Chapter 3 Chat

What belief suggested that life could arise from non-living matter?

Spontaneous generation

Why did spontaneous generation need to be disproven?

If life arose from non-living matter, there would be no point in studying cells or how bacteria spread disease

Who performed an early experiment to challenge spontaneous generation?

Francesco Redi

Who eventually succeeded in disproving spontaneous generation?

Louis Pasteur

Who formulated the cell theory?

Schleiden and Schwann

What does the cell theory state?

All living things are composed of one or more cells

Which scientists were instrumental in establishing the Germ Theory of Disease?

Semmelweis, Lister, Pasteur, Koch, and others

What are the two basic cell types?

Prokaryotic and eukaryotic cells

What are all prokaryotes?

Single-celled bacteria

Which organisms are eukaryotes?

Plants, animals, fungi, and protists

What do both prokaryotic and eukaryotic cells have in common?

They are surrounded by a cell membrane and encode genetic information as DNA

What is pleomorphism?

When the same bacterial species varies widely in shape

Why do prokaryotic arrangements form?

Cells divide but do not separate

What contains a prokaryotic cell's DNA?

The nucleoid and plasmids

What are prokaryotic ribosomes called?

70S ribosomes

What two subunits make up a 70S ribosome?

30S small subunit and 50S large subunit

What are prokaryotic ribosomal subunits composed of?

Proteins and rRNA components

What do granules store in prokaryotic cells?

Substances such as glycogen, starch, or polyphosphate

What are polyphosphate granules called?

Volutin

What do sulfur granules contain and who uses them?

Sulfur for Thiobacillus species used in metabolism

What are vesicles?

Membrane-bound inclusions

What is the function of gas vacuoles?

Regulate gas to adjust floating depth for photosynthesis

What do carboxysomes contain?

RuBisCo and carbonic anhydrase for photosynthesis

What may some inclusions store for carbon usage?

Lipids (polyhydroxybutyrate)

Why are polyhydroxybutyrate inclusions important industrially?

They can be a source of polymers

What do magnetosomes contain?

Magnetic iron for magnetotactic bacteria

When do vegetative cells produce endospores?

When growth conditions are unfavorable

What is an endospore?

A type of resting stage produced by vegetative cells

What characteristics make endospores highly resistant?

They contain very little water

What are endospores resistant to?

Heat, drying, acids, bases, certain disinfectants, and radiation

What layers make up an endospore?

Core, cortex, spore coat, and sometimes an exosporium

What are bacterial cell membranes mostly composed of?

Proteins and phospholipids

What model represents our current understanding of the cell membrane?

The fluid-mosaic model

What is the fluid-mosaic model?

A phospholipid bilayer with embedded proteins

Which part of the phospholipid is hydrophilic?

The phosphate ends

Which part of the phospholipid is hydrophobic?

The fatty acid ends

What molecules are interspersed among membrane lipids?

Protein molecules

What are the functions of the plasma membrane?

Synthesizes wall components, secretes proteins, carries out cellular respiration, and controls what enters and leaves the cell

What type of transport moves substances from high concentration to low concentration without energy?

Simple diffusion

What is osmosis?

The simple diffusion of water molecules

What type of passive transport uses transport proteins?

Facilitated diffusion

What type of membrane transport requires energy?

Active transport

What are the functions of the bacterial cell wall?

Maintains cell shape and prevents bursting from osmotic pressure

What is the most important component of the bacterial cell wall?

Peptidoglycan

How is peptidoglycan structured?

Alternating N-acetylglucosamine and N-acetylmuramic acid molecules cross-linked by tetrapeptides

How many amino acids are in a tetrapeptide cross-link?

Four

How many peptidoglycan layers can Gram-positive bacteria have?

Up to 40 layers

What type of cross-link is found in Gram-positive bacteria?

Pentapeptide crosslink

Which amino acid is in the third position of the Gram-positive tetrapeptide?

Lysine

What acid is found in most Gram-positive species?

Teichoic acid

What structure is present in Gram-positive bacteria?

Periplasm

How many peptidoglycan layers do Gram-negative bacteria have?

Only a few layers

What type of cross-link is found in Gram-negative bacteria?

A simple peptide bond with no pentapeptide crosslink

Which amino acid is in the third position of the Gram-negative tetrapeptide?

Diaminopimelic acid

What structures are characteristic of Gram-negative bacteria?

Periplasmic space and outer membrane

Where is the outer membrane found?

Primarily in Gram-negative bacteria

What is the outermost layer of the Gram-negative cell wall?

The outer membrane

How is the outer membrane attached to peptidoglycan?

By small lipoprotein molecules

What is one function of the outer membrane?

It can prevent some proteins from entering the cell

What molecule is found in the outer portion of the outer membrane?

Lipopolysaccharide

How can lipopolysaccharide be used?

For identification of bacteria

Why is lipopolysaccharide medically important?

It is responsible for the toxicity of some Gram-negative infections

What is another name for lipopolysaccharide?

Endotoxin

What are the three components of lipopolysaccharide?

Polysaccharide, lipid A, and O antigen

Which part of lipopolysaccharide is responsible for toxicity?

Lipid A

What does glycocalyx refer to?

All polysaccharide-containing substances external to the cell wall

What are capsules?

Protective structures secreted by the organism

What is the function of capsules?

Protect the organism from digestion and destruction

How do slime layers differ from capsules?

They are thinner and less tightly bound

What are the functions of slime layers?

Protect from desiccation and help organisms stick to surfaces

Where are S-layers found?

Outside the cell wall

What role can the S-layer play in some archaea?

It serves as the cell wall

What is known about the function of S-layers?

Their exact function is unclear and may differ among microbes

What are pili?

Tiny hollow projections used to attach bacteria to surfaces or each other

What are conjugation pili also called?

Sex pili

What is the function of conjugation pili?

Attach two cells and may provide a pathway for genetic transfer

What are attachment pili also called?

Fimbriae

What is the function of attachment pili?

Help bacteria adhere to surfaces

What surfaces can attachment pili help bacteria adhere to?

Cell surfaces and the interface between water and air

What is a pellicle?

A layer of bacteria held together by attachment pili on top of media

About what fraction of known bacteria are motile?

About half

What structure allows bacteria to move?

Flagella

What are flagella?

Long, thin, helical appendages

What does monotrichous mean?

One flagellum

What does amphitrichous mean?

Two flagella at opposite ends

What does lophotrichous mean?

Two or more flagella at one end

What does peritrichous mean?

Flagella all over the cell

What does atrichous mean?

No flagella

What is chemotaxis?

Movement of bacteria toward or away from a substance in a nonrandom way

What additional eukaryotic topic is required reading?

Evolution by Endosymbiosis