Cell Structures in Eukaryotes

Plasma Membrane

• Found in: All cells (prokaryotic and eukaryotic, plants and animals).
• Structure: Lipid bilayer with proteins (fluid mosaic model).
• **Function: **
  • Semi-permeable barrier separating exterior and interior environments.
  • Allows passage of small molecules (oxygen, nutrients, waste).
  • Cell communication, adhesion, and structure.
  • Dysfunction linked to cystic fibrosis.

Endomembrane System

• Includes: Nuclear envelope, lysosomes, vesicles, ER, Golgi apparatus.
• Function: Modify, package, and transport lipids and proteins.
• Note: Does not include mitochondria, chloroplasts, peroxisomes.

Nucleus

• Found in: Eukaryotes (animal and plant cells).
• Structure: Double membrane nuclear envelope with nuclear pores.
• Function: Contains genetic material (DNA organized into chromosomes).
• Dysfunction: Hereditary diseases like Down syndrome.

Nucleolus

• Found in: Inside nucleus of eukaryotes.
• Function: Site of rRNA synthesis and ribosome assembly.
• Dysfunction: Programmed cell death (cancer).

Rough Endoplasmic Reticulum (Rough ER)

• Found in: Eukaryotic cells.
• Function: Synthesizes proteins and glycoproteins, produces transport vesicles.
• Dysfunction: Improper protein folding.

Smooth Endoplasmic Reticulum (Smooth ER)

• Found in: Eukaryotic cells.
• Function: Synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and toxins, stores calcium ions.
• Dysfunction: Huntington's disease.

Ribosomes

• Found in: All cell types.
• Function: Protein synthesis through RNA translation.
• Structure: Small and large subunits, not membrane-bound.
• Dysfunction: Dyskeratosis congenita.

Golgi Apparatus

• Found in: Eukaryotic cells.
• Function: Modifies (glycosylation), sorts, and packages proteins and lipids for transport, manufactures macromolecules like carbohydrates.
• Dysfunction: Achondrogenesis.

Lysosome

• Found in: Eukaryotic cells (under dispute in plants).
• Function: Enzymatic hydrolysis of macromolecules, phagocytosis, autophagy.
• Dysfunction: I-cell disease.

Vacuole

• Found in: Eukaryotic cells (plants and animals).
• Function: Storage; varies by cell type (food, contractile, central vacuole in plants).
• Dysfunction: Danon's disease.

Peroxisomes

• Found in: All eukaryotic cells.
• Function: Break down organic molecules via oxidation, produce hydrogen peroxide, break down fatty acids and amino acids.

Mitochondria

• Found in: Eukaryotic cells.
• Function: Oxidative metabolism producing ATP.
• Structure: Double membrane, inner membrane folds (cristae).
• Dysfunction: Congenital lactic acidosis.

Chloroplasts

• Found in: Plants and algae.
• Function: Photosynthesis, fix carbon from CO2 to generate glucose.
• Structure: Double membrane, internal thylakoid membrane (contains chlorophyll).
• Dysfunction: Leaf chlorosis.

Cytoskeleton

• Found in: All cell types.
• Function: Organizes cell structures and activities, supports cell shape, enables motility, vesicle transport.
• Structure: Actin filaments, microtubules, intermediate filaments.
• Dysfunction: Alzheimer's.

Centrosomes (Centrioles)

• Found in: Animal cells.
• Function: Microtubule organizing centers, chromosome separation during cell division.
• Dysfunction: Cancer.

Cilia and Flagella

• Found in: Prokaryotes and some eukaryotic cells (e.g., sperm).
• Function: Locomotion, propulsion.
• Structure: Core of microtubules, basal body, motor protein (dynein), flagellin (flagella in prokaryotes).
• Dysfunction: Male infertility.

Cell Wall

• Found in: Plants, prokaryotes, fungi.
• Function: Protects, maintains shape, prevents excessive water uptake.
• Structure: Cellulose in plants, peptidoglycan in prokaryotes.
• Dysfunction: Bacterial soft rot.

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