UNIT II – CELL STRUCTURE & FUNCTION

1. UNIT II – CELL STRUCTURE & FUNCTION • Baby Campbell – Ch 4,5,11 • Big Campbell – Ch 6,7,8,11

2. I. DISCOVERY OF CELLS • History of Microscopes • _____________________________________ • First to try stacking several lenses together to view tiny objects. • Looked at pond water • First scientist to describe living cells as seen through a microscope. • _____________________________________ • Used the microscope to examine thin slices of cork. • He called the tiny boxes he saw cells. He chose the name "cells" because the chambers he saw reminded him of roomsin a monastery which were called cells. • Cell Theory

3. I. DISCOVERY OF CELLS, cont. • Types of Microscopes • Compound Light Microscope • ___________________ • Ratio of an objects image to its real size • __________________ • Measure of clarity of an image • Electron Microscope • __________________ Electron Microscope (SEM) • Used to study the surface of the specimen • __________________ Electron Microscope (TEM) • Used to study the internal structure of cells TEM SEM

4. II. CELL TYPES • _________________ Cells • Typically smaller than eukaryotes • Bacteria • Kingdom Archaebacteria • Kingdom Eubacteria • No true nucleus – DNA found as a single chromosome in region called ________________

5. II. CELL TYPES, cont • Structure found in all prokaryotic cells • _____________ • _____________ • _____________ • _____________ • _____________ • Additional structures that may be present • _____________ • _____________ • _____________

6. II. CELL TYPES, cont • ___________________ Cells • Larger, more complex • Contain true nucleus and membrane-bound organelles suspended in cytosol • Composed of • Nucleus • Ribosomes • Endomembrane System • ER • Golgi Apparatus • Lysosomes • Vacuoles • Mitochondria/Chloroplasts • Peroxisomes • Cytoskeleton

9. III. EUKARYOTIC CELL STRUCTURES • _____________________ • Control center of eukaryotic cell • Made up of • ________________________ • Double membrane that protects nucleus; continuous with ER • Contains _____________ to allow RNA to leave nucleus • ________________________ • Site of ribosome and rRNA production • ________________________ • DNA wrapped in protein • Will condense during cell division to form chromosomes

10. III. EUKARYOTIC CELL STRUCTURES, cont • Endomembrane System – membranes are related either through physical continuity or by the transfer of membrane segments as vesicles • Endoplasmic Reticulum (“within the cytoplasm”; “little net”) • Interconnected network continuous with nuclear envelope • Rough ER • Site of __________________________ • Smooth ER • Synthesis of _______________ • Metabolism of _________________ • ____________________ of drugs & poisons • _________________________________ • “Cell postmaster” • Receives transport vesicles from ER; modifies, stores, and ships products • Receiving side is known as the ________face; shipping side is known as the __________ face

11. III. EUKARYOTIC CELL STRUCTURES, cont • Endomembrane System, cont • ______________________________ • Sacs containing hydrolytic enzymes • Used for recycling cellular materials, destroying pathogens • ______________________________ • Storage sac • Plants typically have large, central vacuole surrounded by membrane called ___________________. Absorbs water and helps plant cell to grow larger • Some protists have contractile vacuole to pump out excess water

12. Endomembrane SystemThe endomembrane system plays a key role in the synthesis (and hydrolysis) of macromolecules in the cell.

13. III. EUKARYOTIC CELL STRUCTURES, cont • ____________________________ • Suspended in cytosol or found on rough ER • Site of protein production in a cell • _____________________________ • Site of ________________________________ (making of ATP) • Contain their own DNA, ribosomes • Found in virtually all eukaryotes cells • Enclosed by 2 membranes; inner membrane has folds called _____________ to increase surface area

14. III. EUKARYOTIC CELL STRUCTURES, cont • _____________________________ • Type of plastid that carries out _____________________ by converting solar energy to chemical energy (glucose) • Contain membranous system of flattened sacs called _______________ – stack is called a _____________ • Fluid surrounding thylakoids is called ___________ • Contains its own DNA, ribosomes

15. III. EUKARYOTIC CELL STRUCTURES, cont • ____________________________________ • Membrane-bound compartments that use O2 to carry out metabolism • H2O2 is produced; broken down by enzymes to produce ______ & ______ • ____________________________________ • Provides structural support to cell • More extensive in animal cells • Composed of three types of proteins • ___________________________ • Thinnest filaments …….AKA………. ____________ filaments. • Bundles of them form microvilli - extensions of the cell membrane found in some cells to increase surface area. • Interact with myosin in muscle cells to create movement • _________________________________ • In between in thickness; more permanent than microtubules/microfilaments. • _________________________________ • Hollow rods that support cell, serve as tracks for movement within cell. • Help separate chromosomes during cell division - occurs in a region called centrosome, which is the location of centrioles in animal cells. • Cilia, flagella are constructed from bundles of microtubules covered by extensions of the cell membrane.

16. IV. CELL BOUNDARIES • Cell Wall • Found in ___________, _______, ________________, and some _________________ • Functions • Rigid structure; protects cell • Maintains shape of cells • Prevents excess water uptake • Plant cell wall • _________ - primary component • Pectin - Sticky polysaccharide found between cell walls of adjacent cells; found in middle lamella • Plasmodesmata - Perforations between adjacent cell walls that allow for movement of materials from one cell to another

17. IV. CELL BOUNDARIES, cont • Extracellular Matrix • Found in animal cells • Holds cells together, protects & supports cells • Allows for communication between cells • Composed primarily of ______________________ – proteins with carbohydrate chains that are covalently-bonded • Must abundant glycoprotein in most animals is _____________ • Intracellular Junctions • Tight Junctions – Fuses membranes together tightly; prevents leakage of fluid • Desmosomes (Anchoring Junctions) – Fasten cells together in sheets • Gap Junctions – Allow for movement of cytoplasm from one cell to another; important in communication between cells

18. IV. CELL BOUNDARIES, cont • ____________________________ • Selectively-permeable barrier found in all cells • Composed primarily of _______________________ bilayer • Fluid Mosaic Model • “Fluid” – Not a rigid structure. Organization due to high concentration of water inside & outside cell

19. IV. CELL BOUNDARIES, cont • Proteins - “Mosaic” – Assortment of different proteins embedded in bilayer; determine most of membrane’s specific functions. Act as channels, pumps, enzymes in metabolism, binding sites, etc • _____________ Proteins – Embedded in phospholipid layer • _____________ Proteins – Bound to surface of membrane • Carbohydrates – “ID tags” that identify cell. Enable cells to recognize each other and foreign cells. May be bonded to lipids (glycolipids) or proteins (glycoproteins) • ____________________ – Found in animal cells for stability

20. V. CELL TRANSPORT

21. V. CELL TRANSPORT, cont • ________________ Transport – Movement of materials from _______ to ______ concentration. No energy output required. • ___________________ - Random movement of a substance across membrane down concentration gradient until equilibrium is reached. • ________________________________________ – Passive transport of molecules across cell membrane with the help of transport proteins. • Water is polar – requires protein channels called aquaporins to move in and out of cell. • Glucose also requires protein channels due to size.

22. V. CELL TRANSPORT, cont • Passive Transport, cont • ______________ – Diffusion of water across a membrane. • ______________ refers to tendency of cell to gain or lose water. • If the solution is • Isotonic to the cell – Solute concentration is same on both sides of membrane. No net movement of water. • Hypertonic to the cell – Concentration of solute is greater outside cell → water moves in until equilibrium is reached. Cell may shrivel. • Hypotonic to the cell – Concentration of solute is lower outside cell → water moves into cell until equilibrium is reached. Cell may swell to bursting point. • Water moves towards the high solute concentration!!!!!

23. V. CELL TRANSPORT, cont • Passive Transport/Osmosis, cont • Osmoregulation • Cells must have mechanism to prevent excess loss, uptake of water • Cell wall, contractile vacuole • _______________________ – Seen in plants; excessive water loss causes cell membrane to pull away from cell wall

24. V. CELL TRANSPORT, cont

25. V. CELL TRANSPORT, cont • ____________ Transport – Movement of materials against concentration gradient. Requires energy output by cell • Carrier Proteins – Na+ / K+ Pump

26. V. CELL TRANSPORT, cont • Active Transport, cont • _________________ – Secretion of biomolecules by fusion of vesicles with cell membrane. Biomolecules “spit out”. • _________________ – “Sucking In”. Cell membrane surrounds, engulfs particle or biomolecule, pinches in to form vesicle. • ______________________ – “Sucking in” food particles • ______________________ – “Sucking in” fluid droplets • Receptor-mediated Endocytosis – Very specific

27. VII. CELL SIGNALING • Coordinates cell activities, development • Initiates series of responses known as signal transduction pathway. Typically involves 3 steps: • ________________ – Target cell’s detection of signal molecule due to binding of signal molecule to receptor protein in cell membrane • ________________– Binding of signaling molecule changes receptor protein; triggers a sequence of events within cell • ________________– Results in specific cellular response; for example, activation of genes, enzyme catalysis, etc. • Cyclic AMP – Intracellular compound often involved in signal transduction pathways.

28. VII. CELL SIGNALING, cont

29. VIII. THE WORKING CELL • Metabolism • _____________________ Pathway – Breaks down molecules; releases energy • _____________________ Pathway – Pathway that synthesizes larger molecules from smaller ones; requires energy • Energy • Kinetic Energy – Associated with relative motion of objects • Potential Energy – Energy that matter possesses; stored energy • Chemical Energy – Potential energy of molecules • Thermodynamics • ________ Law of Thermodynamics states that total amount of energy in universe is constant – can be transferred or transformed, but it cannot be created or destroyed • ________ Law of Thermodynamics states that energy is lost to the environment as heat; that is, some energy becomes unusable

30. VIII. THE WORKING CELL, cont • Chemical Reactions are classified according to whether they require or produce energy • _____________________ – Requires net input of energy. Energy is then stored in products as potential energy. • _____________________ - Release energy. • _____________________– Often used in cellular metabolism. Energy released in exergonic rxn is used to drive endergonic rxn.

31. VIII. THE WORKING CELL, cont • ATP – Adenosine triphosphate. Nucleotide that stores & provides usable energy to the cell • Structure of ATP • Adenine – nitrogen base • Ribose – pentose • 3 Phosphate groups

32. VIII. THE WORKING CELL, cont • ATP, cont • Phosphorylation • ATP contains potential energy, especially between 2nd and 3rd phosphate groups. P – P bond is unstable and easily broken by hydrolysis. Exergonic. • Coupled with endergonicrxn – specifically, by transferring phosphate group from ATP to another molecule. Known as phosphorylation.