- The nucleus houses the cell's genetic material DNA and controls cell reproduction. When a cell divides, the genetic material condenses into chromosomes. - The cytoplasm contains organelles like mitochondria, ER, Golgi apparatus and lysosomes that carry out specialized functions. - The plasma membrane encloses the cell and regulates what enters and exits using passive and active transport processes.

1. Cell Structure and Function

2. • The human body is made
up of many specialised
cells that perform
specific functions.
• Specialised cells arise
from the differentiation
of unspecialised cells
during embryological
development.

3. Cells
• Smallest living unit
• Most are microscopic

4. Discovery of Cells
• Robert Hooke (mid-1600s)
– Observed sliver of cork
– Saw “row of empty boxes”
– Coined the term cell

5. Cell theory
• (1839)Theodor Schwann & Matthias Schleiden
“ all living things are made of cells”
• (50 yrs. later) Rudolf Virchow
“all cells come from cells”

6. Principles of Cell Theory
• All living things are made of cells
• Smallest living unit of structure and
function of all organisms is the cell
• All cells arise from preexisting cells
(this principle discarded the idea of
spontaneous generation)

7. Cell Size

8. Characteristics of All Cells
1. A surrounding membrane
2. Protoplasm – cell contents in thick fluid
3. Organelles – structures for cell function
4. Control center with DNA

9. 2 Cell Types
• Prokaryotic
• Eukaryotic

10. Prokaryotic Cells
• First cell type on earth
• Cell type of Bacteria and Archaea

11. Prokaryotic Cells
• No membrane bound nucleus
• Nucleoid = region of DNA concentration
• Organelles not bound by membranes

12. Eukaryotic Cells
• Nucleus bound by membrane
• Include fungi, protists, plant,
and animal cells
• Possess many organelles
Protozoan

13. Representative Animal Cell

14. Generalized cell
• Have 3 main regions
– Nucleus
usually located near the center of the cell
– Cytoplasm
semifluid surrounding the nucleus
– Plasma membrane
the outer cell boundary enclosing the
cytoplasm

15. Nucleus
• Control center of cell
– Gene containing, genetic
material DNA
(deoxyribonucleic acid)
– DNA is necessary for cell
reproduction
• Double membrane
• Contains
– Chromosomes
– Nucleolus

16. Nucleus
• Has 3 regions
– Nuclear envelope
– Nucleoli
– Chromatin

17. Nuclear Envelope
• Separates nucleus from rest of cell
• Double membrane
– Fluid filled
– The 2 layers fuse…
• Has pores
– Penetrate through the
fuse region

18. Nucleoli
• Dark staining, round bodies
• Sites where ribosomes
are assembled
– Ribosomes migrate
to the
– Cytoplasm
Sites of protein synthesis

19. Nucleolus
• Most cells have 2 or more
• Directs synthesis of RNA
• Forms ribosomes

20. Ribosomes
• Are tiny, bilobed, dark bodies made of
proteins and one variety of RNA called
ribosomal RNA
• Ribosomes are the actual sites of protein
synthesis in the cell.

21. DNA
• Hereditary material
• Chromosomes
– DNA
– Protiens
– Form for cell division
• Chromatin

22. Chromatin
• When a cell is not dividing, its DNA is
combined with protein
and forms a loose
network of bumpy
threads call chromatin
that is scattered
throughout the nucleus

23. Chromatin
• When a cell is dividing to
form two daughter
cells, the chromatin
threads coil and condense
to form dense, rodlike bodies
called chromosomes

24. To summarize:
• Nucleus …
– Control center of the cell
– Site of the “genes”/genetic materials DNA
– It is necessary for cell reproduction
– When the cell is not dividing, the genetic
material is in threadlike form called …
• Chromatin
– When a cell is dividing to form daughter cells,
the chromatin coils and condenses to form
darkly staining rod-like bodies called …
• Chromosomes

25. • Chromosomes
– Stretched spring becomes shorter and thicker
– When it is released…
• Cell division

26. • Nucleoli
– Nucleus contain nucleoli
– Assembly site for ribosomes the protein –
synthesizing “factories” which are abundant in
cytoplasm
• Nuclear membrane
– Nucleus is bound with double-layered porous
membrane nuclear membrane..
– Has large nuclear pores which permit large
molecules like protein and RNA molecules
to pass easily

27. Representative Animal Cell

28. Cytoplasm
• Viscous fluid containing organelles
• components of cytoplasm
– Interconnected filaments & fibers
– Fluid = cytosol
– Organelles (not nucleus)
– storage substances

29. Cytoskeleton
• Filaments & fibers
• Made of 3 fiber types
– Microfilaments
– Microtubules
– Intermediate filaments
• 3 functions:
– mechanical support
– anchor organelles
– help move
substances

30. Organelles
• Cellular machinery
• Two general kinds
– Derived from membranes
– Bacteria-like organelles

31. Mitochondria
• Have their own DNA
• Bound by double membrane

32. Mitochondria
• Break down fuel molecules (cellular respiration)
– Glucose
– Fatty acids
• Release energy
– ATP

33. Centrioles
• Pairs of microtubular structures
• Play a role in cell division

34. Membranous Organelles
• Functional components within cytoplasm
• Bound by membranes

35. Endoplasmic Reticulum
• Helps move substances within cells
• Network of interconnected membranes
• Two types
– Rough endoplasmic reticulum
– Smooth endoplasmic reticulum

36. Rough Endoplasmic Reticulum
• Ribosomes attached to surface
– Manufacture protiens
– Not all ribosomes attached to rough ER
• May modify proteins from ribosomes

37. Smooth Endoplasmic Reticulum
• No attached ribosomes
• Has enzymes that help build molecules
– Carbohydrates
– Lipids

38. Golgi Apparatus
• Involved in synthesis of plant cell wall
• Packaging & shipping station of cell

39. Golgi Apparatus Function
1. Molecules come in vesicles
2. Vesicles fuse with Golgi membrane
3. Molecules may be modified by Golgi

40. Golgi Apparatus Function
(Continued)
4. Molecules pinched-off in separate vesicle
5. Vesicle leaves Golgi apparatus
6. Vesicles may combine with plasma
membrane to secrete contents

42. Lysosomes
• Contain digestive enzymes
• Functions
– Aid in cell renewal
– Break down old cell parts
– Digests invaders

43. To summarize:
the cytoplasmic organelles are…
• Ribosomes
• Endoplasmic reticulum (ER)
• Golgi apparatus
• Lysosome
• Peroxisome
• Mitochondria
• Centrioles
• Cytoskeletal elements
– Microtubules, intermediate filaments, &
microfilaments

44. Plasma membrane

45. Plasma Membrane
• Contains cell contents
• Double layer of phospholipids & proteins

46. Phospholipids
• Polar
– Hydrophylic head
– Hydrophobic tail
• Interacts with water

47. Movement Across the Plasma Membrane
• A few molecules move freely
– Water, Carbon dioxide, Ammonia, Oxygen
• Carrier proteins transport some molecules
– Proteins embedded in lipid bilayer
– Fluid mosaic model – describes fluid nature of
a lipid bilayer with proteins

49. Membrane Proteins
1. Channels or transporters
– Move molecules in one direction
2. Receptors
– Recognize certain chemicals

50. Membrane Proteins
3. Glycoproteins
– Identify cell type
4. Enzymes
– Catalyze production of substances

51. Molecule Movement & Cells
• Passive Transport
• Active Transport
• Endocytosis
(phagocytosis & pinocytosis)
• Exocytosis

52. Passive Transport
• No energy required
• Move due to gradient
– differences in concentration, pressure, charge
• Move to equalize gradient
– High moves toward low

53. Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated diffusion

54. Diffusion
• The movement of molecules from a region
of higher concentration to a region of lower
concentration.
• The diffusion of solutes (particles
dissolved in water) through a
semipermeable membrane is called…
• Simple diffusion

55. Diffusion
• Molecules move to equalize concentration

56. Osmosis
• Special form of diffusion
• Fluid flows from lower solute concentration
• Often involves movement of water
– Into cell
– Out of cell
• The diffusion of water through a
semipermeable membrane

57. Solution Differences & Cells
• solvent + solute = solution
• Hypotonic
– Solutes in cell more than outside
– Outside solvent will flow into cell
• Isotonic
– Solutes equal inside & out of cell
• Hypertonic
– Solutes greater outside cell
– Fluid will flow out of cell

59. Facilitated Diffusion
• Differentially permeable membrane
• Channels (are specific) help molecule
or ions enter or leave the cell
• Channels usually are transport proteins
(aquaporins facilitate the movement of
water)
• No energy is used

60. Process of Facilitated Transport
• Protein binds with molecule
• Shape of protein changes
• Molecule moves across membrane

61. Active Transport
• Molecular movement
• Requires energy (against gradient)
• Example is sodium-potassium pump

62. Endocytosis
• Movement of large material
– Particles
– Organisms
– Large molecules
• Movement is into cells
• Types of endocytosis
– bulk-phase (nonspecific)
– receptor-mediated (specific)

63. Process of Endocytosis
• Plasma membrane surrounds material
• Edges of membrane meet
• Membranes fuse to form vesicle

64. Forms of Endocytosis
• Phagocytosis – cell eating
• Pinocytosis – cell drinking

65. Exocytosis
• Reverse of endocytosis
• Cell discharges material

66. Exocytosis
• Vesicle moves to cell surface
• Membrane of vesicle fuses
• Materials expelled

67. Vacuoles
• Membrane bound storage sacs
• More common in plants than animals
• Contents
– Water
– Food
– wastes

68. Cilia & Flagella Structure
• Bundles of microtubules
• With plasma membrane

69. Cilia & Flagella
• Provide motility
• Cilia
– Short
– Used to move substances
outside human cells
• Flagella
– Whip-like extensions
– Found on sperm cells
• Basal bodies like
centrioles

70. Sperm cell

71. A mature human sperm cell has snake like structure. It has following
parts - head, neck, middle piece and tail.
Head: It is spherical in shape consisting of large nucleus and a dome
shaped acrosome present on the nucleus.
Function: Nucleus contain genetic information and half number of
chromosomes. The acrosome releases a hyaluronidase enzyme
which destroys the hyaluronic acid of the ovum and enters into the
ovum.
Neck: It contains centrioles which are proximal centriole and distal
centriole.
Function: Distal centriole gives rise to axial filament of the sperm
which runs up to the end of the tail.
Middle piece: It is tubular structure in which mitochondria are spirally
arranged.
Function: Middle piece is called power house of sperm because it
gives energy to the sperm to swim in the female genital tract.
Tail: It arises from middle piece and it is the end part of the sperm. It
contains axial filaments.
Function: Tail helps the sperm to swim in the female genital tract. It is
the main part of sperm to move.

72. Review of Eukaryotic Cells

73. Review of Eukaryotic Cells

75. Summary
• Cell structure and their;
• functions

76. Generalized cell
• Have 3 main regions
– Nucleus
usually located near the center of the cell
– Cytoplasm
semifluid surrounding the nucleus
– Plasma membrane
the outer cell boundary enclosing the
cytoplasm

77. Cytoplasm
• Viscous fluid containing organelles
• components of cytoplasm
– Interconnected filaments & fibers
– Fluid = cytosol
– Organelles (not nucleus)
– storage substances

78. Functions of the cell Organelles
Endoplasmic reticulum • Passageway for
transport of materials
within the cell
• Synthesis of lipids
Ribosome • Site of protein synthesis
• Site of destruction of old
or damaged proteins
Golgi apparatus • Synthesis of
carbohydrates
• Packaging of materials
for secretion from the
cell

79. Functions of the cell Organelles
Lysosome • Contains enzymes to
digest ingested material
or damaged tissue
Centrioles • Organized the spindle
fibers during cell
division
Cilia • Sweep the materials
across the cell surface
Flagellum • Enables a cell to move
Microvilli • Increase a cell’s surface
area for absorption