1. Chapter Six
A Tour of the Cell

2. CELLS
A cell is the basic unit of a living thing that can perform all the processes associated with life
Single cell or Unicellular: ex. Paramecium and bacteria
Many cells or Multi-cellular: ex. Animals and plants
Non-living things have no cells

3. The Microscope
Types:
Light microscope (LMs)
visible light passes through the specimen and then through glass lenses.
The lenses refract light such that the image is magnified into the eye or a video screen.
Magnification is the ratio of an object’s image to its real size.
Resolving power is a measure of image clarity
LM cannot resolve the internal anatomy of organnels

6. Electron microscope (EM), focuses a beam of electrons through the specimen or onto its surface
With shorter wavelengths than visible light therefore, finer resolution.
Transmission electron microscopes (TEM) are used mainly to study the internal ultrastructure of cells.
Scanning electron microscopes (SEM) are useful for studying surface structures.
Microscopes are a major tool in cytology, the study of cell structures.

7. Study of cell functions
Cells function can be studied by separating the major organelles
The process used to separate the organelles is called Fractionation
The process involved the centrifugation of cells to separate the different parts and studying the functions

8. Fractionation begins with homogenization, gently disrupting the cell
Fractionation begins with homogenization, gently disrupting the cell. Then, the homogenate is spun in a centrifuge to separate heavier pieces into the pellet while lighter particles remain in the supernatant

9. Three major parts of the cell
Nucleus: this is the control center for all cell’s activities
PLASMA MEMBRANE: controls the entrance and exit of substances in and out of the cell
Cytoplasm: this consists of all living matter in the cell except the nucleus
Organelles float in the cytoplasm

10. A Composite Cell hypothetical cell major parts nucleus cytoplasm
Plasma membrane
3-3

13. Cytoplasmic Organelles
Endoplasmic Reticulum
connected, membrane-bound sacs, canals, and vesicles
transport system
rough ER
studded with ribosomes
protein and lipid synthesis
smooth ER
lipid synthesis
break down of drugs
Ribosomes
free floating or connected to ER
site of protein synthesis
3-8

14. Cytoplasmic Organelles
Golgi apparatus
group of flattened, membranous sacs
packages and modifies proteins
Mitochondria
membranous sacs with inner partitions
generate energy
3-9

15. Cytoplasmic Organelles
Lysosomes
enzyme-containing sacs
digest worn out cell parts or unwanted substances
Centrosome
two rod-like centrioles
used to produce cilia
distributes chromosomes during cell division
Peroxisomes
enzyme-containing sacs
break down organic molecules
3-10

16. Cytoplasmic Organelles
Cilia
short hair-like projections
propel substances on cell surface
Flagellum
long tail-like projection
provides motility to sperm
3-11

17. Cytoplasmic Organelles
Vesicles
membranous sacs
store substances
Microfilaments and microtubules
thin rods and tubules
support cytoplasm
allows for movement of organelles
3-12

18. Cell Nucleus control center of cell nuclear envelope nucleolus
porous double membrane
separates nucleoplasm from cytoplasm
nucleolus
dense collection of RNA and proteins
site of ribosome production
chromatin
fibers of DNA and proteins
stores information for synthesis of proteins
3-13

19. Vacuoles: this serves for the storage of food, water and wastes
Chloroplast: found only in plants, contains chlorophyll which traps energy from the sun to produce glucose
Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact.
Plant cells are perforated with plasmodesmata, channels allowing cysotol to pass between cells.

20. 1. Plant cells are encased by cell walls
The cell wall, found in prokaryotes, fungi, and some protists, has multiple functions.
In plants, the cell wall protects the cell, maintains its shape, and prevents excessive uptake of water.
It also supports the plant against the force of gravity.
The thickness and chemical composition of cell walls differs from species to species and among cell types.

21. Animal have 3 main types of intercellular links: tight junctions, desmosomes, and gap junctions.
In tight junctions, membranes of adjacent cells are fused, forming continuous belts around cells.
This prevents leakage of extracellular fluid.

22. Desmosomes (or anchoring junctions) fasten cells together into strong sheets, much like rivets.
Intermediate filaments of keratin reinforce desmosomes.
Gap junctions (or communicating junctions) provide cytoplasmic channels between adjacent cells.
Special membrane proteins surround these pores.
Salt ions, sugar, amino acids, and other small molecules can pass.
In embryos, gap junctions facilitate chemical communication during development.

23. The cell theory
Living things are composed on one or more cells
Cell is the basic unit of organization of an organism
All cells come from preexisting cells

24. Eukaryotes vs. Prokaryotes
True nucleus
No nucleus
Membrane bound
The genetic material DNA is concentrated in the nucleoid
No membrane
Examples: plants and animals
Examples: Bacteria, virus and amoeba

25. Animals vs. Plant cells
Animal Cells
Plant cells
Home work?