Prokaryotes

Question 1

Prokaryotes are _____ organisms. Members of this group belong to the domains _____ and
_____.

Answer 1

microscopic
Archaea
Bacteria

Question 2

______ were the earliest forms of life on Earth, and they have been evolving on Earth
for over 3 _____ years, and as they continue to live and flourish on Earth, they assist in changing
Earth as well.

Answer 2

Prokaryotes
billions

Question 3

What are bacteria?

Answer 3

Bacteria are small, single-celled organisms (i.e. they are unicellular). As much as the
prokaryotes are such diverse organisms they do share unique unifying molecular and cellular
features.

Question 4

DEFINE what a prokaryote is?

Answer 4

A microscopic single-celled organism which has neither a distinct nucleus with a membrane nor other specialised organelles, including the bacteria and cyanobacteria.

Question 5

What are the general characteristics of prokaryotes? (3)

Answer 5

• Fall under Monera—>Archaea and Eubacteria
• First forms of life that assisted in the changes that allowed for more complex forms of life to occur
• Can adapt to live in almost any environment and therefore are the most abundant organisms on earth

Question 6

What are the features of archaea? (5)

Answer 6

• Unicellular, cell wall of polysaccharides and proteins
• Live in an extreme environment
• Some are methanogens.
• Found in swamps and marshes.
• Produce methane as a waste

Question 7

What are the features of bacteria? (5)

Answer 7

• Thrive almost everywhere
• Unicellular
• Microscopic, 0.8-8μm
• Astonishing diversity
• Many are covered in capsule (polysaccharide or protein layer)

Question 8

What are the 3 shapes of bacteria?

Answer 8

• Cocci (sphere)
• Diplo-,
• strepto-,
• staphylo-
• Bacilli (rods)
• Spirilla (spirals)

Question 9

The 1st layer of a bacterium is the slime layer/capsule, what is the structure of this? (4)

Answer 9

• Not always present
• Made of polysaccharides or proteins
• Dense—> capsule
• Not well organized—> slime layer

Question 10

The 1st layer of a bacterium is the slime layer/capsule, what is the function of this? (2)

Answer 10

• Sticky to allow adherence to substrates or other individuals in a colony
• Prevent dehydration or attack from host’s immune system

Question 11

True or false
The 2nd layer which is the outer polysaccharide layer/membrane is ALWAYS present.

Answer 11

FAlse, it is not always present.

Question 12

The third layer is the cell wall, what is its structure?

Answer 12

Made from peptidoglycan (modified sugars & polypeptides).

Question 13

What is the function of the cell wall? (4)

Answer 13

• Gives bacterium shape
• Provides protection
• Prevents from bursting in hypotonic (low-salt) environment
• Encloses bacterium and anchors molecules extending from surface

Question 14

What is the function of the 4th layer which is the cell membrane?

Answer 14

Encloses cytoplasm

Question 15

What are pilli?

Answer 15

Appendages that pull two cells together prior to DNA transfer from one cell to another.

Question 16

What is a plasmid? (2)

Answer 16

• Circular DNA
• Released into environment upon cell death

Question 17

What is the function of a flagella (flagellum singular) ? (4)

Answer 17

• Aids in motility of cell
• Differs entirely from flagella of eukaryotes
• Can be many or isolated on one end
• Move in response to stimulus

Question 18

What are ribsomes? (3)

Answer 18

• Smaller than eukaryotes
• 2 sub units
• Aids in protein synthesis

Question 19

DNA

• Not enclosed or ______ by membrane
• Circular chromosomes, located in _____.

Answer 19

compartmentalized
nucleoid

Question 20

What are photosynthetic lamellae? (2)

Answer 20

• Not present always
• Can produce food

Question 21

What is the gram stain technique, and who came up with it?

Answer 21

It was a technique curated by Hans Christian Gram, 19th-century Danish Physician. Staining technique used to classify two different groups of bacteria based on their cell wall composition.

Question 22

Describe the gram staining technique method? (5)

Answer 22

• Prepare slide from culture
• Stain cells with crystal violet (primary stain)
• Subsequently, Gram’s iodine (iodine and potassium iodide) is added – the specimen will look blue/violet
• Rinse with a decolouriser (ethyl alcohol or acetone)
• Counterstain with safranin (secondary stain)

Question 23

What can you deduce from the fact that it retains blue/violet colour?

Answer 23

It is a gram positive bacterium.

Question 24

What are the feautures of gram positive bacteria? (3)

Answer 24

• Thick peptidoglycan
• Produce exotoxin (toxin outside their cell). The toxin is the protein secreted during life
• Can be immunised against GP bact. with toxoids (Penicillin)

Question 25

How can gram positive bacteria be immunised? (3)

Answer 25

Gram positive: • Only produces exotoxins—\>proteins excreted during lifespan • Antibiotics such as penicillin prevents peptidoglycan cross-linking • This results in cell wall losing functionality

Question 26

What are the medical implications of staining?

Answer 26

Medicinal/treatment implications: Staining can determine whether infection is gram positive or gram negative and therefore the type of treatment required.

Question 27

What can you deduce from the fact that it retains a red colour?

Answer 27

It is a gram negative bacteria.

Question 28

What are the features of gram negative bacteria? (4)

Answer 28

- Thin peptidoglycan and LPS - Produce endotoxin (wall/LPS layer). - The structural part of the cell - ​​Streptomycin can be used to treat the cell

Question 29

How can gram negative bacteria be immunised? (3)

Answer 29

Lipids of the lipopolysaccharides in the wall are toxic, causing fever or shock. Outer membrane helps protect it from body’s defences. Membrane also makes it difficult to detect. • More resistant to antibiotic than gram positive due to membrane impeding entry of drugs • Produces both endo and exotoxins • Enter body through wound, Treatment—\> Antibiotic: streptomycin

Question 30

What are the sources of antibiotics? (3)

Answer 30

o Actinomycetes o Bacillus o Moulds

Question 31

What does penicillin do?

Answer 31

• Penicillin—\>inhibits cell wall synthesis by activating ‘transpeptidase’

Question 32

Explain penicillin resistance.

Answer 32

o Resistance—\>peniciltase: bond to penicillin molecule active sight.

Question 33

What do fluoroquinolones do?

Answer 33

Fluoroquinolones—\>inhibits DNA replication by bonding to enzyme to prevent division

Question 34

Explain fluoroquinolones resistance.

Answer 34

o Resistance—\>cell blocks bonding of enzyme

Question 35

What does tetracycline do?

Answer 35

Tetracycline—\>binds to ribosome, thereby blocking protein synthesis.

Question 36

Explain tetracycline resistance.

Answer 36

o Resistance—\>bacteria pumps compound out of cell

Question 37

What is the ecological importance of prokaryotes? (5)

Answer 37

1. Nitrogen fixers o Fix nitrogen into a form that can be used by other organisms for protein synthesis 2. Nutrient recyclers + decomposers o Recycle chemical elements between living and non-living components (unblock carbon, nitrogen and other elements) 3. Bioremediation o Remove pollution and pollutants from environment (oil spills, metal rusting) 4. Disease o Maintain strength of gene pool, maintain population 5. Natural antibiotics

Question 38

What is the endosymbiotic theory? (4)

Answer 38

• Theory stating that chloroplasts and mitochondria were integrated into eukaryotic cells - Larger cell took in smaller cell either as prey or entered as a parasite • Chloroplasts and mitochondria are known as endosymbionts • This indicates organelles in eukaryote descended from ancestral prokaryote that was engulfed by another cell (eukaryote or prokaryote) • The engulfed cell specialized into chloroplasts and mitochondria

Question 39

Provide evidence for the endosymbiotic theory. (7)

Answer 39

1. **Two different membranes:** The chloroplast is surrounded by two or more membranes, while the mitochondria are bounded by a double membrane. The inner membrane is similar to that found in prokaryotes whereas the outer membrane is similar in structure and composition to eukaryotes. 2. **Size**: The mitochondria and chloroplasts are similar in size to free**-**living prokaryotes. 3. **Structure of cristae:** The inner membrane of the chloroplasts and mitochondria perhaps derived from the members of the endosymbiotic prokaryotes have several enzymes and transport systems that resemble those found in the plasma membranes of prokaryotes. 4. **Rib**o**somes:** The ribosomes of the chloroplasts are more similar in size in biochemical characteristics to prokaryotic ribosomes than to the ribosomes outside the chloroplasts in the cytoplasm of the eukaryotic cell. 5. **DNA:** The chloroplast and mitochondria contain transferred TRNA, ribosome and other equipment needed to translate and transcribe DNA into proteins. 6. **Division:** The mitochondria and chloroplast reproduce by **a** splitting process similar to binary fission in bacteria. 7. **DNA replication:** The chloroplast and mitochondria contain DNA in the form of circular molecules not associated with histones or other proteins as in prokaryotes.