The nucleus contains chromatin made of DNA and histones that functions in DNA replication and transcription. The rough endoplasmic reticulum contains ribosomes and functions as the site of protein synthesis and folding. Lysosomes contain hydrolytic enzymes that break down macromolecules through autophagy and autolysis. Mitochondria have inner and outer membranes and generate ATP through oxidative phosphorylation.

1. CYTOLOGY
By Nate Rono

3. NUCLEUS
Has the nuclear envelope made up of
• Outer layer - has ribosomes on it’s surface.
• Inner surface - has lamins which perform
chromatin organization, DNA replication, RNA
processing, apoptosis, mitosis and meiosis.
Mutation of Lamin A causes progeria[rapid
premature aging]
Nuclear pore- transport of materials btwn
nucleus and cytoplasm
Nucleolus- rRNA synthesis
rRNA + certain small proteins= Ribosomes

5. NUCLEUS

6. Chromatin made up of DNA and Histones
Types
• Euchromatin[loose] found in centre of nucleus
• Heterochromatin Found in inner membrane of
nucleus
Functions
DNA replication
Transcription DNA> RNA> mRNA, tRNA, rRNA.

7. ROUGH ENDOPLASMIC RETICULUM
Contains ribosomes on it’s outer membrane
Ribosomes- site of protein synthesis e.g proteins in
lysosomes, membranes, excreted proteins.
mRNA to proteins = translation
Functions
• Site of protein folding
• Transport of synthesized proteins

9. RIBOSOMES
Has 2 sub units i.e small and large
There are 2 types
➢Free ribosomes – found in the cytoplasm
➢Membrane bound ribosomes- found on the RER
They make the cytosolic proteins e.g enzymes that do
not leave the cell.
Main function; site of protein synthesis[translation]

11. SMOOTH ENDOPLASMIC
RETICULUM
Lack ribosomes on it’s surface
Functions
• Lipid synthesis e.g fatty acids, phospholipids,
cholestrol
• Site of detoxification e.g drugs alcohol and toxins
• Glucose 6 phosphate metabolism
• Storage of Calcium ions

14. GOLGI APPARATUS
It receives vesicles from RER and SER
Functions
✓Packaging and transportation of substances
e.g glycoproteins
✓Synthesis of lysosomes
✓Formation of vesicles that release special
chemical substances into the cytoplasm

16. CELL MEMBRANE
• Has a phospholipid bilayer
• It is Amphipathic- both hydrophobic and
hydrophilic
• It is made up of mostly lipids[phospholipids,
cholesterol, glycolipids e.t.c] and proteins

17. Functions of Cholesterol
✓Maintains fluidity of the cell
✓Disrupts ability of phospholipid to interact among
themselves
✓Are lipid in nature because their steroid nucleus is
highly fat soluble
✓They determine the degree of permeability of the
bilayer to water constituents
✓Partially immobilize fatty acid chains

18. PROTEINS
They include; Integral and Peripheral proteins
Integral proteins-they protrude all the way through the
membrane
Peripheral membrane-attached to one surface of the protein
and do not penetrate all the way through the membrane.
Functions
▪ Provide structural integrity
▪ Help in diffusion of water soluble substances
▪ Transport proteins
▪ Receptor proteins
▪ Some are enzymes
▪ Some are antigens
▪ Cell adhesions- integral proteins attach neighboring cell to
each other

19. CARBOHYDRATES
❖Negatively charged hence don’t allow
negatively charged substances in and out of the
cell
❖Adhesion of neighboring cells together
❖Some act as receptors for hormones

21. LYSOSOMES
Has hydrolytic enzymes that break down macromolecules
Enzyme Substrate
Ribonuclease RNA
Deoxyribonuclease DNA
Phosphatase Phosphate esters
Glycosidases Complex carbohydrates
glycosides and polysaccharides
Arylsulfatases Sulfate esters
Collagenase Collagens
Cathepsins Proteins
• It undergoes autophagy of organelles and autolysis of the cell

23. PEROXISOMES
Has catalase, oxidase, metabolic enzymes e.t.c
▪ Fatty acid metabolism[oxidation] breakdown of
fatty acid to acetyl-CoA

24. MITOCHONDRIA
• 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. Enzymes involved in the elongation of fatty acids
and the oxidation of adrenaline can also be found on the outer
membrane.
• The space within the inner membrane of the mitochondrion is known as
the matrix, which contains the enzymes of the Krebs (TCA) and fatty
acid cycles, alongside DNA, RNA, ribosomes and calcium granules.
• The inner membrane contains a variety of enzymes. It contains ATP
synthase which generates ATP in the matrix, and transport proteins that
regulate the movement of metabolites into and out of the matrix.
• The inner membrane is arranged into cristae in order to increase the
surface area available for energy production via oxidative
phosphorylation.

25. Functions
✓Immune signaling
✓Store calcium for cell signaling
✓Synthesis of haeme
✓Regulation of cellular metabolism
✓Synthesis of steroids
✓Regulation of membrane potential
✓Apoptosis-programmed cell death
✓Hormonal signaling
✓Heat production
✓Energy production