1. UNIT III – CELL STRUCTURE & FUNCTION
Hillis – Ch 4,5
Baby Campbell – Ch 4,5
Big Campbell – Ch 6,7,11

2. I. DISCOVERY OF CELLS History of Microscopes Cell Theory
Anton van Leeuwenhoek
Robert Hooke
Cell Theory
All living things are made of cells.
Cells are the smallest working unit.
All cells come from pre-existing cells through cell division.

3. I. DISCOVERY OF CELLS, cont.
Types of Microscopes
Compound Light Microscope
Magnification
Resolution
Advances in light microscopy include
Confocal
Fluorescent
Phase Contrast
Super-resolution
Electron Microscope
Scanning Electron Microscope (SEM)
Transmission Electron Microscope (TEM)

4. I. DISCOVERY OF CELLS, cont.
Cell Size
Metabolic needs impose both upper & lower limits on cell size
How small?
Must have enough space for DNA, enzymes
Mycoplasma sp. - < 1 μm
How large?
Surface Area to Volume Ratio
Adaptations

5. II. CELL TYPES Prokaryotic Cells Typically smaller than euks Bacteria
Kingdom
No true nucleus – DNA found as a single chromosome in region called nucleoid

6. II. CELL TYPES, cont
Prokaryotic Cells

7. II. CELL TYPES, cont Eukaryotic Cells Larger, more complex
Contain true nucleus, membrane-bound organelles suspended in cytosol
Composed of
Nucleus
Ribosomes
Endomembrane System ER
Golgi Apparatus
Lysosomes
Vacuoles
Mitochondria/Chloroplasts
Peroxisomes
Cytoskeleton

8. III. EUKARYOTIC CELL STRUCTURES

9. III. EUKARYOTIC CELL STRUCTURES, cont
Control center of eukaryotic cell
Double membrane that protects nucleus; continuous with ER
Contains pores
Site of ribosome production
DNA wrapped in protein

10. III. EUKARYOTIC CELL STRUCTURES, cont
Suspended in cytosol or found on rough ER
Site of protein production in a cell

11. III. EUKARYOTIC CELL STRUCTURES, cont
Endomembrane System
Endoplasmic Reticulum
Interconnected network continuous with nuclear envelope
Rough ER
Smooth ER

12. III. EUKARYOTIC CELL STRUCTURES, cont Endomembrane System, cont
“Cell postmaster”
Receives transport vesicles from ER; modifies, stores, and ships products
Receiving side is known as the cis face; shipping side is known as the trans face

13. III. EUKARYOTIC CELL STRUCTURES, cont Endomembrane System, cont
Sacs containing hydrolytic enzymes
Used for recycling cellular materials, destroying pathogens

14. III. EUKARYOTIC CELL STRUCTURES, cont Endomembrane System, cont
Storage sac
Plants typically have large, central vacuole surrounded by membrane called tonoplast. Absorbs water and helps plant cell to grow larger
Some protists have contractile vacuole to pump out excess water

15. III. EUKARYOTIC CELL STRUCTURES, cont
Site of oxidative respiration
Contain own DNA, ribosomes
Found in virtually all euk cells
Enclosed by 2 membranes; inner membrane has folds called cristae to increase surface area

16. III. EUKARYOTIC CELL STRUCTURES, cont
Type of plastid that carries out photosynthesis by converting solar energy to chemical energy (glucose)
Contain membranous system of flattened sacs called thylakoids – stack is called a granum
Fluid surrounding thylakoids is called stroma
Contains DNA, ribosomes

17. III. EUKARYOTIC CELL STRUCTURES, cont Endosymbiont Theory

18. III. EUKARYOTIC CELL STRUCTURES, cont
Membrane-bound compartments that use O2 to carry out metabolism
H2O2 is produced; broken down by _________________

19. III. EUKARYOTIC CELL STRUCTURES, cont
Provides structural support to cell
Allows for movement
Attachment site for organelles, enzymes
More extensive in animal cells
Composed of three types of proteins
Actin
More fixed
Keratin

20. III. EUKARYOTIC CELL STRUCTURES, cont Cytoskeleton, cont

21. IV. CELL BOUNDARIES Cell Wall Found in
Rigid structure; protects, maintains shape of cells
Prevents excess water uptake
Plant cell wall
Cellulose
Pectin - Sticky polysaccharide found between cell walls of adjacent cells
Plasmodesmata - Perforations between adjacent cell walls that allow for movement of materials from one cell to another

22. IV. CELL BOUNDARIES, cont
Extracellular Matrix of Animal Cells
Holds cells together, protects & supports cells
Allows for communication between cells
Composed primarily of glycoproteins – proteins with covalently-bonded carbohydrate chains attached
Must abundant glycoprotein in most animals is collagen

23. IV. CELL BOUNDARIES, cont
Intracellular Junctions in Animal Cells
Tight Junctions – Press membranes together very tightly; prevents leakage of fluid
Desmosomes (Anchoring Junctions) – Fasten cells together in sheets
Gap Junctions – Allow for movement of cytoplasm from one cell to another; important in communication between cells

24. IV. CELL BOUNDARIES, cont
Cell (Plasma) Membrane
Selectively-permeable barrier found in all cells
Composed primarily of phospholipid bilayer
Fluid Mosaic Model
“Fluid” – Not a rigid structure. Organization due to high concentration of water inside & outside cell

25. IV. CELL BOUNDARIES, cont
Organization of Plasma Membrane

26. IV. CELL BOUNDARIES, cont
Fluidity of Plasma Membrane

27. IV. CELL BOUNDARIES, cont
Cell Membrane, cont
Proteins - “Mosaic” – Assortment of different proteins embedded in bilayer; determine most of membrane’s specific functions. Act as channels, pumps, enzymes in metabolism, binding sites, etc
Integral Proteins – Embedded in phospholipid layer
Peripheral Proteins – Bound to surface of membrane

28. IV. CELL BOUNDARIES, cont Membrane Proteins

29. IV. CELL BOUNDARIES, cont
Cell Membrane, cont
Carbohydrates
“ID tags” that identify cell.
Enable cells to recognize each other and foreign cells.
May be bonded to lipids (glycolipids) or proteins (glycoproteins)

30. IV. CELL BOUNDARIES, cont

31. V. CELL TRANSPORT

32. V. CELL TRANSPORT, cont
Passive Transport – Movement of materials from high to low concentration. No energy output required.
Diffusion
Random movement of a substance across membrane down concentration gradient
No net movement once equilibrium is reached

33. V. CELL TRANSPORT, cont Passive Transport, cont Facilitated Diffusion
Passive transport of molecules across cell membrane with the help of transport proteins
Utilized by large molecules, charged particles, polar molecules
Water

34. V. CELL TRANSPORT, cont Passive Transport, cont
Osmosis – Diffusion of water across a membrane. Tonicity refers to tendency of cell to gain or lose water. If the solution is
Isotonic relative to the cell – Solute concentration is same on both sides of membrane. No net movement of water.
Hypertonic relative to the cell – Concentration of solute is greater outside cell → water moves out of cell until equilibrium is reached. Cell may shrivel.
Hypotonic relative to the cell – Concentration of solute is lower outside cell → water moves into cell until equilibrium is reached. Cell may swell to bursting point.

35. V. CELL TRANSPORT, cont Passive Transport / Osmosis, cont
Water Potential
Used to predict the passive movement of water
Designated as Ψ
Water always moves from an area of higher water potential → lower water potential
ΨS =
ΨP =

36. V. CELL TRANSPORT, cont Passive Transport/Osmosis, cont Osmoregulation
Cells must have mechanism to prevent excess loss, uptake of water
Cell wall, contractile vacuole
Plasmolysis – Seen in plants; excessive water loss causes cell membrane to pull away from cell wall

37. V. CELL TRANSPORT, cont

38. V. CELL TRANSPORT, cont Active Transport
Movement of materials against concentration gradient. Requires energy output by cell
Carrier Proteins – Na+ / K+ Pump

39. V. CELL TRANSPORT, cont
Active Transport, cont
Proton Pump

40. V. CELL TRANSPORT, cont Active Transport, cont Exocytosis
Secretion of biomolecules by fusion of vesicles with cell membrane. Biomolecules “spit out”.
Hormones, neurotransmitters, etc

41. V. CELL TRANSPORT, cont Active Transport, cont
Endocytosis – “Sucking In”. Cell membrane surrounds, engulfs particle or biomolecule, pinches in to form vesicle.
Phagocytosis – “Sucking in” food particles
Pinocytosis – “Sucking in” fluid droplets
Receptor-mediated Endocytosis – Very specific

42. VI. CELL SIGNALING
Autocrine Signaling

43. VI. CELL SIGNALING, cont Coordinates cell activities, development
Typically involves 3 steps:
Reception – Target cell’s detection of signal molecule due to binding of signal molecule to receptor protein in cell membrane
Transduction – Binding of signaling molecule changes receptor protein; triggers a sequence of events within cell
Response – Results in specific cellular response; for example, activation of genes, enzyme catalysis, etc.

44. VI. CELL SIGNALING, cont
Reception
Typically involves G Proteins

45. VI. CELL SIGNALING, cont Transduction Typically multi-step pathway
Relay molecules are usually protein kinases

46. VI. CELL SIGNALING, cont Transduction
Non-protein molecule known as cAMP is often second messenger

47. VI. CELL SIGNALING, cont Response Nuclear
May “turn on” or “turn off” genes
Cytoplasmic
May regulate enzyme activity
Apoptosis
Controlled cell suicide

48. VI. CELL SIGNALING, cont
Regulation