This document summarizes the organelles found in eukaryotic cells and their functions. It describes the nucleus, which controls the cell and stores DNA; the cytoplasm, where most chemical reactions occur; the cell membrane, which regulates what enters and exits the cell; and other organelles like the endoplasmic reticulum, Golgi apparatus, mitochondria, ribosomes, lysosomes, centrioles, cytoskeleton, cilia, and flagella. Each organelle has a specific structure and role in the cell.

1. Biochemistry
Organelles of the cell and their functions

2. Group member
1. Mumtas Abdirahman
2. Nimco Abdirashid
3. Sumia Mohamed Abdirahman

3. Nucleus
• Nucleus is a double-membrane bounded organelle found in eukaryotic cells.
• In eukaryotic cells, most of the genetic material (DNA – deoxyribonucleic acid) is
housed within the nucleus.
Functions of the Nucleus
v control center of the cell.
v It stores the genetic material. (it carries the hereditary information).
v It controls cell reproduction (regulates cell division).
v It regulates the information needed to synthesize proteins.

4. Structure of the Nucleus
• The nucleus is surrounded by a double membrane called nuclear membrane (nuclear
envelope), which separates the nucleus from the cytoplasm.
• The nucleus contains a semi-fluid called nucleoplasm in which both genetic material and
nucleolus are suspended in it.
• The nucleus consists of four main structures, which are:
• (1) Nuclear membrane (nuclear envelope)
• (2) Nuclear pores
• (3) Nucleolus
• (4) Chromatin

5. Cytoplasm
• Cytoplasm is a semi-fluid (jelly-like substance) in the cell, between the cell
membrane and nucleus.
• The cytoplasm is composed of 70% to 90% of water, and also contains
enzymes, salts, organelles and different organic molecules.
• The liquid part of the cytoplasm is called cytosol.
• The living substance of the cell is called protoplasm.

6. Con…
Functions of the Cytoplasm
vSite of most chemical reactions in the cell. (Site of cellular reactions)
v Gives support and maintains the shape of the cell.
vHolds the organelles of the cell.

7. Cell Membrane
• Cell membrane (plasma membrane) is the outer layer of animal cells.
• The cell membrane is a double layer of phospholipids (lipid bilayer) with
proteins and carbohydrates.
• The plasma membrane (cell membrane) acts as a selective barrier between
the cell and its surrounding.
• The plasma membrane is called selectively permeable membrane
(semipermeable membrane) because it allows the passage of some
substances and stops others.

8. Con…
Functions of the Plasma Membrane
vIt regulates movement of substances into and out of the cell. (It regulates
what gets in and out of the cell).
vIt isolates the cytoplasm from the external environment.
vIt gives shape to the animal cells.
vIt allows interaction with other cells.

10. Endoplasmic Reticulum
Endoplasmic reticulum (ER) is a network of parallel and interconnected
membranous tubes in the cytoplasm.
• It is present in eukaryotic cells but absent in prokaryotic cells and RBCs in
mammals.
The two types of endoplasmic reticulum are;
• 1. Rough endoplasmic reticulum (Rough ER)
• 2. Smooth endoplasmic reticulum (Smooth ER)

12. Con…
Functions of the Endoplasmic Reticulum (ER)
vTransports materials in the cell, e.g. proteins.
v Synthesizes lipids.
v Keeps the cell’s shape.
vBreaks down foreign chemical substances.
v Storage of synthesized substances.

13. Golgi Apparatus
• Golgi apparatus is also known as Golgi body or Golgi complex.
• Golgi apparatus is found in the cytoplasm of all eukaryotic cells.
• Golgi apparatus is a specialized flattened membranous sacs derived from the ER.
• Golgi apparatus collects, processes, sort molecules and packages materials into
vesicles (secretary vesicles).
• Secretary vesicles transport substances to other parts of the cell or discharge
(remove) substances to exterior or outside of the cell.

14. Con…
Functions of the Golgi body
v It separates (sorts), modifies and packages substances into vesicles.
v It creates and produces Lysosomes.
v It is the major site of carbohydrate synthesis.
v It produces enzymes.
v It synthesizes cell wall components for plants, e.g. cellulose

15. Mitochondria
Mitochondria (singular = mitochondrion) are rod-shaped and double membrane
bounded organelles found in the cytoplasm of most eukaryotic cells.
• Mitochondrion is surrounded by two membranes (outer and inner membranes).
• The outer membrane of mitochondria is smooth.
• The inner membrane of the mitochondria is folded which forms cristae and filled
with a fluid called matrix.
• Mitochondria contains DNA (deoxyribonucleic acid).
• Mitochondria are the site for aerobic respiration.

16. Con…
• Mitochondria contain enzymes responsible for synthesis of energy for the cell.
• Mitochondria generate most of the energy of the cells and store it in form of
adenosine triphosphate (ATP) which is used as a source of chemical energy.
• ATP (adenosine triphosphate) is a short term energy carrier molecule.
Functions of the Mitochondria
ØSite of energy production (power house of the cell / site of cellular respiration).
ØFormation of ATP molecule.

17. Ribosomes
• Ribosomes are small organelles found in both eukaryotic and prokaryotic
cells.
• Ribosomes are made up of rRNA and proteins.
• Ribosomes are not surrounded by a membrane.
• Ribosomes are rounded organelles found in the cytoplasm which assemble
the amino acids transferred by tRNA to make proteins.

18. Con…
There are two types of ribosomes:
1. Free ribosomes - they are found freely in the cytoplasm
2. Attached or fixed ribosomes – they are attached on the surface of Rough
endoplasmic reticulum.
Function of Ribosomes
v Site for protein synthesis in the cell (make proteins in the cell)

19. Lysosomes
Lysosomes are small spherical bags surrounded by a single membrane and more abundant in animal cells than
in plant cells.
Lysosomes contain digestive enzymes and are known as digestive bags, suicide sacs or cellular keepers.
Functions of the Lysosomes
v They digest proteins, fats and carbohydrates in the cell.
v They digest worn out cells and organelles.
v Lysosomes of white blood cells (phagocytes) digest or break down bacteria.
v They break down unwanted materials in the cell.
v The head of the sperm contains Lysosomes which digest the female egg layers.

20. Centrioles
• Centrioles are pair of small organelles made up of microtubules which lie
close together at right angle to each other.
• Centrioles are only found in animal cells.
• Centrioles are hollow and cylindrical structures made up of nine triplets of
microtubules arranged in a ring.
• Centrioles are found in spherical body called centrosome, found in the
cytoplasm near the nucleus.

21. Con…
Functions of Centrioles
v Centrioles play an important role in cell division.
v Centrioles form spindle fibers which separate chromosomes during cell
division.

22. Cytoskeleton
• Cytoskeleton is an internal framework of the cells, made up of protein filaments and found in
the cytoplasm of most cells.
• There are three kinds of cytoskeleton, microtubules, microfilaments and intermediate filaments.
Functions of Cytoskeleton
• 1) It gives mechanical support to the cell (supports the cell).
• 2) It provides anchorage for organelles inside the cell.
• 3) It provides cell motility (cell movement).
• 4) It plays an important role in cell division.
• 5) It helps muscle cell contraction

24. Cilia and Flagella
• Cilia and flagella are extensions of the plasma membrane.
• The flagella (singular = flagellum) are long, hair-like structures that extend from the plasma
membrane, example, sperm cells and bacteria.
• Cilia (singular = cilium) are short, hair-like structures are present on the entire surface of the
plasma membrane.
Functions of Cilia
vCilia help movement of some single-celled organisms.
v Cilia move mucus or trapped particles out of the respiratory tract.
vCilia lining the fallopian tubes (oviduct) move the fertilized egg toward the uterus (womb).

25. Con…
Functions of Flagella
vFlagella help movement of the unicellular organisms. (Used in motility for
single-celled organisms).
v Sperm cells use flagella to move.

26. Reference
• https://ombiology4u.blogspot.com/