Chapter 6 the Cellular Structure and Characteristics of Prokaryotic Cells

Chapter 6 The Cellular Structure and Characteristics of Prokaryotic Cells

I. Prokaryotic Cell Structure

A. Cell envelope

1. cell membrane

2. cell wall

3. possible capsule

B. Glycocalyces

1. glycocalyx

a. loose meshwork of fibrils - needs glucose

b. helps bacteria stick to surfaces

c. two types: capsule and slime layer

2. capsule

a. bacteria called encapsulated

b. gelatinous - thick

c. made by enzymes at surface of cell membrane

d. composition

-polysaccharides, lipids, and/or proteins

-important to know for id.

e. bacterial colonies appear smooth, glistening, mucoid (S)

f. function

-protection

-reservoir for food storage

-waste disposal

-enhances invasive/infective ability - virulence (ability to cause disease)

g. example: Bacillus anthracis (anthrax)

3. slime layer

a. less thick than capsule

b. not as tightly bound to cell

c. more easily removed

d. example: Streptococcus mutans (cavities)

-bacteria stick on enamel of teeth forming plaque

- plaque - produces acetic substances

-caries/cavities

4. nonencapsulated

a. bacterial colonies appear rough (R)

b. quickly engulfed/destroyed by wbc

c. not as virulent as encapsulated

d. example: Haemophilus influenzae(some forms of meningitis)

C. Cell wall

1. between capsule (if present) and cell membrane

2. provides shape

3. important in cell growth and division

4. have distinct gram staining traits

a. gram positive

b. gram negative

D. Characteristics of gram positive cell walls

1. thicker than gram negative bacteria

2. layer upon layer of peptidoglycan

3. layers connected by amino acid bridges

4. teichoic acids present

a. helps bacteria attach to surfaces

b. provides rigidity

c. helps in cell growth regulation

5. can't be dissolved by solution of acetone-alcohol - stain purple

6. Examples: Streptococcus pneumoniae(bacterial pneumonia),

Streptococcus pyogenes(strep throat)

E. Characteristics of gram negative cell walls

1. made of peptidoglycan

-lipoprotein

-liposaccharide

-phospholipid

2. liposaccharide

-helps bacterium to secrete toxins

-by itself can cause symptoms characteristic of disease caused by bacterium

from which it came

3. not as thick as gram positive bacteria

4. cell wall more easily destroyed

5. can be dissolved by acetone-alcohol solution - stain red

6. Examples: Escherichia coli(food poisoning),Neisseria gonorrhaeae(gonorrhea)

F. Cell Membrane

1. composition - 60% protein 40% lipid

2. function

a. semipermeable

b. contain enzymes - cytochromes and dehydrogenases - used in cellular

respiration (ATP)

3. mesosomes

a. inward foldings of cell membrane

b. where cytochromes and hydrogenases found - therefore part of active transport system producing high energy ATP molecules

c. increase surface area

d. in gram positive only

e. helps to synthesize and divide DNA during cell division

f. helps to form new cell wall

4. exoenzymes

a. location

-outside cell surface

- in periplasmic space - space between cell wall and cell membrane

b. digest large molecules outside cell membrane

5. permeases - enzymes that help transport molecules across cell membrane

6. enzymes for making DNA, cell wall, and membrane lipids found here

G. Nucleoid

1. area where DNA found

2. DNA circular strand

a. acetic

b. 1mm long

c. surrounded by proteins

d. coiled around RNA

3. controls all cell activity

H. Plasmids

1. extra chromosomal DNA molecule

2. transfer genetic info. between bacteria

3. determines whether it is resistant/sensitive to antibiotics

4. not needed for life

I. Ribosomes

1. protein synthesis

2. clusters of ribosomes - polyribosomes

J. Flagella

1. composition - protein - flagellin

2. function - movement

3. long threadlike extension

4. grouped according to number/ arrangement of flagella

a. monotrichous - one

b. lophotrichous - tuft at one end

c. amphitrichous - 2 - one at each end

d. peritrichous - all over

K. Other Appendages

1. Fimbria

a. short/fine threadlike extensions

b. help keep bacteria near surface of liquid

c. help absorb more oxygen/nutrients

d. associated with disease causing bacteria

e. help stick to each other and other cells or surfaces

f. move fluids over surface

g. examples: Escherichia coliand Neisseria gonorrhaeae

2. F or sex pilus

a. transfer of genetic information from one bacterium to another

b. pilus bridge - connects bacteria/used to transfer DNA

c. called conjugation

3. binary fission

II. Endospores

A. definition -

1. several layers of protein surrounding bacterial DNA - called spore/endospore

2. helps bacteria survive unfavorable environment

3. resistant to most chemicals, drying, freezing, heating, and radiation

4. only in rod shaped bacteria

B. Sporogenesis - spore formation

C. Dormant - many years

D. Germinate - begins to grow when environmental conditions improve

E. Refractive

1. able to bend light

2. easily detected under light microscope

F. Some produce deadly toxins

G. Examples:

1. aerobic Bacillus cereus(food poisoning)

2. anaerobic Clostridium tetani(tetanus) and Clostridium botulinum(botulism)