CH 3 - Cells: The Living Units

1. CH 3 - Cells: The Living Units Section 1: Overview of the Cellular Basis of Life (p. 62)

2. Cellular Diversity • Cell - Basic structural & functional unit of living organisms. • Diversity of Cells - Over 200 different types of human cells - Cells vary greatly in size, shape, & function

3. Generalized Cell • All human cells have some common structures • Three basic human cell parts: 1) Plasma membrane - Flexible outer boundary 2) Cytoplasm - Intracellular fluid containing organelles 3) Nucleus - Control center Even though all cells have the same basicinternal parts, it’s the number & combination of those parts that gives each cell it’s specificfunction.

4. CH 3 - Cells: The Living Units Section 2: The Plasma Membrane – Structure (pp. 63-67)

5. Plasma Membrane: Structure • Plasma Membrane - flexible, double membrane surrounding every cell - sometimes referred to as a “cellmembrane” - composed of lipids & proteins - plays critical role in cellularactivity - separates intracellular fluid from extracellular fluid

6. Plasma Membrane: Structure • Phospholipids - 75% of membrane; lipid bi-layer - Phosphate heads; hydrophilic - Fatty acid tails; hydrophobic • Glycolipids - 5% of membrane - Act as markers for cell identification • Cholesterol - 20% of membrane - Maintains membrane stability & flexibility

7. Plasma Membrane: Structure • Membrane Proteins - Responsible for the specialized membrane functions • Membrane protein functions: - Transport of molecules in/out of cell - Act as receptors for signals to/from the cell - Provide ability to recognize & attach to adjacent cells

8. Plasma Membrane: Structure Transport of molecules…

9. Plasma Membrane: Structure Sending & receiving signals…

10. Plasma Membrane: Structure Recognizing & attaching to other cells…

11. Plasma Membrane: Structure • Membrane Junctions - Bind individual cells w/ other cells - Allows cells to communicate w/ others to function correctly • Three main types of junctions: 1) Tightjunctions 2) Desmosomes 3) Gapjunctions

12. Plasma Membrane: Structure • Tight Junctions - Prevent fluids/most molecules from moving between cells - Cells fused together by proteins - Found in places where you don’t want fluids to leak out of tissues (e.g., digestive tract, blood vessels, etc.)

13. Plasma Membrane: Structure • Desmosomes - Act as “rivets” or “spot-welds” that anchor cells together - Prevent cells from separating - Reduce chances of tearing when subjected to pulling forces - Found in areas under mechanical stress (Skin, Heart, etc.)

14. Plasma Membrane: Structure • Gap Junctions - “Communication” junction between cells - Hollow cylinders; allow molecules to pass from cell to cell - Found in areas that need to move ions & other substances between cells (Cardiac cells, Smooth muscle)

15. CH 3 - Cells: The Living Units Section 3: The Plasma Membrane – Transport (pp. 68-79)

16. Plasma Membrane: Transport • Interstitial Fluid - water-based fluid surrounding all cells in our body - “Soup” of amino acids, sugars, fatty acids, vitamins, hormones, neurotransmitters, & salts • Membrane Transport - Plasma membranes are selectively permeable - Some molecules easily pass through; others do not - Substances pass to/from inside of cell & interstitial fluid Animation: Membrane Permeability

17. Plasma Membrane: Transport • Types of Membrane Transport • Passive processes - No cellular energy (ATP) is required • Active processes - Cellular energy (ATP) is always required - Require specialized carrierproteins

18. Plasma Membrane: Passive Transport • Types of passive processes: • Diffusion (aka “Simple Diffusion”) - Movement of molecules from high to lowconcentration - DOWN the concentration gradient - Molecules inherently WANT to moveapart - Speed is influenced by temperature & particle size (Higher temps = faster diffusion; Smaller particles = faster diffusion) Examples = Oxygen, Carbon dioxide, Fat-soluble vitamins Animation: Diffusion

19. Plasma Membrane: Passive Transport • Types of passive processes: • Facilitated Diffusion - Molecules move down concentration gradient - Must have either carrierproteins or channelproteins - Particles are either toolarge to pass through the bi-layer or they are chargedparticles that are repelled - Rate of diffusion is limited by number of carriers/channels

20. Plasma Membrane: Passive Transport • Types of passive processes: • Facilitated Diffusion - Channels may be openallthetime (“Leakage” channels) - Channels may be controlled by chemical/electrical signals (“Gated” channels) Leakage channel Gated channel

21. Plasma Membrane: Passive Transport • Types of passive processes: • Osmosis - Diffusion of water thru selectively permeable membranes - Water moves very freely through lipid bi-layers - Water concentration determined by solute concentration **In this case, b/c solutes cannot diffuse, water will instead. It moves from high water concentration (low solute concentration) to low water concentration (high solute concentration).

22. Plasma Membrane: Passive Transport • Importance of Osmosis - When osmosis occurs, water enters or leaves cell - Changes in cell volume disrupt cell function • Tonicity - Ability of a solution to cause a cell to shrink or swell Animation: Osmosis

23. Plasma Membrane: Tonicity • Isotonic solution - Solution with same solute concentration as the cytoplasm - Cells in these solutions maintain the samevolume - Our extracellular fluid is isotonic

24. Plasma Membrane: Tonicity • Hypertonic solution - Solution with greater solute concentration than cytoplasm - Cells in these solutions lose water & shrink (“crenate”) - Dehydration leads to this

25. Plasma Membrane: Tonicity • Hypotonic solution - Solution with lower solute concentration than cytoplasm - Cells in these solutions gain water & can burst (“lyse”)

26. Plasma Membrane: Active Transport • Types of active processes: • Active transport - Requires carrier proteins & ATP - Moves molecules against concentration gradient - Solutes “pumped” from low to high concentration Example = Na+-K+ pump (found in all cells)

27. Plasma Membrane: Active Transport • Types of active processes: • Vesicular transport - Requires ATP - Cell uses vesicles (hollow capsules) to move largesubstances in/out - Also called “bulk” transport

28. Plasma Membrane: Active Transport Endocytosis: • bulk transport of substances INTO the cell 2 Types: 1) Phagocytosis - Using pseudopods to engulf solids - “Eating” - Macrophages, white blood cells

29. Plasma Membrane: Active Transport Endocytosis: • bulk transport of substances INTO the cell 2 Types: 2) Pinocytosis - Membrane infolds, bringing in extracellular fluid - “Drinking” - Nutrient absorption in smallintest.

30. Plasma Membrane: Active Transport Exocytosis: • bulk transport of substances OUT of the cell Examples: 1) Hormone secretion 2) Neurotransmitter release 3) Mucus secretion

31. CH 3 - Cells: The Living Units Section 4: The Cytoplasm, Organelles, & Nucleus(pp.81-95)

32. The Cytoplasm • Cytoplasm - located between the plasma membrane & nucleus - site where most cellular activities are accomplished Composed of: 1) Cytosol - water w/ solutes (proteins, salts, sugars, etc.) in it 2) Organelles - metabolic machinery of the cell 3) Inclusions - glycogen, pigments, lipid droplets, crystals, vacuoles

33. Cytoplasmic Organelles • Cytoplasmic Organelles - “little organs” - specialized components that perform specificjobs in cell - work together to help cell carry out its specificfunction 1) Mitochondria - Power plants of cell; provide cell with ATP - Contain their own DNA & RNA - Found in abundance in cells requiring huge quantities of energy (kidney, liver, muscle, etc.)

34. Ribosomes Cytoplasmic Organelles • Ribosomes - Sites of protein synthesis - Cells are protein factories; all proteins made by the cell are built here - May be floating freely in cytoplasm or attached to endoplasmic reticulum

35. Cytoplasmic Organelles • Endoplasmic Reticulum (ER) - Interconnected network of passageways through cell Two Types: a) Rough ER - surface is studded w/ ribosomes - make all proteins that are to be secreted by cell - build proteins that will be incorporated into lipid bi-layer - particularly abundant in secretory cells & liver cells

36. Cytoplasmic Organelles • Endoplasmic Reticulum (ER) - Interconnected network of passageways through cell Two Types: b) Smooth ER - surface is smooth - involved in lipid/cholesterol/glycogen breakdown - deals w/ detoxification of drugs & carcinogens - builds steroid-based hormones - abundant in liver, kidney, & intestinal cells

37. Cytoplasmic Organelles • Golgi Apparatus - modifies, concentrates, & packages proteins - proteins pass from ER into Golgi apparatus - proteins placed in vesicles & transported throughout cell Animation: Endomembrane System

38. Cytoplasmic Organelles • Lysosomes - membranous bags containing digestive enzymes - breakdown ingested bacteria, viruses, & toxins - degrade nonfunctional organelles - break down bone to release calcium - destroy cells in injured tissue

39. Cytoplasmic Organelles • Peroxisomes - membranous sacs containing oxidases/catalases - function to detoxify alcohol - most importantly, they neutralizefreeradicals (chemicals that scramble biological molecules)

40. Cytoplasmic Organelles • Cytoskeleton - elaborate series of “rods” running throughout the cytosol - provides a framework that supports all cellular structures 2 Main Types: a) Microfilaments - involved in cell motility, change in cell shape, & endocytosis/exocytosis

41. Cytoplasmic Organelles • Cytoskeleton - elaborate series of “rods” running throughout the cytosol - provides a framework that supports all cellular structures 2 Main Types: b) Microtubules - hollow tubes that can change in shape, size, & location - determine overall cell shape & placement of organelles

42. Cytoplasmic Organelles • Cilia - small, hair-like extensions on the surface of cells - move in a wavelike motion propelling substances across the surfaces of cells (cells lining the respiratory system) • Flagella - long, tail-like extensions that rotate & propel the entire cell through a solution (sperm)

43. Cytoplasmic Organelles 12) Microvilli - fingerlike extensions of plasma membrane - increase surfacearea for absorption - very extensive in the lining of the smallintestine

44. Cytoplasmic Organelles • Nucleus - genetic library w/ blueprints for all cellular proteins - responds to various signals & determines type & amount of proteins to be made - most cells have 1 nucleus - red blood cells have no nucleus - skeletal muscle cells have multiple nuclei

45. Cytoplasmic Organelles 14) Nuclear Envelope - double membrane surrounding nucleus; porous - pores regulate transport of molecules into/out of nucleus 15) Nucleoli - spherical bodies in nucleus - produce new ribosomes that are sent out thru pores in nuclear envelope into the cytoplasm

46. CH 3 - Cells: The Living Units Section 5: Cell Growth & Reproduction (pp.95-107)

47. Cell Growth • Cell Cycle - series of changes cells go through from formation to reproduction - includes interphase & cell division/mitosis

48. Cell Growth • Interphase - period from cell formation to beginning of cell division - cell is essentially doing all routine activities & growing Subphases: 1) G1 phase (Gap 1) – cell is metabolically active, building proteins, & growing vigorously 2) S phase (synthetic) – DNA replication 3) G2 phase (Gap 2) – enzymes & other proteins needed for division are made G0 phase – only seen in cells that neverdivide; continue to function normally until death

49. Cell Growth • Cell Division - period of time where the cell splits into 2 smaller cells - essential for body growth & tissuerepair - very short amount of time compared to interphase Two distinct events: 1) Mitosis - nuclear division - prophase, metaphase, anaphase, telophase 2) Cytokinesis - division of the cytoplasm

50. Mitosis Stages of Mitosis(Quick overview) • Prophase - chromosomes become visible - nuclear envelope breaksdown - spindlefibers begin to form