- Cells are the basic functional units of the human body and come in many shapes and sizes. - All cells come from pre-existing cells through cell division. There are two main types of cells - prokaryotic and eukaryotic. - Eukaryotic cells, like human cells, are more complex and contain membrane-bound organelles that compartmentalize functions. The main organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and plasma membrane.

2. DEFINITION
• The cell is the basic functional in a human
meaning that it is a self-contained and fully
operational living entity.
• Some of the 100 trillion of cells make up
human body.
• All human cell are microscopic in size, shape
and function.
• The diameter range from 7.5 micrometer
(RBC) to 150 mm (ovum).

4. CEL THEORY
• All organisms are composed of cells.
• Cells are the smallest living things.
• Cells arise only from pre-existing cells.
Cell size is limited.
-As cell size increases, it takes longer for
material to diffuse from the cell membrane
to the interior of the cell.

5. Surface area-to-volume ratio:
As a cell increases in size, the volume
increases 10x faster than the surface area.

6. TWO TYPES OF CELL
• Prokaryotic
• Eukariotic

7. PROKARYOTIC
• Do not have structures surrounded by membranes
• Few internal structures
• One-celled organisms, Bacteria
• Prokaryotic cells possess
Genetic material in the nucleoid ; Cytoplasm
Plasma membrane ; Cell wall ; Ribosomes ;
No membrane-bound organelles.

9. EUKARYOTIC
• Contain organelles surrounded by membranes
• Most living organisms.

10. TYPICAL ANIMAL CELL

11. TYPICAL PLANT CELL

12. EUKARYOTIC CELL
Eukaryotic cells
• Possess a membrane-bound nucleus
are more complex than prokaryotic cells
compartmentalize many cellular functions
within organelles and the endomembrane
system.
• Possess a cytoskeleton for support and to
maintain cellular structure.

14. PARTS OF HUMAN CELL
• The cell contains various structural components to allow it to maintain life
which are known as organelles. All the organelles are suspended within a
gelatinous matrix, the cytoplasm, which is contained within the cell
membrane. One of the few cells in the human body that lacks almost all
organelles are the red blood cells.
The main organelles are as follows :
• Cell membrane
• Golgi apparatus
• Lysosomes
• Mitochondria
• Nucleus
• Perioxisomes
• Microfilaments and microtubules
• Endoplasmic reticulum

15. CELL MEMBRANE
• The cell membrane is the outer coating of the cell and
contains the cytoplasm, substances within it and the organelle.
It is a double-layered membrane composed of proteins and
lipids. The lipid molecules on the outer and inner part (lipid
bilayer) allow it to selectively transport substances in and out
of the cell.

16. CELL WALL
• Many types of prokaryotic and eukaryotic cells have a cell wall. The cell
wall acts to protect the cell mechanically and chemically from its
environment, and is an additional layer of protection to the cell membrane.
Different types of cell have cell walls made up of different materials; plant
cell walls are primarily made up of cellulose, fungi cell walls are made up
of chitin and bacteria cell walls are made up of peptidoglycan.

17. NUCLEUS
• The nucleus is the master control of the cell. It contains genes, collections
of DNA, which determines every aspect of human anatomy and
physiology. The DNA which is arranged into chromosomes also contains
the blueprint specific for each type of cell which allows for replication of
the cell. Within the nucleus is an area known as the nucleolus. It is not
enclosed by a membrane but is just an accumulation of RNA and proteins
within the nucleus. The nucleolus is the site where the ribosomal RNA is
transcribed from DNA and assembled.

18. NUCLEAR MEMBRANE
• Surrounds nucleus
• Made of two layers
• Openings allow material to enter and leave nucleus

19. MICROFILAMENTS AND
MICROTUBULES
• Microfilaments and microtubules are rigid protein substances that form
the internal skeleton of the cell known as the cytoskeleton. Some of these
microtubules also make up the centrioles and mitotic spindles within the
cell which are responsible for the division of the cytoplasm when the cell
divides. The microtubules are the central component of cilia, small hair-
like projections that protrude from the surface of certain cells. It is also the
central component of specialized cilia like the tail of the sperm cells which
beats in a manner to allow the cell to move in a fluid medium.

20. CHROMOSOMES
• In the nucleus of each cell, the DNA molecule is
packaged into thread-like structures called
chromosomes. Each chromosome is made up of
DNA tightly coiled many times around proteins
called histones that support its structure.

21. ENDOPLASMIC RETICULUM
• The endoplasmic reticulum (ER) is a membranous structure that contains a network of
tubules and vesicles. Its structure is such that substances can move through it and be kept
in isolation from the rest of the cell until the manufacturing processes conducted within
are completed. There are two types of endoplasmic reticulum – rough (granular) and
smooth (agranular).
• The rough endoplasmic reticulum (RER / granular ER) contains a combination of
proteins and enzymes. These parts of the endoplasmic reticulum contain a number of
ribosomes giving it a rough appearance. Its function is to synthesize new proteins.
• The smooth endoplasmic reticulum (SER / agranular ER) does not have any attached
ribosomes. Its function is to synthesize different types of lipids (fats). The smooth ER
also plays a role in carbohydrate and drug metabolism.

22. GOLGI APPARATUS
• The Golgi apparatus is a stacked collection of flat vesicles. It
is closely associated with the endoplasmic reticulum in that
substances produced in the ER are transported as vesicles and
fuses with the Golgi apparatus. In this way, the products from
the ER are stored in the Golgi apparatus and converted into
different substances that are necessary for the cell’s various
functions.

23. LYSOSOMES
• Lysosomes are vesicles that break off from the Golgi apparatus. It varies in
size and function depending on the type of cell. Lysosomes contain
enzymes that help with the digestion of nutrients in the cell and break down
any cellular debris or invading microorganisms like bacteria.
• A structure that is similar to a lysosome is the secretory vesicle. It contains
enzymes that are not used within the cell but emptied outside of the cell, for
example the secretory vesicles of the pancreatic acinar cell
release digestive enzymes which help with the digestion of nutrients in the
gut.

24. PEROXISOMES
• These organelles are very similar to the lysosomes and contain
enzymes that act together in the form of hydrogen peroxide to
neutralize substances that may be toxic to the
cell. Perioxisomes are formed directly from the endoplasmic
reticulum rather than from the Golgi apparatus like lysosomes.

25. MITOCHONDRIA
• These are the powerhouses of the cell and break down nutrients to yield
energy. Apart from producing its own energy, it also produces a high-
energy compound called ATP (adenosine triphosphate) which can be used
as a simple energy source elsewhere. Mitochondria are composed of two
membranous layers – an outer membrane that surrounds the structure and
an inner membrane that provides the physical sites of energy production.
The inner membrane has many infoldings that form shelves where enzymes
attach and oxidize nutrients. The mitochondria also contain DNA which
allows it to replicate where and when necessary.

26. PLASMA MEMBRANE
• The cell membrane is a thin, dynamic
membrane that encloses the cell and controls
what enters and leaves the cell.
• Fluid Mosaic Model
composed of a double layer (bilayer) of
phospholipid molecules with many protein
molecules dispersed within it.

27. FLUID MOSAIC MODEL
a.The surfaces of the membrane are
"hydrophilic" due to the polar phosphate
heads;
b.The internal portion of the membrane is
"hydrophobic" due to the non-polar fatty acid
tails;
c.The membrane proteins also have both
hydrophilic and hydrophobic.

28. PLASMA MEMBRANE

29. FUNCTIONS
• Plasma membrane separates the components of the cell from its outside
environment.
• It regulates what enters and exits the cell.
• It allows only selected substances into the cell and keeps others out.
• Plasma membrane has a major role in protecting the integrity of the interior
of the cell.
• Plasma membrane serves as a base of attachment for the cytoskeleton in
some organisms and cell walls in other organisms. Thus it supports the cell
and helps in maintaining the shape of the cell.
• Plasma membrane is composed of lipids and proteins. Lipids give
flexibility to membranes and proteins maintain the chemical climate of the
cell and help in transfer of molecules across the membrane.
• The lipid bi layer is semi permeable, that is, it allows selected molecules to
diffuse across the membrane.

30. TRANSPORT ACROSS THE PLASMA
MEMBRANE
– Passive transport
– Active Transport
require no ATP( energy)
Substances move High to low conc.
Examples include
• Simple diffusion
• Osmosis
• facilitated diffusion
• filtration

31. SIMPLE DIFFUSION
• random mixing of
particles in solution
• substances move
down concentration
gradient-
• particles eventually
become evenly
distributed -
Equilibrium reached

32. DIFFUSION THROUGH PLASMA MEMBRANE

33. TONICITY
Tonicity is a measure of the effective osmotic pressure gradient,
as defined by the water potential of two solutions separated by
a semipermeable membrane
Describes how a solution affects cell volume
• hypertonic
– solution with more solutes
– Blood cells shrink and crenate
• hypotonic
– solution with less solutes
– Blood cells swell up and hemolyse
• isotonic
– both solutions have similar concentrations of solutes.
– Cell size is unchanged

34. Solutes Moving Against Concentration
Gradient-uses Carrier Proteins
Can be driven by ATP use or via energy stored in
ionic concentration
Types :
– Primary active transport
– Secondary active transport
Endocytosis
Exocytosis
Tanscytosis

35. PRIMARY ACTIVE TRANSPORT
• Uses ATP protein and transports sodium potassium
pump.

36. Transport in Vesicles Endocytosis
• A form of active transport.
• Transport of large particles across the plasma
membrane
• Types :
1.Phagocytosis
1.Pinocytosis

37. PHAGOCYTOSIS
• Only a few body cells are capable
• Ex. WBC (macrophages , neutrophils)
• Particle binds to plasma membrane
• Pseudopods extend and surround particle
forming phagosome
• Phagosome fuses with lysosomes which
destroy invader.

38. PHAGOCYTOSIS

39. PINOCYTOSIS
• Also called cellular drinking
• most body cells carry out process
– especially absorptive cells in intestines and
kidneys
• Tiny droplets of extracellular fluid taken into
cell
• Lysosomes fuse and degrade particles into
smaller useable particles.

40. PINOCYTOSIS

41. EXOCYTOSIS
• Releases materials form a cell
• All cells carry out process
• Ex. i. secretory cells
• Release digestive enzymes, hormones, mucus, or other secretions
– ii. nerve cells
• Release neurotransmitters
• Vesicles fuse with plasma membrane and release
contents into extracellular fluid.

42. EXOCYTOSIS

43. EXOCYTOSIS

44. CELL DIVISION
• Cell division is the process by which a
parent cell divides into two or more daughter cells.
• The primary concern of cell division is the
maintenance of the original cell's genome.

45. OVERVIEW
ASEXUAL REPRODUCTION
– Many single-celled organisms
reproduce by splitting, budding.
– Some multicellular organisms
can reproduce asexually,
produce clones (offspring genetically
identical to parent).

46. Prokaryotic cells reproduce
asexually
= binary fission
Prokaryotic Cell Division

47. SEXUAL
REPRODUCTION
• Fusion of two gametes to
produce a single zygote.
• Introduces greater genetic
variation, allows genetic
recombination.
• With exception of self-
fertilizing organisms, zygote
has gametes from two
different parents. Peter + Lois = Stewie
Images: Peter, Lois & Stewie, The Family Guy From the Virtual Cell Biology Classroom on ScienceProfOnline.com

48. Eukaryotic Cell Cycle
– Cell grows.
– DNA is replicated.
- Mitotic cell division produces daughter
cell identical to the parent.
Different from prokaryotic
cell cycle, in that…
– Eukaryotic cells have more DNA on many linear chromosomes.
(Q: How many do humans have?).
– The timing of replication and cell division is highly regulated.
Like prokaryotic cell cycle, in that…

49. Mitosis:
– Produces 2 genetically identical cells
– Happens throughout body
Meiosis:
– Produces 4 genetically different cells
– Cells only have ½ of genetic info
– Happens only in gonads
Two Types of Cell Division

50. Mitosis
One part of the cell cycle
Growth, cell replacement, tissue repair
Also used for asexual reproduction
= organisms clone selves
Unique to eukaryotes

51. The Cell Cycle
The period from one cell division to next

52. Interphase: The Longest
Phase
l cycle length

53. Interphase

54. G1: Gap / Growth Phase
Cell growth
# of cytoplasmic
components doubled

55. S: Synthesis Phase
DNA duplicated

56. Chromosome & copy = sister chromatids
Joined at centromere

57. G2: Gap or Growth Phase II
Makes proteins necessary
for cell division
Cell prepares to divide

58. Cells stay in G1 if making macromolecules
Enter S when DNA & accessory proteins are
copied
Rate of DNA replication is same for all cells of
a species

59. Same cycle length for same type of cells
Different cycle lengths for different types of
cells
e.g. cells in red bone marrow divide every second
e.g. nerve cells stay in G1 indefinitely
Rate of cell division is under control
(checkpoints, molecular brakes, etc.)

60. After G2, cell enters mitosis
Mitosis maintains cell’s chromosome #

61. Chromosome Number
Humans have 46
chromosomes
= diploid (2n)
2 of each type of
chromosome
= one set from mother, one
from father

62. During mitosis
Each 2n parent cell produces two 2n
daughter cells
Each daughter cell has each pair of
chromosomes = 23 pairs

63. Late Interphase / Pre-
Prophase
Outside of nucleus, 2 centrioles
duplicate selves

64. Early Prophase
Inside nucleus:
Chromosomes begin to condense
Outside nucleus:
Spindle begins to form
Nuclear envelope begins to fall
apart

65. Late Prophase
Nuclear envelope completely falls
apart
Spindle fibres from each pole
attach to sister chromatids of
each chromosome

66. Metaphase
Chromosomes line up halfway
between spindle poles

67. Anaphase
Sister chromatids of each
chromosome separate & move to
opposite poles
(motor proteins attached to kinetochores
drag chromatids along microtubules)
Spindle poles pushed apart by
growing microtubules

68. Telophase
1 of each type of chromosome
reaches each spindle pole
= 2 identical groups of chromosomes at
each cell pole
Chromosomes decondense
Nuclear envelope forms around
each cluster of chromosomes
= two nuclei, each with 2n # of
chromosomes

69. Cytokinesis
Cytoplasm of cell divides
Results in 2 daughter cells, each with
same number of chromosomes as
parent cell

70. Cytokinesis in Animal Cells
Contractile ring mechanism
Halfway between cell’s poles,
plasma membrane constricts =
cleavage furrow
(ATP energy causes contraction of
actin filaments)
Cleavage furrow deepens until
cytoplasm split into 2

71. Cytokinesis in Plant Cells
Cell plate formation
Golgi vesicles move to cell
equator & fuse
Vesicle membranes become
cell membranes
Contents become cellulose
cell wall

72. Cloning
Donor cells from 1
animal starved so
enter non-dividing
G0 phase
Nucleus removed
from unfertilized
egg cell of another
animal

73. Donor cell & egg cell placed next to each other in
culture dish & electrically stimulated
Cells fuse & enter mitosis

74. Cell continues mitotic divisions & forms embryo
Embryo implanted into surrogate mother
(same spp. as egg cell)
Surrogate mother gives birth to genetic twin of “donor
cell” animal

75. Mitosis:
– Occurs in somatic cells
– Results in 2 genetically identical cells
– Growth, cell replacement, tissue repair
= asexual reproduction
Meiosis:
– Occurs in sex cells
– Results in 4 genetically different cells with ½ genetic
info of parent cell
= sexual reproduction
Mitosis vs. Meiosis

76. So What is Meiosis?
Nuclear division that halves chromosome #
Occurs only in sex (reproductive) cells
1st step in formation of gametes ( or )
Gametes fuse with opposite sex gametes to form
new individual

77. Humans are diploid (2n) with 46 chromosomes
(23 + 23 homologous chromosomes)
Meiosis halves chromosome number so daughter
cells (gametes) are haploid (n) with 23
chromosomes

78. Gametes
Have only 1 set of chromosomes
= haploid (n)
Each gamete has 1 allele for each gene
(One of the variant forms of a gene at a particular (locus) location on a chromosome.
Different alleles produce variation in inherited characteristics (e.g. hair & eye colour, etc.)
In humans = eggs or sperm
During meiosis, one cell goes through 2
divisions to end with formation of 4 cells,
all with haploid (n) nuclei

79. Interphase
Same as in mitosis:
Cell grows & duplicates cytoplasmic components
DNA is replicated

80. Prophase I
Chromosomes condense
Crossing-over occurs between
homologous chromosomes
Centrioles move to opposite sides
of nuclear envelope
Nuclear envelope begins to fall
apart

81. Crossing Over
When chromosomes condense during prophase,
homologous chromosomes stick very closely
together & form a tetrad

82. Maternal & paternal chromosomes swap genes
= exchange segments of genetic info
Homologous chromosomes become mixture of
maternal & paternal info
chiasma

83. Metaphase I
Homologues of chromosomes
tethered by microtubules at
opposite spindle poles
Chromosomes line up along
equator of cell

84. Anaphase I
Chromosomes pulled apart & move
towards respective poles
Poles move further apart

85. Telophase I
Cytoplasm divides
Results in 2 haploid cells
(only have 1 of each pair of
homologous chromosomes)
Chromosomes still duplicated

86. Prophase II
New mitotic spindle forms in each cell
Chromatids of each chromosome become
tethered to opposite poles

87. Metaphase II
Chromosomes line up along equator
of cell

88. Anaphase II
Chromatids separate & move towards
opposite poles
Spindle poles pushed apart

89. Telophase II
Nuclear envelope forms around each
chromosome cluster

90. Cytokinesis
Cytoplasm divides
Results in 4 haploid (n) daughter cells
Chromosomes are unduplicated

91. Male Gamete Formation
Germ cell (spermatogonium) develops into 1°
spermatocyte
Enters meiosis
Results in 4 haploid cells (spermatids) that
differentiate into sperm cells

93. Female Gamete Formation
Germ cell (oogonium) develops into 1° oocyte
(immature egg)
Grows in size
4 daughter cells differ in structure & function
When 1° oocyte divides after meiosis I, one
daughter cell (2° oocyte) gets most of cytoplasm
Other cell (1st polar body) is very small

95. After meiosis II, one of 2° oocyte’s daughter cells is
2nd polar body (also very small)
Other gets most of cytoplasm and develops into ovum
(egg)
1st polar body’s daughter cells are both polar bodies

96. Fertilization: When 2 Gametes
Become 1
Male & female gametes unite
Haploid nuclei fuse
Restores diploid nature of cells
(n + n = 2n)
↑ variation among offspring:
– Random gametes fusing
– Millions of possible chromosome combos in
each gamete

97. Mitosis vs.
Meiosis
• 2n
• Clone
• Same genetic
information in
parent cell and
daughter cell.
• Give me another
one just like the
other one!
• 1n
• Daughter cells different from parent
cell and from each other.
• Daughter cells have ½ the number of
chromosomes as somatic cell.
• Shuffling the genes
(Mix it up!)
• See animation “Unique Features of
Meiosis” from McGraw-Hill

98. Image: Mitosis diagram & Meiosis diagram, Marek Kultys From the Virtual Cell Biology Classroom on ScienceProfOnline.com