Cells

Levels of Organization Cells produce tissues Tissues produce organs Organs produce organ systems Organs systems produce organisms Levels of Organization

3 Introduction The basic organizational structure of the human body is the cell. There are trillion cells in the human body. Differentiation is when cells specialize. As a result of differentiation, cells vary in size and shape due to their unique function. /film/1080/the-human-cell

4 3.2: A Composite Cell Also called a ‘typical’ cell Major parts include: Nucleus contains DNA Cytoplasm cellular contents between plasma membrane & nucleus Plasma membrane selective barrier Microtubules Flagellum Nuclear envelope Basal body Chromatin Ribosomes Cell membrane Mitochondrion Cilia Microtubules Microtubule Centrioles Microvilli Lysosomes Nucleolus Nucleus Phospholipid bilayer Smooth Endoplasmic reticulum Rough Endoplasmic reticulum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Golgi apparatus Secretory vesicles

5 Cell Membrane (aka Plasma Membrane) Outer limit of the cell Controls what moves in and out of the cell Selectively permeable Phospholipid bilayer Water-soluble “heads” form surfaces (hydrophilic) Water-insoluble “tails” form interior (hydrophobic) Permeable to lipid-soluble substances Cholesterol stabilizes the membrane Proteins: Receptors Pores, channels and carriers Enzymes Self-markers

6 Cell Membrane Cell membrane (b) (a) “Heads” of phospholipid “Tails” of phospholipid Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Biophoto Associates/Photo Researchers, Inc. Fibrous protein CarbohydrateGlycolipid Glycoprotein Extracellular side of membrane Cytoplasmic side of membrane Cholesterol molecules Globular protein Double layer of Phospholipid molecules Hydrophobic fatty acid “tail” Hydrophilic Phosphate “head” Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cell Membrane Electrochemical Gradient due to selective permeability difference in concentration of chemicals across membrane difference in distribution of charges across the membrane difference is the membrane potential Cell Membrane Electrochemical Gradient

Cell Membrane Boundary of the cell Made of a phospholipid bilayer Cell Membrane

Cell Organelles Organelle= “little organ” All the stuff in between the organelles is cytosol Everything in a cell except the nucleus is cytoplasm Cell Organelles

10 Cytoplasm Cytosol = water Organelles = solids Cytoplasm is really like a Jello fruit salad where the Jello is the cytosol and the fruits (oranges, grapes, bananas, maybe walnuts, etc.) are the organelles. Cytoplasm

11 Organelles Endoplasmic Reticulum (ER) Connected, membrane-bound sacs, canals, and vesicles Transport system Rough ER Studded with ribosomes Smooth ER Lipid synthesis Added to proteins arriving from rough ER Break down of drugs Ribosomes Free floating or connected to ER Provide structural support and enzyme activity to amino acids to form protein (protein synthesis) Membranes Ribosomes Membranes (b)(c) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organelles

Endoplasmic Reticulum A.k.a. “ER” Connected to nuclear membrane Highway of the cell Rough ER: studded with ribosomes; it makes proteins Smooth ER: no ribosomes; it makes lipids Endoplasmic Reticulum (ER)

Ribosome Site of protein synthesis Found attached to rough ER or floating free in cytosol Produced in a part of the nucleus called the nucleolus Remember where ribosomes are found in the cell and why? Ribosomes

14 Organelles Golgi apparatus Stack of flattened, membranous sacs Modifies, packages and delivers proteins Vesicles Membranous sacs Store substances Inner membrane Outer membrane Cristae (a)(b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Bill Longcore/Photo Researchers, Inc. Mitochondria Membranous sacs with inner partitions Generate energy Golgi Apparatus

Looks like a stack of plates Stores, modifies and packages proteins Molecules transported to and from the Golgi by means of vesicles Golgi Apparatus

16 Organelles Lysosomes Enzyme-containing sacs Digest worn out cell parts or unwanted substances Peroxisomes Enzyme-containing sacs Break down organic molecules Centrosome Two rod-like centrioles Used to produce cilia and flagella Distributes chromosomes during cell division (a)(b) Centriole (cross-section) Centriole (longitudinal section) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Don W. Fawcett/Visuals Unlimited Organelles

Lysosomes Garbage disposal of the cell Contain digestive enzymes that break down wastes Which organelles do lysosomes work with? Lysosomes hill.com/sites/ /student_view0/chapter2/animation__lysosomes.html

Mitochondria “Powerhouse of the cell” Cellular respiration occurs here to release energy for the cell to use Bound by a double membrane Has its own strand of DNA Mitochondria

19 Organelles Cilia Short hair-like projections Propel substances on cell surface Flagellum Long tail-like projection Provides motility to sperm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Oliver Meckes/Photo Researchers, Inc. © Colin Anderson/Brand X/CORBIS Organelles

20 Cell Nucleus Is the control center of the cell Nuclear membrane (envelope) Porous double membrane Separates nucleoplasm from cytoplasm Nucleolus Dense collection of RNA and proteins Site of ribosome production Chromatin Fibers of DNA and proteins Stores information for synthesis of proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Nucleolus Chromatin (a) Nuclear pores Nuclear envelope Cell Nucleus

21 3.3: Movements Into and Out of the Cell Passive (Physical) Processes Require no cellular energy and include: Simple diffusion Facilitated diffusion Osmosis Filtration Active (Physiological) Processes Require cellular energy and include: Active transport Endocytosis Exocytosis Transcytosis

22 Simple Diffusion Movement of substances from regions of higher concentration to regions of lower concentration Oxygen, carbon dioxide and lipid-soluble substances Time Solute molecule Water molecule ABAB (2)(3) Permeable membrane AB (1) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Simple Diffusion

23 Animation: How Diffusion Works 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 hill.com/sites/ /st udent_view0/chapter2/anim ation__how_diffusion_works.html

24 Facilitated Diffusion Diffusion across a membrane with the help of a channel or carrier molecule Glucose and amino acids Region of higher concentration Transported substance Region of lower concentration Protein carrier molecule Cell membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Facilitated Diffusion

25 Animation: How Facilitated Diffusion Works 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 hill.com/sites/ /student_v iew0/chapter2/animation__how_faci litated_diffusion_works.html

26 Osmosis and Osmotic Pressure Osmotic Pressure – ability of osmosis to generate enough pressure to move a volume of water Osmotic pressure increases as the concentration of nonpermeable solutes increases Isotonic – same osmotic pressure Hypertonic – higher osmotic pressure (water loss) Hypotonic – lower osmotic pressure (water gain) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © David M. Phillips/Visuals Unlimited (b) (a) (c) Osmosis and Osmotic Pressure hill.com/sites/ /student_view0/chapter2/animation__how_osmosis_works.html

27 Filtration Smaller molecules are forced through porous membranes Hydrostatic pressure important in the body Molecules leaving blood capillaries Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capillary wall Larger molecules Smaller molecules Blood pressure Blood flow Tissue fluid Filtration

28 Active Transport Carrier molecules transport substances across a membrane from regions of lower concentration to regions of higher concentration Sugars, amino acids, sodium ions, potassium ions, etc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carrier proteinBinding site (a) (b) Cell membrane Carrier protein with altered shape Phospholipid molecules Transported particle Cellular energy Region of higher concentration Region of lower concentration Active Transport

29 Active Transport: Sodium-Potassium Pump Active transport mechanism Creates balance by “pumping” three (3) sodium (Na+) OUT and two (2) potassium (K+) INTO the cell 3:2 ratio Active Transport – Sodium Potassium Na/K Pump

30 Animation: How the Sodium-Potassium Pump Works 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 hill.com/sites/ /student_view0/chapte r2/animation__how_the_sodium_potassium_pum p_works.html

31 Endocytosis Cell engulfs a substance by forming a vesicle around the substance Three types: Pinocytosis – substance is mostly water Phagocytosis – substance is a solid Receptor-mediated endocytosis – requires the substance to bind to a membrane-bound receptor NucleusNucleolus ParticleVesicle Phagocytized particle Cell membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endocytosis hill.com/sites/ /student_view0/chapter2/animation__phagocytosis.html

32 Endocytosis Cytoplasm Vesicle (a)(b)(c)(d) Receptor protein Cell membrane Molecules outside cell Cell membrane indenting Receptor-ligand combination NucleusNucleolus Particle Vesicle Phagocytized particle Cell membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endocytosis

33 Exocytosis Reverse of endocytosis Substances in a vesicle fuse with cell membrane Contents released outside the cell Release of neurotransmitters from nerve cells Nucleus Endoplasmic reticulum Golgi apparatus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Exocytosis