CHAPTER 2: From Cells to Systems
Important topics in cell biology: * Cell theory: 1. All organisms are composed of cells and cell products 2. The cell is the simplest structural and functional form of life 3. An organism’s structure and all of its functions are ultimately due to the activities of cells 4. All cells arise from pre-existing cells 5. All cells share fundamental similarities and metabolic mechanisms * Cell structure: * About 210 different cell types in the human body, including: squamous, polygonal, cuboidal, columnar, spheroid, discoid, stellate, fusiform, fibrous * Fluid-mosaic model of the plasma membrane because the double phospholipid membrane is more liquid than solid * Microvilli- tiny folds of the plasma membrane found on the apical surface of the cells that line the small intestine, and in some other parts of the body. Increase the SA of the cell, enabling a rapid rate of transport of nutrient molecules into the cell * Cilia- tiny hairlike structures that protrude from the plasma membrane into the ECF. Motile cilia are found in places like the respiratory tract & uterine tubes where they move substances past the tissue (“9+2” arrangement of microtubules) * Flagella- found only on sperm cells, it is a single, whiplike structure that propels the sperm through its environment (also has the “9+2”…) * Functions of specific organelles * The cytoskeleton: a latticework of protein microfilaments and microtubules that function as the skeleton of the cell. Makes parts of the cell rigid, serves as a transport system within the cell, can produce cell movement * Mitochondrion: the sites for most of the energy production within a cell. * Contain their own DNA * All mitochondria come from the mother’s egg cell * Endoplasmic reticulum (ER): Two types 1. Rough ER: contain ribosomes (“protein factories”) that read mRNA codes then sends vesicles containing the newly made protein to the Golgi complex… 2. Smooth ER: synthesizes other materials, detoxification, Ca2+ storage. (no ribosomes, no protein synthesis) * Golgi complex: a network of stacked, flattened membranous sacs withing the cytoplasm of cells. * Takes vesicles containing protein from the rough ER and continue synthesis * Sends finished products out as: * Lysosomes which stay in the cell or as * Secretory vesicles that take proteins out of the cell * Nucleus: contains all the instructions for protein synthesis in the form of DNA. * DNA consists of nucleotides which form 2 strands connected together by H-bonds. The sequence of nucleotides gives us our genetic information * Chromatin is the long and threadlike form of DNA and protein that serves as the functioning genetic material within the nuclei of nondividing cells * Chromatin is spooled onto proteins to form nucleosome particles which condense into a more compacted form identified as: * Chromosomes are compacted chromatin visible through a microscope that contain regulatory proteins as well as DNA * Membrane transport* * Energy transduction* * Cell-cell signaling* * Cell cycle and its regulation
3 Types of RNA: 1. Messenger RNA (mRNA): a complementary copy of a gene that codes for the structure of a protein 2. Transfer RNA (tRNA): contains 3 nucleotides at one end which match up with a codon of mRNA (anticodon) and an AA on the other end. Transfers AAs to the messenger RNA, translating the nucleotide base into an AA sequence 3. Ribosomal RNA (rRNA): make up part of the structure of ribosomes
Making Proteins (Transcription and Translation):
DNA acts as a template for the synthesis of RNA: * A gene is a region of DNA that codes for a polypeptide chain * Transcription: The process by which mRNA is