General Zoology 1 (Anatomy & Physiology of Cells) PDF

General Zoology 1 Porf. Dr. Eman Abbas Moussa Lecturer (1) ahmad ata 1 Anatomy & physiology of cells 2 INTRODUCTION ◼ The cell is the basic unit of structure and function in living things. Cells vary in their s...

General Zoology 1 Porf. Dr. Eman Abbas Moussa Lecturer (1) ahmad ata 1 Anatomy & physiology of cells 2 INTRODUCTION ◼ The cell is the basic unit of structure and function in living things. Cells vary in their shape size, and arrangements but all cells have similar components, each with a particular function. ◼ Some of the 100 trillion of cells make up human body. ◼ All human cell are microscopic in size, shape and function. ◼ The diameter range from 7.5 micrometer (RBC) to 150 mm (ovum). 3  Objectives 1. label the components, name a term that describes the cell. 2. Distinguish between passive and active transport processes. 3. Define the terms diffusion, osmosis, filtration and facilitated diffusion, and give an example of each. 4. Define the terms active transport, endocytosis, and exocytosis. 5. List a function(s) for each cellular component and/or organelle. 6. Describe ahmad ata the structure of each cellular organelle. 4 Introduction - Cell is defined as the fundamental living unit of any organism. - Cell is important to produce energy for metabolism (all chemical reactions within a cell) - Cell can mutate (change genetically) as a result of accidental changes in its genetic material (DNA). - Cytology: the study of the structure and functions of cells. 5 ahmad ata 6 Cell structure 1) THE CELL (PLASMA) MEMBRANE ◼ The cell membrane is a thin, dynamic membrane that encloses the cell and controls what enters and leaves the cell. ◼ Fluid Mosaic Model composed of a double layer (bilayer) of phospholipid molecules with many protein molecules dispersed within it; 7 Fluid Mosaic Model a.The surfaces of the membrane are "hydrophilic" due to the polar phosphate heads; b. The internal portion of the membrane is "hydrophobic" due to the non-polar fatty acid tails; c. The membrane proteins also have both hydrophilic and hydrophobic 8 ahmad ata 9 PLASMA MEMBRANE ahmad ata 10 PLASMA MEMBRANE hydrophillic phosphate he hydrophobic fatty acid ta Chemical attractions are th forces that hold membranes together ahmad ata 11 Function of plasma membrane ◼ Serves as boundary of the cell. ◼ Serve as markers that identify the cells. ◼ Play significant role in transportation. ◼ Cell recognition proteins-allow cell to recognize other cells. 12 Membrane proteins – Some membrane proteins have carbohydrates attached to them, forming glycoproteins that act as identification markers – Some membrane proteins are receptors that react to specific chemicals, sometimes permitting a process called signal transduction 13 Cytoplasm ◼ Is a gel-like matrix of water, enzymes, nutrients, wastes, and gases and contains cell structures (organelles). ◼ Fluid around the organelles called cytosol. ◼ Most of the cells metabolic reactions occur in the cytoplasm. 14 2) Endoplasmic reticulum ◼ network of interconnected parallel membranes (maze), that is continuous with the nuclear membrane; 2. Two types: a. Rough Endoplasmic Reticulum (RER) 1. ER studded with ribosomes; 2. Function = protein synthesis and intraceluar transportation of molecules ; b. Smooth Endoplasmic Reticulum (SER) lacks ribosomes; 1. Function = lipid & cholesterol synthesis and Stores calcium. 15  Rough Endoplasmic Reticulum (RER) ahmad ata 16  3) Ribosomes ◼ Every cell contains thousand of ribosome's and many of them attached to the RER. ◼ Each ribosome is nonmembranous structure, made of two pieces large unit and small unit and each subunit composed of rRNA. ◼ Function: protein synthesis ◼ Protein released from the ER are not mature, need further processing in Golgi complex before they are able to perform their function within or outside the cell. ahmad ata 17 ahmad ata 19  3) Golgi Apparatus 1. flattened membranous sacs (cisternae). 2. arranged in stacks ("stack of pancakes") associated with many vesicles (membrane bound sacs containing proteins); 2. Function = modification, packaging, and transport of proteins; 3. Encloses digestive enyzymes into membranes to form lysosomes. ahmad ata 20  4) Lysosomes 1. spherical membranous sacs containing digestive enzymes; 2. "suicide sacs" which destroy anything the cell no longer wants or needs. 3. Autolysis is the process by which worn cell parts are digested by autophagy. 21 ahmad ata 22 ahmad ata 23  Phagocytosis Dr.Eman A. Moussa (KFU) Peroxisomes: ◼ 1. membranous sacs containing oxidase enzymes; ◼ 2. Function = detoxification of harmful or toxic substances (i.e. alcohol, formaldehyde, oxygen free radicals); ◼ H2O2 (peroxide) ----> water 26 Mitochondria ◼ 1. kidney-shaped organelle whose inner membrane is folded into shelf-like partitions called cristae; ◼ 2. "Powerhouse" of the cell = site of cellular respiration where energy is released from glucose. 27  NUCLEUS the central core, control center or "brain" of the cell. 1. the largest organelle of the cell; 2. filled with nucleoplasm; ◼ Nuclear Membrane (or nuclear envelope) is a double membrane that separates the contents of the nucleus from the cytoplasm; ◼ At various point, these two membranes fuse = nuclear pore. ◼ The nuclear membrane is "selectively permeable"; pores serve as sites where mRNA can pass out of the nucleus during protein synthesis, and how ribosomes exit the nucleus. 28 Nucleoli ◼ Nucleolus (s) = a spherical body within the nucleus; ◼ composed of RNA and proteins; ◼ Function = synthesis of ribosomes. 29 Cytoskeleton : ◼ The cytoskeleton – Is a network of fibers extending throughout the cytoplasm – Fibers appear to support the endoplasmic reticulum, mitochondria, and “free” ribosomes Microtubule ahmad ata 30 The cytoskeleton – Gives mechanical support to the cell – Is involved in cell motility, which utilizes motor proteins – Rodlike pieces that provide support and allow movement and mechanisms that can move the cell or its parts 31 ahmad ata 32 ahmad ata 33  Components of cytoskeleton: 1) Microfilaments ◼ Solid rods of globular proteins. ◼ Important component of cytoskeleton which offers support to cell structure. ◼ Microfilaments can slide past each other, causing shortening of the cell ahmad ata 34  Components of cytoskeleton: 2) Intermediate filaments – Intermediate filaments are twisted protein strands slightly thicker than microfilaments; they form much of the supporting framework in many types of cells 35  Components of cytoskeleton: 3) Microtubules ◼ Microtubules – Shape the cell – Guide movement of organelles (their function is to move things around in the cell) – Help separate the chromosome copies in dividing cells 36  Components of cytoskeleton: 4) Microtubules ◼ Centrosomes and Centrioles ◼ The centrosome – An area of the cytoplasm near the nucleus that coordinates the building and breaking of microtubules in the cell – Its considered to be a “microtubule-organizing center” – Plays an important role during cell division – Contains a pair of centrioles 37 Components of cytoskeleton: Centrioles ◼ Self-replicating ◼ Made of bundles of microtubules. ◼ Help in organizing cell division. ahmad ata 38 Centriole ahmad ata 40 ahmad ata 41 ahmad ata 42  Cell Membrane Surface Modifications 1. Cilia / Cilium a. short, hair-like cellular extensions (eyelashes); b. help move substances through passageways; c. located in lining of respiratory tract & fallopian tube. 2. Flagella a. tail-like projection; b. only one per cell in humans; c. aids in cell locomotion; d. sperm cell. 3. Microvilli: a. small finger-like extensions of the external surface of the cell membrane; b. Function ahmad ata = to increase surface area. 43 c. located in the lining of the digestive tract. Membrane Junctions ◼ Tight junction – impermeable junction that encircles the cell & prevents leakage – Blood brain barrier - Skin ◼ Desmosome – anchoring junction scattered along the sides of cells. Prevents tissues from fraying Stomach, uterus , bladder ◼ Gap junction – allows chemical substances to pass between cells ◼ Heart 44  Desmosome Tight Junction ahmad ata 45  Gap Junction ahmad ata 46 ahmad ata 47 ahmad ata 48 ahmad ata 49 Transport Across the Plasma Membrane – 2 types – Passive transport – Active Transport require no ATP( energy) Substances move High to low conc. Examples include ◼ Simple diffusion ◼ Osmosis ◼ facilitated diffusion ◼ filtration 50  Simple diffusion ◼ random mixing of particles in solution ◼ substances move down concentration gradient- ◼ particles eventually become evenly distributed - Equilibrium reached 51 Simple diffusion ahmad ata 52 Facilitated Diffusion ◼ Diffusion Through channel proteins or transport proteins ◼ allow passage of – small inorganic ions – Na+ , K+, Ca+2 – Glucose, water soluble vitamins(B,C) generally slower than diffusion across lipid portion ◼ Depends upon the number of transporters available 53 Diffusion Through the Plasma Membrane ahmad ata 54 Osmosis ◼ passive process ◼ diffusion of water across a selectively permeable membrane ◼ from Hi. Conc. of WATER ( low solute) to lower concentration of WATER( Hi. solute) 55 Membrane Permeability on Diffusion and Osmosis ahmad ata 56 Tonicity Describes how a solution affects cell volume ◼ hypertonic – solution with more solutes – Blood cells shrink and crenate ◼ hypotonic – solution with less solutes – Blood cells swell up and hemolyse ◼ isotonic – both solutions have similar concentrations of solutes. – Cell size is unchanged 57 ahmad ata 58  Water Balance of Cells ◼ Tonicity – Is the ability of a solution to cause a cell to gain or lose water – Has a great impact on cells without walls ◼ If a solution is isotonic – The concentration of solutes is the same as it is inside the cell – There will be no net movement of water ◼If a solution is hypertonic – The concentration of solutes is greater than it is inside the cell – The cell will lose water ◼If a solution is hypotonic – The concentration of solutes is less than it is inside the cell – The cell will gain water  ◼ Animals and other organisms without rigid cell walls living in hypertonic or hypotonic environments – Must have special adaptations for osmoregulation Hypotonic solution Isotonic solution Hypertonic solution (a) Animal cell. An animal cell fares best in an isotonic environ- H2O H2O H2O H2O ment unless it has special adaptations to H2O offset the osmotic uptake or loss of water. Lysed Normal Shrinkage ◼ Active transport - movement of a substance from a lower concentration to a higher concentration using a carrier and energy ◼ Endocytosis - brings substances into the cells 64 ◼ solutes moving against concentration gradient-Uses carrier proteins – can be driven by ATP use or via energy stored in ionic concentration Types : – active transport 1. Endocytosis 2. Exocytosis 65 Transport in Vesicles- Endocytosis ◼A form of active transport. ◼ Transport of large particles across the plasma membrane ◼ Types : 1.Phagocytosis 2.Pinocytosis 66  Phagocytosis ◼ only a few body cells are capable ◼ Ex. WBC (macrophages , neutrophils) ◼ particle binds to plasma membrane ◼ pseudopods extend and surround particle forming phagosome ◼ phagosome fuses with lysosomes which destroy invader 67 Phagocytosis ahmad ata 68  Pinocytosis ◼ Also called cellular drinking ◼ most body cells carry out process – especially absorptive cells in intestines and kidneys ◼ tiny droplets of extracellular fluid taken into cell ◼ lysosomes fuse and degrade particles into smaller useable particles 69 Pinocytosis ahmad ata 70 Exocytosis ◼ releases materials form a cell ◼ all cells carry out process ◼ Ex. i. secretory cells ◼ release digestive enzymes, hormones, mucus, or other secretions – Ii. nerve cells ◼ release neurotransmitters ◼ vesicles fuse with plasma membrane and release contents into extracellular fluid 71 Exocytosis ◼ vesicle fuses with the plasma membrane and then ruptures; used in hormone and neurotransmitter release ahmad ata 72 Exocytosis - ahmad ata 73  Facilitated Diffusion: Passive Transport Aided by Proteins ◼In facilitated diffusion – Transport proteins speed the movement of molecules across the plasma membrane  ◼ Channel proteins – Provide corridors that allow a specific molecule or ion to cross the membrane EXTRACELLULAR FLUID Channel protein Solute CYTOPLASM (a) A channel protein (purple) has a channel through which water molecules or a specific solute can pass.  ◼ Carrier proteins – Undergo a subtle (little) change in shape that translocates the solute-binding site across the membrane Solute Carrier protein (b) A carrier protein alternates between two conformations, moving a solute across the membrane as the shape of the protein changes. The protein can transport the solute in either direction, with the net movement being down the concentration gradient of the solute. ◼ Active transport uses energy to move solutes against their gradients  The Need for Energy in Active Transport ◼ Active transport – Moves substances against their concentration gradient – Requires energy, usually in the form of ATP  ◼ Review: Passive and active transport compared Active transport. Some transport Passive transport. Substances diffuse spontaneously down their proteins act as pumps, moving concentration gradients, crossing a membrane with no substances across a membrane against use of energy by the cell. The rate of diffusion can be their concentration gradients. Energy greatly increased by transport proteins in the for this work is usually supplied by membrane. ATP. ATP Diffusion. Hydrophobic molecules Facilitated diffusion. Many hydrophilic and (at a slow rate) very small substances diffuse through membranes with uncharged polar molecules can diffuse the assistance of transport proteins, either through the lipid bilayer. channel or carrier proteins.  Exocytosis ◼ In exocytosis – Transport vesicles migrate to the plasma membrane, fuse with it, and release their contents  Endocytosis ◼ In endocytosis – The cell takes in macromolecules by forming new vesicles from the plasma membrane 82