1. Energy Organelles & the Cytoskeleton Section 6.5, 6.6, and 6.7

2. Mitochondria & Chloroplasts Convert energy to forms the cell can use for work Mitochondria – site of cellular respiration ◦Found in plants & animals ◦Process that makes ATP from food ◦Oxygen is needed Chloroplasts – site of photosynthesis ◦Found in plants & algae only ◦Convert solar energy to chemical energy Both enclosed by membranes

3. Mitochondria & Chloroplast Membranes are made on free ribosomes Contain their own ribosomes Contain a small amount of DNA

4. Mitochondria Found in all Eukaryotic cells A cell can have hundreds to thousands of mitochondria depending on its function Move around, change shape & divide Surrounded by a double membrane Outer membrane smooth Inner membrane folding (Cristae) ◦Increases surface area Intermembrane space Matrix

5. Mitochondria Sturcture

6. Chloroplasts Member of the plant organelle group plastids ◦Amyloplasts – colorless that store starch in roots and tubers ◦Chromoplasts – pigments that give fruits and flowers orange & yellow colors ◦Chloroplasts – contain the green pigment chlorophyll

7. Chloroplasts Double membrane separated by intermembrane space. Thylakoids are flattened stacks of sacs like pancakes or poker chips Each stack is called a granum (grana) Fluid outside the thylakoids is the stroma (space) Chloroplasts grow, move, & divide

9. Peroxisomes Single membrane Contain enzymes that transfer hydrogen from various substances to oxygen Hydrogen peroxide is produced (H 2 O 2 ) Functions ◦Break fatty acids down ◦Detoxify alcohol H 2 O 2 is converted to water because it is toxic to the cell

10. Peroxisome structure (TEM)

11. Cytoskeleton A network of fibers extending throughout the cytoplasm Plays a role in organizing the structures & activities of the cell, supporting the cell, and maintaining its shape Composed of three types of structures ◦Microtubules ◦Microfilaments ◦Intermediate filaments Differ in size

12. Cytoskeleton

13. Cytoskeleton - Support Gives support Helps the cell maintain shape Provides anchorage for organelles Can be dismantled and reassembled in a new location changing the shape of the cell

14. Cytoskeleton - Motility Changes in cell location Movements of parts of the cell Interaction of cytoskeleton with motor proteins Examples: ◦Movements of cilia & flagella ◦Muscle cell contraction ◦Movement of vesicles on “monorail” ◦Cytoplasmic streaming

15. Motor Proteins

16. Cytoskeleton - Regulation Cytoskeleton can transmit mechanical forces exerted by extracellular molecules via surface proteins of the cell to the interior and even the nucleus

17. 3 Types of Fibers Microtubules – thickest of the three Microfilaments – thinnest of the three Intermediate filaments – middle range size filaments

19. Microtubules Hollow rods Made from protein tubulin (alpha & beta) Shape and support the cell Serve as tracks for motor proteins Examples: ◦Guide secretory vesicles from the golgi to the plasma membrane ◦Responsible for the separation of chromosomes during cell division

20. Centrosomes & Centrioles Microtubules grow out from centrosomes “Microtubule-organizing center” Animal cells contain a pair of centrioles found at right angles to each other Each composed of 9 sets of triplet microtubules arranged in a ring Before the cell divides the centrioles replicate Help in organizing microtubules but not essential Plants lack centrioles

22. Cilia & Flagella Specialized arrangement of microtubules is responsible for beating of cilia & flagella Flagella ◦1-2 per cell, undulating motion Cilia ◦Large numbers on cell surface, work like oars Both are made from 9+2 arrangement Dynein arms responsible for bending movements of cilia & flagella ◦Similar to a cat walking up a tree

23. Motion of Flagella & Cilia

24. 9+2 arrangement of cilia & flagella

25. Dynein “walking”

26. Microfilaments (Actin filaments) Solid rods Also called actin filaments because they are built from actin protein Twisted double chain of actin subunits Function is to bear pulling forces Part of the contractile apparatus of muscle cells Actin & myosin (thicker than actin) interact to produce muscle contraction

27. Role of Microfilaments & motility

28. Intermediate Filaments Mid size filament Specialized for bearing tension Very diverse (keratins) More permanent fixtures of cells Important in reinforcing the shape of a cell and fixing the position of certain organelles

29. Extracellular components Things beyond the plasma membrane Plants – cell wall Animals – Extracellular matrix (ECM)

30. Plant Cell Wall Protects Maintains shape Prevents excess uptake of water Thicker than plasma membrane Strong fibers in a matrix formation like fiberglass make it extremely strong Layers of cell wall are made that include pectin (thickening agent in jams & jellies), cellulose, & hardening substances.

32. Extracellular Matrix of Animals Glycoproteins – proteins with carbohydrate chains Collagen – accounts for ½ total protein found in the body Proteoglycans – Collagen is embedded in Fibronectin – attaches the ECM to integrins Integrins – span the membrane Important communication from the cell to its surroundings

33. Extracellular Matrix

34. Intercellular Junctions Plants – Plasmodesmata Channels between cell walls that allow neighboring cells to communicate with one another Water & small solutes can pass freely from cell to cell

35. Plant Plasmodesmata

36. Intercellular Junctions Animals ◦Tight junctions – form continuous seals around the cells – prevent leakage ◦Desmosomes – fasten cells together into strong sheets - anchoring ◦Gap junctions – communicating junctions – provide cytoplasmic channels from one cell to an adjacent cell

37. Animal cell junctions

38. Macrophage eating bacteria