1. Microscope and Cells
Chapter 4

2. I. The Cell Theory
Schwann, Schleiden and Virchow are credited with coming up with the basics of the cell theory
3 components:
1.All living organisms are made up of cells
2.Cells are the basic units of structure and function in living organisms.
3.All cells come from cells that existed before them by cellular reproduction.

3. Every cell has the following main characteristics:
Cell membrane
Cytoplasm
DNA
Ribosomes

4. II. The Compound Light Microscope
Antone von Leeuwenhoek assembled the first microscope that was useful for scientific research.
Compound light microscopes reflect light through a set of lenses and the specimen to magnify the specimen.
See handout for the parts of the microscope – you must know it.

5. II. The Compound Light Microscope
1. Base:
Part on which the microscope rests
2. Mirror/Light source:
Reflects light through objective lens into barrel of microscope
3. Stage:
Surface on which the slide is placed.
4.Arm
Part by which microscope is carried

6. II. The Compound Light Microscope
5. Fine adjustment
Used for fine, detailed focusing of microscope
6. Coarse adjustment
Used for initial focusing of microscope
7. eyepiece
Tube containing lens through which you look into microscope
8. body tube
Tube extending from eyepiece to objectives

7. III. The Compound Light Microscope
9. Nosepiece
Revolving circular structure containing objectives
10. High power objective
Objective used for focusing minute details on microscope slide
11. Low power objective
First objective used for focusing microscope slide
12. clip
Used to hold slide on stage
13. diaphragm
Controls amount of light that goes through stage into objective lens.

8. Two important characteristics that determine the quality of a light microscope:
Magnification – an increase in the apparent size of an object. We calculate magnification by the following:
Magnification of eyepiece x magnification of objective lens = total magnifying power
Resolution – the measure of clarity of an image. As the magnification increases, the resolution of the image decreases.

9. III. Electron Microscopes
Some microscopes use beams of electrons for magnification instead of light and are thus called electron microscopes.
Two types:
Scanning Electron Microscope (SEM)
Transmission Electron Microscope (TEM)

10. III. Electron Microscopes
Transmission Electron Microscope (TEM)
Scanning Electron Microscope (SEM)

11. III. Electron Microscopes
Scanning electron microscope (SEM) –
used to study the detailed architecture of the surface of the object. Forms a 3D image, but does not show the inside of the object.
Cholera Bacteria- Scanning Electron Microscope

12. III. Electron Microscopes
Transmission electron microscope (TEM) –
used to provide a detailed 2D image of the inside structure of the object that is viewed.
Organelles in a pollen grain of tobacco (Nicotiana tabacum; AF = Actin filaments; G = Golgi apparatus; Mi = Mitochondrion; Mt = Microtubule- Transmission Electron Microscope

13. III. The Size of Cells
Cells are microscopic, they are visible only with light microscopes.
Most of their size ranges from µm.
Cells are small, because they have to be able to carry materials from one side of the cell to the next in a short period of time.
Cells must have a large enough surface area to be able to take in nutrients and oxygen and release waste quickly.

15. IV. Prokaryotic Cells Prokaryotic cells –
small cells (about 1-10 µm) that do not have a nucleus and membrane-bound organelles
Found in bacteria and archaebacteria

16. Nucleoid region – Cell membrane – Cell wall – Capsule –
Prokaryotic Cell Organelles:
Nucleoid region –
part of the prokaryotic cell where the DNA is found
Cell membrane –
innermost covering of the cell
Cell wall –
outside of cell membrane, made up of a special mix of polysaccharides and proteins (antibiotics break it down)
Capsule –
outside of the cell wall, protective covering (not all bacteria have it)

17. Prokaryotic Cell Organelles:
Flagella (sing. Flagellum) –
long, whiplike structure that moves bacteria
Pili –
short, hair-like projection used to stick to other surfaces and for conjugation (exchange of genetic materials between bacteria)
Cytoplasm –
jelly-like fluid that dissolves substances and holds organelles
Ribosomes –
organelles that make proteins in the cytoplasm

19. V. Eukaryotic Cells Protists, Fungi, Plants, and Animals
Have nucleus and membrane-bound organelles
Much larger and more complex than prokaryotic cells.
Reproduce sexually and asexually

20. Eukaryotic Organelles General Function: Manufacturing
Nucleus
Control center of cell; contains most of the cell’s DNA
Nucleolus
Location where ribosomes are synthesized
Nuclear pore
Allows RNA to move in and out of nucleus

21. Eukaryotic Organelles General Function: Manufacturing
Ribosomes
Protein synthesis
Rough ER
Comprised of a network of tubes and flattened sacs.
Continuous with plasma membrane and nuclear membrane
Site of protein synthesis (consists of ribosomes)

22. Eukaryotic Organelles General Function: Manufacturing
Smooth ER
Site of lipid and carbohydrate metabolism
No ribosomes
Golgi Apparatus
Connected with ER; flattened disc-shaped sacs, stacked one on top of the other
Modification, storage, and packaging of proteins.
“tags” proteins so they go to the correct destination.

23. Eukaryotic Organelles General Function: Breakdown
Lysosomes (in animal cells and some protists)
Digestion of nutrients, bacteria, and damaged organelles; destruction of certain cells during embryonic development
Peroxisomes
Diverse metabolic processes with breakdown of H2O2 by-product
Vacuoles
Digestion (like lysosomes); storage of chemicals, cell enlargement; water balance

24. Eukaryotic Organelles General Function: Energy Processing
Chloroplasts
Conversion of light energy to chemical energy of sugars (site of photosynthesis)
Mitochondria
Conversion of chemical energy of food to chemical energy of ATP
“Power House” of cell
Bound by double membrane

25. Mitochondria

26. Eukaryotic Organelles General Function: Support, Movement, and Communication
Cytoskeleton (including cilia, flagella, and centrioles in animal cells)
Maintenance of cell shape; anchorage for organelles; movement of organelles within cells; cell movement; mechanical transmission of signals from exterior of cell to interior.
Cell walls (in plants, fungi, and protists)
Maintenance of cell shape and skeletal support; surface protection; binding of cells in tissues

30. Cell Transport We will be looking at: Cell Membranes
Selective permeability of cell membranes
The phospholipid bilayer that makes up cell membranes
The model that describes cell membrane, the Fluid Mosaic Model
Cell Transport Processes

31. Cell Membrane Functions
Membranes provide the structural basis for metabolic order and surround the cell.
Most organelle’s are made from membranes
Semipermiability- Regulate the transport of molecules in and out of the cell
Immune response
Attaches cells to other cells or surfaces.

32. Selective Permeability
Cell membranes control what goes in and out of the cell
It allows some substances to cross more easily than others
Cell membrane is amazingly thin

33. Phospholipid Bilayer
Lipids, mainly phopholipids, are the main structural components of membranes
Phospolipid has a phosphate group and only two fatty acids
Head, with a charged phosphate group, is hydrophillic
Fatty acid tails are nonpolar and hydrophobic
Thus, the tail end is pushed away by water, while the head is attracted to water

34. Phospholipid Bilayer (continued)

35. Phospholipid Bilayer (continued)
Phospholipids form a two-layer sheet called a phospholipid bilayer.
Hydrophillic heads face outward, exposed to the water on both sides of a membrane
Hydrophobic tails point inward, mingling together and shielded from water.

36. Phospholipid Bilayer (continued)
Hydrophobic interior of the bilayer is one reason membranes are selectively permeable.
Nonpolar, hydrophobic molecules are lipid- soluble can easily pass through membranes
Polar molecules and ions are not lipid-soluble
Ability to pass through membrane depends on protein molecules in the phospholipid bilayer.

37. Fluid Mosaic Model Plasma membrane is described as a “Fluid Mosaic”
Mosaic denotes a surface made of small fragments, like pieces of colored tile
A membrane is considered “mosaic” because it has diverse protein molecules embedded in a framework of phospholipids.
A membrane mosaic is “fluid” in that most of the individual proteins and phospholipids can can drift literally in the membrane

38. Fluid Mosaic Model (“Fluid”)
Tails of phospholipids are kinked.
Kinks make the membrane more fluid by keeping adjacent phospholipids from packing tightly together.
In animal cells, the steroid cholesterol stabilize the phospholipids at body temperature and also keep the membrane fluid at lower temperatures.
In a cell, phospholipid bilayer remains about as fluid as salad oil at room temperature.

39. Fluid Mosaic Model (“Mosaic”)
Cell membrane carbohydrates bonded to proteins and lipids in the membrane:
A protein with attached sugars is called a glycoprotein
whereas a lipid with sugars is called a glycolipid.
Function as cell identification tags that are recognized by other cells.
Significant for cells in an embryo to sort themselves to tissues and organs.
Also functions in the immune system to recognize and reject foreign cells.

40. Fluid Mosaic Model (“Mosaic”)
Cell Membrane Proteins can be…
Enzymes:
catalyze the assembly of molecules
Receptors:
relay messages from other cells to the inside of the cell.
Move substances across the membrane:
like water and glucose

41. Fluid Mosaic Model (“Mosaic”)
Cell Membrane Proteins also function to:
Attach to the cytoskeleton and external fibers
Form junctions between cell

42. Fluid Mosaic Model (“Mosaic”)
Cell Membranes proteins may be located:
Within the cell membrane: integral proteins
Usually act as ion channels or molecular channels
Outside the cell membrane: peripheral proteins
Usually act as receptors

43. Fluid Mosaic Model

44. Cell Transport
Transport means the movement of molecules from one side of the cell membrane to the other
Transport is influenced by:
The size of substances
The polarity of substances
The concentration of substances
The permeability of the cell membrane

45. Types of Cell Transport
Passive
Diffusion
Osmosis
Facilitated diffusion
Active
Bulk
Endocytosis
Exocytosis

46. Passive Transport
Diffusion of a substance across a biological membrane
Diffusion is the movement of particles from high concentration to low concentration.
Moves with a concentration gradient
No energy input required
Eventually reaches equilibrium
Molecules continue to move back and forth, but no net change in concentration will occur
Small, nonpolar molecules that easily diffuse across plasma membranes, such as O2 and CO2

47. Passive Transport
Simple Diffusion

48. Passive Transport Osmosis
the diffusion of water across the cell membrane. Especially important when the solute cannot move through the membrane.
Tonicity:
Describes the tendency of a cell in a given solution to lose or gain water.
Isotonic, hypertonic, and hypotoni

49. Passive Transport Osmosis (continued): Isotonic solution
Equal concentration of solvent inside and outside of cell; water goes in and out
Cell’s volume remains the same; equilibrium
Hypertonic solution
Solute concentration is lower inside cell (solvent concentration is higher inside cell) ;Water goes out
Cell shrivels
Causes plasmolysis in plant cells

50. Passive Transport Osmosis (continued): Hypotonic solution
Solute concentration is greater inside the cell (solvent concentration is lower inside the cell); water goes in
Cell swells and may lyse
Causes cytolysis in animal cells
Refer to figure 5.17

51. Passive Transport
Osmosis

52. Passive Transport Facilitated diffusion
Many substances can’t diffuse freely across membrane because of their size, polarity, or charge
Need the help of specific transport proteins in the membrane to move across the membrane

53. Active Transport
Transport processes that can move substances from the lower concentration area to the higher by using energy.
Energy is gained by using ATP molecules

54. Active Transport A type of active transport is the Na-K ion pump
3 sodium ions move out of the cell with the help of a transport protein, while 2 potassium ions move into the cell.
This process requires energy in the form of ATP.

55. Active Transport

56. Bulk Transport
Type of active transport that involves movement of large particles.
Endocytosis – a process by which large particles can move into the cell by using membrane vesicles
Types of endocytosis:
Phagocytosis – engulfing solid particles
Pinocytosis – engulfing liquids, solutions
Receptor-mediated endocytosis – moving into the cell by first binding with receptor molecules on the cell’s surface.

57. Bulk Transport
Receptor-mediated endocytosis

58. Bulk Transport
Exocytosis – the process by which the cell releases large molecules via vesicles through its cell membrane

59. Summary of Cell Transport