Cellular Form and Function Concepts of cellular structure Cell surface Membrane transport Cytoplasm Modern Cell Theory All living organisms are composed of cells. the simplest structural and functional unit of life. cells are alive An organism s structure and functions are due to the activities of its cells. Cells come only from preexisting cells i.e., all life traces its ancestry to the same original cells Cells of all species have many fundamental similarities in chemical composition and metabolic mechanisms. 3-1 3-2 Cell Shapes, Size, Cell Surface Area, and Volume Generalized Cell Structures 20 m Growth 20 m 10 m 10 m Large cell Diameter = 20 mm Surface area = 20 mm 20 mm 6 = 2,400 mm 2 Volume = 20 mm 20 mm 20 mm = 8,000 mm 3 Three principle parts of a cell 1. Plasma = cell 2. Cytoplasm = everything between the and the nucleus - cytosol = intracellular fluid - organelles = structures with specific functions 3. Nucleus = genetic material of cell Small cell Diameter = 10 mm Surface area = 10 mm 10 mm 6 = 600 mm 2 Volume = 10 mm 10 mm 10 mm = 1,000 mm 3 Effect of cell growth: Diameter (D) increased by a factor of 2 Surface area increased by a factor of 4 (= D 2 ) Volume increased by a factor of 8 (= D 3 ) 3-3 2.-4 Plasma Membrane Extracellular face of Peripheral Glycolipid Extracellular fluid Glyco Phospholipid bilayer Carbohydrate chains Fluid mosaic model 1. Phospholipid bilayer - hydrophillic heads (phosphate heads) - hydrophobic tails (lipid tails) 2. Proteins Peripheral Trans Channel Intracellular fluid Cholesterol Proteins of cytoskeleton Intracellular face of Not all cells contain all of these organelles. 2.-5 1
Membrane Protein Functions 1. Transport s 2. Receptor Proteins 3. Recognition Proteins Chemical Breakdown messenger products Ions CAM of another cell Receptor - Second Messenger System A messenger binds to a receptor 1 First messenger Receptor Adenylate cyclase G G P i 2 Receptor releases ATP P i G, G 3 binds to an enzyme, adenylate cyclase - converts ATP to cyclic AMP (camp), the camp second messenger. (second messenger) Inactive kinase 4 camp activates a cytoplasmic enzyme called a kinase. Activated kinase Inactive enzymes P i 5 Kinases add phosphate groups (P i) to other enzymes. This activates some enzymes or deactivates others, leading to varied metabolic effects in the cell. 3-7 Activated enzymes Various metabolic effects 3-8 Cell Surface Glycos and Glycolipids unique in everyone Functions protection - cell adhesion immunity to infection - fertilization defense against cancer transplant compatibility Cell surface - Cilia Cilia respiratory tract, uterine tubes, ventricles of the brain, efferent ductules of testes Flagella Cilia and flagella composed of Microfilaments. Mucus Saline layer Epithelial cells 1 2 3 4 5 6 7 3-9 (a) Power stroke Recovery stroke (b) Figure 3.12a Figure 3.12b 3-10 The Selective Permeable Membrane!! Permeable to some molecules but not all Diffusion and Osmosis s act as specific channels for some particles Protein carriers How things get in the cell Diffusion- - Dye placed in water Molecules move from a high concentration to region of lower conc. Equilibrium reached in the far right cylinder Vesicles can transport in and out 2.-11 2.-12 2
Diffusion Rates Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. Factors affecting diffusion rate through a temperature molecular weight - larger molecules move slower steepness of concentrated gradient surface area permeability - 3-14 Osmosis Movement of water through a selectively permeable from an area of high water conc. to area of lower water conc. Osmosis: The movement of water across a semi-permeable Water moves through the phospholipid bilayer Trans s can function as water channels (Aquaporins) 2.-15 2.-16 Attraction of water to solute particles forms hydration spheres Aquaporins - channel s specialized for passage of water Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 2.-17 3
Tonicity Tonicity - ability of a solution to affect fluid volume and pressure in a cell depends on concentration and permeability of solute Hypotonic solution has a lower concentration of solutes than intracellular fluid (ICF) high water concentration Cells lyse Hypertonic solution has a higher concentration of solutes low water concentration Cells crenate Isotonic solution concentrations in cell and ICF equal no changes in cell volume or shape 3-19 Effects of Tonicity on RBCs (a) Hypotonic (b) Isotonic (c) Hypertonic 3-20 1. Simple diffusion 2. Diffusion through a channel 3. Carrier Mediated Transport uses a transporter. Diffusion Through Membrane Channels Filtration and osmosis Each channel specific for ions (e.g., K+, Na+, or Ca+2) Channels may be open or gated 2.-21 2.-22 Facilitated Transport: Glucose example Glucose binds to transport Transport changes shape Glucose moves down the concentration gradient Transport Across the Plasma Membrane - So far - 2.-23 2.-24 4
Movement of stuff against its concentration gradient Requires energy from ATP Enables movement into cell against a concentration gradient Active Transport Transport Vesicles (another way of getting things in and out) Vesicles are round sacs of that surround stuff (Requires ATP) Endocytosis = vesicles bringing something into cell Exocytosis = vesicles release something from cell Endocytosis: 1)receptor-mediated endocytosis 2)Phagocytosis 3)Pinocytosis droplets of extracellular fluid 2.-25 2.-26 Plants, fungi, & many bacteria Plasma occurs inside a cell wall - tough durable provides support - movement of molecules in and out can occur - controlled by plasma 2. Cytoplasm = everything between and nucleus 1. cytosol = intracellular fluid 2. organelles = special structures with specific functions 3-27 2.-28 1. Cytosol = Intracellular fluid 2. Cell Organelles 55% of cell volume 75-90% water organic molecules (carbs, lipids, sugars, s, enzymes), ATP, waste products, and ions Dissolved (solutes) Site of many important chemical reactions 2.-29 Some organelles lack s others are surrounded by one or two phospho-lipid bilayer s 2.-30 5
Ribosomes Protein Makers Centrioles Found near nucleus Important site during mitosis Microtrubule formation! Sites where is made!!!!!!!!!!!!!! Tiny packages of ribosomal RNA (rrna) synthesize s (plasma & for export) 1. Free ribosomes are loose in cytosol synthesize s used inside the cell 2. On Surface of Endoplasmic Reticulum (mitochondria, synthesize mitochondrial s) 2.-31 2.-32 Endoplasmic Reticulum Network of s forming flattened sacs (Cisterns) 2 types: Rough ER continuous with nuclear envelope & covered with ribosomes synthesizes, processes & packages s for export Smooth ER -- no attached ribosomes synthesizes phospholipids, steroids and fats detoxifies harmful substances (alcohol) 2.-33 2.-34 Golgi Apparatus Packaging by Golgi Complex Flattened curved membranous sacs (cisterns) Modify, sort, packages s produced by rough ER 2.-35 2.-36 6
Lysosomes Membranous vesicles formed in Golgi Complex digestive enzymes Functions digest foreign substances autophagy recycle own organelles Mitochondria Double bound organelle Function generation of ATP!!!!!!! (Adenosine triphosphate) Cellular respiration Can self-replicate 2.-37 2.-38 Other structures in cytoplasm: Cytoskeleton Network of filaments throughout the cytosol Functions: support and shape organization of cell contents cell & organelle movement The Cytoskeletonal Filaments 1. Microfilaments 2. Intermediate filaments 3. Microtubules 2.-39 Fig 2.6 2.-40 Other structures in cytoplasm Vacuoles: Fluid filled sacs Water regulation and support Nucleolus Chloroplasts: site of photosynthesis - 3. Nucleus Function: Directs all cell activities Double (aka: nuclear envelope) Contains our genetic stuff: chromosomes (DNA) Nucleolus: where ribosomes are produced 2.-41 2.-42 7