Ch. 7 Review

1. Ch. 7 Review

2. Cell Surfaces and Junctions 1. Plant cells are encased by cell walls 2. The extracellular matrix (ECM) of animal cells functions in support, adhesion, movement, and regulation 3. Intercellular junctions help integrate cells into higher levels of structure and function 4. The cell is a living unit greater than the sum of its parts

3. Plant cells are encased by cell walls • The cell wall, found in prokaryotes, fungi, and some protists, has multiple functions. • In plants, the cell wall protects the cell, maintains its shape, and prevents excessive uptake of water. • It also supports the plant against the force of gravity.

4. A mature cell wall consists of a primary cell wall, a middle lamella with sticky polysaccharides that holds cell together, and layers of secondary cell wall.

5. The extracellular matrix (ECM) of animal cells functions in support, adhesion, movement, and regulation • In many cells, fibronectins in the ECM connect to integrins, intrinsic membrane proteins.

6. . Intracellular junctions help integrate cells into higher levels of structure and function • Plant cells are perforated with plasmodesmata, channels allowing cysotol to pass between cells.

7. Animal have 3 main types of intercellular links: tight junctions, desmosomes, and gap junctions • In tight junctions, membranes of adjacent cells are fused, forming continuous belts around cells. • This prevents leakage of extracellular fluid.

8. Desmosomes (or anchoring junctions) fasten cells together into strong sheets, much like rivets. • Gap junctions (or communicating junctions) provide cytoplasmic channels between adjacent cells.

9. Chapter 8 Review

10. Membrane structure, II • Phospholipids~ membrane fluidity • Cholesterol~ membrane stabilization • “Mosaic” Structure~ • Integral proteins~ transmembrane proteins • Peripheral proteins~ surface of membrane • Membrane carbohydrates ~ cell to cell recognition; oligosaccharides (cell markers); glycolipids; glycoproteins

11. Membrane structure, III • Membrane protein function: •transport •enzymatic activity •signal transduction •intercellular joining •cell-cell recognition •ECM attachment

12. Membrane traffic • Diffusion~ tendency of any molecule to spread out into available space • Concentration gradient • Passive transport~ diffusion of a substance across a biological membrane • Osmosis~ the diffusion of water across a selectively permeable membrane

13. Water balance • Osmoregulation~ control of water balance • Hypertonic~ higher concentration of solutes • Hypotonic~ lower concentration of solutes • Isotonic~ equal concentrations of solutes • Cells with Walls: • Turgid (very firm) • Flaccid (limp) • Plasmolysis~ plasma membrane pulls away from cell wall

14. Specialized Transport • Transport proteins • Facilitated diffusion~ passage of molecules and ions with transport proteins across a membrane down the concentration gradient • Active transport~ movement of a substance against its concentration gradient with the help of cellular energy

15. Types of Active Transport • Sodium-potassium pump • Exocytosis~ secretion of macromolecules by the fusion of vesicles with the plasma membrane • Endocytosis~ import of macromolecules by forming new vesicles with the plasma membrane •phagocytosis •pinocytosis •receptor-mediated endocytosis (ligands)

16. Exocytosis • transport large molecules out • transport vesicle budded from the Golgi apparatus is moved by the cytoskeleton to the plasma membrane. • When the two membranes come in contact, the bilayers fuse and spill the contents to the outside

17. Endocytosis • a cell brings in macromolecules and particulate matter by forming new vesicles from the plasma membrane • 3 types: • 1. phagocytosis, “cellular eating”. • the cell engulfs a particle by extending pseudopodia around it and packaging it in a large vacuole.

18. Endocytosis • 2. pinocytosis, “cellular drinking”, a cell creates a vesicle around a droplet of extracellular fluid • This is a non-specific process.

19. Endocytosis • 3.Receptor-mediated endocytosis is very specific in what substances are being transported • triggered when extracellular substances bind to special receptors, ligands, on the membrane surface, especially near coated pits • triggers the formation of a vesicle