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1. Chapter 3 structure and function of cells
Mabast M. Ahmed

2. Chapter 3 structure and function of cell
 Contents
 3-1 introduction to the cell
 3-2 parts of the eukaryotic cell
 3-3 multicellular organization

3. Objectives of this section
 Outline the discoveries that lead to the development of cell
theory
 State the cell theory and their types
 Identify a limiting factor affect on the size of cells .
 Describing the relationship between cell shape and cell function
.
 Differentiate between prokaryotes and eukaryotes.
section 3-1
Structure and functions of the cell

4. Discovery of the cell
• The discovery of cells was made by development of the microscope.
• Robert Hooke
• Was first scientist who used a microscope to examine a thin slice of cork
(dead plant cell).
• He wrote: “I could exceedingly plainly perceive it to be all perforated and
porous,” and he further described it as consisting of “a great many little
boxes”, these “little boxes” reminded him of the small room in which monks
lived, so he called them cell.
• Anton van Leeuwenhoek
• Was first person to observe living cells.
Section 1 Introduction of the cell
Chapter 3

5. A short video about cell discovery

6. The Cell Theory
The Cell Theory has three parts:
1. All living things are composed of one or more cells.
2. Cells are the basic units of structure and function in
organisms.
3. Cells come only from the reproduction of existing cells.
Chapter 3 Section 1 Introduction of the cell

7. • Mattias Schleiden
• He concluded that all plants are composed of cells.
• Theodor Schwann
• He concluded that all animals are composed of cells.
• Rudolf Virchow
• He reasoned that cells come only from other cells.
Section 1 Introduction of the cell
Chapter 3

8. The Diversity
• Not all cells are alike. Cells have different size, shape & internal organization.
• Our bodies contain at least 200 different cell types
• Cell Size
» Most plant and animal cells have a size between
(10 _ 50 ) micrometer
 Some Bacterial cells are only 0,2 micrometer
 Most cells are visible only with aid of microscope
• Cells are limited in size by ratio between surface area and volume.
» For a cuboidal cell:
• Volume increases with the cube of the side length, but surface area increases
with the square of the side length. This means: (if a cell keeps the same shape
as it grows, its volume will increase more rapidly than its surface area.
• This trend is important because the materials needed by a cell (such as
nutrients and oxygen) and the wastes produced by a cell (such as CO2) must
pass into and out of the cell through its surface.
Chapter 3 Section 1 Introduction of the cell

9. V = length X width X height
S.A. = length X width X n.s

10. Cell shape
Cells come in a variety of shapes, such as:
• Nerve cell: The long extensions that reach out in various directions
from the nerve cell, allow the cell to send and receive nerve
impulses.
• Skin cell: The flat shape of dead skin cells is well suited to their
function of covering and protecting the body surface.
• White blood cell (WBC): can change shape, leave the blood, and
enter the areas surrounding blood vessels. This allows them to
move through narrow openings and to isolate, engulf, and destroy
bacteria that invade the body
Chapter 3 Section 1 Introduction of the cell

11. Cell shape

12. • Internal Organization
• Cells contain a variety of internal structures called: Organelles.
• Organelle: is a cell component that performs specific functions for
the cell.
• Cell membrane: is the thin membrane that surround entire cell.
– most of the organelles are surrounded by their own membranes.
• Nucleus: is the large organelle near the center of the cell, that
contains genetic information and directs most of the activities of cell.
Chapter 3 Section 1 Introduction of the cell

14. • Types of cell (depend on membrane bound nucleus)
• Eukaryotic cell: is a cell that have a membrane-bound nucleus and other
organelles
– Such as: human cell, animal cell, plant cell.
• Prokaryotic cell: is a cell that lack a membrane-bound nucleus and other
organelles.
– Such as: bacteria cell.
Chapter 3 Section 1 Introduction of the cell

15. Main components of Eukaryotic cell:
1.Cell membrane 2. Nucleus 3. Cytoplasm
Section 2 Parts of Eukaryotic Cell
Chapter 3

16. The Cell Membrane
• Definition: is a selectively permeable barrier that let some
substances easily cross to inside of cell, while others cannot cross
at all.
• Composition: it is made primarily of:
• Lipids and proteins.
Section 2 Cell Parts
Chapter 3

17. Membrane Lipids:
• Phospholipid:
– is one of the major types of lipids in the cell membranes, which is bilayer.
– Has:
• Polar head: points outward, is (hydrophilic), (water loving)
• Nonpolar tail: is confirmed to the interior of the cell membrane, is
(hydrophobic), (water fearing)
• Steroid:
– is another type of lipid, which fits between the tails of the phospholipids.
• The major membrane steroid in animal cells is (Cholesterol).
• Other steroids are found in the cell membranes of plant.
Section 2 Cell Parts
Chapter 3

20. Lipid Bilayer
Section 2 Cell Features
Chapter 3

21. Phospholipid
Section 2 Cell Features
Chapter 3

22. A video about phospholipid bilayer

23. Membrane Proteins:
• Peripheral proteins:
– Definition: are proteins that attached to the surfaces (outside & inside)
of the cell membrane.
• It can link by weak bond with the “membrane lipids” or to “other
proteins” that are embedded in the lipid bilayer.
• Integral proteins:
– Definition: are proteins that embedded in the bilayer.
• Some are extend across the entire cell membrane and are exposed
to both the inside and the exterior environment.
• Others extend either only to the inside or only to the exterior surface.
Section 2 Cell Parts
Chapter 3

24. Membrane Proteins:
• Carbohydrates
• integral proteins exposed to the cell’s external environment often
have carbohydrates attached.
• Function:
– They may hold adjoining cells together
– They may act as sites where viruses or chemical messengers
such as hormones can attach.
• Functions of Membrane proteins:
– play an important role for transporting molecules through lipid bilayer,
such as:
• Some integral proteins form channels or pores through which certain
substances can pass.
• Other integral proteins can bind to a substance on one side of the
cell membrane and carry it to the other side of the membrane.
Section 2 Cell Parts
Chapter 3

25. Fluid Mosaic Model of Cell Membrane
– Scientist have discovered that cell membranes are very dynamic.
• The fluid mosaic model states that the lipid bilayer behaves like a fluid
more than it behaves like a solid.
• Because of this fluidity, the membrane’s
lipids and proteins can move laterally within
the lipid bilayer, and their patterns in
cell membrane are constantly changing.
Section 2 Cell Parts
Chapter 3

27. Organelles
• Cytoplasm
– Definition: is the fluids and cell organelles inside the cell,
located between cell membrane and nucleus.
• Cytosol
– Definition: is the gelatin like aqueous fluid, in which salts,
minerals and organic molecules are dissolved.
Section 2 Cell Organelles
Chapter 3

28. Organelles
Chapter 3

29. Mitochondria
– Definition: are large organelles, and are the sites of chemical reactions
that transfer energy from organic compounds to ATP.
• Specialties:
– They are usually more numerous in cells that have a high energy
requirement. For example:
» Liver cells: each contain as many as 2,500 mitochondria.
» Muscle cells: contain many mitochondria.
– Mitochondrion is surrounded by 2 membranes:
• Smooth outer membrane: serve as a boundary between the
mitochondrion and the cytosol.
• Inner membrane: has many long folds, known as cristae.
» Cristae: enlarge the surface area of the inner membrane,
providing more space for the chemical reactions that occur
in the mitochondrion.
Section 2 Cell Organelles
Chapter 3

30. Mitochondria
Chapter 3

31. Ribosomes
• Definition: are the most numerous organelles in many cells, and play an
important roles in the synthesis of proteins.
• Specialties:
– They are not surround by a membrane.
– They are an assemblage (collection) of 2 organic compounds: protein &
RNA.
– They are packaged inside the nucleus, then transported to cytosol.
– Some of them remain free within the cytosol, while others become
attached to an organelle called: endoplasmic reticulum.
– play an important roles in the synthesis of proteins;
» Proteins to be used within the cytosol are produced on the
ribosomes that are free in the cytosol.
» Proteins to be inserted into membrane or exported from
cell, are produced on the ribosomes that are attached to
the endoplasmic reticulum.
Section 2 Cell Organelles
Chapter 3

32. Ribosomes and the Endoplasmic Reticulum
Section 2 Cell Organelles
Chapter 3

33. Endoplasmic Reticulum
• Is abbreviated “ER”
• Definition: is a system of membranous tubules and sacs.
• Function: act as an intracellular highway, a path along which molecules
move from one part of the cell to another.
• Types:
– Rough ER: is covered by ribosomes which give the ER rough
appearance.
» is prominent in cells that make large amounts of proteins to
be exported from the cell or inserted into cell membrane.
– Smooth ER: is not covered by ribosomes, and is involved in the:
» Synthesis of steroids in gland cells.
» Regulation of calcium levels in muscle cells.
» Breakdown of toxic substances by liver cells.
Section 2 Cell Organelles
Chapter 3

35. Golgi Apparatus
• Definition: is the processing, packaging, and secreting organelle of the cell,
and is a system of membranes.
• Appearance: appears as a series of flattened sacs with a characteristic
convex shape in the cytosol.
• Function: is working with “ER”, which modifies proteins for export by the cell.
Section 2 Cell Organelles
Chapter 3

36. Lysosomes
• Definition: are small, spherical organelles that enclose hydrolytic enzymes
within single membrane.
– They are common in the cells of animals,
fungi & protists, but they are rare in plant cells.
• Function:
• Can digest protein, carbohydrates, lipids,
DNA & RNA.
• They may also digest old organelles, viruses & bacteria that have
been ingested by a cell.
• In some multicellular organisms, play a role during early
development, for example:
» The human hand begins as a solid structure in the embryo.
As the embryo develops, lysosomal enzymes selectively
destroy tissue to form the spaces between the fingers.
Section 2 Cell Organelles
Chapter 3

37. Cytoskeleton
• Definition: is a network of protein strands, that not surrounded by
membranes.
• Function:
• maintain shape and size of cell
• Participates in the movement of organelles within the cytosol.
• Types:
– microfilaments: are threads made of a protein called actin. And is the smallest
strands that make up the cytoskeleton.
• Function:
– They contribute to cell movement.
– Play role in the muscle cell contraction.
– microtubules: are hollow tubes, and are the largest strands of the cytoskeleton.
• Function:
– When a cell is about to divide, bundles of microtubules (spindle fibers)
come together and extend across the cell.
– Spindle fibers assist in movement of chromosomes during cell division
Section 2 Cell Organelles
Chapter 3

38. Cytoskeleton
Chapter 3

39. Chapter 3
Cytoskeleton

40. Cilia and flagella
• Cilia and flagella:- are hairlike organelles that extend from the
surface of the cell .
 They assist in movement.
 Cilia and flagella can be found in many eukaryotic cells .
 When these organelles are short and present in large number ,
they are called cilia .
 Cilia in unicellular organisms aids in :
 Search for food
 Escape from predator
 Cilia also found in multicellular organisms in the cells that lining
your respiratory tract .
 When the hairlike organelles are long and less numerous on a cell
, they are called flagella .
 Example : sperm cells that have only one flagella .

41. Structure of Cilia and Flagella
Section 2 Cell Features
Chapter 3

42. The Nucleus
• The nucleus is an internal compartment that houses the cell’s DNA.
Most functions of a eukaryotic cell are controlled by the cell’s nucleus.
• The shape of nucleus are maintains with the help of protein skeleton
known as nuclear matrix
• The nucleus is surrounded by a double membrane called the nuclear
envelope.
• Inside nuclear envelope are fine strand known as chromatin.
 Chromatin is a combination of DNA and protein.
 During cell division the chromatin strands coil up and condensed
to form chromosomes .
 Scattered over the surface of the nuclear envelope are many small
channels called nuclear pores.
Section 3 Cell Organelles
Chapter 3

43. The Nucleus, continued
Section 3 Cell Organelles
Chapter 3

44. The Nucleus , continuous
 functions of nucleus :-
1) Storing hereditary information in DNA.
2) Act as a side where RNA is copied from DNA
3) Direct synthesize of protein by producing
ribosome in nucleolus.
Section 3 Cell Organelles
Chapter 3

45. Nucleus of a Cell
Section 3 Cell Organelles
Chapter 3

46. Structures of Plant Cells
Plants have three unique structures that are not found
in animal cells:
• Cell Wall
• Chloroplasts
• Central Vacuole
Section 3 Cell Organelles
Chapter 3

47. Parts of a Plant Cell
Section 3 Cell Organelles
Chapter 3

48. Structures of Plant Cells, continued
• The cell membrane of plant cells is surrounded by a
thick cell wall, composed of proteins and
carbohydrates.
• Cell wall are two types :
1. Primary cell wall :- develops during plant cell forming
2. Secondary cell wall :- forms when a cell reaches the
full size
 secondary cell wall develops between primary cell
wall and cell membrane.
 The cell wall
 helps support and maintain the shape of the cell
 protects the cell from damage
 connects the cell with adjacent cells
Section 3 Cell Organelles
Chapter 3

49. Parts of a Cell Wall
Section 3 Cell Organelles
Chapter 3

50. Structures of Plant Cells, continued
Central Vacuole:
• Most of a plant cell’s volume is taken up by a large,
membrane-bound space called the central vacuole.
• The central vacuole stores water and may contain
enzymes , ions, nutrients, and wastes such as toxics
Section 3 Cell Organelles
Chapter 3

51. Vacuoles
Section 3 Cell Organelles
Chapter 3

52. Plastids
• Plastids:- are organelle that surrounded by two
membrane and contain DNA.
 Function : store starch or fat and contain pigments
which absorb visible light.
 The most familiar type of plastids is chloroplast
Section 3 Cell Organelles
Chapter 3

53. Plastids , continuous
 Chloroplasts are organelles that use light energy to
make carbohydrates from carbon dioxide and water.
 Chloroplast encloses a series of flattened sacs that
called thylakoid.
• Chloroplasts, along with mitochondria, supply much
of the energy needed to power the activities of plant
cells.
• And contains a large amount of green pigment which
gives the leaves their green color
• Chloroplasts, like mitochondria, have their own DNA
and reproduce independently of the plant cell.
• Chloroplasts, like mitochondria, are thought to be
descendants of ancient prokaryotes.

54. Chloroplasts
Section 3 Cell Organelles
Chapter 3

55. Multiple Choice
Use the figure below and your knowledge of science to
answer questions 1–3.
Standardized Test Prep
Chapter 3

56. Multiple Choice, continued
1. Which structures in this cell are also found in
prokaryotic cells?
A. A and B
B. C and D
C. E and F
D. A and E
Standardized Test Prep
Chapter 3

57. Multiple Choice, continued
1. Which structures in this cell are also found in
prokaryotic cells?
A. A and B
B. C and D
C. E and F
D. A and E
Standardized Test Prep
Chapter 3

58. Multiple Choice, continued
2. Which features of plant cells are missing from this
cell?
F. cell wall and chloroplasts
G. Golgi apparatus and mitochondria
H. rough ER and lysosomes
J. smooth ER and nucleus
Standardized Test Prep
Chapter 3

59. Multiple Choice, continued
2. Which features of plant cells are missing from this
cell?
F. cell wall and chloroplasts
G. Golgi apparatus and mitochondria
H. rough ER and lysosomes
J. smooth ER and nucleus
Standardized Test Prep
Chapter 3

60. Multiple Choice, continued
3. What is the function of the structure labeled A?
A. making ATP
B. making carbohydrates
C. making proteins
D. moving proteins through the cell
Standardized Test Prep
Chapter 3

61. Multiple Choice, continued
3. What is the function of the structure labeled A?
A. making ATP
B. making carbohydrates
C. making proteins
D. moving proteins through the cell
Standardized Test Prep
Chapter 3

62. Section 3-3 multicellular organization
 In unicellular organisms , one cell can perform all the
function of life .
 Most cells in multicellular organisms are specialized
to perform one or a few function , because of cell
specialization .
 The cells in multicellular organisms depend on the
other cells in the organism for their survival.

63. Tissues , Organs , And organ systems
• Cells are organized into tissues
• Tissues: are groups of cells that carry out a specific
function.
• Types of tissues:
1- Epithelial tissue
2- Connective tissue
3- Muscle tissue
4- Nervous tissue

64. Types of tissue
1) Epithelial tissue : forms surface covering
• Ex the outermost living layer of skin.
2) Connective tissue: supports and links other tissues.
3) Muscle tissue: is composed of cells that pulls
against one another by contracting
4) Nervous tissue : is composed of cells that are
specialized for transmitting and reciving messages

65. • Organ: is a group of tissues that are specialized to
perform a specific function
• Examples: Heart, kidney, liver, stomach, brain.
stomach
• Muscle tissue: causes movement
• Connective tissue: supports and links stomach together
• Epithelial tissue: secrete enzymes
• Nervous tissue: transmits messages

66. Organ systems
 Organ system :- It is a group of organs that work
together to perform a set or related tasks .
 Example: cardiovascular system, urinary system and
respiratory systems.
 The different organ systems interact with each other
to carry out processes of life
 Non of the body’s organ system could survive without
the others.

67.  plants also have tissues and organs
Types of tissues in plants
• Dermal tissue: forms outer surface of plant
• Ground tissue: makes up a bulk of stems and roots
• Vascular tissue: transports water through out the plant

68. Organs of plants
• Roots
• Stems
• Leaves
• Flowers

69. Colonial organisms
• Some unicellular eukaryotes can lives in groups or
colonies
• A colonial organization: is a group of cells that are
genetically identical and they live together example: green
algae volvox.
 A hollow volvox sphere contains 500 to 60,000 cells
 Many cells in colony are specialized to perform a specific
function example: outer cells use their flagella to move the
colony through the water and a few of other cells are
specialized to reproduce.

70. Volvox colony
 They are a border between unicellular and multicellular
 They are not unicellular because they live together
 They are not multicellular because they lack tissue and
organ