Transcript Topic 1 Cells - s3.amazonaws.com

Topic 1 Cells
Mrs : Jackie
Cell theory
 States that all living organism are
made of one or more cells
 Cells arise from other cells
 Chemical reactions such as
respiration and other metabolic
reactions occur within these cells
 Cells carry genetic material that can
be passed to the daughter cell
Cell theory
 Organisms can be
divide into the
following groups
 Unicellular
organisms which
are also called
acellular. Amoeba
or bacteria
 Multicellular made
of many cells such
as mammals
Cell theory
 Some organisms
are made of cells
with no partitions
resulting in a
structure with
many nuclei
 Multinucleated
 Muscle fibers
Viruses
 Non cellular organism
 Lack very important
structures
 They depend on other
organism for their living
and so they are parasites
 Made of nucleic acid
molecules surrounded by a
protein coat
Types of viruses
 RNA viruses-
 Contain RNA as their genetic material and they
have an enzyme reverse transcriptase which
transcribes RNA into DNA.
 Call retroviruses
 Example AIDS caused by HIV virus
 Tobacco Mosaic Virus
 DNA viruses
 Contain DNA as their genetic material
 They have an enzyme RNA polymerase which
transcribes DNA into RNA in the process of
protein synthesis
Advantages of using microscopes
 Light microscope
 Living cells and organisms can be
observe alive
 The resolution power of the microscope
is about .2 micrometers and a typical cell
is about 10 micrometers in length
 Wide range of magnification (40-400X)
 Easy to maintain
 Portable can be use in the field
 Tissues and small organ can be view
Magnification and resolving power
 Resolving Power
 Show things more clearly
 Ability to show two close
points as separate points to
distinguish them as separate
points
 Magnification
 Power of making things larger
in order to see them more
clearly
FOR HIGHER MAGNIFICATION
AND STONGER RESOLVING
POWER AN ELECTRON
MICROSCOPE CAN BE USED
Resolving power- Huber Telescope
Electron Microscope
 Has a resolving power of about .2
nanometer
 1000 times higher than the light
microscope.
Electron microscope picture
Aspect
Light
microscope
Electron
microscope
Natural color of tissue can be seen, since
tissue can be viewed without the addition
of any substances or stains
Yes
NO
Living material such as live insect can be
observed. Specimen can be prepared
without the addition of any chemicals
Yes
No
Movement of organisms. Method of
feeding and other processes can be
viewed
Yes
NO
A larger field of microscope view can be
observed
Yes
No
More suitable for studying organs and
large structure
Yes
No
More suitable for studying the details of
small structures such as cell and
organelles
NO
Yes
Cheap, portable and easy to use
Yes
No
Cells and organelles
 Cell contain formed structures inside
them called organelles.
 Comparison of relative sizes of certain
structures inside the cell
Structure
Measurement
Molecules
0.5-1 nm
Membrane
10nm
Virus
50-100nm
Bacteria
1-5micrometers
Organelles
5-10micrometers
Cells
10-100micrometers
1micrometer=0
.001mm
1nm=0.001mic
rometer
Cells
 Has a three dimensional figure
 Its surface to area volume provides
enough surface to exchange
 As the cell increases in size its surface
area to volume decreases
1cm
5cm
1x1x6/1x1x1=6
5x5x6/5x5x5=1.2
Surface area to volume ratio of the 5cm is smaller than
that of the 1cm cube
Surface area to volume ratio
 A small cell has a bigger surface to area
ratio than a big cell
 Advantages
 Faster rate of diffusion, osmosis and other
kinds of transport
 More control by the nucleus
 Getting rid of excess heat is more efficient
in smaller cells.
Surface area to volume ratio
 Materials such as resources such as RNA
proteins and enzymes would be adequate
enough in a small cell
 Small cells such as sperm can move fast
enough to reach their destination
 Production of energy for different reactions and
functions is more efficient in small cell
 IN big cells substances would need to travel a
longer distance in the cytoplasm to reach
certain organelles
Surface area to volume ratio
 When cell divide they increase in
number and lead to a multicellular
structure, which enables
specialization and differentiation into
different tissues and organs
 A small organism can be made of
many small cells that can carry out
different functions