The document discusses the key components and functions of animal and plant cells. It begins by establishing cells as the fundamental unit of life and discusses the cell theory. It then describes the major organelles found in eukaryotic cells like the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and cytoskeleton. It highlights how these organelles work together to synthesize proteins, produce energy, transport materials, and give shape to the cell. The document also compares and contrasts animal and plant cells, noting unique features of plant cells like cell walls, central vacuoles, and chloroplasts.

1. Chapter 8
CELL- THE UNIT OF LIFE
CBSE Class-XI
By Punya Mohanty
Biology Faculty

2. The key to every biological problem must finally be sought in the cell, forThe key to every biological problem must finally be sought in the cell, for
every living organism is, or at some time has been, a cell. E.B. Wilson,every living organism is, or at some time has been, a cell. E.B. Wilson,
19251925
Why Study Cell Biology?Why Study Cell Biology?
THE FUNDAMENTAL UNIT OF LIFETHE FUNDAMENTAL UNIT OF LIFE

3. Cells are Us
Cilia on a protozoan Sperm meets egg

4. ANIMAL CELL

5. PLANT CELL

6. Cells are Us
A person contains about 100 trillion cells.
That’s 100,000,000,000,000 or 1 x 1014
cells.
There are about 200 different cell types in
mammals (one of us).
Cells are tiny, measuring on average about
0.002 cm (20 um) across. That’s about
1250 cells, “shoulder-to-shoulder” per
inch.
nerve cell
Red and
white blood
cells above
vessel-
forming cells.

7. The Cell Theory
All organisms are composed of one or more cells.
Cells are the smallest living things.
All organisms living today are descendents of an
ancestral cell.
Cells arise only by division of previously existing cells.
The cell theory (proposed independently in 1838 and
1839) is a cornerstone of biology.
Schleiden
Schwann

8. A Sense of Scale and Abundance – Bacteria on the Head of a Pin

9. Two Fundamentally Different Types of Cells
A prokaryotic cell
A eukaryotic cell

10. Us vs. Them
-Eukaryotes
and
Prokaryotes

11. An Idealized Animal Cell

12. Major Divisions of the Eukaryotic Cell

13. A rat liver cell (with color enhancement to show organelles)

14. It’s Crowded In There
An artist’s conception of the cytoplasm - the region of a cell
that’s not in the nucleus or within an organelle.

15. A micrograph showing
cytoskeleton (red),
ribosomes (green), and
membrane (blue)
It’s Crowded In There

16. Animal and Plant Cells Have More
Similarities Than Differences

17. Cellular Anatomy
We’ll start by seeing what role these parts play in making
and moving proteins.

18. The Nucleus Think of the nucleus as the cell’s
control center.
Two meters of
human DNA fits
into a nucleus
that’s 0.000005
meters across.

19. Ribosomes and the Endoplasmic Reticulum

20. The Rough Endoplasmic Reticulum
Protein movement
(trafficking)
Protein synthesis (about
half the cell’s proteins are
made here).
Protein “proofreading”
Functions:

21. Cystic Fibrosis
Click here to see the article.

22. The Lysosome
Cell suicide (suicide is bad for
cells, but good for us!)
Recycling cellular components
Functions:
Digesting food or cellular invaders
(The lysosome is not found in plant
cells)

23. The
Lysosome
This bacterium
about to be
eaten by an
immune system
cell will spend
the last minutes
of its existence
within a
lysosome.

24. Many Diseases are Caused by Lysosome Malfunction

25. Cellular Anatomy

26. The Mitochondrion
Think of the mitochondrion as the
powerhouse of the cell.
Both plant and animal cells contain
many mitochondria.
(Mitochondria is the
plural of mitochondrion)

27. The Mitochondrion
A class of diseases that causes
muscle weakness and
neurological disorders are due
to malfunctioning
mitochondria.
Worn out mitochondria may be an important factor in aging.

28. Mitochondrial Diseases

29. Mitochondria and Health

30. Animal vs. Plant Cells – Chloroplasts Are a Big Part of
the Difference

31. Cells In a Leaf

32. The Chloroplast
Think of the chloroplast as the solar panel of the plant cell.
Only plants have chloroplasts, but animals reap the benefits too.

33. Two Other Unique Features of Plant Cells
The central
vacuole may
occupy 90%
of a plant
cell.

34. A Consequence of Cell Walls –
the Great Strength of Woody
Plants

35. The Central Vacuole Controls Turgor Pressure
flaccid
turgid

36. Cellular Anatomy

37. The name is misleading. The
cytoskeleton is the skeleton
of the cell, but it’s also like
the muscular system, able to
change the shape of cells in a
flash.
The Cytoskeleton
An animal cell cytoskeleton

38. A Cytoskeleton Gallery

39. A white
blood cell
using the
cytoskeleton
to “reach
out” for a
hapless
bacterium.
The
Cytoskeleton
in Action

40. The Cytoskeleton in Action
Cilia on a protozoan Beating sperm tail at fertilization
Smoker’s cough is due to destruction of cilia linking the airways.