Biologija - Prvi Tjedan

Review of First Week of Biology

• All Cells: Consist of membrane, cytosol (a viscous substance), chromosomes (hereditary instructions), ribosomes, cytoplasm (cytosol + organelles), protoplasm (cytoplasm + nucleus with nucleoplasm).
• Prokaryotes (bacteria and archaea): Lack organelles; their chromosome floats in the cytoplasm as they do not have a nucleus. Their hereditary material is circular DNA.
• Eukaryotes (animals and plants): Have a nucleus with DNA separate from the cytoplasm. They have centrosomes which form the mitotic spindle.
• Animal + Plant Cells: Contain nucleus, endoplasmic reticulum (ER), Golgi apparatus, mitochondria (plants have chloroplasts). Plant cells have a cell wall.
• Nucleus: Enclosed by a double membrane (nuclear envelope) with 4 phospholipid layers (2 bilayers), continuous with the endoplasmic reticulum (ER). Contains chromosomes packaged as chromatin; nucleolus (where ribosome subunits form). Contains nuclear pores for material passage. Perinuclear space (between the two membranes of the nuclear envelope). Nucleoplasm is the viscous fluid inside the nucleus. Nuclear lamina (protein filaments) lines the inner nuclear membrane.
• Chromosomes: Are the transport form of DNA molecules and are composed of DNA and proteins called histones and DNA.
• Ribosomes: Consist of two ribosomal subunits made of RNA and protein. They are either free in the cytosol or bound to the rough ER; their function is protein synthesis.
• Genomic information: Is contained in the nucleus and is transmitted through ribosomes and DNA.

Second Week of Biology

• Endoplasmic Reticulum (ER): Smooth ER produces lipids, metabolizes carbohydrates, stores calcium ions and detoxifies harmful substances. Rough ER helps in the synthesis, modification, and packaging of secretory proteins.
• Golgi Apparatus: Modifies, organizes, packages, and secretes proteins and polysaccharides. Has a cis and trans face (entering and exiting regions, respectively).
• Lysosomes (animal cells): Responsible for digestion, recycling, and breaking down cellular macromolecules and damaged organelles.
• Vacuoles (plant cells): Crucial for digestion, storage, protection, and growth; they regulate water balance.
• Endosymbiotic Theory: Explains the origin of eukaryotic organelles (like mitochondria and chloroplasts) through symbiotic relationships between prokaryotic cells.
• Mitochondria: Produces energy through cellular respiration. Has two membranes.
• Chloroplasts (plant cells): Site of photosynthesis. Have two membranes, thylakoids, and stroma.
• Peroxisomes (animal cells): Contain enzymes that use oxygen to break down fatty acids and other molecules. Contain a single membrane.
• Cytoskeleton: A network of protein filaments (microtubules, microfilaments, intermediate filaments) that gives shape, structure, motility, and transport.
• Microtubules: Involved in cell division (movement of chromosomes) and cell morphology (making cilia and flagella).
• Microfilaments: Involved in cell contraction, cell division and movement (cytoplasmic streaming).
• Intermediate filaments: Provide structural support to cell, maintaining cell shape and resisting mechanical stress.
• Extracellular matrix: Supports, connects, and regulates cells (in tissue or cell layers)

Cell Processes and Structures

• Plasma (cell) membrane: Exhibits selective permeability; controls what enters and leaves the cell.
• Microbial Communities (Microbiome/Microbiota): Collectively encompass all the microbes (bacteria, viruses, protists), their genomes, and their genetic material, inhabiting a specific environment.
• Microscopy: Includes light and electron microscopy (SEM-scanning and TEM-transmission electron) used to observe cells and their components.
• Osmosis and Tonicity: Movement of water across selectively permeable membranes (hypertonic, isotonic, hypotonic solutions).
• Transport across membranes: Passive transport (diffusion, facilitated diffusion, osmosis) does not require energy. Active transport requires energy (moving substances against their concentration gradient).
• Endocytosis: (phagocytosis, pinocytosis, receptor-mediated endocytosis) is the cell taking material into itself; this is an active process.
• Exocytosis: The cell expelling material from the cell. This is an active process for secretion.
• Desmosomes: Cell junctions that attach cells together, providing strength. Present in tissues that experience stress (skin).