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Chapter 7: A View of the Cell

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Title: Chapter 7: A View of the Cell


1
Chapter 7 A View of the Cell
  • 7.1. The Discovery of Cells

2
The Cell Theory (History)
  • The microscope was invented by Anton van
    Leeuwenhoek.
  • The first person to see a cell (in cork) was
    Robert Hooke.
  • Matthias Schleiden concluded that all plants have
    cells
  • Theodore Schwann observed that animals were also
    composed of cells

3
The Cell Theory
  • 3 main ideas
  • All living things are composed of one or more
    cells
  • The Cell is the basic unit of organization of
    organisms
  • All cells come from cells

4
The Light Microscope
  • Uses light and lenses
  • The Simple light Microscope used one lens and
    natural light (Leeuwenhoek)
  • The Compound light microscope Uses multiple
    lenses
  • Magnifies up to 1500 times

5
The Electron Microscope
  • Invented in the 1940s
  • Uses a beam of electrons
  • Magnifies up to 500,000 times
  • Two Kinds
  • Scanning electron microscope (SEM) Scans the
    surface of cells.
  • Transmission electron microscope (TEM) Allows
    for study of structures inside cells.

6
The Electron Microscope
SEM
TEM
7
Two Basic Cell Types
  • Prokaryotes Cells lacking internal
    membrane-bound structures
  • Eukaryotes Cells containing internal
    membrane-bound structures
  • The membrane-bound structures are called
    organelles
  • Contains a nucleus organelle that manages
    cellular function. First observed by Robert
    Brown. Rudolf Virchow concluded that it was
    responsible for cell division.

8
Chapter 7 A View of the Cell
  • 7.2 The Plasma Membrane

9
Maintaining a Balance
  • The Plasma membrane is the boundary between the
    cell and its environment
  • Needs to let the good stuff (e.g. nutrients) in
    and the bad stuff (waste) out
  • The plasma membrane maintains homeostasis.

10
Plasma Membrane
11
The Plasma Membrane
  • Maintains Homeostasis regulates internal
    environment Good in (but not too much), Bad Out
  • Selective permeability Allows some molecules
    into the cell and keeps some out.
  • Some molecules can cross the plasma membrane
    (i.e. water). Others must go through channels
    (i.e. Na, Ca, etc)

12
Structure of the Plasma Membrane
  • Composed of a phospholipid bilayer.
  • A Lipid with a phosphate group attached
  • Has only 2 fatty acid tails
  • Forms a sandwich
  • The phosphate group forms the polar head
  • The fatty acid tails form the nonpolar tail

13
Fluid Mosaic Model
  • The membrane is fluid It is flexible and
    phospholipids can move in the membrane like water
    in a lake.
  • The membrane is mosaic There are proteins
    embedded in the membrane that also move (like
    boats in the lake)

14
Other components
  • Cholesterol Helps stabilize the plasma membrane,
    and prevents the phospholipids from sticking
    together.
  • Transport Proteins Proteins that span the entire
    membrane and form channels for specific molecules
    to enter and leave (like a door).
  • Other Proteins and carbohydrates on the external
    surface Helps with identification.
  • Proteins on internal surface Provides
    flexibility by attaching the plasma membrane to
    the cells internal structure.

15
Chapter 7 A View of The Cell
  • 7.3 Eukaryotic Cell Structure

16
Cellular Boundaries
  • Plasma membrane surrounds the cell
  • In plants, fungi, most bacteria and some
    protists, the cell wall surrounds the plasma
    membrane
  • Fairly rigid
  • Provides support and protection
  • Made up of the carbohydrate cellulose
  • Has pores to allow molecules through

17
Nucleus and cell control
  • The Nucleus is the leader of the cells
  • Gives directions for the making of proteins
  • The master set of directions is in chromatin
  • During cell division, chromatin condenses to form
    chromosomes.

18
Nucleus and Cell Control
  • Inside the nucleus there is also the nucleolus
  • Makes ribosomes
  • Ribosomes are sites where proteins and other
    enzymes are made, according to instructions from
    DNA
  • Ribosomes leave the nucleus, into the cytoplasm
    in order to make proteins
  • Cytoplasm The fluid inside the cell

19
Nucleus and cell control
  • The Nuclear envelope is a double membrane that
    surrounds the nucleus.
  • Made up of 2 phospholipid bilayers
  • Contains small nuclear pores

20
Assembly and Transport
  • The endoplasmic reticulum A series of highly
    folded membranes
  • Where cellular chemical reactions take place
  • Like a large workspace
  • Some parts have ribosomes attached (rough
    endoplasmic reticulum - RER)
  • Others dont (smooth endoplasmic reticulum SER)

21
Assembly and Transport
  • RER Proteins made in the RER may
  • form part of the plasma membrane
  • be released from the cell
  • transported to other organelles
  • SER involved in production and storage of lipids.

22
Assembly and Transport
  • The Golgi apparatus flattened system of tubular
    membranes and vessicles
  • Modifies proteins
  • Sorts and packages proteins
  • Its kind of like the post office Sorts the mail
    and sends it to the right place

23
Assembly and Transport
  • RER

Golgi apparartus
vessicles
24
Vacuoles
  • A vacuole is a sac surrounded by membrane
  • Used for temporary storage of
  • Food
  • Enzymes
  • Waste
  • Plant cells usually have one large vacuole,
    animal cells have many smaller ones

25
Lysosomes and recycling
  • Lysosomes are organelles that contain digestive
    enzymes
  • They digest food particles, organelles and
    engulfed viruses or bacteria
  • Can fuse with vacuoles and digest the contents.
  • Can also digest cells that contain them.
  • i.e. tadpoles tail

26
Energy Transformers
  • For all the cellular processes to happen, energy
    is needed
  • Two organelles provide that energy
  • Choloroplasts (in plants)
  • Mitochondria (in animals and plants)

27
Chloroplasts
  • Chloroplasts are organelles that captures light
    energy and produces food to store for later
  • Has a double membrane (like the nucleus)
  • The inner membrane folds in to form stacks of
    membranous sacs called grana/thylakoids.

28
Chloroplasts
  • In the thylakoid membrane there is the green
    pigment called Chlorophyll
  • Traps light energy
  • Gives leaves and stems their green color

29
Mitochondria
  • Mitochondria produces energy in a form that can
    be used by the cell when necessary.
  • Has an outer membrane and a highly folded inner
    membrane.
  • Provides large surface area.

30
Structures for Support and Locomotion
  • Cytoskeleton forms the framework of the cell
  • Maintains shape
  • Composed of
  • Microtubules thin hollow cylinders made of
    protein
  • Microfilaments thin, solid protein fibers

31
Structures for Support and Locomotion
  • Cilia and flagella Structures that aid in
    locomotion and feeding.
  • Composed of pairs of microtubules, with a central
    pair surrounded by 9 additional pairs.
  • Cilia are short, numerous, hair-like projections
    that move in a wavelike motion
  • Flagella are longer projections, move in a
    whip-like motion.

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