Download Chapter 3 Notes

Chapter 3 Notes, part 1
“Looking at Cells”
Cells were discovered in the 17th century,
when microscopes were invented….
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 cells
 Anton von Leeuwenhoek used a
microscope ten years later to view
water from a pond, and he called the
tiny organisms he saw ‘animalcules’
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
Know these words…..
 Magnification: the amount of times a
specimen being viewed is enlarged in order
to be seen, varies with power of microscope
 Resolution: the ability that the microscope
has to distinguish between two different
objects, ie. The nucleus vs. the
endoplasmic reticulum
 Contrast: ability to see detail within the
specimen clearly
Types of microscopes
 Light microscope
 Transmission and scanning electron
microscopes
 Scanning tunneling microscope
Compound light microscopes
 What we work with in
class
 Light 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.
Transmission Electron Microscopes
 Use electrons to
pass through
specimens to view
detail; image
projected onto
screen or
photographic film
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
Scanning tunneling microscopes
 New video and
computer techniques
are increasing
microscope resolution
and magnification
 This type of
microscope uses a
needle-like probe to
measure voltages of
electrons. It can track
the movement of
electrons and can see
atoms!
Compare the images produced by
different microscopes…..
 See p. 52 for a light microscope
image of sperm
 See p. 53 for a T.E.M. image of sperm
 See p. 54 for an S.E.M. image of
sperm
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 plant
 Schwann who claimed that animals are
also made of cells
 Virchow who determined that cells come
from other cells.
The cell theory summarized…
 All living things are made of one or
more cells
 Cells are the basic unit of structure
and function in organisms
 All cells arise from existing cells
Cell size and sufrace area:volume
ratio
 Small cells function more efficiently than
larger cells
 If 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 cell
 See table 2 p. 55
Common features of cells:
 Most cells have…
 A cell membrane: encloses cell, separates
interior
 Cytoplasm: the fluid in which interior cell
structures are suspended, also called cytosol
 Cytoskeleton: for cellular structure
 Ribosomes: make proteins
 DNA: 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.
Prokaryotes
 A single-celled organism that lacks a
nucleus and other internal
compartments
 Common prokaryotes which cause
infection and spoil food: Bacteria
Characteristics of Prokaryotes:
 Have little internal structure
 Many have a capsule and flagella
 DNA is located near the center of the
cell and is not contained in a nucleus
 A cell wall surrounds the membrane
and provides structure and support
 Many have flagella which propel them
along
Typical prokaryote:
Eukaryotic Cells
 Cells with a nucleus and other
organelles
 An organelle is a structure within a
cell that carries out specific activities
for that cell
 Some eukaryotic cells have cilia which
are short hairlike structures that
protrude from the surface of the cells
cytoskeleton
 Provides the internal framework of an
animal cell, much as our skeleton provides
the internal framework of our bodies
 Three types of cytoskeleton fibers:
 Actin fibers: found just inside of the cell
membrane; helps cell membrane move
 Microtubules: transport information from
nucleus to different parts of the cell
 Intermediate fibers: keep ribosomes and
enzymes in place within cell
The cell membrane
 to separate the internal from external
environment of the cell
 Regulates materials entering and
leaving the cell.
 Helps the cell, in turn the organism,
maintain homeostasis
cell membrane structure
 Made up of a
phospholipid
bilayer
 Phospholipid: a
molecule with a
hydrophilic (waterloving) head and a
hydrophobic
(water-fearing) tail
Cell membrane proteins
 Proteins embedded in the membrane have
polar and nonpolar ends just like the
membrane; this keeps them embedded
inside of the membrane
 These proteins have different functions:
 Receptor proteins recognize and bind to
substances outside the cell
 Enzymes assist chemical reactions in the cell
 Transport proteins help substances move across
the membrane
Upcoming Biology Schedule:
 This weekend’s homework: worksheet
packet
 Monday: chapter 3 lab (read)
 Wednesday: go over lab/test review
 Friday (Happy Halloween!) TEST!!!