Cell Biology and Structure

Cell Biology

Cell Structure

• Plasma Membrane: Semi-permeable membrane separating cell from environment
• Cytoplasm: Jelly-like substance inside cell where metabolic reactions occur
• Cytosol: Liquid component of cytoplasm where metabolic reactions occur
• Organelles: Specialized structures within cell performing specific functions
• Nucleus: Controls cell growth, division, and contains genetic material (DNA)

Cell Organelles

• Mitochondria: Generates energy for cell through cellular respiration
• Endoplasmic Reticulum (ER): Synthesizes and transports proteins and lipids
• Ribosomes: Site of protein synthesis
• Lysosomes: Contains digestive enzymes to break down and recycle cellular waste
• Golgi Apparatus: Modifies and packages proteins and lipids for transport

Cell Transport

• Passive Transport: Movement of molecules from high to low concentration without energy
  • Diffusion: Random movement of molecules to equalize concentration
  • Osmosis: Movement of water molecules through selectively permeable membrane
• Active Transport: Movement of molecules against concentration gradient using energy
  • Carrier Proteins: Transport molecules across membrane using ATP

Cell Division

• Mitosis: Process of cell division resulting in two daughter cells with same number of chromosomes as parent cell
• Meiosis: Process of cell division resulting in four daughter cells with half the number of chromosomes as parent cell

Cell Signaling

• Signal Transduction Pathways: Series of molecular interactions allowing cells to respond to stimuli
• Receptors: Proteins on cell surface or within cell that respond to signaling molecules

Cell Biology

Cell Structure

• Plasma Membrane: Semipermeable membrane separating cell from environment, regulating what enters and leaves the cell.
• Cytoplasm: Jelly-like substance inside cell where metabolic reactions occur, maintaining cellular shape and provides mechanical support.
• Cytosol: Liquid component of cytoplasm where metabolic reactions occur, making up about 70% of cell volume.
• Organelles: Specialized structures within cell performing specific functions, each with unique composition and function.
• Nucleus: Controls cell growth, division, and contains genetic material (DNA), serving as the cell's genetic library.

Cell Organelles

• Mitochondria: Generates energy for cell through cellular respiration, producing ATP through aerobic respiration or anaerobic respiration.
• Endoplasmic Reticulum (ER): Synthesizes and transports proteins and lipids, with two types: rough ER (with ribosomes) and smooth ER (without ribosomes).
• Ribosomes: Site of protein synthesis, reading messenger RNA (mRNA) to assemble amino acids into polypeptides.
• Lysosomes: Contains digestive enzymes to break down and recycle cellular waste, maintaining cellular cleanliness.
• Golgi Apparatus: Modifies and packages proteins and lipids for transport, adding carbohydrates to form glycoproteins and lipids to form lipoproteins.

Cell Transport

• Passive Transport: Movement of molecules from high to low concentration without energy, driven by kinetic energy and concentration gradient.
  • Diffusion: Random movement of molecules to equalize concentration, increasing entropy and disorder.
  • Osmosis: Movement of water molecules through selectively permeable membrane, equalizing solute concentrations.
• Active Transport: Movement of molecules against concentration gradient using energy, requiring ATP or other energy sources.
  • Carrier Proteins: Transport molecules across membrane using ATP, often involving specific binding and conformational changes.

Cell Division

• Mitosis: Process of cell division resulting in two daughter cells with same number of chromosomes as parent cell, maintaining genetic consistency.
• Meiosis: Process of cell division resulting in four daughter cells with half the number of chromosomes as parent cell, shuffling genetic information.

Cell Signaling

• Signal Transduction Pathways: Series of molecular interactions allowing cells to respond to stimuli, involving receptors, signaling molecules, and response elements.
• Receptors: Proteins on cell surface or within cell that respond to signaling molecules, recognizing specific ligands or signals.

Microorganisms

Viruses

• Definition: Small, infectious particles that replicate inside cells of living organisms
• Characteristics:
  • Not considered living cells
  • Composed of genetic material (DNA or RNA) surrounded by a protein coat
  • Can only replicate inside host cells
• Types: DNA viruses (e.g., herpesvirus, poxvirus) and RNA viruses (e.g., influenza virus, HIV)
• Infection process: Attachment to host cell, penetration of host cell membrane, uncoating of viral genome, replication of viral genome, and assembly and release of new viral particles

Bacteria

• Definition: Single-celled, prokaryotic microorganisms that lack a true nucleus
• Characteristics:
  • Cell wall composed of peptidoglycan (also known as murein)
  • Genetic material is a single circular chromosome
  • Can be autotrophic (produce own food) or heterotrophic (obtain food from environment)
• Types: Gram-positive (e.g., Staphylococcus, Bacillus) and Gram-negative (e.g., Escherichia, Pseudomonas)
• Importance: Decomposition and nutrient cycling, food production (e.g., yogurt, cheese), and human health (e.g., gut microbiome)

Fungi

• Definition: Eukaryotic, heterotrophic organisms that obtain food by decomposing organic matter or forming symbiotic relationships
• Characteristics:
  • Cell wall composed of chitin
  • Multicellular or single-celled (e.g., yeast)
  • Can form mycorrhizal relationships with plants
• Types: Mushrooms (e.g., Agaricus, Boletus), Molds (e.g., Aspergillus, Penicillium), and Yeast (e.g., Saccharomyces)
• Importance: Decomposition and nutrient cycling, food production (e.g., bread, wine), and medicine (e.g., antibiotics, vaccines)

Protozoa

• Definition: Single-celled, eukaryotic microorganisms that feed on bacteria, other microorganisms, or organic matter
• Characteristics:
  • Motile (capable of movement)
  • Feed using pseudopodia (e.g., Amoeba) or flagella (e.g., Giardia)
  • Can form cysts for survival
• Types: Amoebas (e.g., Amoeba proteus), Flagellates (e.g., Giardia, Trichomonas), and Ciliates (e.g., Paramecium)
• Importance: Decomposition and nutrient cycling, human health (e.g., intestinal parasites)