Ch03_Cell Structure and Function- Part I.pdf

Cell structure and Function (Part I) Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023 Cell Structure and Function Learning Outcomes: Explain how the surface-area-to-volume ratio limits cell size. Summa...

Cell structure and Function (Part I) Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023 Cell Structure and Function Learning Outcomes: Explain how the surface-area-to-volume ratio limits cell size. Summarize the role of microscopy in the study of cells. Distinguish between the structure of a prokaryotic cell and that of a eukaryotic cell. Identify the roles of the plasma membrane and the organelles of a cell. Distinguish between the processes of diffusion, osmosis, facilitated transport, active-transport mechanisms, endo- and exo–cytosis. 2 ©2020 McGraw-Hill Education  The Cell Theory Cell—the basic unit of life. All living things are made up of cells. New cells arise only from preexisting cells. Cells Vary in Structure and Function 3 ©2020 McGraw-Hill Education  Cell Size Cells are small because of their surface-area-to- volume ratio. Smaller cells have a larger amount of surface area compared to the volume. An increase in surface area allows for more nutrients to pass into the cell and more wastes to exit the cell. There is a limit to how large a cell can be while remaining efficient and metabolically active. 4 ©2020 McGraw-Hill Education  Surface-Area-to-Volume Ratio Limits Cell Total surface area 96 cm2 192 cm2 384 cm2 (height × width × number of sides × number of cubes) Total volume 64 cm3 64 cm3 64 cm3 (height × width × length × number of cubes) Surface area: 1.5:1 3:1 6:1 Volume per cube (surface area ÷ volume) 5 ©2020 McGraw-Hill Education  Microscopy 1 Resolution of the image varies among different types of microscopes. 1.Compound light microscope. Lower magnification than other microscopes. Uses glass lenses and light beams to view images. Can view live specimens. 6 ©2020 McGraw-Hill Education  Micrographs of Human Red Blood Cells Access the text alternative for these images 9 ©2020 McGraw-Hill Education (a): ©Ed Reschke/Getty Images; (b): ©Steve Gschmeissner/Science Photo Library/Getty Images; (c): ©Science Photo Library/Getty Images  Microscopy 2 2. Transmission electron microscope. 2-D image. Uses a stream of electrons to view magnified images. The human eye cannot see the image; it must be projected onto a screen. High magnification, no live specimens. 8 ©2020 McGraw-Hill Education  Microscopy 3 3. Scanning electron microscope. 3-D image. Uses a beam of electrons to view surface structures of specimens. High magnification, no live specimens. 9 ©2020 McGraw-Hill Education  Microscopy 3 4.  How Cells Are Organized 2 Cells are classified into two categories: prokaryotes and eukaryotes. Prokaryotic cells (prokaryotes). Lack a nucleus. Include two groups of bacteria: eubacteria and archaebacterial. Eukaryotic cells (eukaryotes). Have a nucleus. Include animals, plants, fungi, protists. 11 ©2020 McGraw-Hill Education  The Structure of a Typical Eukaryotic Cell 12 ©2020 McGraw-Hill Education ©Alfred Pasieka/Science Source  The Structure of a Typical Eukaryotic Cell Access the text alternative for these images 16 ©2020 McGraw-Hill Education  How Cells are Organized 3 Both types of cells have: A plasma membrane. Surrounds the cell. Made of a phospholipid bilayer that is selectively permeable (regulates what enters and leaves the cell). A cytoplasm: the semifluid substance inside the cell. Includes organelles (internal compartments with specialized functions). 14 ©2020 McGraw-Hill Education  Check Your Progress Summarize the role of the plasma membrane in a cell. Describe the main differences between a eukaryotic and a prokaryotic cell. 15 ©2020 McGraw-Hill Education  The Plasma Membrane 1 Plasma membrane. Phospholipid bilayer with proteins that are attached and embedded. Hydrophilic heads face the cytoplasm and extracellular fluid. Hydrophobic tails face inward. 16 ©2020 McGraw-Hill Education  The Plasma Membrane 2 Plasma membrane Contains cholesterol for support. Glycoproteins and glycolipids—carbohydrate chains attached to proteins and lipids. Identify the cell as “self” or “foreign” and act as receptors. 17 ©2020 McGraw-Hill Education  The Plasma Membrane 3 Plasma membrane Some membrane proteins act as channels. Allow some things in while keeping other substances out. Small, hydrophobic substances pass freely through the phospholipid bilayer. Eg: gases like oxygen and carbon dioxide. Ions and large molecules need help passing through. Water can cross the membrane by passing through channels called aquaporins. 18 ©2020 McGraw-Hill Education  Selective Permeability of the Plasma Membrane 19 ©2020 McGraw-Hill Education  Ways Substances Cross the Plasma Membrane 1 Diffusion. Osmosis. Facilitated diffusion. Active transport. Endocytosis and exocytosis. Diffusion, Facilitated Diffusion & Active Transport: Movement across the Cell Membrane: https://youtu.be/UgN76naeA1Q What is Osmosis? - Part 1: https://youtu.be/SD1AKWUazPU Osmosis Process - Part 2: https://youtu.be/MCvbfqz7ASs Endocytosis and Exocytosis: https://youtu.be/_dlbw8ubjgc 20 ©2020 McGraw-Hill Education  Ways Substances Cross the Plasma Membrane 2 Diffusion—the random movement of molecules from a higher concentration to a lower concentration. Until they are equally distributed. Passive movement; no energy is required. Molecules move in both directions, but the net movement is from high to low concentration. At equilibrium, the same number of molecules move in and out of the cell. 21 ©2020 McGraw-Hill Education  Diffusion Across the Plasma Membrane Access the text alternative for these images 22 ©2020 McGraw-Hill Education  Osmosis Osmosis—the diffusion of water molecules; from high to low water concentration. Normally body fluids are isotonic to cells. The same concentration of impermeable solutes. Cells do not change in size. Hypotonic solutions have fewer solutes. Cells swell and can burst (lysis). Hypertonic solutions have more solutes. Cells shrink (crenation). Osmotic pressure drives osmosis. 23 ©2020 McGraw-Hill Education  Effects of Changes in Tonicity on Red Blood Cells Access the text alternative for these images 31 ©2020 McGraw-Hill Education (a–b): ©Power and Syred/Science Photo Library/Getty Images; (c): ©Steve Gschmeissner/Science Photo Library/Getty Images  Facilitated Transport Facilitated transport. The transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier. Passive transport (no energy required). Protein transporters are very specific and only move certain molecules. 32 ©2020 McGraw-Hill Education  Facilitated Transport Across a Plasma Membrane Access the text alternative for these images 33 ©2020 McGraw-Hill Education  Active Transport Active transport—the movement of molecules from a lower to higher concentration. Uses ATP as energy. Requires a protein carrier, which is often called a pump. 34 ©2020 McGraw-Hill Education  Active Transport and the Sodium- Potassium Pump Access the text alternative for these images 35 ©2020 McGraw-Hill Education  Bulk Transport 1 Cells use bulk transport to move large molecules across the membrane. Endocytosis transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle. Phagocytosis—endocytosis of pathogens (that is, bacteria) by white blood cells. Pinocytosis—endocytosis of fluid with small particles. Receptor-mediated endocytosis—particles first bind to receptors in the plasma membrane; this initiates endocytosis. 36 ©2020 McGraw-Hill Education  Examples of Bulk Transport Access the text alternative for these images 30 ©2020 McGraw-Hill Education  Bulk Transport 2 Exocytosis transports molecules outside the cell via the fusion of a vesicle with the plasma membrane. Sort of like reverse endocytosis. 31 ©2020 McGraw-Hill Education  Check Your Progress Describes the structure of the plasma membrane. Compare and contrast diffusion, osmosis, facilitated transport, and active transport. Discuss the various ways cells can move materials in bulk into and out of the cell. 32 ©2020 McGraw-Hill Education