Cell biology studies the structure and function of cells. A cell is the basic unit of life and contains organelles that allow it to carry out essential functions like metabolism, energy production, waste removal, response to stimuli, and reproduction. There are two main types of cells - prokaryotic cells which lack organelles and eukaryotic cells which contain organelles within membranes. Organisms are classified into five kingdoms - Monera, Protista, Fungi, Plantae, and Animalia - based on characteristics like cell structure, nutrition, and complexity. The cytosol is the gel-like fluid found inside cells that allows for transport and chemical reactions and contains dissolved molecules, ions, and enzymes.

1. Cell Biology
Dr.Harinath Reddy
Christ University
Bangalore

2.  Cell biology or cytology is a branch of biology that studies the
different structures and functions of the cell .
 Cell biology explains the structure and functions of the organelles,
metabolic processes, signalling pathways, life cycle, and
interactions with their environment.
 Research in cell biology is closely related to genetics,
biochemistry, molecular biology, immunology, and developmental
biology.

3.  The cell was discovered by Robert Hooke in 1665 and named the
biological units.
 Cell theory, first developed (Proposed) in 1839 by Matthias Jakob
Schleiden and Theodor Schwann.
1. A/c to cell theory that all organisms are composed of one or more
cells, that cells are the fundamental unit of structure and
function in all living organisms.
2. All cells come from pre-existing cells, and that all cells contain
the hereditary information necessary for regulating cell functions
and for transmitting information to the next generation of cells.

4.  BASIC PROPERTIES OF CELLS
 The cell is the basic structural, functional, and biological unit of all
known living organisms.
 A cell is the smallest unit of life that can replicate independently,
and cells are often called the "building blocks of life".

5. Cells Are Highly Complex and Organized.
 The more complex with variety of organelles and with the
greater the number of parts.
 The cells are less tolerance of errors in the nature.
 For example DNA duplication occurs with an error rate of
less than one mistake every ten million nucleotides
incorporated.

6. Cells Possess a Genetic Program:
 Organisms are built according to information present in the DNA.
 Discovering of genetic information has been one of the greatest
achievements of science in recent decades.
 The changes in genetic information (mutations) that lead to
variation among individuals, which forms the basis of biological
evolution.

7. Cells Are Capable of Producing :
 Cells reproduce by division, a process in which the contents
of a “mother” cell are distributed into two “daughter” cells.
 Prior to division, the genetic material is faithfully duplicated,
and each daughter cell receives a complete genetic information,
cytoplasm and organelles.
 In most cases, the two daughter cells have approximately equal
volume.

8. Cells Acquire and Utilize Energy:
 Light energy is converted by photosynthesis into chemical energy
that is stored in energy-rich carbohydrates, such as sucrose or
starch.
 For most animal cells obtained energy in the form of the glucose.
 In animals, glucose is released into the blood where it circulates
through the body delivering chemical energy to all the cells.
 Once in a cell, the glucose undergoes oxidation and release energy in
the form of ATPs.

9. Cells Carry Out a Variety of Chemical Reactions:
 All chemical changes that take place in cells require enzymes
and ATP molecules.
 The chemical reactions in a cell represents that cell’s
metabolism.
 Even the simplest bacterial cell is capable of hundreds of
different chemical reactions.

10. Cells Are Able to Respond to Stimuli:
 Cells possess receptors to hormones, growth factors, and
extracellular materials.
 A cell’s receptors provide pathways through which specific
responses are triggered in target cells.
 Cells may respond to specific stimuli by altering their metabolic
activities, moving from one place to another, or even committing
suicide.

11.  Two basic classes of cells—prokaryotic and eukaryotic—
distinguished by their size and the types of internal structures, or
organelles, they contain.
 The structurally simpler, prokaryotic cells include bacteria.
 Whereas the structurally more complex eukaryotic cells include
protista, fungi, plants, and animals.

12. Classification of organisms:
Currently there are five kingdoms.
Classification of organisms is done based on the following criteria.
 Type of cell structure- prokaryotic or eukaryotic,
 Complexity of organism’s body- unicellular or multicellular,
 Mode of nutrition- autotrophs or heterotrophs,
 Major ecological role- Producer, consumer or decomposer ,
 Phylogenetic relationship- evolutionary relationship or Genetic
relationship.

13.  R.H. Whittaker (1969) proposed a Five Kingdom system of
classification where the organisms are classified into Five
Kingdoms namely:
 Monera, Protista, Fungi, Plantae and Animalia.

14.  They have a prokaryotic cell structure. Their mode of nutrition is
autotrophic and heterotrophic.
 They include various types of bacteria and blue-green algae.
Major group Examples
Archaebacteria Methanogens(Methenobacterium)
Halophiles (Halobacterium)
Thermoacidophiles (Thermoplasma)
Eubacteria Bacteria- (Vibrio, Mycobacterium
tuberculosis, Staphylococcus, E.coli)
Cyanobacteria (Blue
green algae)
Nostoc, Anabaena
KINGDOM MONERA

15.  All organisms of the kingdom are prokaryotes.
 They are unicellular organisms.
 Some organisms can survive in harsh and extreme climatic
conditions like in hot springs, acidic soils etc.
 Membrane bound nucleus is absent.
 DNA is in double stranded form, suspended in the cytoplasm
referred as nucleoid.
 Membrane bound cellular organelles like mitochondria are absent.

16.  Movement - is with the help of flagella.
 Reproduction: Asexual reproduction is by binary fission.
 Sexual reproduction is by conjugation, transformation and
transduction.

17. KINGDOM PROTISTA:
 These are unicellular eukaryotes.
 Some possess cilia or flagella.
 They reproduce asexually and sexually.
 They have mitochondria for cellular respiration and some have
chloroplasts for photosynthesis (Example: Euglena).
 Nutrition - they can be both autotrophic and hetreotrophic.
 Membrane bound organelles and nucleus is present.
Euglena

18.  Organisms feed by the process of endocytosis (formation of
food vacuole by engulfing a bacteria and extending their cell
membrane).
 Reproduction - some species have complex life cycle involving
multiple stages.
 Example: Plasmodium.
Example: Protozoans

19. KINGDOM Fungi:
 Fungi are eukaryotic organisms.
 Depending on the species and conditions both sexual and
asexual spores may be produced.
 They are typically non-motile.
 The vegetative body of the fungi may be unicellular or
muticellular composed of microscopic threads called hyphae.
 The fungi cell wall are composed of chitin.

20.  Fungi are heterotrophic organisms.
 Nutrition in fungi - they are saprophytes, or parasites or symbionts.
 They fungi digest the food by exoenzymes and inject the food by the
process of endocytosis.
 Fungi store their food as starch.
 The nuclei of the fungi is very small.
 During mitosis the nuclear envelope is not dissolved.

21. KINGDOM Plantae:
 Most of the plants are eukaryotic and chlorophyll containing
organisms, Multicellular and autotrophic.
 Cell walls of plant cells are comprised of cellulose.
 They have an ability to grow by cell division.
 Plants have both organs and organ systems.
 Typically, plants are green due to chlorophyll, or green pigment that
helps the plant get energy from the sun.

22.  They obtain their energy from sun through photosynthesis.
 Plants reproduce both by sexual and asexual.
 Plants develop a self defense mechanism to protect them from fungi,
viruses and bacteria.


23. Kingdoms Animalia:
 Animals are eukaryotic, multicellular and heterotrophic organisms.
 They have multiple cells with mitochondria and they depend on
other organisms for food.
 Cell structure - The animal cell contains organelles like the nucleus,
mitochondria, Golgi complex, ribosomes, endoplasmic reticulum,
lysosomes, centrioles, cytoskeleton.

24.  Animals are made up of many organ systems, that aids in
performing specific functions that are necessary for the survival of
the organism.
 Organ systems are skeletal system, muscular system, digestive
system, respiratory system, circulatory system, excretory system,
reproductive system, immune system and the endocrine system.

25. Viruses:
 Viruses did not find a place in classification since they do not have a cell
structure and are not true living beings.
 Viruses are non cellular, obligate, intracellular parasites.
 They have a genetic material
 They can multiply (inside host cells)
 They exhibit heredity and the genetic material can undergo mutation.
 The viruses contain DNA or RNA as a genetic material.
 Viruses contain protein coat called capsid which is made of subunits
called capsomeres.

26. Cytosol:

27. Cytosol:
 The cytosol or cytoplasmic matrix is the liquid found inside cells.
It constitutes most of the intracellular fluid (ICF).
 Cytosol is in fact just a part of the cytoplasm.
 The cytosol is a liquid matrix around the organelles.
 In eukaryotes and prokaryotes many metabolic pathways occur in
the cytosol, others are contained within organelles.

29. Cytoplasm Cytosol
 The cytoplasm is the material
within a living cell, excluding
the cell nucleus.
 It comprises cytosol and the
organelles
 Cytosol is in fact just a part
of the cytoplasm. The gel-
like translucent fluid.
 Structurally, the cytosol
consists mostly of water.

30. Cytoplasm Cytosol
 The organelles that are held
within the cytoplasm include
the mitochondria, the golgi
apparatus, the endoplasmic
reticulum, and other organelles.
 Cell consisting of 75%
cytosol in total volume.
 Many of the cell's chemical
reactions,
 Transportation of
metabolites and cell
communication functions
that occur within the
cytosol.

31. Cytoplasm Cytosol
 The cytoplasm contains
materials that are known as
cytoplasmic inclusions.
 These inclusions are typically
starch granules, mineral crystals,
or lipid droplets that are floating
around within the cytoplasm.
 The cytosol is composed of,
protein complexes,
enzymes, water, salts,
organic compounds, and
dissolved ions.

32. Properties and composition:
 The cytosol consists mostly of water, dissolved ions, enzymes and
proteins.
 The majority protein molecules have a molecular mass of less than
30 kDa.
 The pH of the cytosol is 7.0 to 7.4.

33. Ions:
 The concentrations of the other ions in cytosol are quite different
from those in extracellular fluid.
 Cytosol has a high concentration of potassium ions (K+) and a
low concentration of sodium (Na+), calcium ions (Ca+).

34. Macromolecules:
 In prokaryotes the cytosol contains the cell's genome, within a
structure known as a nucleoid. This is an irregular mass of DNA.
 In eukaryotes the genome (DNA) is held within the cell nucleus,
which is separated from the cytosol by nuclear membrane.

35. Macromolecules:
 Protein molecules that do not bind to cell membranes or the
cytoskeleton are dissolved in the cytosol.
 Enzymes which are involved in a wide variety of metabolic
pathways that are tightly bound to each other in the cytosol.

36. Functions of cytosol:
 The cytosol is the site of multiple cell processes.
 Cytosol involved in the signal transduction from the cell
membrane to cell nucleus or organelles.
 Another major function of cytosol is to transport metabolites from
their site of production to where they are used.

37.  The water-soluble molecules, such as Glucose and amino acids,
which can diffuse rapidly through the cytosol.
 The majority of both metabolic processes and metabolites occur
in the cytosol.
 Major metabolic pathways like protein biosynthesis, the pentose
phosphate pathway, glycolysis and gluconeogenesis.