HumAnaPhy (CYTOLOGY).pdf

BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) II. CELLULAR LEVEL OF ORGANIZATION 2. SMALLEST LIVING UNITS OF LIFE 1. INTRODUCTION TO CELLS...

BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) II. CELLULAR LEVEL OF ORGANIZATION 2. SMALLEST LIVING UNITS OF LIFE 1. INTRODUCTION TO CELLS ❑ CELL COMPONENTS ❑ TYPICAL CELL PLASMA MEMBRANE (CELL MEMBRANE) - Smallest living unit in the body Separates cell contents from extracellular fluid – - ~0.1 mm in diameter - Could not be examined until invention of microscope CYTOPLASM in 17th century Material between cell membrane and nuclear - the biggest cell to be observed without the use of membrane microscope is Egg. Colloid containing many proteins TWO SUBDIVISIONS 1. Cytosol - Intracellular fluid 2. Organelles (“little organs”) - Intracellular structures with specific functions TYPES OF ORGANELLES a. Non-membranous ❑CELL THEORY Not completely enclosed by membranes In direct contact with cytosol Examples: Cytoskeleton, Microvilli, Centrioles, Cilia, Ribosomes b. Membranous Enclosed in a phospholipid membrane Isolated from cytosol Examples: Mitochondria, Nucleus, Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Peroxisomes MICROVILLI STRUCTURE: Membrane extensions containing microfilaments. FUNCTION: Increase surface area to facilitate absorption of extracellular materials. CYTOSKELETON STRUCTURE: fine protein filaments or tubes - Proteins organized in fine filaments (microfilaments) or slender tubes (microtubules); organizing center at the centrosome, a cytoplasmic region that contains a pair of centrioles. Centrosome – organizing center containing pair of centrioles. FUNCTION: – Strength and support – Intracellular movement of structures and materials - Strengthens and supports cell; aids in movement of cellular structures and materials.  BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) RIBOSOMES 3. PLASMA MEMBRANE STRUCTURE: RNA and proteins PLASMA MEMBRANE – Fixed: attached to endoplasmic reticulum – Selectively permeable membrane that controls: – Free: scattered in cytoplasm Entry of ions and nutrients FUNCTION: Protein synthesis. Elimination of wastes Release of secretions PEROXISOME STRUCTURE: Vesicles (membranous sacs) containing degradative enzymes. FUNCTION: Breakdown of organic compounds; neutralization of toxic compounds generated in the process. – Catabolism of fats/other organic compounds – Neutralization of toxic compounds ❑ PLASMA MEMBRANE COMPONENTS 1. GLYCOCALYX LYSOSOME - Superficial membrane carbohydrates STRUCTURE: Vesicles containing digestive enzymes. COMPONENTS OF COMPLEX MOLECULES FUNCTION: Breakdown of organic compounds and – Proteoglycans (carbohydrates with protein damaged organelles or pathogens. attached) – Removal of damaged organelles or pathogens – Glycoproteins (protein with carbohydrates attached) GOLGI APPARATUS – Glycolipids (lipids with carbohydrates attached) STRUCTURE: Stacks of flattened membranes FUNCTIONS (cisternae) containing chambers. – Cell recognition FUNCTION: Stores, alters, and packages synthesized – Binding to extracellular structures products. – Lubrication of cell surface MITOCHONDRION 2. INTEGRAL PROTEINS STRUCTURE: Double membrane, with inner Part of cell membrane membrane folds enclosing important metabolic Cannot be removed without damaging cell enzymes. Often span entire cell membrane FUNCTION: Produces 95% of the ATP required by the – Transmembrane proteins cell. Can transport water or solutes NUCLEUS 3. PERIPHERAL PROTEINS STRUCTURE: A fluid nucleoplasm containing enzymes, Attached to cell membrane surface proteins, DNA, and nucleotides; surrounded by a Removable double membrane, the nuclear envelope. Fewer than integral proteins FUNCTION: Controls metabolism; stores and Regulatory or enzymatic functions processes genetic information; controls protein synthesis. ❑ PLASMA MEMBRANE STRUCTURE – Thin (6–10 nm) and delicate ENDOPLASMIC RETICULUM (ER) Phospholipid bilayer - Mostly comprised of STRUCTURE: Network of membranous sheets and phospholipid molecules in two layers channels extending throughout the cytoplasm. – Hydrophilic heads at membrane surface FUNCTION: Synthesis of secretory products; – Hydrophobic tails on the inside intracellular storage and transport; detoxification of Isolates cytoplasm from extracellular fluid drugs or toxins. Smooth ER, which has no attached ribosomes, synthesizes lipids and carbohydrates. Rough ER, which has ribosomes bound to the membranes, modifies and packages newly synthesized proteins.  BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) Typically composed of actin ❑ PLASMA MEMBRANE FUNCTIONS Commonly at periphery of cell – Physical isolation Microvilli – Regulation of exchange with external environment – Finger-shaped extensions of cell membrane – Sensitivity to environment – Has core of microfilaments to stiffen and anchor – Structural support – Enhance surface area of cell for absorption – Lipid bilayer provides isolation Terminal web (layer inside plasma membrane in – Proteins perform most other functions cells forming a layer or lining) ❑ FUNCTIONAL CLASSES OF MEMBRANE PROTEINS 1. ANCHORING PROTEINS – attach the plasma membrane to other structures and stabilize its position. Inside the cell, membrane proteins are bound to the cytoskeleton. 2. INTERMEDIATE FILAMENTS 7–11 nm in diameter 2. RECOGNITION PROTEINS- are detected by cells of Strongest and most durable cytoskeletal elements the immune system. Enzymes in plasma membranes may be integral or peripheral proteins. 3. MICROTUBULES ~25 nm in diameter 3. RECEPTOR PROTEINS – bind to specific extracellular Largest components of cytoskeleton molecules called ligands. Built form the globular protein called tubulin. LIGANDS – can be anything from a small ion like Extend outward from centrosome (near nucleus) calcium, to a relatively large and complex hormone. 4. CARRIER PROTEINS- bind solutes and transport them across the plasma membrane 5. CHANNELS- are integral proteins containing central pore (channel) that forms a passageway completely across the plasma membrane. The channel permits the passage of water and small solutes that cannot CENTRIOLES otherwise cross the lipid layers of the plasma – Cylindrical structures membrane. – Composed of microtubules (9 groups of triplets) – Two in each centrosome CYTOSKELETON – Control movement of DNA strands during cell Cytoskeleton - provides an internal protein division framework that gives the cytoplasm strength and Cells without centrioles cannot divide flexibility – Red blood cells COMPONENTS OF THE CYTOSKELETON – Skeletal muscle cells 1. Microfilaments 2. Intermediate filaments 3. Microtubules CILIA – Long, slender plasma membrane extensions – Common in respiratory and reproductive tracts – Also composed of microtubules CYTOSKELETON (CELLULAR FRAMEWORK) Nine groups of pairs surrounding a central pair COMPONENTS – Anchored to cell surface with basal body 1. Microfilaments – Beat rhythmically to move fluids or secretions across 100,000 different proteins may be involved in regulating genetic activity. Coded in sequence of nucleotides Nucleoplasm also contains ions, enzymes, RNA and Determines cell structure/function DNA nucleotides, small amounts of RNA, and DNA. – Usually only one per cell Fluid contents of nucleus – Fine filaments (Nuclear matrix) Exceptions: – Ions – Multiple: skeletal muscle cell – Enzymes – None: mature red blood cells – RNA and DNA nucleotides The nucleus directs cellular responses to – Small amounts of RNA environmental (ECF) changes – DNA – Short-term adjustments Enzyme activity changes NUCLEOLI (noo-KLE-6-it singular, nucleolus)- are – Long-term adjustments transient nuclear organelles that synthesize ribosomal Changes in enzymes produced RNA. They also assemble the ribosomal subunits win Changes in cell structure from changes in structural enter the cytoplasm by carrier-mediated transport at proteins the nuclear pores. Nucleoli are composed of RNA. Often occur as part of growth, development, and enzymes, and proteins called histones. When the aging instructions for producing ribosomal proteins and RNA are being carried out, nucleoli form around the portions of DNA containing those instructions. Nucleoli is most prominent in cells that manufacture large amounts of proteins, such as Iver, nerve, and muscle cells. Transient, clear nuclear organelles Composed of: NUCLEAR STRUCTURE – rRNA Nuclear structures and functions – Enzymes – Nuclear envelope – Proteins (histones) Separates nucleus from cytoplasm Form around DNA instructions for forming Double membrane proteins/RNA Perinuclear space (peri-, around) - Space between Assemble RNA subunits layers Many found in large, protein-producing cells – Liver  BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) – Nerve – Muscle Transfer RNA (tRNA) – Contains triplets (anticodons) that bind to mRNA PERINUCLEAR SPACE- separates the two layers of the codons nuclear envelope. Each type carries a specific amino acid linked to form a polypeptide DNA – Instructions for protein synthesis – Strands coiled Wrap around histone molecules forming nucleosomes Loosely coiled (chromatin) in nondividing cells Tightly coiled (chromosomes) in dividing cells – To begin, two copies of each chromosome held together at centromere – 23 paired chromosomes in somatic (general body) cells » One each from mother/father – Carry instructions for proteins and RNA – Also some regulatory and unknown functions PROTEIN SYTHESIS DNA – Long parallel chains of nucleotides – Two adjacent DNA chains held by hydrogen bonds Four nitrogenous bases 1. Adenine (A) 2. Thymine (T) REPLICATION 3. Cytosine (C) TRANSCRIPTION 4. Guanine (G) Transcription (“to copy” or “rewrite”) – Genetic code (sequence of nucleotides) – Production of RNA from DNA template Triplet code (three nucleotides specify single amino – All three types of RNA are formed acid) – Example: mRNA (information for synthesizing proteins) A gene is the functional unit of heredity. It contains all STEPS OF TRANSCRIPTION the DNA nucleotides needed to produce specific 1. Gene activation proteins. The number of nucleotides in a gene Occurs at control segment (1st segment of gene) depends on the size of the polypeptide represented. A Template strand (One DNA strand used to synthesize short polypeptide chain might need fewer than 300 RNA) nucleotides, but the instructions for building a large protein might involve 3000 or more nucleotides. 2. RNA polymerase (enzyme) Functional unit of heredity Binds to promoter All the DNA nucleotides needed to produce a Assembles mRNA strand specific protein – Complementary to DNA Size varies (~300 3000 nucleotides) » Example: (DNA triplet TAC = mRNA AUG) – Hydrogen bonds between nucleotides GENE ACTIVATION – Removal of histones and DNA uncoiling 3. Transcription ends Messenger RNA (mRNA) Stop codon reached Assembled by enzymes mRNA detaches Connecting complementary RNA nucleotides Complementary DNA strands reassociate – (A, G, C, U) (hydrogen bonding between complementary base Contains information in triplets (codons) pairs) Leaves nucleus through pores  BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) – Other factors Immature RNA 2. Characteristics of membrane – Contains triplets not needed for protein synthesis – What lipids and proteins present – “Edited” before leaving nucleus through pores – How components are arranged Introns (removed nonsense regions) Exons (remaining coding segments) TYPES OF MEMBRANE TRANSPORT Creates shorter, functional mRNA 1. Passive (do not require ATP) Changing “edits” can produce mRNAs for different – Diffusion Proteins – Carrier-mediated transport 2. Active (require ATP) TRANSLATION – Vesicular transport Translation (translate nucleic acids to proteins) – Carrier-mediated transport – Uses mRNA created in nucleus Leaves via nuclear pores IMPERMEABLE (none can pass) – Occurs in cytoplasm » No living cell is impermeable – Produces a typical protein in ~20 seconds – mRNA can interact with other ribosomes and 5. HOW SUBSTANCES ENTER AND LEAVE THE CELL produce more proteins DIFFUSION – Multiple ribosomes can attach to a single mRNA Diffusion – Continuous random movement of ions or strand to quickly produce many proteins molecules in a liquid or gas resulting in even distribution STEPS OF TRANSLATION Gradient – Concentration difference or when 1. mRNA binds to small ribosomal subunit molecules are not evenly distributed Binding between mRNA and tRNA – At an even distribution, molecular motion continues – mRNA codons with tRNA anticodons but no net movement 2. Small and large ribosomal subunits assemble – Slow in air and water but important over small around mRNA strand distances Additional tRNAs arrive – More than 20 kinds In ECF » At least one for each amino acid – Water and solutes diffuse freely 3. Ribosome attaches to next complementary tRNA Across plasma membrane 4. Ribosome links amino acids forming dipeptide – Selectively restricted diffusion More tRNAs arrive and continue forming Movement across lipid portion of membrane polypeptide – Examples: lipids, lipid-soluble molecules, soluble 5. Stops once stop codon is reached on mRNA gases Ribosomal subunits detach Movement through membrane channel – Leaves intact mRNA and new polypeptide – Examples: water, small water-soluble molecules, ions MEMBRANE TRANSPORT Movement using carrier molecules Plasma membrane – Example: large molecules – Acts as a barrier separating cytosol and ECF – Must still coordinate cellular activity with Factors that influence diffusion rates: extracellular environment – Distance (inversely related) Permeability (determines which substances can – Molecule size (inversely related) cross membrane) – Temperature (directly related) – Gradient size (directly related) – Electrical forces FREELY PERMEABLE (any substances) Attraction of opposite charges (+,–) SELECTIVELY PERMEABLE (some substances cross) Repulsion of like charges (+,+ or –,–) Selective based on: 1. Characteristics of material to pass OSMOSIS – Size Osmosis (osmos, a push) – Electrical charge – Net diffusion of water across a membrane – Molecular shape – Maintains similar overall solute concentrations – Lipid solubility between the cytosol and extracellular fluid  BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) Osmotic flow- Movement of water driven by osmosis – Examples: Osmotic pressure - Indication of force of pure water » Ion pumps (Na+, K+ , Ca2+, and Mg2+) moving into a solution with higher solute » Sodium–potassium ATPase concentration Hydrostatic pressure – Fluid force – Can be estimate of osmotic pressure when applied to stop osmotic flow Osmolarity (osmotic concentration) – Total solute concentration in an aqueous solution Tonicity – Effect of osmotic solutions on cell volume Three effects 1. Isotonic (iso-, same + tonos, tension) \ – Solution that does not cause osmotic flow 3. Secondary active transport – Transport mechanism across membrane does not require ATP 2. Hypotonic – Causes osmotic flow into cell – Cell often needs ATP to maintain homeostasis – Example: hemolysis (hemo-, blood + lysis, loosening) associated with transport 3. Hypertonic – Causes osmotic flow out of cell – Example: crenation of RBCs VESICULAR TRANSPORT Vesicular transport – Materials move across cell Importance of tonicity vs. osmolarity: Example membrane in small membranous sacs – Administering large fluid volumes to patients with Sacs form at or fuse with plasma membrane blood loss or dehydration Two major types (both require ATP) Administered solution has same osmolarity 1. Endocytosis- (into cell using endosomes) as ICF but higher concentrations of individual a. Receptor-mediated endocytosis ions/molecules 1) Ligand binds to receptor – Diffusion of solutes may occur across cell 2) Plasma membrane folds around receptors bound to membrane ligands – Water will follow through osmosis 3) Coated vesicle forms – Cell volume increases 4) Vesicle fuses with lysosomes – Normal saline 5) Ligands freed and enter cytosol 0.9 percent or 0.9 g/dL of NaCl 6) Lysosome detaches from vesicle Isotonic with blood 7) Vesicle fuses with plasma membrane again CARRIER – MEDIATED TRNASPORT Carrier-mediated transport – Hydrophilic or large molecules transported across cell membrane by carrier proteins – Many move specific molecules through the plasma membrane in only one direction Cotransport (>1 substance same direction) b. Pinocytosis (“cell drinking”) Counter transport (2 substances in opposite » Formation of endosomes with ECF directions) » No receptor proteins involved – Carrier called exchange pump c. Phagocytosis (“cell eating”) Three types » Produces phagosomes containing solids 1. Facilitated diffusion » Phagocytes or macrophages perform phagocytosis – Requires no ATP (= passive) – Movement limited by number of available carrier 2. Exocytosis – Vesicle discharges materials into ECF proteins (= can become saturated) 6. CELL LIFE CYCLE 2. Active transport Cell division – Requires energy molecule or ATP (= active) – Production of daughter cells from single cell – Independent of concentration gradient  BEGONIA, ANA PAULENE P. BS BIOLOGY 4-A Human Anatomy and Physiology (CYTOLOGY) – Important in organism development and survival 2. Metaphase (meta, after) – Chromosomes align at – Cells have varying life spans and abilities to divide metaphase plate Often genetically controlled death occurs (apoptosis) 3. Anaphase (ana-, apart) – Chromatids separate » Two types Drawn along spindle apparatus 1. Mitosis (2 daughter cells, each with 46 4. Telophase (telo-, end) – Cells prepare to enter chromosomes) interphase – Pair of daughter cells half the size of parent cell – Cytoplasm constricts along metaphase plate (= Grow to size of original cell before dividing cleavage furrow) – Identical copies of chromosomes in each – Nuclear membranes re-form – Ends at complete cell separation (= – Chromosomes uncoil cytokinesis) – Followed by nondividing period (= Cytokinesis (cyto-, cell + kinesis, motion) interphase) – Begins with formation of cleavage furrow Cell performs normal activities OR – Continues through telophase Prepares to divide again – Completion marks end of cell division – Chromosomes duplicated – Associated proteins synthesized TUMORS AND CANCER Cancer – Illness that disrupts normal rates of cell 2. Meiosis (sex cells, each with only 23 chromosomes) division – Characterized by permanent DNA sequence changes Phases (= mutations) – G0 (performing normal cell functions) – Most common in tissues with actively dividing cells Examples: Examples: skin, intestinal lining – Skeletal muscle cells (stay in this phase forever) – Compete with normal cells for resources – Stem cells (never enter G0; divide repeatedly) – G1 (normal cell function plus growth and duplication TYPES OF CANCER of organelles) 1. Benign – Remain in original tissue – S (duplication of chromosomes) 2. Malignant – Accelerated growth due to blood – G2 (last minute protein synthesis and centriole vessel growth and supply to the area replication) – Invasion (cells migrating into surrounding tissues) DNA replication – Strands unwind – Metastasis (formation of secondary tumors) – DNA polymerase binds Assembles new DNA strand covalently linking nucleotides Works only in one direction – One polymerase works continuously along one strand toward “zipper” – One polymerase works away from “zipper” » As “unzipping” occurs, another polymerase binds closer point of unzipping » Two new DNA segments bound with ligases – Two identical DNA strands formed Mitosis – Division and duplication of cell’s nucleus – Phases 1. Prophase (pro-, before) – Paired chromosomes tightly coiled » Chromatid (each copy) » Connected at centromere with raised area (kinetochore) – Replicated centrioles move to poles » Astral rays (extend from centrioles) » Spindle fibers (interconnect centriole pairs)