My first lecture about Cell and Cell organelles. Delivered to students of Bannu Medical College on 12-Jan-2018.

1. CELL BIOCHEMISTRY
By:
Dr. Tehmas Ahmad Khan
Demonstrator, Biochemistry Department

2. DEFINITION OF CELL
• A cell is the smallest unit that is capable of performing life
functions.

3. CELL THEORY
• (1839)Theodor Schwann & Matthias Schleiden
All living things are made up of cells.
• Cells are the smallest working units of all living things.
• (1889) Rudolf Virchow
All cells come from preexisting cells through cell division.

4. EXAMPLES OF CELLS
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria

5. CELL SIZE

6. TWO TYPES OF
CELLS
•Prokaryotic
•Eukaryotic

7. PROKARYOTIC
• Do not have structures surrounded
by membranes
• Few internal structures
• One-celled organisms, Bacteria

8. EUKARYOTIC
• Contain organelles surrounded by membranes
• Most living organisms
Plant Animal

9. DIFFERENCE BETWEEN PROKARYOTIC
AND EUKARYOTIC CELL
• Prokaryotic
• Single membrane
• No well defined nucleus
• No membrane bounded
organelles
• Lysosome absent
• RNA and Protein synthesis in
same compartment
• Eukaryotic
• Bilayer membrane
• Nucleus containing
DNA + histones
• Membrane bounded
• Lysosome present
• RNA in nucleous and
proteins in cytosol

10. CELL ORGANELLES

11. NUCLEUS
• Nuclear envelope Double layer membrane
• Nuclear pore complexes
• Chromatin: DNA in the nucleus is coiled into a dense mass called chromatin, stains
darkly with certain dyes.
• Nucleolus: A second dense mass closely associated with the inner nuclear
envelope is called nucleolus.
• Nucleoplasm: Nucleoplasm of nucleus contain various enzymes such as DNA
polymerases, and RNA polymerases, for m-RNA and t-RNA synthesis.

12. FUNCTIONS OF NUCLEUS
• DNA replication and RNA transcription of DNA occur in the nucleus. Transcription
is the first step in the expression of genetic information and is the
major metabolic activity of the nucleus.
• The nucleolus is nonmembranous and contains RNA polymerase, RNAase, ATPase
and other enzymes but no DNA polymerase. Nucleolus is the site of synthesis of
ribosomal RNA (r-RNA).
• Nucleolus is also the major site where ribosome subunits are assembled.

13. MITOCHONDRION
• Mitochondrion is the power house of cell
• Number: The number of mitochondria in a cell varies dramatically. Some algae contain
only one mitochondrion, whereas the protozoan Chaos contain half a million. A
mammalian liver cell contains from 800 to 2500 mitochondria.
• Size: They vary greatly in size. A typical mammalian mitochondrion has a diameter of 0.2
to 0.8 μ and a length of 0.5 to 1.0 μm.
• Shape: The shape of mitochondrion is not static. Mitochondria assume many different
shapes under different metabolic conditions.
• Structure and Functions
The mitochondrion is bounded by two concentric membranes that have markedly different
properties and biological functions.

14. MITOCHONDRION (CONTD)
• Outer mitochondrial membrane:
made up of lipid bilayer and proteins.. (Porins and enzymes)
• Inner mitochondrial membrane:
have cristae and rich in protein then lipids… is almost impermeable…. And cristae
disappears when activated
• Intermembrane space
acts like cytosol and have same composition like cytosol

15. MITOCHONDRION (CONTD.)
• Mitochondrial matrix: The region enclosed by the inner membrane is known as the
mitochondrial matrix.
• matrix also contains circular DNA, ribosomes and enzymes required for the
biosynthesis of the proteins coded in the mitochondrial genome.
Functions of mitochondria:
• Power house of the cell
• Generation of power in cell i.e. ATP from TCA and Oxidative phosphorylation.
• Conversation of NADH and FAD to ATP to release them for contribution in
reactions again.

16. ENDOPLASMIC RETICULUM
• membrane complexes that are interconnected by separate organelles
• Varying in shape, size and amount, the endoplasmic reticulum (ER) extends from
the cell membrane, coats the nucleus, surrounds the mitochondria and appears to
connect directly to the Golgi apparatus.
• These membranes and the aqueous channels they enclose are called
cisternae.
• Two types
• Rough surfaced ER: Near nucleus, contains ribosomes.
• Smooth surfaced ER: have no ribosomes

19. FUNCTIONS OF ER
• Function of rough ER: Rough ER synthesizes membrane lipids, and secretory
proteins. These proteins are inserted through the ER membrane into the lumen of
the cisternae where they are modified and transported through the cell.
• Function of smooth ER:
(i) lipid synthesis and
(ii) Modification and transport of proteins synthesized in the rough ER
• Note: Cytochrome P450 is present in ER in Liver.

20. GOLGI COMPLEXES
• Also called dictyosomes.
• unique stack of smooth surfaced compartments or
cisternae that make up the Golgi complex. The ER is
usually closely associated with the Golgi complexes,
which contain flattened, fluid filled golgi sacs.
• The Golgi complex has a Proximal or Cis compartment,
a medial compartment and a distal or trans
compartment.
• It is interesting to note that those proteins with no signal
or transit peptides regions are rejected by golgi
complexes.

21. FUNCTION OF GOLGI COMPLEXES
• On the proximal or cis side, the Golgi complexes receive the newly synthesized
proteins by ER via transfer vesicles.
• The post-translational modifications take place in the golgi lumen where
precursors are added.
• On the distal or trans side they release proteins via modified membranes called
secretory vesicles. That are excreted by exocytosis.

22. LYSOSOMES
• Small organelles, surrounded by lipoprotein membrane.
• Contains Proteolytic enzymes
• Enzymes acts locally but when the lysosomal membrane ruptures then autolysis
occurs and cell death is imminent.
Enzymes present in Lysosomes
1. Proteolytic enzymes: collagenase, elastase.
2. Nucleic acid hydrolysing enzymes: ribonucleases
3. Lipid hydrolysing enzymes: fatty acyle esterase
4. Carbohydrate splitting enzymes: α-glucosidase
5. Other enzymes: acid phosphatase

23. PEROXISOMES
• Peroxisomes are small organelles also called Micro bodies,
• formed by budding from smooth endoplasmic reticulum (ER).
• They carryout oxidation reactions in which toxic hydrogen peroxide (H2O2) is
produced, which is destroyed by the enzyme catalase.
• Recently it has been shown that liver peroxisomes have an unusually active β-
oxidative system capable of oxidizing long chain fatty acids

24. CYTOSKELETON
• For long it was thought that the cytosol is chiefly jelly like substance and supports
cell organelles and nucleus while maintaining cell integrity. But now it has been
found that there are finer compartments that supports cell integrity.
• These structures are
• Micro-tubules: made up of tubulin protein forms spindles during cell division. May
be involved in signal transduction.
• Micro-filamints: produces force inside cell
• Micro-trabaculae: role not clearly understood.

25. CYTOSOL
• Organelle free sap is called as cytosol.
• Many metabolic reactions take place in cytosol where substrates and cofactors
interact with various enzymes.
• There is no specific structure for cytosol.
• It has a high protein contents. The actual physio-chemical state of cytosol is poorly
understood.
• A major role of cytosol is to support synthesis of proteins on the rough
endoplasmic reticulum by supplying cofactors and energy.
• Cytosol also contains free ribosomes often in the polysome form. They contain
many different types of proteins and ribosomal RNA or r-RNA. They exist as 2
subunits and act as the site of protein synthesis.

26. QUESTION # 1
• Which of the following two organelles look most alike structurally?
• A. Nucleus and vesicle
• B. Golgi apparatus and smooth ER
• C. Vacuole and cytoskeleton
• D. Lysosome and chloroplast

27. ANSWER
• Which of the following two organelles look most alike structurally?
• A. Nucleus and vesicle
• B. Golgi apparatus and smooth ER
• C. Vacuole and cytoskeleton
• D. Lysosome and chloroplast

28. QUESTION # 2
• Where in a eukaryotic cell, DNA can be found?
• A. Nucleus
• B. Mitochondrion
• C. Vacuole
• D. Both (a) and (b)

29. ANSWER
• Where in a eukaryotic cell, DNA can be found?
• A. Nucleus
• B. Mitochondrion
• C. Vacuole
• D. Both (a) and (b)

30. QUESTION # 3
• Which of the following organelles is directly connected to the outer membrane of
the nucleus in a eukaryotic cell?
• A. Mitochondrion
• B. Lysosome
• C. Golgi apparatus
• D. Endoplasmic reticulum

31. ANSWER
• Which of the following organelles is directly connected to the outer membrane of
the nucleus in a eukaryotic cell?
• A. Mitochondrion
• B. Lysosome
• C. Golgi apparatus
• D. Endoplasmic reticulum

32. QUESTION # 4
• Microtubules, motor proteins, and actin filaments are all part of
• A. the mechanism of Glycolysis that occurs in cytosol
• B. the rough ER (endoplasmic reticulum)
• C. the cytoskeleton of eukaryotic cells
• D. the process that moves small molecules across cell membranes

33. QUESTION # 4
• Microtubules, motor proteins, and actin filaments are all part of
• A. the mechanism of Glycolysis that occurs in cytosol
• B. the rough ER (endoplasmic reticulum)
• C. the cytoskeleton of eukaryotic cells
• D. the process that moves small molecules across cell membranes

34. CAN ORGANELLES GET SICK?
• Assignment:
• Find out some information about the young boy whose story is told in the movie
“Lorenzo’s Oil”. Then answer the above question with the information you found