DR Medhat MRCP

It contains :
- 46 (23 pairs) of chromosomes
o 44 Autosomes + 2 sex chromosomes (XX or XY).
o Each chromosome is formed of 2 chromatids joined at centromer.
o Chromatide is formed of DNA
• DNA is a double helical structure ,each helix is made up of
four chemical bases (nucleotide bases) which are
represented by letters: adenine (A), guanine (G), cytosine
(C), and thymine (T) .These bases are repeated in the same
helix in a specific arrangement & length and are attached
to their fellows of the other helix where they strung
together in pairs (base pairs) in specific combinations and
lengths to spell the genes.
• Base pairs code for certain proteins. So, ultimately, a gene
(= a section of DNA) makes a protein in the nucleus.
• DNA is stored , replicated & transcripted into another
nucleic acid RNA.
• DNA is copied and inherited across generations.
- Nucleolus :
o Where ribosomal subunits are assembled → then to cytoplasm.
II. Cytoplasm : is a clear gel enclosed within the cell membrane & contains :
- Cell organelles : ER(S&R) , golgi app., mitochondria, vacules & lysosomes.
- Cell inclusions : carbohydrates , proteins , FA , ions , vitamins.
Organelle/macromolecule
Main function
Endoplasmic
reticulum
- Translation and folding of new proteins (rER).
- Expression of lipids (sER)
Golgi apparatus - Present adjacent to endoplasmic reticulum
سؤال - Sorting &modification of cellular proteins & lipids.
Mitochondria
- Energy production (ATP).
- Contains mitochondrial genome as circular double
stranded DNA i.e it has its own self replicating DNA
Nucleus
- DNA maintenance and RNA transcription
Lysosome
- Breakdown of large molecules such as proteins and
polysaccharides
Nucleolus
- Ribosome production
Ribosome
- Present on rER ,Translation of RNA into proteins
Peroxisome
سؤال - Metabolism of fatty acids inside the cell
- Breakdown of metabolic hydrogen peroxide
Proteasome
- Degradation of large protein molecules
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