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Cell Biology Chapters 7-8.

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Presentation on theme: "Cell Biology Chapters 7-8."— Presentation transcript:

1 Cell Biology Chapters 7-8

2 Cell theory Chapter 7

3 Discovery of cells  light microscopes
Anton van Leeuwenhoek  1st light microscope Simple  1 lens, natural light First living unicellular organism  pond water Compound light microscope  series of lenses Greater magnification

4 Discovery cont. Robert Hooke  studies cork
Cells  monk’s rooms Matthias Schleiden  all plants are made of cells Theodore Schwann  all animals are made of cells Rudolph Virchow  cells arise from other cells

5 Statements of cell theory
All organisms are made of one or more cells and their products The cell is the basic unit of structure of organisms All cells come from preexisting cells

6 Exceptions to cell theory
The first cell Simple organisms lack separations that divide their bodies into cells Fungi and algae Viruses Mitochondria and chloroplasts divide on their own

7 Electron microscopes No light  beam of electrons
Magnifies up to 500,000 X

8 Scanning electron microscope (SEM)
Scans surface of objects  3-D image

9 Transmission electron microscope (TEM)
Can see internal structures

10 Scanning tunneling microscope (STM)
Atoms on surface

11 Cell types

12 Prokaryotes Simple Lack internal structure
No membrane- bound organelles Smallest organisms  bacteria

13 Eukaryotes More complex Definite internal structure
Presence of membrane- bound organelles

14 The plasma membrane

15 Maintains balance between internal and external conditions
Regulates entering and departing substances Maintains cellular homeostasis

16 Selectively permeable
Also known as semipermeable Allows only certain molecules in or out Water may move freely Ions allowed in only at certain times

17 Structure of the plasma membrane
Phospholipid bilayer Lipids with phosphate groups (replace 1 fatty acid) Fatty acid tails nonpolar  avoid water Water insoluble  dissolved substances can’t easily pass through Inner portion of membrane

18 Structure cont. Phosphate heads polar  attracted to water
Cell can interact with watery environment Edges of membrane Cholesterol  stabilizes phospholipids Prevents fatty acids from sticking together Transport proteins  span membrane Act as channels (doors) through membrane

19 Structure cont. Protein and carb identity markers
Extend from outer surface for communication Proteins along inner surface attach membrane to internal support structures Fluid mosaic model  phospholipids move within the membrane Provides flexibility


21 Eukaryotic cell structure

22 Cellular boundaries All cells have plasma membranes
Some also have cell walls Rigid structure outside the membrane providing extra support and protection Plant cells, fungi, some protists (unicellular) Fibrous  made of cellulose Porous  allows substances through arbitrarily

23 Cellular boundaries cont.
Nucleus  control center Contains blueprints for making proteins  chromatin (DNA) Separated from cell by porous nuclear envelope Nucleolus  located within nucleus Site of ribosome production

24 Cellular boundaries cont.
Ribosomes  protein synthesis Not membrane-bound Cytoplasm  clear, gelatinous fluid inside cells Mostly water Site of cellular metabolism

25 Assembly, transport, and storage
Endoplasmic reticulum (ER)  highly folded membrane in the cytoplasm Rough ER  has ribosomes Protein synthesis and transport Smooth ER  no ribosomes Lipid synthesis and transport

26 Assembly cont. Golgi apparatus  flattened system of tubular membranes
Modify proteins and lipids Enclose finished products in vacuoles Vacuoles  sacs surrounded by a membrane Temporary storage of food, enzymes, wastes, cell secretions

27 Assembly cont. Lysosomes  organelles containing digestive (hydrolytic) enzymes Digestion of excess or worn out organelles, food, engulfed viruses or bacteria Fuse with vacuoles to digest contents Can digest cells that made them Tadpole tails Fetal finger webbing Natural aging

28 Energy transformers Chloroplasts  plant cells & some protists
Capture light energy to make food Surrounded by a double membrane Grana  stacks of membranous sacs Contain chlorophyll  light-capturing pigment Stroma  fluid-filled spaces


30 Energy transformers cont.
Mitochondria  all cells Transform carbs into energy Smooth outer membrane Highly folded inner membrane  increased surface area for chemical reactions This is where energy molecules are produced


32 Support and locomotion
Cytoskeleton  provides support, maintains shape Microtubules  hollow tubes made of protein Microfilaments  smaller, solid protein fibers Intermediate fibers  mid-sized

33 Support cont. Cilia and flagella
Both composed of 9 pairs of microtubules surrounding a tenth pair Microtubules slide along each other  bending Cilia  short, numerous, wave-like motion Flagella  long, 1 or 2, whip-like motion

34 Cilia and flagella Paramecium Human spermatozoa

35 Cellular Transport Chapter 8

36 Osmosis Diffusion of water across a selectively permeable membrane
Important in maintaining homeostasis Caused by concentration gradient of particles

37 Water moves in and out at the same rate No change in cell shape
Isotonic solutions Concentration of solutes in solution = concentration of solutes inside cell Water moves in and out at the same rate No change in cell shape

38 Water moves into cell  cell bursts (plasmolysis)
Hypotonic solutions Concentration of solutes in solution is lower than that inside the cell Water moves into cell  cell bursts (plasmolysis)

39 Water moves out of cell  cell shrivels Wilting plants
Hypertonic solutions Concentration of solutes in solution is higher than that inside the cell Water moves out of cell  cell shrivels Wilting plants


41 Passive transport Uses no energy Osmosis and diffusion
Facilitated diffusion  uses transport proteins Moving sugars and amino acids

42 Active transport  requires energy
Uses carrier proteins Molecule binds to carrier protein Release of energy changes protein shape Molecule released on other side of membrane Protein returns to original shape

43 Active transport cont. Endocytosis  cell surrounds and take in particles Particle engulfed and enclosed by a membrane Membrane breaks away  vacuole Exocytosis  opposite of endocytosis

44 Cell growth and reproduction

45 Size limitations Diffusion is slow  inefficient if cell is large
It would take too long for nutrients to reach cell organelles DNA  there must be enough to provide blueprints for sufficient amounts of protein Larger cells  more than 1 nucleus

46 Size limitations cont. Surface area-to-volume ratio
Volume increases faster that surface area The higher the ratio, the more efficient diffusion will be Small cells have high ratios


48 Cell reproduction  chromosomes
Chromatin  long strands of DNA wrapped around proteins Chromosomes are in this form for most of a cell’s life During cell division, chromosomes become tightly coiled and visible under a microscope

49 The cell cycle  sequence of growth and division
Most of the cycle is spent in growth Following growth, cells undergo nuclear division Mitosis  process by which 2 daughter cells are formed, each identical to the original parent After mitosis, the entire cell divides


51 Interphase  3 parts Growth and protein synthesis  G1
Cell copies chromosomes S Mitochondria and other organelles replicate  G2 Not considered a part of mitosis

52 Mitosis

53 Prophase  longest phase
Chromatin coils into compact chromosomes Sister chromatids  2 halves of doubled structure Exact copies of each other Held together by a centromere Nuclear membrane and nucleolus disappear

54 Prophase cont. Centrioles begin to migrate to opposite poles
Organelles found only in animal cells Spindle fibers form between centrioles


56 Metaphase Spindle fibers attach to centromeres
Chromosomes line up along cell equator  metaphase plate


58 Anaphase Chromatids move to opposite poles  pulled by shortening spindle fibers


60 Telophase Chromatids reach opposite poles Reversal of prophase


62 Cytokinesis Division of the cytoplasm
Animal cells  membrane pinches in at edges (cleavage furrow) Plant cells  cell plate forms along equator from center of cell

63 Differences in Cytokinesis
Animal cell Plant cell

64 Results of mitosis 2 new daughter cells identical to the original parent, but smaller Unicellular organisms  remain as single cells Multicellular organisms  organization

65 Multicellular cellular organization
Tissue  group of cells performing a specific function Smooth muscle Organ  combination of tissues performing a specific function Stomach Organ system  combination of organs performing a specific function Nervous system

66 Control of the cell cycle

67 Normal control  enzymes
Enzymes monitor cell’s progress from phase to phase Specific enzymes are used for each phase Enzymes encoded by genes on DNA

68 Abnormal cell cycles  cancer
Cancer  uncontrolled cell division Results from changes in genes encoding enzymes that control cell cycle Form masses of tissue  tumors Deprive normal functioning cells of nutrients May metastasize  spread through body #2 killer in USA

69 Cancer cont. Causes: Genetic  inherited
Environmental  cigarette smoke, air and water pollution, radiation, exposure to chemicals Viral infections

70 Cancer cont. Prevention: Low fat, high fiber diets
Vitamins and minerals Exercise Avoiding risk situations

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