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Question 1

wohler

Answer 1

The idea that organic chemicals could come only from living
organisms had to be abandoned in 1828, when Friedrich
Wöhler (1800–1882) synthesized urea, an organic molecule,
using only inorganic reactants in his laboratory.

Question 2

Biologists agree that all living things share at

least four processes of life:

Answer 2

• grow in size
• reproduce (increase in number)
• respond to env
• Metabolism can be defined as the ability of
  organisms to take in nutrients from outside themselves and
  use the nutrients in a series of controlled chemical reactions
  to provide the energy and structures needed to grow,
  reproduce, and be responsive.

Question 3

schwann n schleiden

Answer 3

developed the theory that all

living things are composed of cells.

Question 4

The distinctive feature

of prokaryotes is that

Answer 4

they can make proteins simultaneously
to reading their genetic code because a typical prokaryote does
not have a membrane surrounding its genetic material (DNA).
In other words, a typical prokaryote does not have a nucleus. Moreover, electron microscopy has revealed
that prokaryotes typically lack various types of internal structures
bound with phospholipid membranes that are present in
eukaryotic cells.

Question 5

glycocalyx

Answer 5

Some cells have a gelatinous, sticky substance that surrounds
the outside of the cell. This substance is known as a glycocalyx
(plural: glycocalyces), which literally means “sweet cup.” The
glycocalyx may be composed of polysaccharides, polypeptides,
or both. These chemicals are produced inside the cell and are
extruded onto the cell’s surface. Glycocalyces protect cells from desiccation (drying) and can
also play a role in the ability of pathogens to survive and cause
disease.

Question 6

slime layer

Answer 6

In contrast, a loose, water-soluble glycocalyx is called a slime
layer. For example, slime layers are often sticky and provide
one means for bacteria to attach to surfaces as biofilms, which are
aggregates of many bacteria living together on a surface.

Question 7

capsule

Answer 7

When the glycocalyx of a bacterium is composed of organized
repeating units of organic chemicals firmly attached to
the cell’s surface, the glycocalyx is called a capsule.The chemicals in many bacterial capsules can be similar
to chemicals normally found in the body preventing bacteria
from being recognized or devoured by defensive cells of
the host.

Question 8

what are flagella

Answer 8

long structures that extend beyond
the surface of a cell and its glycocalyx and propel the cell
through its environment. Not all bacteria have flagella, but for
those that do, the flagella are very similar in composition, structure,
and development

Question 9

flagella structure

Answer 9

three parts: a long, thin filament,

a hook, and a basal body

Question 10

filament

Answer 10

The hollow filament is
a long hollow shaft, about 20 nm in diameter, that extends out
into the cell’s environment. It is composed of many identical globular molecules of a protein called flagellin. The cell secretes
molecules of flagellin through the hollow core of the flagellum,
to be deposited in a clockwise helix at the lengthening tip.
Bacterial flagella sense external wetness, inhibiting their own
growth in dry habitats.

Question 11

hook

Answer 11

No membrane covers the filament of bacterial flagella. At
its base, a filament inserts into a curved structure, the hook,
which is composed of a different protein.

Question 12

basal body

Answer 12

the basal body, which is composed of still different proteins, anchors the
filament and hook to the cell wall and cytoplasmic membrane
by means of a rod and a series of either two or four rings of
integral proteins. Together the hook, rod, and rings allow the
filament to rotate 360°.

Question 13

serovars

Answer 13

Differences in the proteins associated
with bacterial flagella vary enough to allow classification of
species into groups (strains) called serovars.

Question 14

peritrichous

Answer 14

Flagella that cover the surface of the cell are termed

peritrichous

Question 15

polar

Answer 15

polar flagella are only at the ends.

Some cells have tufts of polar flagella.

Question 16

spirochetes

Answer 16

Some spiral-shaped bacteria, called spirochetes have flagella at both ends that spiral tightly around the cell instead
of protruding into the surrounding medium. These flagella called endoflagella, form an axial filament that wraps around
the cell between its cytoplasmic membrane and an outer membrane. Rotation of endoflagella evidently causes
the axial filament to rotate around the cell, causing the spirochete
to “corkscrew” through its medium.
- syphilis n Lyme disease, Some scientists think that the corkscrew
motility of these pathogens allows them to invade human tissues.

Question 17

motion of a peritrichous bacterium

Answer 17

Bacteria move with a series of “runs” interrupted by “tumbles.”
Counterclockwise flagellar rotation produces movements
of a cell in one direction for some time; this is called a run. If
more than one flagellum is present, the flagella align and rotate
together as a bundle. Tumbles are abrupt, random changes
in direction. Tumbles result from clockwise flagellar rotation
where each flagellum rotates independently.

Question 18

positive chemotaxis motion

Answer 18

runs last longer than tumbles, resulting in motion toward the
chemical attractant.

Question 19

flagella movement mechanism

Answer 19

Although the precise mechanism by which bacterial flagella
move is not completely understood, we do know that they rotate
360° like boat propellers rather than whipping from side to
side. The flow of H+ and Na+ through the cytoplasmic membrane near the basal body powers
the rotation, propelling the bacterium through the environment
at about 60 cell lengths per second. Flagella rotate at more than
100,000 rpm and can change direction from counterclockwise to
clockwise.

Question 20

flagella responding to the env

Answer 20

Receptors for light or chemicals on the surface of the cell
send signals to the flagella, which then adjust their speed and
direction of rotation. A bacterium can position itself in a more
favorable environment by varying the number and duration of
runs and tumbles. The presence of favorable stimuli increases
the number of runs and decreases the number of tumbles; as a result, the cell tends to move toward an attractant.
Unfavorable stimuli increase the number of tumbles, which increases
the likelihood that it will move randomly in another direction,
away from a repellent.

Question 21

what are fimbriae

Answer 21

rodlike proteinaceous extensions. These sticky, bristlelike
projections adhere to one another and to substances in the environment.
There may be hundreds of fimbriae per cell, and they
are usually shorter than flagella. ex: gonorrhea bacterium. Pathogens must be able to
adhere to their hosts if they are to survive and cause disease.
This bacterium is able to colonize the mucous membrane of the
reproductive tract by attaching with fimbriae. Neisseria cells that
lack fimbriae are nonpathogenic.

Question 22

fimbriae movement

Answer 22

Bacteria may use fimbriae to move across a surface via a
process similar to pulling an object with a rope. The bacterium
extends a fimbria, which attaches at its tip to the surface; then
the bacterium retracts the fimbria, pulling itself toward the attachment
point.

Question 23

biofilms

Answer 23

Fimbriae also serve an important function in biofilms,
slimy masses of microbes adhering to a substrate by means
of fimbriae and glycocalyces. Some fimbriae act as electrical
wires, conducting electrical signals among cells in a biofilm. It
has been estimated that at least 99% of bacteria in nature exist
in biofilms

Question 24

pilus

Answer 24

A special type of fimbria is a pilus, also called conjugation pilus. Pili are longer than other fimbriae
and usually shorter than flagella. Typically only one to a few
pili are present per cell in bacteria that have them. Cells use pili
to transfer DNA from one cell to the other via a process termed
conjugation

Question 25

cuboidal packets

Answer 25

(of cocci) sarcinae

Question 26

strepto vs staphylo

Answer 26

strepto: chains
staphylo: clusters

Question 27

cell wall

Answer 27

provides structure and shape to the cell and protects it
from osmotic forces. In addition, a cell wall assists some cells in attaching to other cells or in resisting antimicrobial drugs. Note
that animal cells do not have walls, a difference that plays a key
role in treatment of many bacterial diseases with certain types of
antibiotics. For example, penicillin attacks the cell wall of bacteria
but is harmless to human cells, which lack walls.
Cell walls give bacterial cells characteristic shapes.

Question 28

bacilli

Answer 28

Rod-shaped cells, called

bacilli, typically appear singly or in chains.

Question 29

peptidoglycan

Answer 29

Bacterial cell walls are composed of peptidoglycan, a complex polysaccharide. Peptidoglycan in turn
is composed of two types of regularly alternating sugar molecules,
called N-acetylglucosamine (NAG) and N-acetylmuramic
acid (NAM), which are structurally similar to glucose. Millions
of NAG and NAM molecules are covalently linked in chains in
which NAG and NAM alternate. Chains of NAG and NAM are attached to other chains by
crossbridges of four amino acids (tetrapeptides). Depending
on the bacterium, tetrapeptide bridges are either bonded to
one another or held together by short connecting chains of other
amino acids.