This document provides an introduction and overview of the Cell Biology course SBL 203. It outlines the course goals, learning outcomes, delivery mode, assessment, references and reading materials, course outline, and contact information for the lecturer. The course aims to provide an introduction to basic cell biology principles including the structure and function of cellular components in prokaryotic and eukaryotic cells, cellular division processes, and the synthesis of biomolecules like DNA, RNA, and proteins. Students will learn through lectures, group work, assignments, essays and practical experiments. Their performance will be evaluated through exams, tests, and practical assessments.

1. SBL 203: CELL BIOLOGY
Lecture 1: Introduction to cells and Organelles
Dr. Geraldine D. Kavembe
With credit to Ms. Bernabeth Jo T.Tendero
11th September 2023

2. Lecture time & venue: Fridsay:7:00-10:00 am - N6
Lecturer contact: Dr. Geraldine Dorcas Kavembe; dkavembe@seku.ac.ke
Office hours: By appointment. Please email in advance to book appointment.
Course goals: The primary goal of this course is to provide you with an introduction to
basic principles in cell biology
Expected learning outcomes
By the end of this course unit, the student should be able to:
i. Describe the structure, function and composition of cellular components of both
prokaryotic and eukaryotic cells
ii. Explain the process of cellular division in both somatic and germ cells
iii. Explain the structure biomolecules (DNA,RNA and protein) and how they are
synthesized
iv. Demonstrate the ability to perform practical experiments related to cell biology.
Course delivery Mode: Lectures, GroupWork, Assignments, Essays and practicals
Course Assessment: End of semester examinations (70%), Continuous assessment
tests and practicals (30%)
SBL 203: Cell Biology

3. References & Reading Materials
CourseText Books
Essential Cell Biology, 4th edition (2014). Alberts, et al. Garland Science Publishing
Course Journals
The Journal of Cell Biology
Plant Cell
Molecular and Cellular Biology
ReferenceText Books
1. Molecular Biology of the Cell Alberts, Bruce; Johnson,Alexander; Lewis, Julian; Raff, Martin;
Roberts, Keith;Walter, Peter NewYork and London: Garland Science; c2002
2. Molecular Cell Biology 4th ed., Lodish, Harvey; Berk,Arnold; Zipursky, S. Lawrence;
Matsudaira, Paul; Baltimore, David; Darnell, James E., NewYork:W. H. Freeman & Co., 1999.
3. The Cell - A Molecular Approach 2nd ed., Cooper, Geoffrey M., Sunderland (MA): Sinauer
Associates, Inc., 2000.
4. Celis, Julio E.; Carter, Nigel; Simons, Kai; Small, J.Victor; Shotton, David (2005). Cell Biology,
Four-Volume Set :A Laboratory Handbook

4. Course Outline
▪ History, philosophy and concepts:
▪ The cell theory; prokaryote and eukaryote cells, structure and function of organelles and the
generalized cell; membranes.
▪ Molecular models of structure and function of cell membranes.
▪ The nucleus and the cell cycle; DNA replication and cell division
transcription.
▪ The endoplasmic reticulum; Golgi complexes; the mitochondria and
oxidative-phosphorylation. Plant chloroplasts and cell walls. Cytoskeleton
and cell motility.The cytosol and cytoskeleton, microtubules,
microfilaments, microtubule organelles.
▪ Molecular aspects of protein synthesis; molecular components of
polysomes, chain initiation, elongation and termination.

5. Organization Levels of Life
▪Consists of both Non-living and living levels

6. 6
ATOMS → MOLECULES → ORGANELLES
Nonliving Levels
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7. 7
CELLS TISSUES – Similar cells working together
Living Levels
→
→
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8. 8
ORGANS
ORGAN
SYSTEMS
ORGANISM
Different tissues
working together
Different organs
working together
→ →
More Living Levels
copyright cmassengale

9. Cell: Definition
 Smallest living unit
 Most cells are
microscopic

10. 10
Discovery of Cells
 In 1665, Robert Hooke used a microscope to
examine a thin slice of cork (dead plant cell walls)
and saw structures that looked like small boxes
 Hooke coined the term “CELLS” for the boxes
because they looked like the small rooms that
monks lived in called Cells
copyright cmassengale

11. Cell Theory
1. All living things are made of cells; may be
cellular or unicellular
2. The cell is the basic structural and
functional unit of life.
3. All cells arise from pre-existing cells
(this principle discarded the idea of
spontaneous generation)
Principles of CellTheory
Cell theory is one of the basic principles
of biology.

12. Who came up with this theory?
1. Matthias Schleiden (~ 1838); a German
botanist
All plants are
made of cells!
Onion skin cells

13. 2. Theodor Schwann (~ 1838)
A German Zoologist
Who came up with this theory?
All animals are
made of cells!
Human red blood cells

14. Who came up with this theory?
3. RudolphVirchow; a German Medical
Doctor
All cells come from
pre-existing cells
(by cell division)

15. The modern version of the Cell
Theory
 Includes the ideas that:
➢Energy flow (metabolism and
biochemistry) occurs within cells.
➢All cells have the same basic chemical
composition.
➢Cells carry genetic material passed to
daughter cells during cellular division

16. 16
ENDOSYMBIOTIC THEORY
 Lynn Margulis (1970), American
biologist, provided evidence
that some organelles within
cells were at one time free
living cells themselves
 Supporting evidence included
organelles with their own DNA
e.g. chloroplast and Mitochondria
copyright cmassengale

17. Cell Size (Micro to Macro sizes!)

18. Cells Have Large Surface
Area-to-Volume Ratio

19. 19
Number of Cells
Although all living beings are made of cells,
organisms may be:
 Unicellular – composed of one cell
 Multicellular- composed of many cells that
may organize into tissues, etc.
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20. 20
Cell Specialization
 Cells in a multi-cellular
organism become specialized
by turning different genes on
and off
 This is known as CELL
DIFFERENTIATION
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21. Nerve Cell
Muscle Cell
Stem Cell

22. 22
Specialized Animal Cells
Muscle cells Red blood cells
Cheek cells
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23. 23
Specialized Plant cells
Xylem cells
Pollen
Guard Cells
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24. Cell types
 There are two primary types of
cells: eukaryotic and prokaryotic cells.
Examples of eukaryotic cells
include animal cells, plant cells, and fungal
cells.
 Prokaryotic
cells include bacteria and archaeans.

25.  First cell type on earth
 Common in Bacteria and Archaea
 No membrane bound nucleus
 Nucleoid = region of DNA concentration
 Have few organelles
 Organelles are not bound
by membranes
CellTypes:Two primary types
1. Prokaryotic cells

26. Prokaryotic organisms
• All prokaryotic organisms Prokaryotic
Prokaryotes can live in environments that
would be deadly to most other organisms.
• These extremophiles are able to live and thrive
in various extreme habitats. Achaeans for
example, live in areas such as hydrothermal
vents, hot springs, swamps, wetlands, and even
animal intestines.

27. 2. Eukaryotic Cells
 Nucleus bound by membrane
 Include fungi, protists, plant, and
animal cells
 Possess many organelles
 Some organelles are
membrane bound

28. Prokaryotic vs Eukaryotic cells

29. Representative Animal Cell

30. Representative Plant Cell

31. Animal vs Plant Cell
Animal cells store carbohydrates as glycogen vs starch in plants
Plant cells are often larger (10 to 100 micrometers) than animal
cells (10 to 30 micrometers)
Animal cells have cilia & flagella often lacking in plant cells
Plant nucleus is often peripherial vs a central nucleus in animals

32. Cell Structure and Composition
Major Parts of the Cell
 Nucleus
 Cytoplasm
 Cell Surface (Cell membrane and Cell wall)

33. Nucleus
 Region of the cell where the genetic
material is located
 Generally oval-shaped or spherical shaped
 Most conspicuous part of the cell
 Regulates and coordinates all the
activities of the cell
 Denser (& often darker viewed under
microscope) than surrounding cytoplasm

34. Parts of the Nucleus
a) Chromosomes
- in form of chromatin
- contains genetic information
- Composed of DNA
- Thicken for cellular division
- Set number per species (i.e. 23 pairs for
human)

35. Chromosomes

36. Chromatin

37. b) Nuclear Membrane
 Surrounds the nucleus
 Double membrane
 Has numerous opening called nuclear
pores which serves as pathways for
exchange of materials between the
nucleus and the cytoplasm

38. Nuclear Membrane

39. c) Nucleolus
 Spherical shape
 Visible when cell is not dividing
 Contains RNA for protein manufacture

40. Nucleolus

41. Cytoplasm
 Protoplasm found outside the nucleus
 Collective term for cytosol and organelles
 Colloidal suspension
 Cytosol composed mainly of water with
free floating molecules
 Viscosity constantly changes

42. Organelles
 Discrete structures of a cell having
specialized functions

43. Centrioles: Helper in Cell Division
 Paired cylindrical organelles near nucleus
 Composed of nine tubes, each with three
tubules
 Involved in cellular division
 Lie at right angles to each other

44. Centrioles

45. Cytoskeleton: Framework of the
Cell
 Composed of microtubules
 Supports and provides shape
 Aids movement of materials in and out of
cells
 Microtubules provide pathways for
certain cellular molecules to move about

46. Cytoskeleton

47. Endoplasmic Reticulum:
Manufacturers and Builders of the
Cell
 Tubular network fused to nuclear
membrane
 Goes through cytoplasm onto cell
membrane
 Stores, separates and serves as cell’s
transport system

48. Endoplasmic Reticulum

49. Endoplasmic Reticulum:
Manufacturers and Builders of the
Cell
 2 types
a) Rough Endoplasmic Reticulum (RER)
- occurs as flattened sheets studded on its
outer surface with small spherical bodies
called ribosomes
- aids in protein and glycoprotein
synthesis
- prevalent in cells that specializes in
secreting proteins

50. Rough Endoplasmic Reticulum

51. Endoplasmic Reticulum:
Manufacturers and Builders of the
Cell
 b) Smooth Endoplasmic Reticulum (SER)
- occurs as tubes of membranes without
ribosomes attached
- site for fat metabolism and forms
vesicles for transporting large molecules
to other cell parts

52. Smooth Endoplasmic Reticulum

53. Golgi Apparatus: Packaging
Counters of the Cell
 Discovered and named after Camillo Golgi, an
Italian Biologist in 1898 by observing nerve cells
of an owl
 A system of membrane-bound sacs that look
like a stack of pancakes
 Believed to be part of ER and where new
membranes for the ER are manufactured
 Believed to prepare proteins for secretion after
they are released from the ER
 Involved in modifying, sorting & packaging of
proteins & transportation of lipids around the
cells as well as secretion of lysosomes

54. Golgi Apparatus

55. Lysosomes: Suicide Bags of the Cell
 “Lyso” – dissolving power and “some” –
body
 Discovered in 1952
 Contains hydrolytic/digestive enzymes for
proteins, lipids and carbohydrates
 Transports undigested material to the cell
membrane for removal
 Destroys cells when lysosomes burst

56. Lysosomes

58. Mitochondria: Powerhouses of the
Cell
 2nd largest organelle with its own DNA
(mtDNA)
 Double layered outer membrane with
inner folds called cristae
 Energy-producing chemical reactions
(produces ATP) takes place on cristae
 Controls level of water and other
materials in cell
 Recycles and decomposes proteins, fats
and carbohydrates, and forms urea

59. Mitochondria

60. Mitochondria

61. Ribosomes: Protein Factories of the
Cell
 Composed of nucleic acids (RNA) and
proteins
 Numerous in cells
 Manufacture proteins

62. Ribosomes

63. Ribosomes

66. Vacuoles: Storage Tanks of the Cell
 Membrane-bound sacs for storage,
digestion and waste removal
(tonoplast is a name used for the vascular
membrane of the vacuole; it sorrounds
the vacuole)
 Contains water solution
 Contractile vacuoles for water removal

67. Vacoules

70. Peroxisome
 Contain enzymes that transfer hydrogen
to various substrate of oxygen to
produce hydrogen peroxide
 Use oxygen to break fats to use as fuel
for cellular respiration
 Detoxify alcohol and other harmful
compounds

71. Peroxisomes

72. Plastids
 Plastids are organelles found only in
plants.There are three different types:
 Leucoplasts:White plastids found in
roots.
 Chloroplasts: Green-coloured plastids
found in plants and algae.
 Chromoplasts: Contain red, orange or
yellow pigments and are common in
ripening fruit, flowers or autumn leaves.

73. Plastids

74. Chloroplast: Site of Photosynthesis
 Plastid found in plant cells
 Contains green chlorophyll where
photosynthesis takes place
 Has its own DNA and ribosomes
 Double membrane bound organelle
 Mobile and move around the cell through
cytosleleton

75. Chloroplast

76. Cell Surface
 Protectively surrounds the cell
 Plasma membrane
 Cell wall
 Plasmodesmata

77. Plasma Membrane
 Double layer of phospholipid molecules
 Each phospholipid is composed of fats,
phosphate and carbohydrates
(oligosaccharide)
 Protein molecules are embedded in
phospholipids
 Because of its structure the membrane has a
semi-permeable property that allows only
chosen substances to enter and leave the
cell

78. Plasma Membrane

79. Cell Wall
 Lies outside the plasma membrane
 Compose of cellulose
 Protects the cells and provide rigid
structure for cells
 Remains intact even after the rest
of the cell has died

80. Cell Wall

81. Cell Homogenization &
Fractionation
 Each cell organelle has characteristics (e.g. size, shape
and density) which make it different from other
organelles within the same cell.
 Homogenization refers to the process of breaking
open cells to expose the organelles
 Fractionation refers to isolating or separation of
the organelles.

82. Homogenization
 The method employed depends on the cells under
consideration, some cells are found in isolation e.g.
blood cells, while others are part of solid tissue e.g
kidney and will need to be separated from other cells
before homogenization is done.
 Separation can be achieved by chelating the
environment (removing Ca and/or Mg ), but in most
instances the cells will need to be enzymatically or
mechanically disaggregated which results in subtle
changes to the cells (e.g. disruption of cell-cell
communication such as tight junctions).

83. Homogenization techniques
 Homogenization techniques can be divided into those
brought about by osmotic alteration of the media
which cells are found in, or those which require
physical force to disrupt cell structure.
Osmotic alterations
 Many organelles are easier to separate if the cells are
slightly swollen. In most cases hypo-osmotic buffer is
used.The imbibition of buffer (or water) into a cell
will cause osmotic swelling of the cell and/or
organelle, which can often assist in the rupture of the
cell and subsequent organelle separation of the
organelles.

84. Homogenization
Physical alterations
 This involves the use of mortars and pestles, blenders,
compression and/or expansion, or ultrasonification.
 In all forms of physical cell homogenization, the shear
force must be carefully controlled.Too little force
means the cell and the organelles will not be
separated, too much and even the molecules can be
broken.

85. Fractionation
 This may range from use of simple sieves, gravity
sedimentation or differential precipitation, to
ultracentrifugation of fluorescent labeled organelles in
computer generated density gradients.
Gravity sedimentation
• Following homegenization, the samples are allowed
to sit, and separation occurs due to the natural
differences in size and shape (density) of the cells.
• e.g. red blood cells are denser than white cells, and thus
whole blood separates into an RBC-rich bottom layer,
an intermediate "buffy coat" layer of WBC's and an
upper plasma portion of settled blood samples (an anti-
coagulant is added to prevent coagulation, which would
otheriwise interfere with the separation).

86. Fractionation
Centrifugation
 This involves the use of centripetal force
to separate the homogenate this may
include simple centrifuges to
ultracentrifuges.