Introduction Structure of Plasma Membranes Functions of Plasma Membranes Cytoplasm: Cytosol, Organelles Functions of Cytoplasm Ribosome, Functions of Ribosomes 2. Endoplasmic reticulum (ER) a. Rough Endoplasmic Reticulum and its Functions b. Smooth ER  and its Functions 3. Golgi complex and its Functions 4.Lysosomes and its Functions 5. Peroxisomes and its Functions 6. Proteasomes and its Functions 7.Mitochondria and its Functions 8. Cytoskeletal a. Microfilaments and its Functions b. Intermediate filaments and its Functions c. Microtubules and its Functions 9. Centrosome and its Functions 10. Cilia and Flagella and its Functions 11. Nucleus and its Functions a. Nuclear Membrane and its Functions b. Nucleoplasm and its Functions c. Chromosomes and its Functions d. Nucleolus and its Functions

1. Miss. Sheetal Patil M. Pharm
Rani Chennamma College Of Pharmacy,
Belagavi

2. Index
Cell Introduction
I. Cell Membrane
II. Cytoplasm
a. Cytosol
b. Organelles
Ribosomes, endoplasmic reticulum, Golgi complex, Lysosome, Peroxisomes,
Proteasomes, Mitochondria, Cytoskeleton,, Centrosome, Cilia and Flagella.
III. Nucleus

3. Introduction
Cells are the structural, functional, and biological units of all living beings.
The study of cells from its basic structure to the functions of every cell
organelle is called Cell Biology.
Robert Hooke was the first Biologist who discovered cells.

4.  A cell consists of three parts: the cell membrane, the nucleus, and between
the two, the cytoplasm.
I. Cell membrane : It forms outer flexible surface of the cell that separates its
internal environment from the external environment.
II. Cytoplasm : The cytoplasm is a fluid matrix that usually surrounds the
nucleus and is bound by the outer membrane of the cell.
III. Nucleus : The nucleus is surrounded by a nuclear envelope and contains
DNA in the form of chromosomes.

6. I. Structure of Plasma Membranes
 The plasma membrane (also known as the cell membrane or cytoplasmic
membrane) is a biological membrane that separates the interior of a cell from
its outside environment.
 The fluid mosaic model describes the structure of the plasma membrane as a
mosaic of components —including phospholipids, cholesterol, proteins, and
carbohydrates—that gives the membrane a fluid character.
 According to this biological model, there is a lipid bilayer (two molecules
thick layer consisting primarily of phospholipids) in
which protein molecules are embedded.

7.  Membrane lipids are strongly amphipathic molecules with a polar
hydrophilic “head group” and a polar hydrophobic “tail.”
 The polar head group attached to two hydrophobic fatty acid tails; the head
group faces the aqueous environment, the fatty acid tails the interior of the
bilayer.
 The lipid bilayer gives fluidity and elasticity to the membrane. Small
amounts of carbohydrates are also found in the cell membrane.

9.  Functions of Plasma Membranes
 Plasma membrane separates the interior of a cell from its outside
environment.
 The primary function of the plasma membrane is to protect the cell from its
surroundings.
 The plasma membrane also plays a role in anchoring the cytoskeleton to
provide shape to the cell, and in attaching to the extracellular matrix and
other cells to help group cells together to form tissues.
 The plasma membrane is selectively permeable to ions and organic
molecules and regulates the movement of substances in and out of cells.
 Contains cell surface receptors (e.g., glycoprotein receptors).
 Plasma membrane also keep toxic substances out of the cell

10. II. Cytoplasm
 The main components of the cytoplasm are:
1. Cytosol– a gel-like substance
2. Organelles – the cell’s internal sub-structures
 Cytosol : It is the fluid portion of cytoplasm that contains water, ions, glucose,
amino acids, proteins, lipids, ATP and waste products.
 Organelles : Cytoplasm contains all of the organelles. Among such organelles
are the mitochondria, endoplasmic reticulum, golgi apparatus, peroxisomes, sacs
of digestive enzymes and lysosomes.
 The cytoplasm is made of 70% – 80% water and is usually colourless.
 The cytoplasm constitutes of dissolved nutrients and also dissolved waste
products.

11. Cytosol

12. Functions of Cytoplasm
1. The cytoplasm is the site for most of the enzymatic reactions and metabolic
activity of the cell.
2. The cytoplasm is the place where the cell expands and the growth of the
cell takes place.
3. The cytoplasm provides a medium for the organelles to remain suspended.
4. The cytoplasm acts as a buffer and protects the genetic material of the cell
and also the cellular organelles from damage caused due to movement and
collision with other cells.
5. Cytoplasm helps the movement of the cellular materials around the cell.

13. 1. Ribosome
 Ribosomes are tiny spheroidal dense particles that are primarily found in
most prokaryotic and eukaryotic.
 A ribosome is made from complexes of RNAs and proteins and is, therefore,
a ribonucleoprotein.
 Ribosomes are situated in two areas of the cytoplasm.
 They are seen scattered in the cytoplasm and a few are connected to the
endoplasmic reticulum.
 Ribosomes joined to the ER they are called the rough endoplasmic reticulum
(RER).

14.  Ribosomes consist of two major components: Small and large ribosomal
subunits. Each subunit consists of one or more ribosomal RNA molecules
and many ribosomal proteins.
 In eukaryotes, ribosomes are present in mitochondria.
 Eukaryotes have 80S ribosomes located in their cytosol, each consisting of
a small (40S) and large (60S) subunit.
 Every living cell requires ribosomes for the production of proteins.
 The structure of free and bound ribosomes is similar and is associated with
protein synthesis.

16. Ribosome

17. Functions of Ribosomes
1. It assembles amino acid to form proteins that are essential to carry out
cellular functions.
2. The DNA produces mRNA by the process of DNA transcription.
3. The mRNA is synthesized in the nucleus and transported to the cytoplasm
for the process of protein synthesis.
4. The ribosomal subunits in the cytoplasm are bound around mRNA
polymers. The tRNA then synthesizes proteins.
5. The proteins synthesized in the cytoplasm are utilized in the cytoplasm
itself.
6. Proteins made on the RER are used for usage inside the cell or outside the cell.

18. 2. Endoplasmic reticulum (ER)
 Endoplasmic reticulum (ER) is a continuous membrane system that forms a
series of flattened sacs within the cytoplasm of eukaryotic cells.
 All eukaryotic cells contain an endoplasmic reticulum (ER).
 Differences in certain physical and functional characteristics distinguish the
two types of ER, known as rough ER and smooth ER.
 The endoplasmic reticulum membrane system can be morphologically
divided into two structures - cisternae and sheets.

19. a. Rough Endoplasmic Reticulum
 Rough ER is named for its rough appearance, which is due to
the ribosomes attached to its outer surface.
 Rough ER lies immediately adjacent to the cell nucleus, and its membrane is
continuous with the outer membrane of the nuclear envelope.
 Functions of RER
1. Protein synthesis occurs in the rough endoplasmic reticulum.
2. RER plays a central role in synthesis and export of proteins and glycoproteins
in secretory cells. For e.g., liver cells secreting serum proteins (albumin).
3. The RER also makes phospholipids for cellular membranes.

20. b. Smooth ER
 Smooth ER, is not associated with ribosomes, and its functions differ.
 SER contains unique enzymes that make it functonally more diverse than RER.
 Functions of Smooth ER (SER)
1. The SER is involved in the synthesis of lipids, including cholesterol
and phospholipids, which are used in the production of new cellular membrane.
2. In certain cell types, SER plays an important role in the synthesis of steroid
hormones from cholesterol. In cells of the liver, it contributes to the detoxification
of drugs and harmful chemicals.
3. Store and release calcium ion concentration in the cytoplasm of muscle cells.
4. The SER is enriched in enzymes involved in sterol and steroid biosynthetic
pathways and is also necessary for the synthesis of steroid hormones (e.g., estrogen
and testosterone).

22. 3. Golgi complex
 Golgi apparatus, also called Golgi complex or Golgi body, is a membrane-
bound organelle of eukaryotic cells that is made up of a series of flattened,
stacked pouches called cisternae.
 It is located in the cytoplasm next to the endoplasmic reticulum and near the cell
nucleus.
 the Golgi apparatus is made up of approximately four to eight cisternae.
 The cisternae are held together by matrix proteins, and the whole of the Golgi
apparatus is supported by cytoplasmic microtubules.
 The apparatus has three primary compartments, known generally as “cis”
(cisternae nearest the endoplasmic reticulum), “medial” (central layers of
cisternae) and “trans” (cisternae farthest from the endoplasmic reticulum).

23.  Functions Of Golgi Complex
• Golgi complex functions as a factory in which proteins received from the ER are
further processed and sorted for transport to their destination : lysosome, plasma
membrane or secretion.
• The processing of proteins i. e. glycosylation, phosphorylation , sulphation takes
place in golgi cmplex.
• Golgi complex is site for synthesis and processing of polyscaccharides,
glycolipids.
• Delivers synthesized materials to various targets inside the cell and
outside the cell.
• Produces vacuoles and secretory vesicles.
• Forms plasma membrane and lysosomes.

24. Golgi Complex

25. 4. Lysosomes
 Lysosomes are specialized vesicles within cells that digest large molecules
through the use of hydrolytic enzymes.
 Vesicles are small spheres of fluid surrounded by a lipid bilayer membrane, and
they have roles in transporting molecules within the cell.
 The word “lysosome” is made up of two words “lysis” meaning breakdown and
“soma” meaning body.
 Lysosomes are only found in animal cells.
 They are formed from golgi complex and contain 60 different kinds of powerful
digestive and hydrolytic enzymes.
 The pH of lysosomes is acidic (around pH 5) because their hydrolytic enzymes
function best at this pH instead of at the neutral pH of the rest of the cell.
 Hydrolytic enzymes specifically break down large molecules through
hydrolysis.

27.  Functions of Lysosomes
 They digest substances that enter a cell via endocytosis and transport final
products of digestion into cytosol.
 They carry out autophagy, the digestion of worn-out organelles.
 They can carry out autolysis, the digestion of entire cells. Therefore they are
called “suicidal bags”.
 They also carry out extracellular digestion, e.g., sperm head releases lysosomal
enzymes that help its penetration into the oocyte.
 Lysosomes digest many complex molecules such as carbohydrates, lipids,
proteins, and nucleic acids, which the cell then recycles for other uses.
 One other function of the lysosome is to ingest bacteria so that the bacteria can
be destroyed. So the lysosomes also provide a function against infection.

28. 5. Peroxisomes
 Peroxisomes are membrane-bound organelles in most eukaryotic cells.
 They are similar in structure to lysosomes but are smaller and contain several
oxidase, enzymes that can oxidize (remove hydrogen atoms from) various organic
substances, eg., amino acids and fatty acids.
 They are considered as an important type of microbody found in both plants and
animal cells.
 Approximately 60 known enzymes are present in the matrix of peroxisomes.
 They involved in a variety of metabolic reactions, including several aspects of energy
metabolism.
 It consists of a single limiting membrane of lipid and protein molecules enclosing the
granular matrix.
 They are found floating freely in the cytoplasm in close association of ER,
mitochondria within the cell.

29. Peroxisomes

30.  Functions Of Peroxisomes
1. As part of normal metabolism, they oxidize amino acids and fatty acids.
2. They oxidize toxic substances such as alcohol in liver cells.
3. They are primarily involved in lipid metabolism and the conversion of reactive
oxygen species such as hydrogen peroxide into safer molecules like water and
oxygen.
4. Lipid biosynthesis : Synthesis of cholesterol occurs in both ER and
peroxisomes.

31. 6. Proteasomes
 Proteasomes are tinny barrel sshaped structure, many thousands in numbers, in
both the cytosol and the nucleus of a typical body cell.
 They are recently discovered organellel contain protease an enzymes that break
down protein into amino acids.
 Function of Proteasomes
1. They degrade unneeded, damaged or faulty proteins into small peptides, which
are then broken down into amino acids by other enzymes.
2. Abnormal functioning of proteasomes may result into accumulation of
defective proteins.

32. Proteasomes

33. 7. Mitochondria
 Mitochondria are double membrane-bound cell organelles referred to as the
‘powerhouse of the cell’, they are the site of the majority of ATP synthesis.
 Mitochondria have an inner and outer membrane, with an intermembrane
space between them.
 The outer membrane contains proteins known as porins, which allow movement
of ions into and out of the mitochondrion.
 The space within the inner membrane of the mitochondrion is known as
the matrix, which contains the enzymes of the Krebs and fatty acid cycles.
 The inner membrane contains a variety of enzymes. It contains ATP
synthase which generates ATP in the matrix.

34.  The inner membrane is arranged into cristae in order to increase the surface area
available for energy production via oxidative phosphorylation.
 The amount of mitochondria in a cell depends on how much energy that cell
needs to produce.
 For example Muscle cells, have many mitochondria because they need to
produce energy to move the body.

35. Mitochondria

36.  Function Of Mitochondria
1. Mitochondria produce ATP through process of cellular respiration
specifically, aerobic respiration, which requires oxygen.
2. They can store calcium, which maintains homeostasis of calcium levels in the
cell.
3. They also regulate the cell’s metabolism and take part in fat metabolism.
4. They have roles in apoptosis (controlled cell death), cell signaling, and
thermogenesis (heat production).
5. The mitochondria also help in building certain parts of blood and hormones
like testosterone and estrogen.
6. The liver cell’s mitochondria have enzymes that detoxify ammonia.
7. They can synthesize some of their proteins and can self replicate before cell
division.

37. 8. Cytoskeletal
 The cytoskeleton is a network of filaments and tubules that extends
throughout a cell.
 The eukaryotic cytoskeleton consists of three types of filaments, which are
elongated chains of proteins: microfilaments, intermediate filaments, and
microtubules.

38. a. Microfilaments
 Microfilaments are also called actin filaments because they are mostly composed
of the protein actin and are prevalent at the periphery of the cell.
 Functions of Microfilaments
1. They help to generate movement and provide mechanical support.
2. They are involved in muscle contraction, cell division and cell locomotion.
3. They anchor the cytoskeleton to integral proteins in the plasma membrane.
4. They provide mechanical support to microvilli (nonnmotile microscopic finger
like projection of the plasma membrane).

39. Cytoskeletal

40. b. Intermediate filaments
 Intermediate filaments are thicker they are called intermediate because they are
in-between the size of microfilaments and microtubules.
 Intermediate filaments are made of different proteins such as keratin.
 Functions of Intermediate filaments
1. They help to stabilize the position of organelles such as nucleus and help to
attach cells to one another.
2. Provide structural support to the cell.

41. c. Microtubules
 Microtubules are the largest of the cytoskeleton’s fibers. They are hollow tubes
made of alpha and beta tubulin.
 Microtubules form structures like flagella, which are “tails” that propel a cell
forward. They are also found in structures like cilia, which are appendages that
increase a cell’s surface area and in some cases allow the cell to move.
 Most of the microtubules in an animal cell come from a cell organelle called
the centrosome, which is a microtubule organizing center (MTOC).
 Functions of Microtubules
 They help to determine the cell shape.
 They help in the movement of secretory vesicles, of chromosomes during cell
division and of specialized cell projections such as cilia and flagella.

42. 9. Centrosome
 Eukaryotic cells contain two cylindrical, rod-shaped, microtubular structures,
called centrioles, near the nucleus.
 the centrosome is an organelle that serves as the main microtubule organizing
center (MTOC) of the animal cell.
 Centrosomes are composed of two centrioles arranged at right angles to each
other.

43. Functions of Centrosome
1. They are responsible for cell division, cytokinesis, formation of cytoskeleton
and cell signalling pathway.
2. Centrioles are involved in the formation of the spindle apparatus, which
functions during cell division.
3. Centrioles are very important part of centrosome which are involved in
organizing microtubule in the cytoplasm .
4. The position of centrioles determines the position of the nucleus and plays
crucial role in spacial arrangement of cell organelles.

44. Centrosome

45. 10. Cilia and Flagella
 Cilia and Flagella are complex filamentous cytoplasmic structures protruding
through a cell wall.
 They are minute, especially differentiated appendices of the cell.
 Flagella (singular = flagellum) are long, hair-like structures that extend from the
plasma membrane and are used to move an entire cell.
 Cilia (singular = cilium) are short, hair-like structures that are used to move
entire cells or substances along the outer surface of the cell, e.g., cilia lining the
cells of the respiratory tract that trap particulate matter and move it toward the
nostrils.
 Generally, cilia are shorter than flagella.

46. Flagella

47. Cilia

49. Functions of Flagella
 Flagellum moves the whole cell.
 It propels the sperm towords the oocyte for fertilization.
 Functions of Cilia
 The coordinated movement of many cilia on the surface of cell causes the
steady movement of fluid along the cell surface. They help to sweep foreign
particles trapped in mucus away from the lungs.
 They help to sweep oocytes toword the uterus .

50. III. Nucleus
 The structure of a nucleus contains the nuclear membrane, nucleoplasm,
chromosomes and nucleolus.
 It is the largest organelle of the eukaryotic cell, accounting for around 10% of
its volume.
 Eukaryotic cell has only one nucleus. However, some eukaryotic cells are
enucleated cells (without a nucleus) for example, red blood cells (RBC).
 The nucleus is separated from the rest of the cell or the cytoplasm by a
nuclear membrane.
 As the nucleus regulates the integrity of genes and gene expression, it is also
referred to as the control center of a cell.

51. Nucleus

52. Nucleus

53. i. Nuclear Membrane
• Nuclear membrane is a double-layered structure that encloses contents of the
nucleus. Outer layer of the membrane is connected to the endoplasmic reticulum.
• Like the cell membrane, the nuclear envelope consists of phospholipids that
form a lipid bilayer.
• The envelope helps to maintain the shape of the nucleus and assists in regulating
the flow of molecules into and out of the nucleus through nuclear pores. The
nucleus communicates with the remaining of the cell or the cytoplasm through
several openings called nuclear pores.
• Such nuclear pores are the sites for the exchange of large molecules (proteins
and RNA) between the nucleus and cytoplasm.
• A fluid-filled space is present between the two layers of a nuclear membrane.

54. ii. Nucleoplasm
• Nucleoplasm is the gelatinous substance within the nuclear envelope.
• This semi-aqueous material is similar to the cytoplasm and is composed
mainly of water with dissolved salts, enzymes, and organic molecules
suspended within.
• The nucleolus and chromosomes are surrounded by nucleoplasm, which
functions to protect the contents of the nucleus.
• Nucleoplasm also supports the nucleus by helping to maintain its shape.
• Nucleoplasm provides a medium by which materials, such as enzymes
and nucleotides (DNA and RNA), can be transported throughout the nucleus.
Substances are exchanged between the cytoplasm and nucleoplasm through
nuclear pores.

55. iii. Nucleolus
 Nucleolus present within the nucleus is a dense, membrane-less structure
composed of RNA and proteins called the nucleolus.
 The nucleolus contains nucleolar organizers, which are parts of chromosomes
with the genes for ribosome synthesis on them. The nucleolus helps to
synthesize ribosomes by transcribing and assembling ribosomal
RNA subunits. These subunits join together to form a ribosome during
protein synthesis.
 The nucleolus disappears when a cell undergoes division and is reformed
after the completion of cell division.

56. iv. Chromosomes
 The nucleus is the organelle that houses chromosomes.
 Chromosomes consist of DNA, which contains heredity information and
instructions for cell growth, development and reproduction.
 Chromosomes are present in the form of strings of DNA and histones
(protein molecules) called chromatin.
 The chromatin is further classified into heterochromatin and euchromatin
based on the functions. The former type is a highly condensed,
transcriptionally inactive form, mostly present adjacent to the nuclear
membrane. On the other hand, euchromatin is a delicate, less condensed
organization of chromatin, which is found abundantly in a transcribing cell.

57.  Functions of Nucleus
1. It controls the hereditary characteristics of an organism.
2. The organelle is also responsible for protein synthesis, cell division, growth,
and differentiation.
3. Storage of hereditary material, the genes in the form of long and thin DNA
(deoxyribonucleic acid) strands, referred to as chromatin.
4. Storage of proteins and RNA (ribonucleic acid) in the nucleolus.
5. Nucleus is a site for transcription in which messenger RNA (mRNA) are
produced for protein synthesis.
6. During cell division, chromatins are arranged into chromosomes in the nucleus.
7. Production of ribosomes (protein factories) takes place in the nucleolus.
8. Nuclear pores control he movement of substances between the nucleus and
cytoplasm.

58. Thank you