Cell Biology: Basic Unit of Life

Cell Biology

Basic Unit of Life

• Cells are the fundamental units of life.
• All living organisms are composed of cells.
• Two main types of cells: prokaryotic and eukaryotic.

Prokaryotic Cells

• Lack a nucleus and membrane-bound organelles.
• Smaller and simpler than eukaryotic cells.
• Genetic material is located in a nucleoid region.
• Examples: Bacteria and Archaea.

Eukaryotic Cells

• Contain a true nucleus and membrane-bound organelles.
• Larger and more complex than prokaryotic cells.
• Types: Plant cells, animal cells, fungal cells, and protist cells.

Cell Structure and Organelles

• Nucleus: Contains DNA, controls cell activities.
• Mitochondria: Powerhouse of the cell, site of ATP production.
• Ribosomes: Protein synthesis.
• Endoplasmic Reticulum (ER):
  • Rough ER: Studded with ribosomes, synthesizes proteins.
  • Smooth ER: Synthesizes lipids, detoxifies.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
• Lysosomes: Contain digestive enzymes for waste processing.
• Cell Membrane: Semi-permeable barrier, regulates entry and exit of substances.
• Cytoplasm: Jelly-like fluid, site of metabolic processes.

Cell Division

• Mitosis: Process of somatic cell division, results in two identical daughter cells.
• Meiosis: Process of gamete formation, results in four genetically diverse cells.

Cellular Metabolism

• Catabolism: Breakdown of molecules to obtain energy.
• Anabolism: Building up of molecules, requires energy.
• Cellular Respiration: Conversion of glucose and oxygen into ATP, carbon dioxide, and water.

Cell Communication

• Cells communicate through chemical signals (hormones, neurotransmitters).
• Receptors on cell surfaces detect signals and initiate responses.

Transport Mechanisms

• Passive Transport: Movement of molecules without energy (e.g., diffusion, osmosis).
• Active Transport: Movement of molecules against a concentration gradient, requires energy (e.g., sodium-potassium pump).

Cell Cycle

• Composed of interphase (G1, S, G2) and mitotic phase (M).
• Regulation by checkpoints to ensure proper division and function.

Specialization and Differentiation

• Cells can differentiate into specialized types (e.g., muscle cells, nerve cells) based on gene expression and environmental factors.

Cell Theory

• All living things are made of cells.
• Cells are the basic unit of life.
• All cells arise from pre-existing cells.

Basic Unit of Life

• Cells serve as the fundamental units of all living organisms.
• There are two main categories of cells: prokaryotic and eukaryotic.

Prokaryotic Cells

• Characterized by the absence of a nucleus and membrane-bound organelles.
• Smaller and simpler than eukaryotic cells, facilitating rapid reproduction.
• Genetic material is organized within a nucleoid region.
• Examples include Bacteria and Archaea, which are some of the most ancient life forms.

Eukaryotic Cells

• These cells possess a true nucleus where DNA is stored, along with membrane-bound organelles.
• Larger and more complex, allowing for compartmentalization of cellular processes.
• Include various types such as plant cells (which have cell walls and chloroplasts), animal cells, fungal cells, and protist cells.

Cell Structure and Organelles

• Nucleus: Responsible for housing DNA and regulating cellular activity.
• Mitochondria: Known as the powerhouse, where ATP (energy currency) is generated.
• Ribosomes: Sites of protein synthesis, found free in the cytoplasm or attached to the ER.
• Endoplasmic Reticulum (ER):
  • Rough ER: Studded with ribosomes for protein synthesis, involved in processing.
  • Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification processes.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
• Lysosomes: Contain digestive enzymes to break down waste materials and cellular debris.
• Cell Membrane: A semi-permeable barrier regulating the movement of substances in and out of the cell.
• Cytoplasm: A gel-like substance where metabolic processes occur.

Cell Division

• Mitosis results in two identical daughter cells, ensuring equal genetic material distribution.
• Meiosis creates four genetically diverse gametes, essential for sexual reproduction.

Cellular Metabolism

• Catabolism involves the breakdown of complex molecules to release energy.
• Anabolism refers to the synthesis of larger molecules from smaller ones, requiring energy input.
• Cellular Respiration transforms glucose and oxygen into ATP, along with carbon dioxide and water by-products.

Cell Communication

• Cells interact through chemical signals such as hormones and neurotransmitters.
• Cell surface receptors recognize these signals and trigger appropriate responses.

Transport Mechanisms

• Passive Transport occurs without energy expenditure, including processes such as diffusion and osmosis.
• Active Transport requires energy to move substances against their concentration gradients, exemplified by the sodium-potassium pump.

Cell Cycle

• Comprises interphase, divided into G1 (growth), S (DNA synthesis), and G2 (preparation for mitosis), along with the mitotic phase (M).
• Checkpoints throughout the cycle ensure proper cell growth and division processes.

Specialization and Differentiation

• Cells can become specialized types based on gene expression and environmental influences, allowing various functions in multicellular organisms.

Cell Theory

• All living organisms are composed of one or more cells.
• Cells are recognized as the basic unit of life.
• All cells originate from pre-existing cells, establishing continuity in life.