Biology 94

Front 1

Chapter 27

Bacteria and Archaea

Front 2

Concept 27.1

Structural and functional adaptations contribute to prokaryotic success

Front 3

A key feature of nearly all prokaryotic cells is the

Back 3

Cell wall

Front 4

Most bacterial cell walls contain

Back 4

Peptidoglycan

A polymer composed of modified sugars cross-linked by short polypeptides.

This molecular fabric encloses the entire

bacterium and anchors the molecules that extend from its surface.

Front 5

Archaeal cell walls contain

Back 5

A variety of polysaccharides and proteins but

lack peptidoglycan

Front 6

Gram-positive bacteria

Back 6

Have a thick wall made of peptidoglycan. The crystal violet enters the cell, where it forms a complex with the iodine in the stain. Too large to pass through the thick cell wall, this complex is not removed by the alcohol rinse. Result: The crystal violet masks the safranin dye.

Front 7

Gram-negative bacteria

Back 7

Have a thin layer of peptidoglycan, which is located between the plasma membrane and an outer membrane that contains

lipopolysaccharides. The crystal violet-iodine complex can pass through this thin cell wall and hence is removed by the alcohol rinse. Result: The safranin dye stains the cell pick or red.

Front 8

Back 8

Gram-negative bacteria

Front 9

Back 9

Gram-positive bacteria

Front 10

The cell wall of many prokaryotes is surrounded by a sticky layer of polysaccharide or protein. This layer is called a

Back 10

Capsule, if it is dense and well defined, or a slime layer if it is no as well organized. Both kinds of sticky outer layers enable prokaryotes to adhere to their substrate or to other individuals in a colony. Some capsules and slime layers protect against dehydration, and some shield

pathogenic prokaryotes from attacks by their host's immune system.

Front 11

In another way of withstanding harsh conditions, certain bacteria develop resistant cell called ___

when they lack an essential nutrient

Back 11

Endospores

Front 12

Some prokaryotes stick to their substrates or to one another by means of

Back 12

Fimbriae

Hairlike appendages

Front 13

Pili or Sex pili

Back 13

Appendages that pull two cells together prior to DNA transfer from one cell to the other

Front 14

Taxis

Back 14

A directed movement toward or away from a stimulus

For example, chemotaxis is a directed movement in response to a chemical

Front 15

Of the various structures that enable prokaryotes to move, the most common are

Back 15

Flagella

Front 16

Prokaryotic flagella differ greatly from eukaryotic flagella

Back 16

Prokaryotic flagella are one-tenth the width and typically are not covered by an extension of the plasma membrane. The flagella or prokaryotes and eukaryotes also differ in their molecular compositions and their mechanism of

propulsion.

Front 17

Internal Organization and DNA:

Bacteria don’t have mitochondria or

chloroplasts, but still need to metabolize

Back 17

Some prokaryotic cells have specialized membranes that perform metabolic functions. These membranes are usually infoldings of the plasma membrane.

Front 18

Prokaryotes have ___ chromosomes

Back 18

Circular

Front 19

Since prokaryotes lack a nucleus, their

chromosome is located in the

Back 19

Nucleoid

A region of the cytoplasm that is not enclosed by a membrane

Front 20

Plasmids

Back 20

Smaller rings of DNA

Front 21

Three factors that contribute to the vast genetic diversity of prokaryotes.

Back 21

1. Rapid reproduction

2. Mutation

3. Genetic recombination

Front 22

Prokaryotes can reproduce quickly in favorable conditions by

Back 22

Binary fission

Front 23

Mutation

Back 23

Due to insertions, deletions and base-pair

substitutions in DNA, some offspring may differ genetically.

New mutations, though are on a per gene basis, can increase genetic diversity quickly in species with short generation times and large

populations.