1. CHAPTER 7 A TOUR OF THE CELL

2. Cytology: science/study of cells
Light microscopy resolving power~ measure of clarity
Electron microscopy
TEM ~ electron beam to study cell ultrastructure (internal anatomy)
SEM ~ electron beam to study cell surfaces
Cell fractionation ~ cell separation; organelle study
Ultracentrifuge ~ cell fractionation; 130,000rpm

3. A cell is a living unit greater than the sum of its parts
While the cell has many structures that have specific functions, they must work together.
Cell Theory
Cells are the basic unit of structure and function
All cell arise from other cells
All living things are made of one or more cells

4. Cell Types: Prokaryotic Domains: Bacteria and Archaea
Nucleoid: DNA
concentration
No membrane bound
organelles
Ribosomes:protein synthesis
Plasma membrane: (all
cells); semi-permeable
Cytoplasm/cytosol(all cells)

5. Cell types: Eukaryotic Domains: Protist, fungi, Plants, and Animals
Nucleus:membrane enclosed organelle containing chromosomes
Membrane bound organelles of specialized form and function
Generally larger than prokaryotic cells

6. Cell Size
As cell size increases, the surface area to volume ratio decreases (as well as the % Diffusion)
Rates of chemical exchange may then be inadequate for cell size
Cell size, therefore, remains small

7. Nucleus Genetic material… Nuclear Envelope: double membrane
chromatin
Chromosomes
Nucleolus: rRNA;
ribosome synthesis
Nuclear Envelope:
double membrane
with pores
mRNA~ protein synthesis

8. Ribosomes Protein manufacture
Types: a) free cytosol;protein function in cell
b) bound: on ER; proteins function in membranes, organelles and export

9. The Endomembrane System
Endoplasmic reticulum(ER)
Continuous with nuclear envelope
Smooth ER
no ribosomes
Synthesis of lipids
Metabolism of carbohydrates
Detoxification of drugs &poisons
Rough ER
With ribosomes
Synthesis of secretory proteins
(glycoproteins)
Membrane production

10. The Golgi apparatus
ER products are modified, stored, and then shipped to either: lysosomes, central vacuole, plasma membrane
Cisternae: flattened membranous sacs
Trans face(shipping) & cis face (receiving)
Transport vesicles

11. Lysosomes Sac of hydrolytic enzymes; digestion of macromolecules
Phagocytosis
Autophagy: recycle cell’s
own organic material
Tay-Sachs disease~
lipid digestions disorder

12. Vacuoles Membrane-bound sacs(larger than vesicles) Food (phagocytosis)
Contractile (pump excess
water)
Central (storage in plants
as well as lysosomal functions)
Tonoplast membrane

13. Other Membranous Organelles
Mitochondria and chloroplasts are the main energy transformers of cells
Both organelles have small quantities of DNA that direct the synthesis of the polypeptides produced by their internal ribosomes.
Mitochondria and chloroplasts grow and reproduce as semiautonomous organelles.
Peroxisomes generate and degrade H2O2 in performing various metabolic functions
What enzyme breaks down H2O2?

14. Mitochondria Site of cellular respiration have a smooth outer membrane
and a highly folded inner membrane, the cristae
inner membrane encloses the mitochondrial matrix,
a fluid-filled space with DNA, ribosomes, and enzymes. si

15. chloroplasts found in plants, and eukaryotic algae (protista)
site of photosynthesis.
Inside the innermost membrane is a fluid-filled space, the stroma, in which float membranous sacs, the thylakoids.

16. Peroxisomes
generate and degrade H2O2 in performing various metabolic functions
bounded by a single membrane.
They form not from the endomembrane system, but by incorporation of proteins and lipids from the cytosol.

17. The Cytoskeleton
Providing structural support to the cell, the cytoskeleton also functions in cell motility and regulation

18. There are three main types of fibers in the cytoskeleton: microtubules, microfilaments, and intermediate filaments.

19. Microtubules
the thickest fibers, are hollow rods about 25 microns in diameter.
They move chromosomes during cell division.
Another function is as tracks that guide motor proteins carrying organelles to their destination.

20. cilia and flagella. Microtubules are the central structural support
Cilia usually occur in large numbers on the cell surface.
There are usually just one or a few flagella per cell

21. cilia and flagella.
A flagellum has an undulatory movement

22. cilia and flagella.
Cilia move more like oars with alternating power and recovery strokes.

23. cilia and flagella
have the same ultrastructure.

24. Microfilaments form a three-dimensional network just inside
the thinnest class of the
cytoskeletal fibers,
are solid rods of the globular protein
actin.
designed to resist tension
form a three-dimensional
network just inside
the plasma membrane.

25. Microfilaments
In muscle cells, thousands of actin filaments are arranged parallel to one another.
Thicker filaments, composed of a motor protein, myosin, interdigitate with the thinner actin fibers

26. Microfilaments
In other cells, these actin-myosin aggregates are less organized but still cause localized contraction
Pseudopodia, cellular extensions, extend and contract through the reversible assembly and contraction of actin subunits into microfilaments.

27. Microfilaments
In plant cells (and others), actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming.

28. Intermediate filaments,
more permanent fixtures
of the cytoskeleton than
are the other two classes
reinforce cell shape
and fix organelle location.

29. Cell Surfaces and Junctions
1. Plant cells are encased by cell walls
2. The extracellular matrix (ECM) of animal cells functions in support, adhesion, movement, and regulation
3. Intercellular junctions help integrate cells into higher levels of structure and function
4. The cell is a living unit greater than the sum of its parts

30. 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.

31. A mature cell wall consists of a primary cell wall, a middle lamella with sticky polysaccharides that holds cell together, and layers of secondary cell wall.

32. The extracellular matrix (ECM) of animal cells functions in support, adhesion, movement, and regulation
In many cells, fibronectins in the ECM connect to integrins, intrinsic membrane proteins.

33. . Intracellular junctions help integrate cells into higher levels of structure and function
Plant cells are perforated with plasmodesmata, channels allowing cysotol to pass between cells.

34. 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.

35. Desmosomes (or anchoring junctions) fasten cells together into strong sheets, much like rivets.
Gap junctions (or communicating junctions) provide cytoplasmic channels between adjacent cells.

36. Microtubules
In many cells, microtubules grow out from a centrosome near the nucleus.
In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring.
During cell division the centrioles replicate.