Cells and Tissues

1. Cells and Tissues

2. Cell Physiology: Membrane Transport • Membrane transport— movement of substances into and out of the cell • Two basic methods of transport: • Passive Transport • No energy is required • Active transport • Cell must provide metabolic energy (ATP)

3. Solutions and Transport Solvent + Solute = Solution dissolving + Components in = Homogeneous mixture medium smaller quantity of 2 or more components Parts of a solution:

4. Solutions in the Body • Contain small amounts of gases, nutrients,and salts dissolved in water • Intracellular fluid – refers to both nucleoplasm and cytosol (“inter” = inside) • Interstitial fluid – fluid on the exterior of the cell

6. Selective Permeability • Cells need to extract materials from the interstitial fluid as needed, but repel unneeded materials • The plasma membrane allows some materials to pass while excluding others • This permeability influences movement both into and out of the cell

7. Passive Transport Processes • Diffusion • Particles tend to distribute themselves evenly within a solution; no energy required for movement • Movement is from high concentration to low concentration, or down a concentration gradient PLAY Figure 3.9

8. Passive Transport Processes • Types of Diffusion: • Simple Diffusion • An unassisted process • Solutes are lipid-soluble materials or small enough to pass through membrane pores

9. Passive Transport Processes • Facilitated Diffusion • Substances require a protein carrier for passive transport • Transports lipid-insoluble and large substances

10. Passive Transport Processes • Osmosis • Simple diffusion of water • Highly polar water moleculeseasily cross the plasma membrane through aquaporins Video Clip: Active & Passive Transpoort

11. Passive Transport Processes • Filtration: • Water and solutes are forced through a membrane by fluid (hydrostatic) pressure • A pressure gradient must exist • Solute-containing fluid is pushed from a high-pressure area to a low pressure area Video Clip: Active & Passive Transpoort

12. Active Transport Processes • Substances are transported that are unable to pass by diffusion • Substances may be too large • Substances may not be able to dissolve in the fat core of the membrane • Substances may have to move against a concentration gradient • ATP energy is needed for transport PLAY

13. Active Transport Processes • Types of active transport: • Active transport (solute pumping) • Vesicular transport • Exocytosis • Endocytosis • Phagocytosis • Pinocytosis PLAY

14. Active Transport Processes • Solute Pumping • Amino acids, some sugars, and ions are transported by protein carriers called solute pumps • ATP energizes protein carriers • In most cases, substances are moved against concentration gradients

15. Extracellular fluid Na+ K+ Na+ P Na+ P Na+ Na+ K+ K+ Na+ P K+ ATP ADP Loss of phosphate restoresthe original conformation ofthe pump protein. K+ isreleased to the cytoplasm andNa+ sites are ready to bind Na+again; the cycle repeats. Binding of cytoplasmic Na+to the pump proteinstimulates phosphorylationby ATP, which causes thepump protein to change itsshape. The shape change expelsNa+ to the outside.Extracellular K+ binds,causing release of thephosphate group. Cytoplasm Figure 3.11

16. Active Transport Processes • Vesicular Transport • Exocytosis • Moves materials out of the cell • Material is carried in a membranous vesicle • Vesicle migrates to plasma membrane • Vesicle combines with plasma membrane • Material is emptied to the outside PLAY

17. Active Transport Processes: Exocytosis Figure 3.12a

18. Active Transport Processes: Exocytosis Figure 3.12b

19. Active Transport Processes • Vesicular transport: • Endocytosis • Extracellular substances are engulfed by being enclosed in a membranous vescicle • Types of endocytosis • Phagocytosis—“cell eating” • Pinocytosis—“cell drinking”

20. Extracellularfluid Extracellularfluid Plasmamembrane Cytoplasm Pit Recycling of membraneand receptors (if present)to plasma membrane Transport to plasmamembrane andexocytosis ofvesicle contents Ingestedsubstance Vesicle Lysosome Detachmentof vesicle Release ofcontents tocytoplasm Vesicle containingingested material Plasmamembrane Vesicle fusingwith lysosomefor digestion (a) Active Transport Processes: Endocytosis Figure 3.13a

21. Active Transport Processes: Endocytosis Receptor-mediated endocytosis Phagocytosis Figure 3.13b–c

22. Cell Life Cycle • Cells have two major periods in their life span: • Interphase • Cell grows • Cell carries on metabolic processes • Separate stage from mitosis • Cell Division (Mitosis) • Cell replicates itself • Function is to produce more cells for growth and repair processes

23. DNA Replication • Occurs toward the end of interphase • Genetic material is duplicated and readies a cell for division into two cells • DNA uncoils and each side serves as a template

24. Cell Cycle Two Major Events of Cell Division • Mitosis—division of the nucleus • Results in the formation of two daughter nuclei • Cytokinesis—division of the cytoplasm • Begins when mitosis is near completion • Results in the formation of two daughter cells

25. Stages of Mitosis — “PMAT” • Prophase (“Pro”- before) • First part of cell division • Centrioles migrate to the poles to direct assembly of mitotic spindle fibers • DNA appears as double-stranded chromosomes • Nuclear envelope breaks down and disappears PLAY PLAY

26. Stages of Mitosis • Metaphase • Chromosomes are aligned in the center of the cell on the metaphase plate • Metaphase (“meta” = middle) • Chromosomes are aligned in the center of the cell on the metaphase plate PLAY

27. Stages of Mitosis • Anaphase • Chromosomes are pulled apart and toward the opposite ends of the cell • Cell begins to elongate PLAY

28. Stages of Mitosis • Telophase • Chromosomes uncoil to become chromatin • Nuclear envelope reforms around chromatin • Spindles break down and disappear

29. Stages of Mitosis • Cytokinesis • Begins during late anaphase and completes during telophase • A cleavage furrow forms to pinch the cells into two parts

30. Centrioles Spindlemicrotubules Centrioles Chromatin Centromere Centromere Formingmitoticspindle Chromosome,consisting of twosister chromatids Plasmamembrane Fragments ofnuclear envelope Spindlepole Nuclearenvelope Nucleolus Interphase Early prophase Late prophase Nucleolusforming Metaphaseplate Spindle Cleavagefurrow Nuclearenvelopeforming Sisterchromatids Daughterchromosomes Metaphase Anaphase Telophase and cytokinesis Stages of Mitosis Figure 3.15