Cell structure and function

• Prokaryotes and eukaryotes Prokaryotes: Simplest cells, no nucleus or membrane-bound organelles. Bacteria and Archaea. Eukaryotes: More complex cells, have a nucleus and membrane-bound organelles. Plants, animals, fungi, protists.

• Cell membrane structure and function: Phospholipid bilayer, semi-permeable, controls what enters and leaves the cell. Contains membrane proteins for transport, receptors, and cell signaling.

• Nucleus structure and function including nuclear envelope, nucleolus, and chromosomes: Contains genetic material (DNA), surrounded by a nuclear envelope with pores for transport. Nucleolus: Site of ribosome synthesis Chromosomes: Thread-like structures made of DNA and proteins.

• Cytoplasm and cytosol: Cytoplasm: All contents of the cell besides the nucleus. Cytosol: Jelly-like substance within the cytoplasm.

• Endoplasmic reticulum (ER): Network of membranes, two types: rough ER (with ribosomes) and smooth ER (without ribosomes). Site of protein synthesis, lipid synthesis, and drug detoxification.

• Golgi apparatus: Stack of flattened membranes, modifies and packages proteins and lipids for transport to their destination.

• Lysosomes: Membrane-bound organelles that contain digestive enzymes, break down waste and worn-out cell parts.

• Mitochondria: Bean-shaped organelles, site of cellular respiration, generate ATP (energy currency of the cell).

• Chloroplasts: Found in plant cells, contain chlorophyll, convert light energy into sugar (photosynthesis).

• Vacuoles: Membrane-bound sacs, store various substances, such as water, salts, and waste products.

• Microtubules, microfilaments, and intermediate filaments: Microtubules: Thicker, made of tubulin, give the cell shape and structure, involved in cell division. Microfilaments: Thinner, made of actin, involved in cell movement and cytokinesis. Intermediate filaments: Provide support and strength to the cell.

• Cell wall structure and function: Found in plant cells, bacteria, and some fungi, made of cellulose, rigid, protects the cell and gives it shape.

Cell cycle and cell division

• The cell cycle including interphase, prophase, metaphase, anaphase, and telophase: Interphase: Longest phase, consists of G1, S, and G2 stages, DNA replication occurs during S phase. Prophase: Chromosomes become visible, the nuclear envelope breaks down, and the spindle apparatus begins to form. Metaphase: Chromosomes align at the center of the cell (equatorial plane). Anaphase: Sister chromatids separate and move to opposite poles of the cell. Telophase: New nuclear envelopes form around the chromosomes at opposite ends of the cell, and the spindle apparatus breaks down.

• Mitosis and meiosis: Mitosis: Cell division that results in two genetically identical daughter cells. Meiosis: Specialized cell division that occurs in reproductive cells, results in four genetically unique daughter cells with half the number of chromosomes as the parent cell.

• Binary fission in prokaryotes: Prokaryotic cell division, involves the replication of the single chromosome and the splitting of the cell into two identical daughter cells.

• Cytokinesis: Process of dividing the cytoplasm after mitosis or meiosis, can occur by furrowing (animal cells) or cell plate formation (plant cells).

• Regulation of the cell cycle (cyclins and cyclin-dependent kinases): Cyclins and cyclin-dependent kinases (CDKs) regulate the progression of the cell cycle, checkpoints ensure the cell is ready to proceed to the next phase.

• Cancer and the cell cycle: Uncontrolled cell division, can result from mutations in genes involved in cell cycle regulation.

• Cell differentiation and stem cells: Process by which cells become specialized in structure and function, stem cells can differentiate into various cell types.