Chapter 3 Cell Biology PDF

C H A P T E R THREE Cell Biology Seeley’s Anatomy & Physiology, 12th Edition VanPutte C., Regan J., Russo A., Seeley R., Stephens T., Tate P. McGraw-Hill Education Lecture Outline 3.1 Functions of the Cell 3.2 How We See Cells 3.3 Pl...

C H A P T E R THREE Cell Biology Seeley’s Anatomy & Physiology, 12th Edition VanPutte C., Regan J., Russo A., Seeley R., Stephens T., Tate P. McGraw-Hill Education Lecture Outline 3.1 Functions of the Cell 3.2 How We See Cells 3.3 Plasma Membrane 3.4 Membrane Lipids 3.5 Membrane Proteins 3.6 Movement Through the Plasma Membrane 3.7 Cytoplasm 3.8 The Nucleus and Cytoplasmic Organelles 3.9 Cell Cycle 3.10 Cellular Aspects of Aging Functions of the Cell 3.1  Cell metabolism and energy use Synthesis of molecules Communication Reproduction and inheritance Organelles: specialized structures performing specific functions Cytoplasm: jelly-like substance that holds the organelles Cell Membrane: plasma membrane; forms the outer boundary of the cell How We See Cells 3.2  Light Electron Microscope Microscope Visualization of Visualization of the general fine structure of a features of a cell cell Transmission Scanning Atomic force electron electron microscope microscope microscope (AFM) (TEM) (SEM) Plasma Membrane 3.3 Plasma Membrane Outermost component of a cell o Structure o Attachment o Cell signaling o Selective permeability o Physical barrier Lipid (45-50%) = phospholipids & cholesterol Protein (45-50%) Carbohydrates (4-8%) = glycolipid, glycoprotein, (glycocalyx) Membrane Lipids 3.4 Membrane Lipids Phospholipids (~75%): contains a polar (charged, hydrophilic) head and a nonpolar (uncharged, hydrophobic) tail; readily forms the lipid bilayer Cholesterol (~25%): present in much smaller amounts in the lipid bilayer compared to phospholipids; contributes to the fluid nature of the membrane  Fluid-mosaic model describes the plasma membrane as being neither rigid nor static in structure, but instead has a highly flexible structure and can change its shape and composition through time. Membrane Proteins 3.5 Membrane Proteins These are protein molecules that are attached to, or associated with, the cell membrane or with an organelle Based on location: integral or peripheral Movement Through The Plasma Membrane 3.6 Cytoplasm 3.7 Cytoplasm Cytoplasm is the material outside the nucleus and inside the plasma membrane Cytosol consists of a fluid part (the site of chemical reactions), the cytoskeleton, and cytoplasmic inclusions The cytoskeleton supports the cell and is responsible for cell movements. It consists of protein fibers. Cytoplasmic inclusions, such as lipochromes, are not surrounded by membranes The Nucleus and Cytoplasmic Organelles 3.8 General Cell Structure Organelles are structures within the cells that are specialized for a particular function They may be membrane bound or not The nucleus is the largest organelle of the cell The number and type of cytoplasmic organelles within each cell are related to the specific function of the cell Nucleus The nuclei of human cells contain 23 pairs of chromosomes w/c consists of DNA and proteins During most of a cell’s life, the chromosomes are loosely coiled and collectively called chromatin When it prepares to divide the chromosomes condense and can be visible through microscope Nucleus A large, membrane-bound organelle usually located near the center of the cell The nucleus is bounded by a nuclear envelope, which consists of outer and inner membranes with a narrow space between them The nuclear membrane contains nuclear pores, through which materials can pass into or out of the nucleus Ribosomes Sites of protein synthesis Ribosomes may be attached to other organelles, such as the endoplasmic reticulum; produce integral membrane proteins and proteins that are secreted from the cell Ribosomes that are not attached to any other organelle are called free ribosomes; produce proteins used primarily within the cell Endoplasmic Reticulum This is a series of membranes forming sacs and tubules that extends from the outer nuclear membrane into the cytoplasm Rough ER: involved in protein synthesis and is rough due to attached ribosomes Smooth ER: no attached ribosomes, site for lipid synthesis, cellular detoxification, stores calcium ions Golgi Apparatus Consists of closely packed stacks of curved, membrane-bound sacs It collects, modifies, packages, and distributes proteins and lipids manufactured by the ER The Golgi Apparatus forms vesicles, some of which are secretory vesicles, lysosomes, and other vesicles Secretory Vesicle Membrane-bound structures that pinches off from the Golgi apparatus to move to the surface of the cell, releases materials via exocytosis Lysosome Membrane-bound vesicles formed at the Golgi body They contain various hydrolytic enzymes that function as intracellular digestive system Able to digest nucleic acids, proteins, polysaccharides, lipids Autophagy (self-eating) Peroxisome Smaller than lysosomes; functions for detoxification Contain enzymes w/c breaks down fatty acids & amino acids Catalase, an enzyme w/c breaks down H2O2  H2O + O2 Proteasomes Large protein complexes containing enzyme for breaking down and recycling other proteins w/in the cell Mitochondria Are small organelles which provides the majority of the energy for the cell Inner and outer membranes separated by intermembrane space Outer has smooth contour, inner has infoldings called cristae The material within the inner membrane is called matrix, where mitochondrial enzymes and DNA can be found Centriole The centrosome is a specialized area of cytoplasm close to the nucleus where microtubule formation occurs It contains two centrioles, which are normally oriented perpendicular to each other Each centriole is a small, cylindrical organelle composed of microtubules The centriole is involved in the process of mitosis Cilia and Flagella Cilia project from the surface of cells They are responsible for movement of materials over the top of cells, i.e., mucus Cylindrical, 10 um in length, 0.2 um diameter Flagella have similar structure to cilia, but longer (45-55 um) Locomotion (sperm cells) Microvilli Cylindrically shaped extensions of the plasma membrane 0.5-1.0 um in length; 90 nm in diameter Found in the cells of the intestine, kidney, and other areas where absorption is an important function Increase the surface area Highly modified to function as sensory receptors Genes and Gene Expression 3.9 Gene and Gene Expression Genes: functional units of heredity A sequence of nucleotides that provides a chemical set of instructions for making a specific protein Heredity: transmission of genetic traits from parents to offspring Gene Expression: production of RNA/protein from the information stored in DNA; transcription and translation Transcription Synthesis of RNA (mRNA, tRNA, rRNA) based on the nucleotide sequence of a gene in a DNA molecule RNA Polymerase: enzyme that synthesizes RNA 5 subunits: α | ω | β | β’ | σ Apoenzyme: α2ωββ’ Holoenzyme: α2ωββ’σ  Posttranscriptional processing: produces the functional mRNA that is used for translation o Addition of 7- methylganosine cap and poly-A tail Alternative splicing: various combinations of exons are incorporated into mRNA depending on the cell/tissue; allows a single gene to produce more than one specific protein Genetic Code Information contained in mRNA, which relates the nucleotide sequence of mRNA to the amino acid sequence of a protein mRNA is grouped into three nucleotide sequences called codons (each specifies an amino acid during translation) o 64 codons exist for the 20 amino acids o Start Codon: AUG (Met) o Stop Codon: UAA, UGA, UAG Translation mRNA  polypeptide  protein Translation occurs in the cytoplasm after mRNA has exited the nucleus through the nuclear pore PROCESS The mRNA attaches to the ribosome Codons (3 nucleotide bases) on the mRNA are read by anticodons (3 nucleotide base) on transfer RNA (tRNA) tRNA transports specific amino acids and initiates the formation of the polypeptide chain The process continues until the entire polypeptide is completely formed Cell Cycle 3.10 Cell Cycle This includes the changes a cell undergoes from the time it is formed until it divides Interphase + Cell Division Interphase Phase in between cell divisions where nearly all of the life cycle of a typical cell is spent. Metabolic activities + Prep for cell division Subphases o G1 (first gap phase): cell carries out routine metabolic activities o S phase (synthesis phase): DNA replication o G2 (second gap phase): preparation for cell division o G0 phase: resting/not follow the normal pattern of the cell cycle and will remain at this phase unless stimulated to enter cell division DNA Replication the process in which two strands of a DNA molecule separate and each serves as templates for making complementary new strands of nucleotides. Cell Division A parent cell divides to form two daughter cells, each having the same amount and type of DNA as the parent cell (diploid) Two major events: (1) nuclear division or mitosis and the (2) cytoplasmic division or cytokinesis Mitosis Division of a cell’s nucleus into two new nuclei, each containing the same amount and type of DNA as the original nucleus o Phases: PMAT (Papa Mama Are Together) o Prophase o Metaphase o Anaphase o Telophase Prophase Chromatin condenses to form visible chromosomes Centrioles divide and migrate to opposing poles Spindle fibers extend from the centriole to the centromeres Metaphase Chromosomes align near the center of the cell Anaphase Chromatids separate, cytoplasm starts to divide (cleavage furrow) Telophase Two new nuclei form; chromosomes begins to uncoil; enters interphase Apoptosis programmed cell death; normal cell process in which cell number within various tissues are adjusted and controlled; regulated by specific genes o Expression of the apoptotic genes produces proteins that carry out many apoptotic events o Chromatin condenses and fragments o Fragmentation of the nucleus o Fragmentation of the cell o Recycled via phagocytosis Cellular Aspects of Aging 3.11 Five Major Hypotheses to Aging A.Cellular Clock: In which at a certain passage of time/ no. of cell divisions, a given cell line dies B.Death Genes: A specific set of genes turns on later in life causing for cells to deteriorate and die C.DNA Damage: DNA damage through time causes for cells to degenerate and die D.Free Radicals: Direct damage via atoms or molecules with unpaired electrons E.Mitochondrial Damage: Damage to this sensitive genetic information may cause loss of mitochondrial function, ultimately to cell death