What is the Surface Area to Volume Ratio of a sphere with a radius of 5mm? Of 10 mm? What sphere can eliminate wastes and move materials quicker?

Transcription

1 Warm Up What is the Surface Area to Volume Ratio of a sphere with a radius of 5mm? Of 10 mm? What sphere can eliminate wastes and move materials quicker?

2 Cell Membrane and Function Chapter 7 Big Idea #2: Biological systems use energy to grow, reproduce, and maintain dynamic homeostasis.

3 Essential Knowledge 2B1:Cell membranes are selectively permeable due to their structure 2B2: Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes 2B3: Eukaryotic cells maintain internal membranes that partition the cell into specialized regions

4 Separates internal and external env. Is selectively permeable: some substances can cross

5 Semi-Permeability Due to structure Has phosholipids, proteins, cholesterol, glycoproteins, and glycolipids

6 Fig. 7-2 Made of a double phospholipid layer that is amphipathic (hydrophobic and hydrophilic areas) Hydrophilic head WATER Hydrophobic tail WATER

7 Fig. 7-3 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein

8 Embedded Proteins Can be hydrophilic w/ charged and polar side groups. Can be hydrophobic w/ nonpolar side groups

9 Fig. 7-8 Hydrophobic area ex: coiled, nonpolar alpha helices N-terminus EXTRACELLULAR SIDE C-terminus Helix CYTOPLASMIC SIDE

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11 Cholesterol Steroid found in b/t phospholipids. In high temps less fluid membrane. In low temps Stops solidification of membrane

12 Fig. 7-5a Membrane is fluid Moves Lateral movement ( 10 7 times per second) Flip-flop ( once per month) (a) Movement of phospholipids When Cold, Moves Less!!

13 Cell to Cell Recognition Cells talk w/ membrane carbs may be covalently bonded to lipids (glycolipids) or to proteins (glycoproteins)

14 Permeability of Lipid Bilayer Pass: Small, uncharged molecules and small nonpolar molecules (N 2 ) Others need help with channels or pumps

15 Aquaporins Channel protein that allows water to move across

16 Transport Proteins Binds to molecules and changes shape to shuttle them across membrane extremely specific

17 Cell Walls Cell Wall Provides a structural boundary

18 Bacteria Cell Wall: Made of peptidoglycan

19 Plant Cell Wall: Made of Cellulose

20 Fungi Cell Wall: Made of Chitin

21 Passive Transport Movement of molecules in and out of cell w/out using energy. AKA Diffusion

22 Concentration Gradient High to low concentrations! Import resources/ export of wastes

23 Osmosis Passive transport: movement of H2O across membrane. High to Low!

24 Fig Lower concentration of solute (sugar) Higher concentration of sugar Same concentration of sugar H 2 O Selectively permeable membrane Osmosis Video Clip! Osmosis

25 Tonicity Ability of a solution to cause a cell to gain or lose water osmoregulation Isotonic solution: Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane Hypertonic solution: Solute concentration is greater out of cell; cell loses water Hypotonic solution: Solute concentration is high inside cell; cell gains water

26 Fig Hypotonic solution Isotonic solution Hypertonic solution H 2 O H 2 O H 2 O H 2 O (a) Animal cell Lysed Normal Shriveled H 2 O H 2 O H 2 O H 2 O (b) Plant cell Turgid (normal) Flaccid Plasmolyzed

27 Facilitated Diffusion Channel protein carries molecules across (high to low conc.) Polar molecules

28 Facilitated Diffusion Fig EXTRACELLULAR FLUID Channel protein (a) A channel protein Solute CYTOPLASM Carrier protein Solute (b) A carrier protein

29 Active Transport Energy-requiring: move across cell membrane from low to high conc. Uses ATP Embedded proteins

30 Ex: Sodium-Potassium Pump Allows cells to maintain concentration gradients that differ from their surrounding hered.mcg rawhill.com/si tes/ /stud ent_view0 /chapter2/ animation how_th e_sodium _potassiu m_pump_ works.ht ml

31 Fig Passive transport Active transport Diffusion Facilitated diffusion ATP

32 Exocytosis Internal vesicles fuse w/ plasma mebrane to secrete large macromolecules out of cell. Requires ATP!

33 Endocytosis Cell takes in macromolecules by forming new vesicles derived from plasma membrane.

34 Eukaryotes Compartmentalize Minimizes competing interactions and increases surface area. Keep reactions and enzymes localized Bacteria and Archaea (ancient) can t do this