Cells and Organelles

Arts 1–4

Foreign Languages 1–4

Structure and function of prokaryotic and eukaryotic cells, including the roles of organelles.

📘 Topic Summary

Cells are the basic structural and functional units of life, with prokaryotic cells lacking a true nucleus and eukaryotic cells having membrane-bound organelles that perform specific functions.

📖 Glossary

Prokaryote: A cell without a true nucleus or membrane-bound organelles.
Eukaryote: A cell with a true nucleus and membrane-bound organelles.
Organelle: A specialized structure within a eukaryotic cell that performs specific functions.
Mitochondria: The site of cellular respiration, responsible for generating energy.
Nucleus: The control center of the cell where DNA is stored.

⭐ Key Points

Prokaryotic cells are typically smaller than eukaryotic cells.
Eukaryotic cells have a true nucleus and membrane-bound organelles.
Mitochondria generate energy for the cell through cellular respiration.
Chloroplasts are responsible for photosynthesis in plant cells.
Lysosomes contain digestive enzymes that break down waste and foreign substances.
Ribosomes are found throughout the cytoplasm and are involved in protein synthesis.

🔍 Subtopics

Cell Structure

Prokaryotic cells, such as bacteria, have a single circular chromosome and lack membrane-bound organelles. Eukaryotic cells, including plants and animals, have linear chromosomes and are compartmentalized into different organelles. The cell membrane surrounds the cell and regulates what enters and leaves. The cytoplasm is the jelly-like substance inside the cell where metabolic processes take place.

Cellular Processes

Metabolic processes such as glycolysis, the citric acid cycle, and oxidative phosphorylation occur in the cytoplasm to generate energy for the cell. Protein synthesis takes place on ribosomes, while DNA replication and repair happen in the nucleus of eukaryotic cells.

Organelle Functions

Mitochondria are the site of cellular respiration, generating most of the cell's energy through the process of oxidative phosphorylation. Chloroplasts in plant cells perform photosynthesis to produce glucose and oxygen. Lysosomes contain digestive enzymes that break down and recycle cellular waste.

Cellular Transport

Passive transport, such as diffusion and osmosis, allows molecules to move across the cell membrane without energy input. Active transport, which requires energy, helps maintain proper ion balances and nutrient uptake. The Golgi apparatus packages proteins and lipids for secretion or storage.

Cell Signaling

Signaling pathways involve the binding of signaling molecules to receptors on the cell surface, triggering a cascade of chemical reactions that affect cellular behavior. This process is crucial for responding to environmental stimuli, regulating growth and development, and maintaining tissue homeostasis.

Cell Division

Mitosis is the process by which eukaryotic cells divide to produce two daughter cells with identical genetic material. Meiosis occurs in reproductive cells to create gametes with unique combinations of chromosomes. Binary fission is the method used by prokaryotic cells to reproduce.

Cellular Adaptation

Cells can adapt to changing environments through gene expression, protein modification, and cellular reorganization. This allows them to respond to stressors, such as temperature changes or nutrient availability, and maintain proper function.

Cellular Disease

Mutations in DNA can lead to genetic disorders, while environmental toxins and radiation can cause DNA damage and mutations. Cancer occurs when normal cellular processes are disrupted, leading to uncontrolled cell growth and division.

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