1. Chapter 4 A Tour of the Cell
SC 101
General Biology
Essential Biology
CM Lamberty

2. The Microscopic World of Cells
Cells are marvels of complexity
Trillions of cell in human body
Many specialized types
Main tool for exploration--Microscope

3. Microscopes as Windows on the World of Cells
Light Microscope (LM)
Visible light projected through specimen
Lenses enlarge the image and project to eye
View living cells
Magnification
Increase in size, depends on lens
Resolving Power
Clarity of magnified image
Electron Microscope (EM) beam of electrons
Scanning Electron Microscope (SEM)
View cell surfaces
Transmission Electron Microscope (TEM)
View internal structures

4. Microscopes as Windows on the World of Cells

5. Microscopes as Windows on the World of Cells

6. The 2 Major Categories of Cells
The countless cells on earth fall into two categories:
Prokaryotic cells — Bacteria and Archaea
Eukaryotic cells — plants, fungi, and animals
All cells have several basic features.
They are all bound by a thin plasma membrane.
All cells have DNA and ribosomes, tiny structures that build proteins

7. The 2 Major Categories of Cells
Prokaryotic and eukaryotic cells have important differences.
Prokaryotic cells are older than eukaryotic cells.
Prokaryotes appeared about 3.5 billion years ago.
Eukaryotes appeared about 2.1 billion years ago.
Prokaryotes
Are smaller than eukaryotic cells
Lack internal structures surrounded by membranes
Lack a nucleus
Have a rigid cell wall

8. Idealized Prokaryotic Cell

9. The 2 Major Categories of Cells
Eukaryotes
Only eukaryotic cells have organelles, membrane-bound structures that perform specific functions.
The most important organelle is the nucleus, which houses most of a eukaryotic cell’s DNA.

10. Idealized Eukaryotic Cell

11. Overview of Eukaryotic Cells
Eukaryotic cells are fundamentally similar.
The region between the nucleus and plasma membrane is the cytoplasm.
The cytoplasm consists of various organelles suspended in fluid.
Unlike animal cells, plant cells have
Protective cell walls
Chloroplasts, which convert light energy to the chemical energy of food

12. Membrane Structure Separates living cell from nonliving surroundings
Regulates traffic of chemicals in and out of cell
Key to how it works is the structure

13. Plasma Membrane: Lipids & Proteins
Phospholipids
Related to dietary fats
Only 2 fatty acid tails not 3
hydrophobic
Phosphate group in 3rd position
Charged, hydrophilic
Phopholipid bilayer
2-layered membrane
Proteins embedded in bilayer
Regulate traffic

14. Plasma Membrane: Lipids & Proteins
Fluid Mosaic
Not static (fluid)
Diverse proteins (mosaic)
Phospholipids and proteins free to drift about in the plane of the membrane
Illness can result if membrane is compromised
Superbugs: staphylococcus aureus
MRSA
Flesh eating disease!!

15. Cell Surfaces
Plant cells have rigid cell wall surrounding plasma membrane
Made of cellulose
Protect the cells
Maintain cell shapes
Keep cells from absorbing too much water
Cells connected via channels through cell walls
Join cytoplasm of each cell to neighbor
Allow water and small molecules to move between cells

16. Cell Surfaces Animal cells lack cell wall Cells junctions
Extracellular matrix
Sticky coating to hold cells together
Protects and supports cells
Cells junctions
Connect cells togther
Allow cells in tissue to function in coordinated way

17. Genetic Control of Cell
Nucleus chief of the cell
Genes store information necessary to produce proteins
Proteins do most of the work of the cell

18. Structure and Function of Nucleus
Nuclear Envelope
Double membrane that surrounds nucleus
Similar in structure to plasma membrane
Pores allow transfer of materials
Nucleolus
Prominent structure
Where ribosomes are made
Chromatin
Fibers formed from long DNA and associated proteins
Chromosome
One chromatin fiber

19. The nucleus

20. DNA, chromatin and chromosomes

21. Ribosomes Responsible for protein synthesis
In eukaryotic cells, ribosomes make in nucleus and transported into cytoplasm
Suspended in fluid making proteins that remain in fluid
Attached to outside of endoplasmic reticulum, making proteins incorporated into membranes or secreted by cell

22. How DNA Directs Protein Production
DNA programs protein production in cytoplasm via mRNA
mRNA exits through pores in nuclear envelope, travels to cytoplasm, and binds to ribosomes
As ribosomes move along mRNA, genetic message translated into protein with specific amino acid sequence.

23. How DNA Directs Protein Production
DNA RNA Protein

24. The Endomembrane System
Cytoplasm of eukaryotic cells partitioned by organelle membranes
Some are connected
Directly by membranes
Indirectly by transfer of membrane segments
Together form endomembrane system
Includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes and vacuoles

26. Endoplasmic Reticulum (ER)
Main functioning facility in cell
Rough ER
Ribosomes stud the surface
Produce membrane and secretory proteins (i.e. salivary glands)
Products transferred via transport vesicles
Smooth ER
Lacks ribosomes on surface
Synthesis of lipids (steroids)
Helps liver detoxify drugs

27. Endoplasmic Reticulum (ER)

28. The Golgi Apparatus Refinery, warehouse and shipping center
Products made in ER reach Golgi in transport vehicles
Receiving dock and shipping dock
Modifications by enzymes as products move from receiving to shipping
Phosphate groups added as tags for different destinations

29. The Golgi Apparatus

30. Lysosomes Sac of digestive enzymes (animal cells)
Proteins
Polysaccharides
Fats
Nucleic acids
Develop from vesicles budding from Golgi
Food vacuoles
fuse with lysosomes, exposing food to enzymes for digestion
Small molecules from digestion leave the lysosome and nourish the cell.
Breakdown damaged organelles
Sculpturing feature
Digest webbing between fingers and toes

31. Lysosomes

32. Vacuoles Sacs that bud from ER, Golgi or plasma membranes
Variety of size and function
Contractile vacuoles of protists pump out excess water in the cell.
Central vacuoles of plants
Store nutrients
Absorb water
May contain pigments or poisons

33. Vacuoles

34. Review of Endomembrane System

35. Chloroplasts and Mitochondria
Energy Conversion
Cellular power stations

36. Chloroplasts Photosynthetic cells of plants and algae 3 compartments
Space between membranes that surround chloroplast
Stroma: thick fluid
Network of disks and tubes
Grana: interconnected stacks of disks
Solar power pack

37. Chloroplasts

38. Mitochondria Site of cellular respiration
Harvest E from food MQ and converts to ATP
Found in all eukaryotic cells
Structure
Enveloped by 2 membranes filled with matrix
Inner membrane has several infoldings (cristae)
Contain DNA that encodes their own protein

39. Mitochondria

40. The Cytoskeleton Network of fibers extending throughout cytoplasm
Skeleton and muscles
Support and movement

41. Maintaining Cell Shape
Series of fibers
Microtubules
Straight hollow tubes composed of proteins
Guide movement of chromosomes when cells divide
Intermediate filaments and Microfilaments
Both thinner and solid
Anchorage and reinforcement for organelles
Dynamic cytoskeleton (amoeboid movements)

42. Maintaining Cell Shape

43. Cilia and Flagella Mobile appendages Aid in movement Flagella Cilia
Generally occur singly
Propel cell
Undulating whiplike motion
Cilia
Shorter and more numerous than flagella
Promote movement by back and forth motion
Some function to move fluid over tissue surfaces

44. Cilia and Flagella