Understanding Active and Passive Transport in Cellular Function and Structure

1. Active & Passive Transport The Four Tissues Phys/Path A – Fall 2006

2. The Cell Functions Bridge between molecules & humans Structure Plasma (cell) membrane Nucleus Cytoplasm 6 types of organelles Endoplasmic reticulum Golgi complex Lysosomes Peroxisomes Mitochondria Vaults

3. The Cell

4. The Cell Membrane

5. The Cell Membrane

6. Cell Membrane Fluid lipid bilayer Embedded with proteins Consist mostly of lipids (fats) + proteins Also small amounts of carbohydrates Mostly phospholipids w/ little cholesterol Polar head (charged) Hydrophilic Water-loving Two non-polar fatty acid tails Hydrophobic “water-fearing”

7. Cell Membrane Membrane proteins Variety of diff proteins serve following specialized functions: Channels across membrane Carrier molecules Receptor sites Membrane-bound enzymes Proteins arranged in filamentous meshwork Cell adhesion molecules (CAM’s) Proteins along with carbohydrates (antigens)

8. Cell Membrane Transport • Two main types • Passive transport • Active transport

9. Cell Membrane Transport Passive Transport – 4 different types Diffusion Osmosis Facilitated Diffusion Filtration

10. Passive Transport • Diffusion • Movement of molecules • High concentration -> Low concentration • No energy involved • No barriers

11. Passive Transport • Osmosis • Movement of water • Semipermeable membrane • Low concentration of solutes -> High concentration of solutes • No energy involved • Water moves easily

12. Passive Transport • Facilitated Diffusion • Movement of water-like substances • Proteins in membrane • Channels/guides • High concentration of solutes -> Low concentration of solutes • No energy involved

13. Passive Transport • Filtration • Molecules not moving randomly • Forced to other side • Requires membrane • Channel membrane proteins necessary • No energy involved • EX: Automatic drip coffee maker

14. Active Transport • Substances moved against concentration gradient • High concentration -> low concentration • Requires energy • Na+ plays key role • Na+ conc. kept low inside cell • Na+ conc. high outside cell • Difference in concentration provides energy to move other substances across their energy gradient

15. Active Transport Kidney tubule Peritubular capillary

16. Active Transport • Requires energy • Requires carrier proteins • Carrier proteins span membrane • Act as gates/guides for transport of substances • Different types • Endocytosis • Phagocytosis • Pinocytosis • Exocytosis • Sodium-Potassium pump

17. Active Transport

18. Active Transport - Phagocytosis • Type of endocytosis • Large, multimolecular, solid particles • Engulfed by cell • EX: food

19. Active Transport - Pinocytosis • Type of endocytosis • Like phagocytosis • Fluid engulfed • Rich in nutrients • Solution • EX: egg cells nourished by nurse cells • Secrete nutrients close to cell membrane • Bring in nutrients

20. Active Transport - Exocytosis • Fusion of membrane-enclosed intracellular vesicle w/ plasma membrane • Vesicle opens • Contents emptied outside cell • EX: hormones

21. Active Transport – Na+-K+ Pump

22. Active Transport – Na+-K+ Pump • Na+-K+ ATPase pump • In all cell membranes • Sequentially active • Transports 3 Na+ ions out of cell • Concentrates in ECF • Transports 2 K+ ions into cell • Concentrates in ICF • Requires ATP (energy) to change carrier protein

23. Active Transport – Na+-K+ Pump • Na+-K+ ATPase pump (cont.) • Most important two roles • Establishes Na+ and K+ concentration gradients across plasma membrane of all cells • Critically important for nerve & muscle cells • Helps regulate cell volume • Controls concentration of solutes in cell • Minimizes osmotic effects • Induce swelling of cell • Induce shrinking of cell

24. Tissues • Four main types • Epithelial • Connective • Muscle • Nerve (Many Cats Enjoy Naps – Muscle, Connective, Epithelial, Nerve)

25. Tissues • Three principal types of junctions between cells • Some epithelial, some muscle, & some nerve cells • Tightly joined • Form close functional unit • Tight junctions • Fluid-tight seal between cells (Ziploc seal) • Anchoring junctions • Fasten cells together or extracellular material • Gap junctions • Permit electrical or chemical signals to pass from cell to cell.

26. Tissues - Epithelial • Two types • Covering & lining epithelium • Forms superficial layer of skin & some internal organs • Inner lining of blood vessels, ducts, body cavities • Interiors of respiratory, digestive, urinary, & reproductive tracts • Glandular epithelium • Constitutes secreting portion of glands • Also combines with nervous tissue to form special sense organs • Smell, hearing, vision, & touch

27. Tissues - Epithelial • General features • Consist of largely or entirely of close packed cells • Little EC material between adjacent cells • Arranged in continuous sheets • Single or multiple layers • Have apical (free) surface (exposed to “outside”) & basal surface (attached to basement membrane) • Cell junctions plentiful • Provides secure attachments among cells • Avascular • Blood vessels in adjacent connective tissue • Exchange materials thru diffusion

28. Tissues - Epithelial • General features (cont.) • Adhere firmly to nearby connective tissue • Attachment – thin extracellular layer – basement membrane • Have nerve supply • High capacity for renewal (regeneration) • Diverse in origin • Derived from all three primary germ layers

29. Tissue - Epithelial

30. Tissues - Epithelial • General functions • Protection • Filtration • Lubrication • Secretion • Digestion • Absorption • Transportation • Excretion • Sensory reception • Reproduction

31. Tissues - Epithelial • Covering & Lining Epithelium • Four basic cell shapes • Squamous • Flat cells • Attach like tiles • Thinness – rapid movement of substances thru them • Cuboidal • Thicker • Cube or hexagon shaped • Produce important body secretions (sweat, enzymes, etc) • May also function in absorption – fluids & other substances

32. Tissues - Epithelial • Covering & Lining Epithelium • Four basic cell shapes (cont.) • Columnar • Tall & cylindrical • Protect underlying tissues • May be specialized for secretion/absorption • Transitional • Readily change shape – flat -> columnar • Change shape due to distention, expansion, or movement

33. Tissues - Epithelial • Covering & Lining Epithelium • Arrangement of layers • Simple epithelium • Single layer of cells • Diffusion, osmosis, filtration, secretion, absorption • Stratified epithelium • Two or more layers of cells • Protect underlying tissues • Ares of wear & tear

34. Tissues - Epithelial • Covering & Lining Epithelium • Arrangement of layers (cont.) • Pseudostratified epithelium • One layer of mixture of cell shapes • Multilayered appeareance • Nuclei lie at different levels • Not all cells reach surface • Cells that reach surface • Ciliated • Or secrete mucus

35. Tissues - Epithelial • Covering & Lining Epithelium • Classification • Simple • Squamous • Cuboidal • Columnar • Stratified • Squamous • Cuboidal • Columnar • Transitional • Pseudostratified columnar

36. Tissues - Epithelial • Glandular Epithelium • Function • Secretion • Glandular cells lie in clusters deep in C & L epithelium • Glands • One cell or group of highly specialized epithelial cells • Secrete substances into ducts, onto surface, or into blood • All glands classified – exocrine or endocrine • Exocrine • Secrete onto free surface • Tubelike ducts • Sweat, digestive enzymes, etc. • Endocrine • Secrete enter ECF, diffuse into bloodstream • Hormones

37. Tissues - Epithelial • Glandular Epithelium • Structural Classification of Exocrine Glands • Multicellular glands • Most of glands of this type • Many cells • Distinct microscopic structure or macroscopic organ • Examples • Sweat glands • Oil glands • Salivary glands

38. Tissues - Epithelial • Glandular Epithelium • Structural Classification of Exocrine Glands (cont.) • Unicellular glands • Single-celled • Goblet cells • Do not contain ducts • Unicellular mucus-secreting exocrine glands • Epithelial lining of digestive, respiratory, urinary, & reproductive systems • Produce mucus

39. Tissues - Epithelial • Glandular Epithelium • Structural Classification of Endocrine Glands • Functional classification depends on whether secretion is product of a cell or consists of entire or partial glandular cells • Holocrine glands • Accumulate secretory product in their cytosol • Cell dies – dishcarged w/ contents as glandular secretions • New cell replaces old cell • Ex: sebaceous (oil) gland of skin

40. Tissues - Epithelial • Glandular Epithelium • Structural Classification of Endocrine Glands (cont.) • Merocrine glands • Form secretory product • Discharge it from cell • Most exocrine glands this type • Ex: salivary glands • Apocrine glands • Accumulate secretory product at apical surface of secreting cell • Pinches off from rest of cell – forms secretion • Remaining repairs itself • Ex: mammary glands

41. Tissues - Connective • Most abundant & widely distributed tissue • Binds together, supports, & strengthens other tissue • Protects & insulates internal organs • Compartmentalizes structures (skeletal muslces) • Blood • Fluid connective tissue • Major transport system w/in body • Adipose (fat) tissue • Major site of stored energy reserves

42. Tissues - Connective • General Features • Consists of three basic elements • Cells • Ground substance • Fibers • Matrix – noncellular • Ground substance & fibers • Outside cells • Cells rarely touch • Separated by matrix

43. Tissues - Connective • General Features (cont.) • Do not usually occur on free surfaces • Joint cavities • Lined with aerolar connective tissue • Has nerve supply • Except cartilage • Highly vascular – rich blood supply • Except cartilage – avascular • Tendons – scanty blood supply

44. Tissues - Connective • General Features (cont.) • Matrix & adjacent cells determines tissue’s qualtities • Matrix may be • Fluid • Semifluid • Gelatinous • Fibrous • Calcified • Usually secreted by connective tissue cells & adjacent cells • Blood – matrix is fluid not secreted by blood cells • Cartilage – firm but pliable • Bone – harder & not pliable

45. Tissues - Connective • Connective tissue cells • Fibroblasts • Large, flat, spindle-shaped • Branching processes • Secrete molecules that form matrix • Macrophages • Develop from white blood cells • Irregular shape, short branching processes • Engulf bacteria & cellular debris – phagocytosis • Vital defense for body • Wandering & fixed

46. Tissues - Connective • Connective tissue cells (cont.) • Plasma cells • Small, round or irregular • Develop from type of white blood cell – B lymphocyte (B cell) • Secrete antibodies – defense mechanism – immunity • Most reside in connective tissue • Gastrointestinal tract • Mammary glands

47. Tissues - Connective • Connective tissue cells (cont.) • Mast cells • Abundant alongside blood vessels • Produce histamine • Chemical dilates small blood vessels during inflammation • Produce heparin • In this case – poor anticoagulant • Binds certain intracellular constituents of mast cells