@Tmhrt_Minister BIOLOGY GRADE 11 UNIT 4 SUMMARY.pdf

BIOLOGY GRADE 11 UNIT 4 SUMMARY

1. BIOLOGY GRADE 11
UNIT 4 SUMMARY
BY:ADDIS ABABA EDUCATION BUREAU
APRIL 2020

2.  
   
 
               
Cell
Biology
4.1
Cell theory
By
the end of this section you should be
able
to:
•
Tell the history of cell biology.
•
Describe cell theory and investigate the
size,
structure and
shape of cells
•
State the basic functions of cells.

3. A timeline for the development
of the cell theory
•A) In 1665 Robert Hooke:-
•Saw tiny structures that he called ‘cells’
With one of the earliest compound
microscopes, made drawings of cork.
•His microscope magnifies more than 30×
are very blurred and do not show much
detail.
•Hooke saw only dead cells.

4. 1665 – Robert Hooke


Observed
cells in cork.
Coined
the term "cells”.
Cork Cells

5. •B) In 1674 Anton van Leeuwenhoek:-
• Saw living, moving unicellular organisms in
a drop of water.
•He was using a simple microscope with only
one lens.
•It is really little more than amagnifying glass
with a mount for the specimens.
• His microscope magnifies 300×.
•He called the moving organisms
‘animalcules’.
•He also saw bacteria (from his teeth), which
he also called ‘tiny animalcules’.

6. 1673-
Anton van Leeuwenhoek
Created
a powerful
microscope

7. C)
In 1824 Rene Dutrochet
•The
French biologist concludes that all
organisms
are composed of cells.
•He
also discovered:

-The stomata in the epidermis of leaves. -
The
process of osmosis. -
Chlorophyll
is needed for photosynthesis to
occur
-
Respiration
occurs in both animals and plants.
He
also conclude that:
•
‘
All
growth occurs because of the increase in
volume by
the addition of more little cells’.

8. D)
In 1838 - Matthias Schleiden
-A botanist who concluded that all plants are
made of cells.
Typical
Plant Cell

9. Theodor Schwann
E)
In 1839 - Theodor Schwann
-A
zoologist who concluded that all animals
are
made of cells.
Nerve
Cells

10. •Matthias
Schleiden and Theodor Schwann put
forward
the first clearly stated cell
theory(1839).

•It
states that:-

-The cell is the unit of structure,
physiology
and organisation in living things.
•The
cell retains a dual existence as:

– a distinct entity, and

– a ‘building block’ in the form
n

of
org
ms
•Cells
form by free-cell formation (spontaneous
generation)
w/h has now been proved false
.

11. Stay
at home
F)
In 1855 - Rudolph Virchow
A
physician who did
research
on cancer cells
and
concluded
“Omnis
cellula e cellula”.
“All
cells comes from
other

pre-existing
cells.”

12. •Rudolph Virchow...
•He
completed the first accepted version of the
cell
theory:
•All
organisms are made up of one or more cells.
•All
cells come from pre-existing cells.
•The
cell is the unit of structure, physiology and
organisation
in living things.
• The
cell retains a dual existence as a distinct
entity
and a building block in the construction of
organisms

13. The
modified and extended cell theory are:
•All
known living things are made up of cells
•The
cell is a basic structural and functional unit
of
all living things.
•All
cells come from pre-existing cells by division.
•Cells
contain hereditary information which is
passed
from cell to cell during cell division.
•All
cells have basically the same chemical
composition
•All
energy flow occurs within cells
.

14. Questions(2min)
•1.The
scientist who observed living cells for
the
first time was_________
•2.
Mention two statements from modern cell
theory.

15. Cells
are Diverse…
In
size, shape,
and
internal
organization.

16. How big are cells?
•A chicken’s egg are just one huge cell
up to 5 cm (0.05 m) in length.
•The smallest bacterial cells are only
just over 100 nm in length.
•This is approximately one hundred-
thousandth of the size of the
chicken’s egg.
-That’s quite a range of sizes!
•It all depends on which cells can you
measure

17. •There
are 3 smaller units commonly used:


•a)
Millimetres (mm) – 1/1000 of a metre
•b)
Micrometres (μm) – 1/1000 of a millimetre,
and
1/1 000 000 of a metre
•c)
Nanometres (nm) – 1/1000 of a micrometre,
 1/1
000 000 of a millimetre,
and
1/1000 000 000 of a metre
•Our
red blood cell that was 0.000007 m in
diameter
is 0.007 mm
or

7 μm in diameter.
•This is a much more comprehensible
number.

18. •We
can convert the units from one to
another
as shown below:


•To
convert a larger unit to the next smaller
unit,
multiply by 1000:
E.g:
convert 3.5 mm
to
μm. 3.5 mm = 3.5 × 1000 = 3500 μm
•To
convert a smaller unit to the next larger
unit,
divide by 1000:
E.g:-Convert
87 nm to
μm.
87 ÷ 1000 = 0.087 μm

19. Check
points(2 min)
Convert
the following units
•1.
22mm into μm
•2.
500nm into mm
•3.
700μm into nm

20. What
are the consequences of the different
sizes
of cells?
•When
a cell gets bigger, all its dimensions
change.

•It
is easy to be tricked into thinking that
when
a cell doubles all its dimensions it is
twice
as big.
•But
the surface area and volume of the cell
doesn’t
double.

21. •Eg.There
are six sides to a cube.

/See Fig.
4.13
on page 118/
• We
calculate the area of each side by
multiplying
length by breadth.

•The

volume
of a cube is length × breadth ×
height. 
•In
this case 1 a.u. × 1 a.u. × 1 a.u. So the
volume
of the first cube is 1 a.u.3.
•The
ratio of the surface area to the volume
is
6:1.

22. •So
what about the second cell?
•The
linear dimensions have doubled, but the
surface
area is 24 a.u2 and the volume is 8 a.u.3
•The
ratio of the surface area to volume is now
24
÷ 8 = 3:1. It is half that of the smaller ‘cell’.
•The
surface area to volume ratio of the third cell
is
in fact 1.5:1.
•As
the linear dimensions have doubled, the
Surface
area to Volume ratio decreases by half
of
the smaller cell.

23. So,
does it matter if the surface-area-to
volume
ratio changes?
• For
example In order to respire,the cell
needs
oxygen, w/c enters through the
surface
of the cell. -
The
volume determines how much activity
there
is in a cell.
-
A large cell will have more processes
happening,
or at least the same processes
happening
faster, than a smaller cell.

- The amount of energy that must be
released
in respiration is therefore decided
largely
by the volume.

24. •The
amount of oxygen that can be
delivered
into the cell is decided largely by
how
much ‘surface’ there is, since it is
through
the surface of the cell that the
oxygen
enters.
•A
large surface-area-to-volume ratio
means
that it is likely that the surface will
be
able to supply the oxygen demands of
the
cell.
•But
as cells increase in size, the surface-
area-to-volume
ratio decreases.

25. •Think
of this surface-area to-volume ratio
interms
of ‘supply’ and ‘demand    

• -The
volume of the cell creates the
‘demand’
for oxygen,

-which is ‘supplied’ through the
surface
(area) of the cell.                              
 
        

26. Why
Are Cells So Small?
•Transport-
Cell volume to surface area
ratios
favor small size.




•Control-
Nucleus to cytoplasm
consideration.
•Metabolic
requirements-

27. Check
points(3Min)
•1. If the diameter of each cell on the
microscope slide is found 0.5mm,what
will be the diameter of the cells in nm?
•2. Cube A has a side measuring
3mm.Cube B has 12mm.The surface
area to volume ratio of Cube A
compared with Cube B is ___________
times__________.

28. Stay
at home
Stay
safe
Work
hard