Cell & Cell organelles. pptx

The human cell is the body’s fundamental building block, functioning as the smallest unit of life. It is equipped with specialized structures called organelles, each of which performs specific tasks that keep the cell alive and functional. Collectively, these organelles enable processes like energy production, waste removal, growth, and reproduction.

1. Cell structure and functions Shivaputra Patil Medical Biochemistry

2. CONTENTS

3. Cell Cell = Plasma membrane + cytoplasm Cytoplasm = Cytosol + Subcellular organelles All subcellular organelles, except ribosomes and cytoskeleton, are compartments within the cell, surrounded by cell membrane and containing their own aqueous fluid.

4. Cells- Structure INTRODUCTION The cell is the Basic Structural and Functional Unit of all Living Organisms. It is the basic unit of biological activity. Therefore, the Evolution of cells is a crucial milestone in the evolution of life.

5. The cells of biological systems are divided into two categories. Prokaryotes Eukaryotes Prokaryotes ( Pro - before, karyon – Nucleus). Lack a well-defined nucleus and possess a relatively simple structure. Lower organism - bacteria. Eukaryotes ( Eu – true/good, karyon – Nucleus) Have a membrane-enclosed nucleus encapsulating their DNA. Higher organisms - Plants and animals. Cell types:

6. Differences Between Eukaryotic and Prokaryotic Cell

7. Cell Organelles can be Separated by Ultracentrifugation.

8. Sub Cellular Organelles Nucleus Endoplasmic Reticulum Golgi apparatus Mitochondria Lysosomes Peroxisomes

9. Nucleus Structure : Enclosed by a double membrane called the nuclear envelope, which has pores allowing the transport of molecules between the nucleus and cytoplasm . Function : Acts as the control center of the cell, housing the cell’s DNA and coordinating activities like growth, metabolism, protein synthesis, and reproduction (cell division).

10. Nucleus Contains DNA→ condensed with protein →chromatin → chromosomes (23 pairs) Controls structure and function through genes. Nucleolus: RNA processing and ribosome synthesis. Functions: DNA synthesis

11. Endoplasmic reticulum Network of interconnected membranes (railway track appearance) Continuation of the outer nuclear membrane Two types Rough endoplasmic reticulum (ribosomes)(RER) Smooth endoplasmic reticulum (SER)

12. Functions of Endoplasmic reticulum

13. Mitochondria Power house of cell Spherical, oval – 0.5 μ m diameter,7 μ m length. 2 membranes – inner – enzymes of ETC Outer – phospholipase A2,MAO Soluble matrix: enzymes of the citric acid cycle and urea cycle. It contains its own specific DNA.

14. Spherical, oval or rod-like bodies Size: 0.2- 0.8 μ m The number of mitochondria in a cell varies. Erythrocytes no mitochondrion Liver cell 800-2500 Mitochondria

15. Bilayer OMM – Smooth IMM – convolutes into folds - Cristae 2 Compartments Intermembrane space Matrix Mitochondria are the ‘Power House’ of the Cell. IMM contains the ETC Matrix- Enzymes of the TCA cycle, Beta Oxidation of FA, etc. Mitochondria

16. Mitochondria Supply Most of the Cell’s Need for ATP Production of ATP Cellular respiration Oxidation of Carbohydrates and lipids Urea and heme synthesis.

17. Clinical Significance Luft’s disease – Defective energy transduction Mt. Myopathies – OXPHOS diseases Due to mutation in Mt DNA Parkinson’s, Cardiomyopathies – age-related degenerative diseases. Antibiotics inhibiting bacterial protein synthesis do not affect cellular processes but inhibit mitochondrial protein synthesis. Mitochondria are considered ‘parasites’ that enter the cell during the course of evolution!

18. Golgi apparatus Network of flattened smooth membranes and vesicles Functions Sorting, packing, and secretion of proteins. It is composed of Cis, Medial and Trans cisternae. Glycoproteins transported from ER to Cis, then to medial Golgi and finally trans Golgi for temporary storage. Vesicle traffic in cell.

19. Lysosomes Suicidal bag Contain digestive enzymes (alpha-glucosidase, collagenase, ribonuclease, phospholipases) Fuse with phagosomes → secondary lysosomes → foreign particles are progressively digested Clinical significance: lysosomal storage disorder

20. Clinical application 1. In gout, urate crystals are deposited around the knee joint. When it is phagocytosed, it causes damage to the lysosome, causing the release of enzymes, inflammation and arthritis results. 2. Postmortem autolysis: following cell death, the lysosomes rupture , releasing the hydrolytic enzymes that bring the above changes. 3. Cathepsins and proteases: involved in the tumor metastasis.

21. 4. silicosis: Inhalation of silica into the lungs is engulfed by phagocytes, which leads to the rupture of the lysosomal membrane, leading to the release of enzymes . This stimulates fibrosis and decreases the elasticity of the lung. 5. Inclusion cell disease: a rare condition in which lysosomes lack the enzymes but are seen in blood. It is a type of protein-targeting defect. The mannose-6-P deficient enzymes cannot reach their destination. Continue…

22. Peroxisomes They have granular matrix. Contain peroxidases, catalase Platelets, leukocytes Destroy unwanted peroxides & free radicals.

23. Clinical note: deficiency of peroxisomal matrix proteins can lead to adrenoleukodystrophy (ALD) (Brown-children’s disease), Zellweger syndrome and primary hyperoxaluria. Adrenoleukodystrophy is rare autosomal recessive with progressive degeneration of the brain, liver, and kidney, and it is characterized by the defect of insufficient oxidation of long-chain fatty acids (VLCFA). Zellweger syndrome: proteins are not transported to the peroxisomes, leading to the formation of empty peroxisomes or ghosts inside the cells.