A2.2 Prokaryote Cell Structure

Question 1

Prokaryote cells are _____________________.

Answer 1

Single celled organisms that lack a membrane bound nucleus and organelles.

Question 2

Gram Positive Bacteria have _____________________.

Answer 2

Simpler cell walls with a large amount of peptidoglycan.

Question 3

Gram Negative Bacteria have _____________________.

Answer 3

An additional outer membrane and a lesser amount of peptidoglycan.

Question 4

Cell Wall: Description/Composition

Answer 4

The cell wall is composed primarily of peptidoglycan (a carbohydrate macromolecule).

Question 5

Cell Wall: Location

Answer 5

The cell wall lies outside the plasma membrane, surrounding the cell.

Question 6

Cell Wall: Function

Answer 6

The cell wall gives the cell shape, prevents rupture, and serves as an anchorage point for flagella. Essentially, its function is structural support and protection.

Question 7

Fimbriae: Description/Composition

Answer 7

Fimbriae are hair-like structures that are shorter, straighter, and thinner than flagella.

Question 8

Fimbriae: Location

Answer 8

Fimbriae are typically located on the surface of the cell.

Question 9

Fimbriae: Function

Answer 9

Fimbriae are used for attachment. Special fimbriae known as sex pili are used to exchange genetic material (plasmids) in conjugation.

Question 10

Circular Chromosome: Description/Composition

Answer 10

A chromosome in bacteria that takes the form of circular DNA. The DNA is ‘naked’, meaning it is not associated with proteins.

Question 11

Circular Chromosome: Location

Answer 11

The circular chromosome occurs within the nucleoid.

Question 12

Circular Chromosome: Function

Answer 12

The circular chromosome allows for faster replication than in eukaryotic cells. However, it is essentially genetic material.

Question 13

Spherical Prokaryote Cell

Answer 13

Coccus (Plural: Cocci)

Question 14

Rod-Shaped Prokaryote Cell

Answer 14

Bacillus (Plural: Bacilli)

Question 15

Spiral-Shaped Prokaryote Cell

Answer 15

Spirillum (Plural: Spirilla)

Question 16

Occurs in Pairs

Answer 16

Diplo—

Question 17

Occurs in Clumps

Answer 17

Staphylo—

Question 18

Occurs in Strings

Answer 18

Strepto—

Question 19

Plasma Membrane: Description/Composition

Answer 19

The plasma membrane is similar in composition to eukaryotic membranes, although less rigid. It consists of a lipid bilayer that is semipermeable.

Question 20

Plasma Membrane: Location

Answer 20

The plasma membrane is found inside the cell wall.

Question 21

Plasma Membrane: Function

Answer 21

The plasma membrane controls the entry and exit of substances in the cell, pumping some of them in by active transport.

Question 22

Cytoplasm: Description/Composition

Answer 22

The cytoplasm is a gel-like matrix that contains cell structures such as ribosomes, a chromosome, and plasmids.

Question 23

Cytoplasm: Location

Answer 23

The cytoplasm is enclosed in the cytoplasmic membrane.

Question 24

Cytoplasm: Function

Answer 24

The cytoplasm contains enzymes needed for all metabolic processes. It is where functions for cell growth, metabolism, and replication are carried out.

Question 25

Flagella: Description/Composition

Answer 25

The flagella have a whip-like appearance. They are longer and thicker than fimbriae.

Question 26

Flagella: Location

Answer 26

The flagella are anchored in the plasma membrane.

Question 27

Flagella: Function

Answer 27

The flagella are used for locomotion.

Question 28

Ribosomes (70S): Location

Answer 28

70S ribosomes are free in the cytoplasm.

Question 29

Ribosomes (70S): Function

Answer 29

70S ribosomes are used for protein synthesis.

Question 30

Define Exotoxins.

Answer 30

Exotoxins are proteins that are released from gram positive bacteria.

Question 31

Define Endotoxins.

Answer 31

Endotoxins are parts of the bacterial cell wall that are released when a gram negative bacteria cell breaks down.

Question 32

What is conjugation?

Answer 32

Prokaryotes can also transfer DNA in the process of conjugation, in which two cells are temporarily joined and one cell transfers DNA to the other.

Question 33

Describe the steps of conjugation.

Answer 33

1. A cell with a plasmid forms a mating bridge with another cell.
2. A single strand of the plasmid breaks and begins to move into the recipient cell.
3. The plasmid begins to be replicated (to become double stranded).
4. Finally, the transfer is complete. Both cells now contain a copy of the plasmid.

Question 34

What is binary fission?

Answer 34

Binary fission is a form of asexual reproduction, in which the parent cell divides into two genetically identical daughter cells.

Question 35

Outline the stages of binary fission.

Answer 35

1. Reproduction Signal
2. Replication of DNA
3. Segregation of DNA
4. Cytokinesis

Question 36

What occurs in the first stage of binary fission?

Answer 36

1) Reproduction Signal: The cell receives a signal, internal or external, that initiates the cell division.

Question 37

What occurs in the second stage of binary fission?

Answer 37

2) Replication of DNA: Bacterial cells have a single condensed loop of DNA. This is copied to produce two identical copies of the DNA molecule, one for each of the daughter cells.

Question 38

What occurs in the third stage of binary fission?

Answer 38

3) Segregation of DNA: The two DNA loops become attached to some contractile proteins that pull them to opposite ends of the cell.

Question 39

What occurs in the fourth and final stage of binary fission?

Answer 39

4) Cytokinesis: The cytoplasm divides. As the plasma membrane begins to pinch and constrict, the membrane fuses and seals with an additional new membrane also being formed.