscopes were invented….
2 Cells were discovered by….. Robert Hooke, in 1665 he looked at a thin piece of cork and ‘saw a lot of little boxes’ which reminded him of the small rooms where monks live, so he called them cellsAnton von Leeuwenhoek used a microscope ten years later to view water from a pond, and he called the tiny organisms he saw ‘animalcules’
3 Measurement See table 1, p. 50 Cells are measured in units of micrometers, abbreviated μm. The symbol μ stands for the prefix ‘micro’See figure 2, page 51, which shows the sizes of different objects
4 Know these words…..Magnification: the amount of times a specimen being viewed is enlarged in order to be seen, varies with power of microscopeResolution: the ability that the microscope has to distinguish between two different objects, ie. The nucleus vs. the endoplasmic reticulumContrast: ability to see detail within the specimen clearly
5 Types of microscopes Light microscope Transmission and scanning electron microscopesScanning tunneling microscope
6 Compound light microscopes What we work with in classLight rays pass through specimen and come into focus through two glass lenses.The eyepiece lens gives a total of 10x magnification. The objective lens varies with microscopes but can be up to 100x magnification. Total magnification is found by multiplying eyepiece lens by objective lens.
7 Transmission Electron Microscopes Use electrons to pass through specimens to view detail; image projected onto screen or photographic film
8 Scanning electron microscopes The specimen is first coated with a thin layer of metal and an image is produced by the electrons which bounce off of the image
9 Scanning tunneling microscopes New video and computer techniques are increasing microscope resolution and magnificationThis type of microscope uses a needle-like probe to measure voltages of electrons. It can track the movement of electrons and can see atoms!
10 Compare the images produced by different microscopes….. See p. 52 for a light microscope image of spermSee p. 53 for a T.E.M. image of spermSee p. 54 for an S.E.M. image of sperm
11 Section 3.2: Cell Features The cell theory: was bulit on the ideas of Hooke and Leeuwenhooek by the following:Schleiden who said that cells make up every part of a plantSchwann who claimed that animals are also made of cellsVirchow who determined that cells come from other cells.
12 The cell theory summarized… All living things are made of one or more cellsCells are the basic unit of structure and function in organismsAll cells arise from existing cells
13 Cell size and sufrace area:volume ratio Small cells function more efficiently than larger cellsIf the surface area of a cell is larger than it’s volume, then the cell can gather essential nutrients and water and they can get in fast.If the surface area to volume ratio is close in number to the volume, it takes too long for materials to reach the interior of the cellSee table 2 p. 55
14 Common features of cells: Most cells have…A cell membrane: encloses cell, separates interiorCytoplasm: the fluid in which interior cell structures are suspended, also called cytosolCytoskeleton: for cellular structureRibosomes: make proteinsDNA: all cells have DNA which contains instructions for making proteins, regulating the activities of the cell, and allowing the cell to reproduce. Red blood cells lose their DNA at a certain point in their life.
15 ProkaryotesA single-celled organism that lacks a nucleus and other internal compartmentsCommon prokaryotes which cause infection and spoil food: Bacteria
16 Characteristics of Prokaryotes: Have little internal structureMany have a capsule and flagellaDNA is located near the center of the cell and is not contained in a nucleusA cell wall surrounds the membrane and provides structure and supportMany have flagella which propel them along
18 Eukaryotic Cells Cells with a nucleus and other organelles An organelle is a structure within a cell that carries out specific activities for that cellSome eukaryotic cells have cilia which are short hairlike structures that protrude from the surface of the cells
19 cytoskeletonProvides the internal framework of an animal cell, much as our skeleton provides the internal framework of our bodiesThree types of cytoskeleton fibers:Actin fibers: found just inside of the cell membrane; helps cell membrane moveMicrotubules: transport information from nucleus to different parts of the cellIntermediate fibers: keep ribosomes and enzymes in place within cell
20 The cell membraneto separate the internal from external environment of the cellRegulates materials entering and leaving the cell.Helps the cell, in turn the organism, maintain homeostasis
21 cell membrane structure Made up of a phospholipid bilayerPhospholipid: a molecule with a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail
22 Cell membrane proteins Proteins embedded in the membrane have polar and nonpolar ends just like the membrane; this keeps them embedded inside of the membraneThese proteins have different functions:Receptor proteins recognize and bind to substances outside the cellEnzymes assist chemical reactions in the cellTransport proteins help substances move across the membrane
23 Upcoming Biology Schedule: This weekend’s homework: worksheet packetMonday: chapter 3 lab (read)Wednesday: go over lab/test reviewFriday (Happy Halloween!) TEST!!!
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