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What is the primary function of lysosomes in cells?
What is the primary function of lysosomes in cells?
- Transportation of molecules across cell membranes
- Digestion of nutrients and removal of old organelles (correct)
- Production of energy through ATP synthesis
- Synthesis of proteins for cellular functions
Which enzyme is responsible for converting hydrogen peroxide into water and oxygen in peroxisomes?
Which enzyme is responsible for converting hydrogen peroxide into water and oxygen in peroxisomes?
- Protease
- Amidase
- Lipase
- Catalase (correct)
How do primary lysosomes differ from secondary lysosomes?
How do primary lysosomes differ from secondary lysosomes?
- Primary lysosomes are larger and contain more diverse contents
- Secondary lysosomes are smaller and more round
- Both types are the same size and shape
- Primary lysosomes are smaller and round, while secondary lysosomes are larger and less round (correct)
What type of pigment can accumulate in nerve cells as a result of wear and tear?
What type of pigment can accumulate in nerve cells as a result of wear and tear?
Which of the following statements is true about peroxisomes?
Which of the following statements is true about peroxisomes?
Which of the following are classified as membranous organelles in a cell?
Which of the following are classified as membranous organelles in a cell?
What characterizes a primary lysosome?
What characterizes a primary lysosome?
Which type of lysosome is formed by the fusion of a primary lysosome with a phagosome?
Which type of lysosome is formed by the fusion of a primary lysosome with a phagosome?
What happens to the remaining undigested portion after the digestion process in lysosomes?
What happens to the remaining undigested portion after the digestion process in lysosomes?
Which organelles are typically abundant in macrophages due to their phagocytic activity?
Which organelles are typically abundant in macrophages due to their phagocytic activity?
The contents of which structure are digested by the enzymes in the lysosome?
The contents of which structure are digested by the enzymes in the lysosome?
What type of secondary lysosome is formed when a primary lysosome fuses with pinocytotic vesicles?
What type of secondary lysosome is formed when a primary lysosome fuses with pinocytotic vesicles?
Which organelle is responsible for intra-cytoplasmic digestion in cells?
Which organelle is responsible for intra-cytoplasmic digestion in cells?
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Study Notes
The Cell
- Membranous organelles: Structures enclosed by a membrane
- Cell membrane: Outermost layer of the cell, regulates what enters and exits
- Mitochondria: Powerhouse of the cell, responsible for ATP production
- Endoplasmic reticulum (ER): Network of interconnected membranes, involved in protein synthesis and lipid metabolism
- Rough ER: Studded with ribosomes, involved in protein synthesis
- Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification
- Golgi apparatus: Stack of flattened membrane-bound sacs, modifies and packages proteins
- Lysosomes: Membrane-bound sacs containing hydrolytic enzymes for intracellular digestion
- Non-membranous organelles: Structures not enclosed by a membrane
- Ribosomes: Sites of protein synthesis
- Cytoskeleton: Network of protein fibers that provides structural support and facilitates movement
- Microtubules: Tubular structures that form centrioles, cilia, and flagella
- Filaments: Thin, intermediate, and thick protein fibers that provide strength and support
Lysosomes
- Function: Intracellular digestion
- Location: Abundant in phagocytic cells like macrophages
- Structure:
- Primary lysosomes: Spherical vesicles containing hydrolytic enzymes, not yet engaged in digestion
- Electron microscopy: homogenous, moderate electron dense granular core
- Secondary lysosomes: Formed by fusion of primary lysosomes with phagosome, pinocytotic vesicles, or dead organelle
- Electron microscopy: heterogenous electron dense core
- Types:
- Heterolysosome: Fusion of primary lysosome with phagosome
- Multivesicular body: Fusion of primary lysosome with pinocytotic vesicles
- Autophagic vacuole: Fusion of primary lysosome with dead organelle
- Primary lysosomes: Spherical vesicles containing hydrolytic enzymes, not yet engaged in digestion
- Residual bodies: Undigested portion of material within a secondary lysosome, can accumulate in cells as lipofuscin pigment
Functions of Lysosomes
- Digestion of nutrients
- Defense against pathogens
- Removal of old organelles
- Activation of hormones
- Sperm penetration of the ovum
- Postmortem degeneration and autolysis
Peroxisomes
- Function: Fatty acid metabolism, detoxification, and protection against reactive oxygen species
- Structure: Tiny spherical membrane-bound organelles
- Contains: enzymes like hydroxy acid oxidase, D-amino acid oxidase, uricase (in rodents), and catalase
- Electron microscopy: membrane-bound vesicles containing a homogenous electron dense granular material (in humans); possess a semicrystalline core rich in uricase enzyme (in rodents)
- Light microscopy: Cannot be identified with H&E stain, but can be visualized histochemically using a catalase assay
Functions of Peroxisomes
- Segregation of harmful hydrogen peroxide (H2O2)
- Bile acid synthesis
- Beta-oxidation of long-chain fatty acids
- Alcohol metabolism
MCQs on Lysosomes
- b) Lysosomes are histochemically studied by acid phosphatase activity.
Practical Observations
- Primary lysosomes: Small, round, and numerous
- Secondary lysosomes: Larger, less round, variable in size, shape, and content
- Mitochondria: Rod-shaped, contain cristae (folded inner membrane)
- Heterolysosomes: Contain engulfed material within a lysosome
- Autophagic vacuoles: Contain a portion of the cell's own cytoplasm within a lysosome
- Lipofuscin pigment (wear and tear pigment) in nerve cells: Accumulated residual bodies
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