Eukaryotic and Prokaryotic Cells
1. Define:
Organelle - the term means "little organ", but refers to structures found within cells. These structures have specific functions and may be more or less numerous depending on the type of cell being studied. Some texts indicate that organelles must be membrane bound; others indicate that they may or may not be membrane bound.
Ribosome - a granular body made up of two sub-units composed of nucleic acid (r-RNA) and protein. Ribosomes are the site of protein synthesis within cells. They may or may not be considered organelles. They are not surrounded by membranes.
Histone - a type of homogeneous protein found in chromatin. DNA molecules appear to be wrapped around the histone proteins in chromatin and the histones help to maintain the structural integrity of the DNA. They also have some regulatory function.
Glycocalyx - also known as a capsule or slime layer. This is a layer of polysaccharide or sometimes protein that is deposited outside the cell wall. It can serve as a reservoir of stored food, as a means of attachment to smooth surfaces, as a protection against phagocytosis by white blood cells or other predatory cells, and to prevent desiccation (drying out). This structure is more common on prokaryotic cells that eukaryotic cells.
Sporulation - the process by which endospores are made within certain bacteria. It involves forespore formation and covering formation and may be stimulated by a variety of factors. Note - this term is also applied to spore formation as it occurs in other types of organisms (fungi, algae, etc.).
2. Cytology
3. organelles
4. smooth endoplasmic reticulum/ protein
5. golgi apparatus (body or complex)/ packaging and secretion
6. chloroplasts /mitochondria
7. These organelles have inner folded membranes that lack cholesterol and are involved in ATP synthesis, they also contain 70s ribosomes and have DNA in closed loops. Like bacteria, they can reproduce themselves by means of binary fission. Antimicrobial agents that kill or inhibit the growth of bacteria also act on mitochondria and chloroplasts.
8. cristae/ thylakoids
9. hydrolase enzymes or hydrolases/ lysosomes/ peroxisomes
10. contractile vacuoles
11. microtubules/ cilia/ flagella
12. tubulin proteins or tubulins/ kinesin and dynein (Kinesins move particles toward the plus end and dynein moves particles toward the minus end of a microtubule)
13. centrioles
14. nuclei (singular=nucleus) / chromatin/ DNA
15. nucleolus/ ribosomal RNA (r-RNA)
16. cell walls/ Cell walls provide protection against changes in osmotic pressure and predators. They also give cells a characteristic shape significant to their function. (We use the unique shapes of cells as a means of identifying and categorizing them, but cell shapes have functional significance to organisms.)
17. Eukaryotic cells contain a true nucleus surrounded by a nuclear membrane or envelope, prokaryotic cells do not (they have a nucleoid or nuclear region that is not membrane bound). Eukaryotic cells contain many membrane bound organelles while prokaryotic cells do not (prokaryotes often contain inclusions, but these are not surrounded by unit membrane). Eukaryotic cells contain two or more linear chromosomes while prokaryotic cells typically contain a single circular chromosome (many prokaryotes also contain plasmids and some contain more than one circular chromosome). Eukaryotic cells contain 80s ribosomes (60s and 40s subunits) while prokaryotes contain 70s ribosomes (50s and 30s subunits). The cell membranes of eukaryotic cells contain about 25% cholesterol, while the cell membranes of ordinary bacteria contain little or no cholesterol. Eukaryotic cells make most of their ATP in association with internal organelles (mitochondria and chloroplasts), while prokaryotes make their ATP in their cytoplasm, or in association with their cell membranes. In general, eukaryotic cells are larger than prokaryotic cells, but their are some exceptions.
18. flagella/ microtubules
19. peritrichous (Such cells are also polytrichous, but peritrichous is a better answer.)/ amphitrichous
20. Prokaryotic flagella are made of flagellin proteins, they are not membrane bound, and they move by spinning (they have rotary motion). Eukaryotic flagella are made up of microtubules that are arranged in 9 sets of 2 with 2 in the center. These are inside the cell membrane, so are surrounded by a layer of membrane. They move with a back-and-forth or whip-like motion.
21. pili and fimbriae Note - In some texts these terms are used interchangeably, but pili and fimbriae do differ in both structure and function. Fimbriae are more numerous per cell, shorter, and are used for attachment to various surfaces while pili are few in number (1-2 per cell), longer, and are used for attaching bacteria together during genetic exchange. They are sometimes called sex pili.
22. sex pili
23. axial filaments or endoflagella
24. capsule/ slime layer/ reservoir of stored food materials
25. Matching (Cell structure and function) B=both, E=eukaryotic, P=prokaryotic
C/E
F/B
G/B
D/P
J/B
A/E
I/P
H/E
B/P
E/P
Note - Some prokaryotic cells have histone-like proteins or histones, but histones are more likely to be found in eukaryotic cells. Some eukaryotic cells may have a glycocalyx, and a few contain plasmids, but these structures are more common to prokaryotes.
26. glycocalyx/The glycocalyx (capsule or slime layer) serves as a reservoir of stored food, it aids in attachment to smooth surfaces, it provides protection from predators, desiccation or phagocytosis by white blood cells. In the case of pathogenic bacteria, the glycocalyx aids pathogenicity by protecting the cells against host defenses.
27. peptidoglycan
28. physical factors (heat, drying, radiation, pressure)/ chemicals
29. mesosomes
30. thylakoids/ ATP
31. carboxysomes
32. metachromatic granules/ they are used to regulate buoyancy of cells in water
33. nucleoid/ plasmids
34. endospores/ heat, drying, radiation, pressure changes and toxic chemicals
35. Vegetative cells contain considerable water, RNA and enzymes and their metabolic activities occur at a rapid rate. Endospores contain little or no water and so lack metabolic activity. They contain mostly DNA and very little RNA, but also have high levels of calcium and dipicholinic acid within their cytoplasm. Endospores can remain viable (alive) much longer than typical vegetative cells (evidence is now available that indicates they can survive within amber for millions of years), they do not reproduce, and they tend to be extremely resistant to environmental factors such as heat, radiation, pressure and toxic chemicals; much more so than are vegetative cells. While vegetative cells typically have a single membrane and wall, endospores have multiple layers of covering material (cortex, spore coat, inner and outer spore membranes). These help provide extra protection against damage.
36. endospores/ They allow cells to survive periods of unfavorable conditions. The vegetative cells of the population may die, but the spores survive and give rise to new cells when conditions improve.
37. germination
38. heterocysts/ akinetes
Copyright 2002 Sierra College Biological Sciences Department
Last updated: 01/18/02.
