Prokaaryotics PT 2

What are the three main membrane transport mechanisms?

Simple diffusion, facilitated diffusion, and active transport.

What is simple diffusion?

Movement of molecules from high concentration to low concentration without assistance.

Does simple diffusion require energy?

No.

What is facilitated diffusion?

Movement of molecules across the membrane with the help of transport proteins.

Does facilitated diffusion require ATP?

No.

What is active transport?

Movement of molecules against the concentration gradient.

Does active transport require ATP?

Yes.

What is the function of the bacterial cell wall?

Maintains cell shape and protects against osmotic lysis.

What is the bacterial cell wall primarily composed of?

Peptidoglycan.

Which organisms have peptidoglycan?

Bacteria only.

Which type of bacteria has a thick peptidoglycan layer?

Gram-positive bacteria.

Which type of bacteria has a thin peptidoglycan layer?

Gram-negative bacteria.

Which bacteria have an outer membrane?

Gram-negative bacteria.

Why are Gram-negative bacteria often more resistant to antibiotics?

Their outer membrane acts as an additional barrier.

How do many antibiotics kill bacteria?

By preventing peptidoglycan synthesis.

What happens to bacteria if the cell wall is destroyed?

The cell undergoes osmotic lysis.

Do Archaea contain peptidoglycan?

No.

What may archaeal cell walls contain instead of peptidoglycan?

Pseudopeptidoglycan, polysaccharides, or protein layers.

What are glycocalyces?

Structures outside the cell wall that protect the cell and aid in attachment.

What is the function of a glycocalyx?

Protection, adhesion, and biofilm formation.

What is a capsule?

A well-organized glycocalyx firmly attached to the cell wall.

What is a slime layer?

A loose, unorganized glycocalyx that is easily removed.

Which is more difficult to remove: a capsule or a slime layer?

Capsule.

What is a biofilm?

A community of microorganisms attached to a surface.

Why are biofilms important medically?

They increase resistance to antibiotics and disinfectants.

What is an S-layer?

A protein layer surrounding some prokaryotic cells.

Where is the S-layer found?

Outside the plasma membrane.

What are fimbriae?

Short, hair-like protein appendages.

What is the primary function of fimbriae?

Attachment to surfaces and host cells.

What are pili?

Longer protein appendages than fimbriae.

What is the primary function of pili?

DNA transfer during conjugation.

Which pilus is responsible for bacterial conjugation?

Sex pilus.

What is conjugation?

Transfer of DNA from one bacterium to another through a pilus.

What are flagella used for?

Motility.

What protein makes up bacterial flagella?

Flagellin.

What is the basal body of a flagellum?

The anchor embedded in the cell envelope.

What is a monotrichous bacterium?

A bacterium with one flagellum.

What is an amphitrichous bacterium?

A bacterium with one flagellum at each end.

What is a lophotrichous bacterium?

A bacterium with a tuft of flagella at one or both ends.

What is a peritrichous bacterium?

A bacterium with flagella all over its surface.

What determines bacterial movement?

Rotation of the flagella.

What is chemotaxis?

Movement in response to chemical stimuli.

What environmental signals can bacteria respond to?

Chemicals, magnetic fields, magnetosomes, and light.

What is a run?

Straight movement in one direction.

What is a tumble?

Random reorientation that changes direction.

During chemotaxis, what happens when bacteria move toward an attractant?

Runs become longer and tumbles become less frequent.

What happens when bacteria encounter a harmful substance?

Tumbling increases.

Which bacterial structures are involved in attachment?

Fimbriae, capsules, and slime layers.

Which bacterial structure is most associated with DNA transfer?

Pili.

Which bacterial structure is most associated with movement?

Flagella.

Which bacterial structure protects against osmotic pressure?

Cell wall.

Which bacterial structure protects against drying and immune defenses?

Capsule.

Which bacterial structure stores extra DNA?

Plasmid.

Which bacterial structure synthesizes proteins?

Ribosomes.

Which bacterial structure contains the chromosome?

Nucleoid.

Which bacterial structure is selectively permeable?

Plasma membrane.

Which bacterial structure is the primary target of penicillin?

Cell wall.