NUR 101 HB1 Lecture 2 - Cells & Tissues (PDF)

Cells Cells • The basic structural and functional units of all living organisms • Primary formed by carbon, oxygen, hydrogen, and nitrogen • All cells are created by cell division. After division, they differentiate into different cell types for their purpose • Classification by size, shape and fu...

Cells Cells • The basic structural and functional units of all living organisms • Primary formed by carbon, oxygen, hydrogen, and nitrogen • All cells are created by cell division. After division, they differentiate into different cell types for their purpose • Classification by size, shape and function • Each cell maintains homeostasis at the cellular level • 2 main types of cells in human body: • Sex Cells (Germ Cells) • Reproductive cells, reproduce by meiosis, e.g. Male sperm, Female oocyte • Somatic Cells • All body cells except sex cells, reproduce by mitosis (Shier, 2015) Cell Structure A General View of the Cell • A cell consists of 3 main parts: Plasma Membrane • A sturdy yet flexible outer surface • A selective barrier • Very important in cell communication Cytoplasm • Cytosol • Organelles Nucleus • Cell control center • Contain heredity information (Shier, 2015) Plasma Membrane • A semipermeable lipid bilayer found outside the cytoplasm of a cell and surround the inner contents. The membrane consists of • Phospholipids (~75-98%): The polar heads of the phospholipid are hydrophilic which are attracted to water; The non-polar tails of the phospholipid are hydrophobic which avoid water and line up in the center of the membrane • Glycolipids (~5%): Protect plasma membrane from injury; Enable immune system to recognize the host cell; Forms the basics of transfusion and transplant compatibility; Allow cells stick to other tissues; Enable sperm to recognize and bind to egg; Guides embryonic cells to their destination • Cholesterol (~20%): Holds the phospholipid together; Stiffen the membrane • Proteins (2%): Act as receptors; Involved in second messenger systems, Act as enzymes, carriers, channel proteins, cell marker, and cell adhesion molecules (Shier, 2015) Function of Plasma Membrane Isolation and Protection Selectively Permeability • Allow some substances to move into or out of the cell but restricts the passage of other substances • E.g. Permeable to water, most lipid soluble molecules • Not permeable to ions and charged/ polar molecules • A physical barrier that separate the inside of the cell from the surrounding extracellular fluid • Protect the cellular organelles Sensitivity to the environment and communication • Consists of receptors to allow the cell to recognize and respond to the environment • Receive chemical signals from other cells to activate or deactivate cellular activities Channels and Transporters • Pores to allow substances move in and out • Transporters (Carriers) change shape as they move a substance one side of the membrane to the other Structural Support Control materials entry and exit the cell • Entry of ions and nutrients • Elimination of waste • Release of secretions Membrane Transport Active Transport • 01 Passive Transport Passive Transport • A simple process that no energy is required for molecules movement • Substances move across the membrane down their concentration or electrical gradient, E.g. • Simple diffusion • Facilitated diffusion • Osmosis The movement of ions or molecules from a region of low concentration to a region of high concentration • Occurs against the concentration gradient • Require energy- ATP for transportation • Active transport • Vesicular transport • Action Potential Active Transport 02 (Shier, 2015) Passive TransportSimple Diffusion (Martini, 2015) • Molecules movement from a region of high concentration to low concentration region, down the concentration gradient • Membrane may not be needed • Factors like increased temperature, light and small particles, increase in membrane surface area, steeper the concentration gradient speed up the diffusion rate (Martini, 2015) Diffusion Across the Plasma Membrane • In the body, diffusion occurs across the lipid bilayer, e.g. • Exchange of O2 and CO2 between blood and cells, between blood and air within lungs • Absorption of lipid-soluble molecules • Release waste from body cells • Diffusion occurs through pores of channels, e.g. • Ion channels • “Gated” channels- moving in one direction to open, and in another direction to close (Martini, 2015) Passive TransportOsmosis • Diffusion of Water • Net movement of water through a selectively permeable membrane, from an area of higher water concentration to an area of lower water concentration • Occurs when a membrane is permeable to water, but is permeable to certain solutes (Martini, 2015) Osmolarity and Tonicity • Osmolarity of body fluids is ~300mOsm/L • Tonicity- the ability of a solution to affect the fluid volume or pressure in a cell • Water moves in and out of a cell depends on whether the cell’s environment is isotonic, hypotonic or hypertonic Hypertonic Isotonic • In a hypertonic solution, the concentration of • When two environments are isotonic, the solute particles is greater than the concentration of solutes is same in both of them concentration in a cell • Water comes in and out during cell • Water comes out from the cell to the solution • No net gain or net loss of water from cell Hypotonic • In a hypotonic solution, the concentration of solute is less than that of a cell • Water comes into the cell You can simply impress your audience and add a unique zing and appeal to your Presentations. 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(Martini, 2015) Passive TransportFacilitated Diffusion • Substances that cannot diffuse through the lipid bilayer or ion channels • Transport assisted by carrier protein- Specific transporter for the specific substance • Substance binds to specific transporter on one side of the membrane, then released on the other side after the transporter undergoes a change in shape • Not require energy • E.g Transport of glucose into the cells Active Transport Primary Active Transport • Movement of molecules from a low concentration area to a high concentration area with the help of an Ionic Pump which uses ATP to provide energy to move the ions against the concentration gradient • Energy is required • E.g. Na+, K+, Ca2+, amino acids, monosaccharides (Martini, 2015) Secondary Active Transport (Martini, 2015) • Require energy indirectly • Carrier protein can move another substance at the same time as with facilitated diffusion, without regard to its concentration gradient • Another substance gets a “free ride” • E.g Sodium-glucose transporters • The transporter does not need energy • Need the energy to pump out the sodium in the Na+-K+ pump Endocytosis • Materials move into a cell in a vesicle formed from the plasma membrane • Require ATP • Three types of endocytosis• Pinocytosis • Phagocytosis • Receptor-mediated endocytosis Vesicular Transport You can simply impress your audience and add a unique zing and appeal to your Presentations. Easy to change colors, photos and Text. Get a modern PowerPoint Presentation that is beautifully designed. You can simply impress your audience and add a unique zing and appeal to your Presentations. Easy to change colors, photos and Text. 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Exocytosis • Materials move out of a cell by the fusion with the plasma membrane of vesicular inside the cell • All cells carry out exocytosis, especially important in• Secretory cells that secrete digestive enzymes, hormones, mucus or other secretions • Nerve cells that release neurotransmitters Pinocytosis (Cell drinking) • Tiny droplets of extracellular fluid are taken up Vesicle TransportEndocytosis Receptor- mediated Endocytosis • A more selective form of phagocytosis or pinocytosis • Minimum unnecessary matter is taken Phagocytosis (Cell eating) • The cell engulf large solid molecules like bacteria, dust • Vesicle is call phagosome (Martini, 2015) Cytoplasm • Consists of all cellular contents between the plasma membrane and the nucleus • 2 components included• Cytosol (Intracellular fluid) • Site of many chemical reactions • Organelles (Tiny structures that perform different functions in the cell) Organelles Organelles with Membrane • • • • • Endoplasmic reticulum Golgi apparatus Mitochondria Lysosomes Peroxisomes Non-membranous Organelles • • • • • (Martini, 2015) Centrosome & Centrioles Cytoskeleton Cilia & Flagella Microvilli Ribosome Endoplasmic Reticulum (ER) • System of interconnected channels • Extends from the nuclear membrane throughout the cytoplasm, more than half of membrane surface within the cytoplasm of the cell • 2 forms of endoplasmic reticulum (ER): Rough ER • Covered with ribosomes • Functions: • Involved in protein synthesisattach sugar groups to proteins • Proteins are bound in vesicles for transport to Golgi apparatus • External face synthesize phospholipids Smooth ER • No ribosomes • Functions: • Involved in the synthesis of fatty acid and steroid • Detoxification of drugs/ toxic • Calcium storage (Shier, 2015) Mitochondria • Rod-like organelle surrounded by a double membrane • The powerhouse of a cell • Generate ATP to provide energy through aerobic respiration • A cell may have thousands of mitochondria, depending on its activity (Shier, 2015) Golgi Apparatus/ Complex • Small flattened membrane and associate vesicles close to the nucleus • Cupcake shape • Functions: • Synthesis carbohydrates • Package, modifies, and segregates proteins for secretion from the cell, inclusion of lysosomes, and incorporation into the plasma membrane (Shier, 2015) Lysosome & Peroxisomes Lysosome • Membrane-enclosed vesicles • Form from the Golgi apparatus • Contain digestive and hydrolytic enzymes • Break down a wide variety of molecules • Help recycle worn-out cell structures • Removal of pathogens Peroxisomes/ Microbodies • Structurally similar to lysosomes but smaller • Contain oxidases- enzyme that can break down fats and other organic compounds • Neutralize toxic compound • Abundant in liver and kidney • In mitochondria, peroxisomes decompose fatty acids to generate energy for ATP synthesis (Martini, 2015) Centrosome • Consists of 2 hollow cylinders called centrioles • Located near the Golgi apparatus and nucleus • Contain a pair of centrioles at right angle • Form mitotic spindle- essential for the movement of chromosomes during the cell division • Form the basal bodies found at the base of cilia and flagella Centrosome & Centrioles (Shier, 2015) Microvilli, Cilia & Flagella Flagella • Similar structure with cilia but much longer • Generate forward motion of the entire cell (e.g.sperm) (Martini, 2015) (Martini, 2015) (Shier, 2015) Cytoskeleton • A network of protein filaments that extends throughout the cytosol • Support the cell shape • Organize the contents in cell • Direct movements within the cell • Contribute movement of cell • Consist of 3 structures: Microtubules Microfilaments • Assist movement • Provide support Intermediate filaments • • Assist in stabilize organelles position Help attach cells to others • Determine cell shapes • Help the organelles movement (Shier, 2015) Ribosomes • Free or attached to rough ER • High content of ribosomal RNA (rRNA) • Some are free in the cytosol, some located within the mitochondria • Contain of 2 tRNA binding sites • Function: • Site of protein synthesis (Shier, 2015) Nucleus (Shier, 2015) • Large organelle and most prominent feature of a cell • Most cells have a single nucleus except mature red blood cells (no cell nuclei) and skeletal muscle cells (with multiple nuclei) • Contain fluid nucleoplasm, nucleoli, and chromatin • Functions: • Control center of a cell • Storage and processing of genetic information, provide instructions for protein synthesis • Nuclear envelope: separate the nucleoplasm from the cytoplasm and regulates the passage of substances to and from the nucleus • Chromatin: DNA constitutes the genes DNA, Chromatin, Chromosome & Chromatid • • • • • • Chromatin is a complex of macromolecules composed of DNA, RNA, and protein, which is found inside the nucleus of eukaryotic cells The primary protein components of chromatin are histones that help to organize DNA into “bead-like” structures called nucleosomes by providing a base on which the DNA can be wrapped around The nucleosome can be further folded to produce the chromatin fiber Chromatin fibers are coiled and condensed to form chromosomes when cell is preparing for division Chromatin makes it possible for a number of cell processes to occur including DNA replication, transcription, and cell division Chromatid is one half of a duplicated chromosome (Shier, 2015) Section Break TOILET TIME Cellular Metabolism Cellular Respiration Protein Synthesis; Package, Processing & Secretion Cell Cycle & Cell Division • Cellular respiration is a series of chemical reaction process that take place within a cell for generation of energy, usually in the form of ATP, from dietary proteins, fats, and carbohydrates • 3 main processes arei. Glycolysis ii. The Citric Acid Cycle (Krebs Cycle) iii. Oxidative phosphorylation/ Electron transport chain • Glycolysis start in cytosol and the others occurs in the mitochondria Cellular Respiration Cellular Respiration 1. Glycolysis (Anaerobic pathway) • Glycolysis breaks down 6-carbon glucose molecule producing two 3-carbon pyruvic acid molecules and a net gain of 2 ATP molecules that the body uses as cellular energy • Each 3-carbon pyruvic acid molecules enters the mitochondria to start the Citric Acid Cycle 2. The Citric Acid Cycle (Aerobic pathway) • 2 more ATP are created and carbon dioxide is released as a waste product 3. The Oxidative Phosphorylation • Involves the electron transport chain and chemiosmosis in the inner mitochondrial membrane. • Most ATP molecules are created • 3 steps of cellular respiration can produce up to 38 ATP molecules (Shier, 2015) Nucleic Acid, DNA & RNA • Nucleic acid- huge molecule contain carbon, hydrogen, oxygen, nitrogen, and phosphorus • Monomers is nucleotides made with pentose sugar-deoxyribose & ribose, phosphate group and nitrogen bases (Adenine, Guanine, Thymine, Cytosine, Uracil) • 2 types of nucleic acid• DNA- Deoxyribose Nucleic Acid • Long double helix chain of nucleotides • Consists of deoxyribose and bases (A,T,G,C) • Complementary base pairing- A with T, G with C • Forms the inherited genetic material inside each human cell • Gene- a segment of a DNA molecule • RNA- Ribose Nucleic Acid • Single strain of nucleotides • Consists of ribose and bases (A,U,G,C) • Relays instructions from the genes to transcript amino acids (Martini, 2015) Types of RNA Amino acid Anticodon Messenger RNA (mRNA) 01 • • • Formed in nucleus Rewrite the sequences of bases in a section of DNA during transcription Serve as template for the protein synthesis 02 Ribosomal RNA (rRNA) • Involved in the synthesis of peptides in the ribosomes 03 06 Transfer RNA (tRNA) • • • • 05 Found in the cytoplasm Carries anticodon Transfer specific amino acids to ribosomes Ensure the alignment of these amino acids in the proper sequence prior to the peptide bond formation