This document summarizes the structure and function of cells. It describes the basic components of the cell membrane including phospholipids and cholesterol. It then discusses various organelles in cells such as the nucleus, endoplasmic reticulum, Golgi complex, lysosomes, peroxisomes, mitochondria and cytoskeleton. The document explains how cell fractionation can be used to isolate these organelles by breaking open cells and separating components by centrifugation based on size and density. Finally, it briefly touches on other cell biology topics such as DNA replication, cell division, aging, and cancer.

1. THE CELL
V.S.RAVIKIRAN, MSc.

2. V.S.RAVIKIRAN, MSc.,
Department of Biochemistry,
ASRAM Medical college,
Eluru-534005.AP, India.
vsravikiran2013@gmail.com

3. V.S.RAVIKIRAN
CELLS

7. Two generations of membrane
models

9. Fatty acids (FAs) form the
basic structures of
phospholipids
1.2.1 Simplified structure of lipid bilayer and phospholipids
Polar group
Phosphat
e
Glycerol
Fatty acid-
(unsaturated)
Phospholipid molecule
Fatty acid (saturated)
Hydrophilic
head
Hydrophobic
fatty acid
tails
Hydrophobiccore
oflipidbilayer
Hydrophilic head to cytoplasm
Hydrophili
c head on
surface

11. 1.4.1 Lipid composition of different plasma membranes: note
cholesterol contents

12. Cell Membrane

14. • Ion channel
• Transporter
• Receptor
• Enzyme
• Cell Identity marker
• Linker

15. Endocytosis

16. Phagocytosis

17. Pinocytosis

20. Cytoskeleton

21. The Cytoskeleton
• Made of filamentous proteins
• Helps give the cell its shape
• Coordinates cellular movements.
• Three categories:
– microfilaments
– intermediate filaments
– microtubules
2-21

22. 22

33. Centrosome

34. Non-membranous Organelles
• Centrioles and the centrosome
– Centrosome
• Area close to the nucleus
• Organization site for microtubules
– Centrioles (exist as a pair)
• In the centrosome
• Perpendicular to each other
• 9 sets of microtubule triplets
• Important in cell division (spindle)
2-34

35. 35

36. Microvilli, Cilia and Flagella
• Appendages extending from the surface of some cells.
– Microvilli:
• short, cytoplasmic extensions
• For absorption
– Cilia:
• usually occur in large numbers
• work together to move materials or fluids along the surface of a cell.
– Flagella:
• longer than cilia, and usually occur as single appendages.
• Move the cell
2-36

37. 37

38. Cilia
Flagella

40. Ribosome

43. Endoplasmic
Reticulum
(smooth and
rough)

49. Golgi Complex

50. Protein Export by Golgi Complex

61. Lysosome

66. Peroxisomes
• Modify molecules
through redox
reactions (fatty acid)
• Produce peroxide as
a result (H2O2)
• Split into two as they
grow

70. Mitochondria

77. Nucleus

84. Interactions between nucleus and cytoplasm

86. 86

89. Isolating Organelles by Cell
Fractionation
• Cell fractionation
– Takes cells apart and separates the major
organelles from one another

90. • The centrifuge
– Is used to fractionate cells into their component
parts

91. Cell fractionation is used to isolate
(fractionate) cell components, based on size and density.
First, cells are homogenized in a blender to
break them up. The resulting mixture (cell homogenate) is then
centrifuged at various speeds and durations to fractionate the cell
components, forming a series of pellets.
• The process of cell fractionation
APPLICATION
TECHNIQUE
Figure 6.5

92. Tissue
cells
Homogenization
Homogenate1000 g
(1000 times the
force of gravity)
10 min Differential centrifugation
Supernatant poured
into next tube
20,000 g
20 min
Pellet rich in
nuclei and
cellular debris
Pellet rich in
mitochondria
(and chloro-
plasts if cells
are from a
plant) Pellet rich in
“microsomes”
(pieces of
plasma mem-
branes and
cells’ internal
membranes)
Pellet rich in
ribosomes
150,000 g
3 hr
80,000 g
60 min
Figure 6.5

94. In the original experiments, the researchers
used microscopy to identify the organelles in each pellet,
establishing a baseline for further experiments. In the next series of
experiments, researchers used biochemical methods to determine
the metabolic functions associated with each type of organelle.
Researchers currently use cell fractionation to isolate particular
organelles in order to study further details of their function.
RESULTS
Figure 6.5

97. DNA to mRNA to Ribosome
to make Proteins

98. Transcription

99. Translation

101. Replication
of DNA

103. Mitosis and Meiosis

104. Aging and Cells
Geriatrics
Telomeres
Free radicals

105. Cancer Terms
• Neoplasia
• Benign
• Malignant
• Metastases
• Carcinoma
• Sarcoma
• Angiogenesis
• Mutation

106. Terms to Know
• Anaplasia
• Atrophy
• Dysplasia
• Hyperplasia
• Hypertrophy
• Progeny
• Progeria

107. THANKS FOR YOUR
ATTENTION