1. CELLS: The Living Units
BIO 200
Chp 3

2. The Living Units Cell Theory:
The cell is the basic structural and functional unit of life
Organismal activity depends on individual and collective activity of cells
Biochemical activities of cells are dictated by subcellular structure
Continuity of life has a cellular basis

3. Figure 3.1

4. Cell Structure

5. Cell Structure Plasma Membrane
Separates intracellular fluids from extracellular fluids
Plays a dynamic role in cellular activity
Glycocalyx (a glycoprotein) bordering the cell that provides highly specific biological markers by which cells recognize one another

6. Plasma Membrane Structure The Fluid Mosaic Model
Figure 3.3

7. Fluid Mosaic Model Double bi-layer of lipids with imbedded proteins
Forms the basic “fabric” of the cell membrane
Bi-layer consists of phospholipids, cholesterol and glycolipids
Hydrophilic – attracts water (polar head)
Hydrophobic – repel water (nonpolar tails)

8. Cell Plasma Membrane Functions of Membrane Proteins Transport
Enzymatic activity
Receptors for signal transduction

9. Cell Plasma Structure The plasma aims to maintain homeostasis
Lipid molecules of the by-layer move freely
Polar-nonpolarity interactions keeps stability
Microvilla – (hairs) increase the plasma membrane surface

10. Plasma Membrane Membrane Junctions – help to knit or
adhere cellular tissue (enzymes)
Tight junction – impermeable junction that encircles the cell, prevents molecules from passing through
Desmosome – anchoring junction scattered along the sides of cells, aid in mechanical stress
Gap junction – a nexus that allows chemical substances (electrical activity) to pass between cells

11. Functions of Plasma Membrane Membrane transport
Cells are surrounded by extacelluar or interstitial fluid
Interstitial fluid is rich and nutritious
Derives from the blood stream
Ingredients: amino acids, sugars, fatty acids, vitamins, hormones, salts, waste products.

12. Functions of Plasma Membrane Membrane transport
Substances move continuously across the plasma membrane
It allows some substances to pass and excludes others
Selective barrier
Differential barrier
Permeable barrier
Characteristics of
a healthy cell
*Damage barriers will imbalance homeostasis

13. Passive Transport: Diffusion
1. Simple diffusion – nonpolar and lipid-soluble substances
Diffuse directly through the lipid bilayer
Diffuse through channel proteins
Molecules disperse evenly

14. Figure 3.6

15. Passive Transport Diffusion 2. Facilitated diffusion
Allows transport of glucose, amino acids, and ions
Transported substances bind carrier proteins or pass through water-filled protein channels

16. Passive Transport Facilitated diffusion 2. Carrier Proteins
Are integral transmembrane proteins
Show specificity for certain polar molecules like sugars and amino acids
Molecules too large to pass so they are carried through by transport receptor carriers

17. Passive Transport 3. Diffussion through Osmosis
Occurs when concentration of a solvent is different on opposite sides of a membrane
Diffusion of water across a semi-permeable membrane
Osmolarity – total concentration of solute particles in a solution
Tonicity – how a solution affects cell volume

18. Figure 3.7

19. Figure 3.8

20. Active Transport Uses ATP to move solutes across a membrane
Requires carrier proteins
Types of Active Transport
Primary active transport – hydrolysis of ATP phosphorylates the transport protein causing conformational change
Secondary active transport – use of an exchange pump (such as the Na+-K+ pump) indirectly to drive the transport of other solutes

21. Figure 3.10

22. Vesicular Transport
Transport of large particles and macromolecules across plasma membranes
Exocytosis – moves substance from the cell interior to the extracellular space
Endocytosis – enables large particles and macromolecules to enter the cell

23. Vesicular Transport
Transcytosis – moving substances into, across, and then out of a cell
Vesicular trafficking – moving substances from one area in the cell to another
Phagocytosis – pseudopods engulf solids and bring them into the cell’s interior

24. Figure 3.12

25. Figure 3.13a

26. Figure 3.13b

27. Membrane Potential Voltage (electrical potential) across a membrane
Resting membrane potential – the point where K+ potential is balanced by the membrane potential
range -50 to -100 millivolts (mV)
Cells become polarized
Results from Na+ and K+ concentration gradients across the membrane
Steady state – maintained by active transport of ions

28. Cell Membrane
Cell adhesion molecules - anchor cells to the extracellular matrix, assist in movement,
Membrane Receptors - important in immunity, regulates voltage in nerve and muscle tissue and neurotransmitters

29. Cytoplasm Cytoplasm – material between plasma membrane and the nucleus
Cytosol – viscous semi-fluid, largely water with dissolved protein, salts, sugars, and other solutes
Cytoplasmic organelles – metabolic machinery of the cell
Inclusions – chemical substances such as glycosomes, glycogen granules, and pigment

30. Cytroplasmic Organelles

31. Cytoplasmic Organelles
Membranous - mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, and Golgi apparatus
Nonmembranous - cytoskeleton, centrioles, and ribosomes

32. Mitochondrion
Figure 3.17

33. Mitochondria Double membrane structure with shelf-like cristae
Provide most of the cell’s ATP via aerobic cellular respiration
Contain their own DNA and RNA

34. Ribosomes Granules containing protein and rRNA
Site of protein synthesis
Free ribosomes synthesize soluble proteins
Membrane-bound ribosomes synthesize proteins to be incorporated into membranes

35. Endoplasmic Reticulum (ER)
Interconnected tubes and parallel membranes enclosing cristernae (cristae)
Continuous with the nuclear membrane
Two varieties – rough ER and smooth ER

36. Endoplasmic Reticulum (er)
Figure 3.18

37. Rough (ER) External surface studded with ribosomes
Manufactures all secreted proteins
Responsible for the synthesis of integral membrane proteins and phospholipids for cell membranes

38. Smooth (ER) Looping tubule network
Catalyzes the following reactions in various organs of the body:
Liver – lipid & cholesterol metabolism, breakdown of glycogen, detoxification of drugs
In the testes – synthesis steroid-based hormones
In the intestinal cells – absorption, synthesis, and transport of fats
In skeletal and cardiac muscle – storage and release of calcium

39. Golgi Apparatus Stacked and flattened membranous sacs
Functions in modification, concentration, and packaging of proteins
“Traffic director” for cellular protein
Transport vesicles from the ER and are received by Golgi apparatus

40. Golgi Apparatus
Figure 3.20

41. Lysosomes Spherical membranous bags containing digestive enzymes
Digest ingested bacteria, viruses, and toxins
Degrade nonfunctional organelles
Breakdown glycogen and release thyroid hormone
Autolysis – self-digestion of the cell

42. Lysosomes Breakdown nonuseful tissue Breakdown bone to release Ca2+
Secretory lysosomes are found in white blood cells, immune cells, and melanocytes

43. Lysosomes
Figure 3.22

44. The Endomembrane System
Figure 3.23

45. Endomembrane System System of organelles that function to:
Produce, store, and export biological molecules
Degrade potentially harmful substances
Contains the following system: Nuclear envelope, smooth and rough ER, lysosomes, vacuoles, transport vesicles, Golgi apparatus, and the plasma membrane

46. Peroxisomes “Peroxide bodies”
Membranous sacs containing oxidases and catalases
Detoxify harmful or toxic substances
Neutralize dangerous free radicals
Free radicals – highly reactive chemicals with unpaired electrons

47. Cytoskeleton The “skeleton” of the cell
Dynamic, elaborate series of rods running through the cytosol
Consists of microtubules, microfilaments, and intermediate filaments

48. Cytoskeleton Microtubules
Dynamic, hollow tubes made of the spherical protein tubulin
Determine the overall shape of the cell and distribution of organelles
Microfilaments
Dynamic strands of protein Actin
Attached to the cytoplasmic side of the plasma membrane
Braces and strengthens the cell surface

49. Cytoskeleton Intermediate Filaments
Tough, insoluble protein fibers with high tensile strength
Resist pulling forces on the cell and help form desmosomes
Pg 91

50. Centrioles
Small barrel-shaped organelles located in the centrosome near the nucleus
Pinwheel array of nine triplets of microtubules
Organize mitotic spindle during mitosis
Form the bases of cilia and flagella
Whip-like, motile cellular extensions on exposed surfaces of certain cells
Move substances in one direction across cell surfaces
Cilia

51. Figure 3.26

52. Figure 3.27a

53. Cellular Motion CELIA
Cellular extensions that provide motility in a whiplike motion.
Typically found in large numbers
Located in the exposed surface of the cell
Move substances in one direction across cell surface

54. Figure 3.27c

55. Cellular Motion Flagella
Projections are longer
A single propulsive flagellum
Movement is achieved by propelling itself across the surface or environment
Basal bodies in the centrioles form the bases for ceia and flagella

56. Nucleus The control center containing genetic
Largest cytoplasmic organelle - 5µm
Nuclear envelop –dbl membrane barrier
Nucleoli – DNA & RNA for genetic synthesis
Chromatin – threadlike coils that form chromosomes in cell division. Genes

57. Figure 3.28

58. DNA Replication
Figure 3.31b

59. Cell Growth and Reproduction Cell Life Cycle
Cell division – essential for growth and tissue repair.
Cells die and continuously reproduce
Some reproduce faster than others (skin, intestinal vs. liver).
Some loose ability to maturation
(nervous tissue, skeletal muscle, heart, RBCs)
The DNA replicates before cell division

60. Cell Growth and Reproduction
Cell Division - M Phase (Mitotic)
2 phases: Mitosis & Cytokinesis
Phase 1: Mitosis – nuclear division
prophase
metaphase
Anaphase
telophase
Phases merge together

61. Cell Division - Mitosis
Phase 2 – Cytokinesis
Cytokinesis - cytoplasmic division
Cleavage furrow formed in late anaphase by contractile ring
Cytoplasm is pinched into two parts after mitosis ends
The forming of 2 daughter cells

62. Figure 3.32

63. Figure 3.32