Prokaryotic cells

microbio summer portion

What is a prokaryote?

A unicellular organism that lacks a true nucleus and membrane-bound organelles; belongs to Bacteria or Archaea.

What four structures do ALL prokaryotic cells have?

Plasma membrane, cytoplasm, DNA (nucleoid), and 70S ribosomes.

Where is DNA found in prokaryotes?

In the nucleoid, which is not surrounded by a nuclear membrane.

Do prokaryotes have membrane-bound organelles?

No.

What is found in the cytoplasm?

Water, ribosomes, nucleoid, plasmids, inclusion bodies, proteins, carbohydrates, lipids, and ions.

What are plasmids?

Small circular double-stranded DNA molecules that replicate independently.

Why are plasmids important?

They often carry genes for antibiotic resistance, toxins, and other advantageous traits.

Are plasmids required for bacterial survival?

No, but they improve survival under stressful conditions.

What type of ribosomes do prokaryotes have?

70S ribosomes (50S + 30S).

What does the 'S' in 70S stand for?

Svedberg unit.

Functions of the plasma membrane?

Selective permeability, transport, metabolic enzymes, separates inside from outside.

Composition of the plasma membrane?

Phospholipid bilayer with hydrophilic heads and hydrophobic tails.

Difference between passive and active transport?

Passive requires no ATP and moves down the gradient; active requires ATP and moves against the gradient.

Define osmosis.

Movement of water across a selectively permeable membrane; water follows salt.

Why do salt and sugar preserve food?

They create a hypertonic environment that pulls water out of bacteria.

What is the bacterial cell wall made of?

Peptidoglycan composed of NAG and NAM.

Functions of the bacterial cell wall?

Maintains shape, protection, prevents osmotic lysis.

How does penicillin kill bacteria?

Prevents peptidoglycan cross-linking, weakening the wall and causing lysis.

Characteristics of Gram-positive bacteria?

Thick peptidoglycan, teichoic acids, no outer membrane, stain purple.

Characteristics of Gram-negative bacteria?

Thin peptidoglycan, outer membrane containing LPS.

Which bacteria are generally more antibiotic resistant?

Gram-negative bacteria.

What makes acid-fast bacteria unique?

They contain mycolic acid in the cell wall.

Function of bacterial flagella?

Motility; made of flagellin.

What is chemotaxis?

Movement toward or away from chemical stimuli.

Difference between a run and tumble?

Run = straight movement; tumble = reorientation.

Function of fimbriae?

Attachment to surfaces.

Functions of pili?

Attachment, gliding motility, and DNA transfer during conjugation.

What is the glycocalyx?

A capsule or slime layer surrounding some bacteria.

Functions of the glycocalyx?

Protection, adhesion, immune evasion, prevents desiccation, food storage.

What are inclusion bodies?

Storage granules for glycogen, sulfur, phosphate, or lipids.

What are endospores?

Dormant, highly resistant structures formed in harsh conditions.

Which genera produce endospores?

Bacillus and Clostridium.

How do bacteria reproduce?

Binary fission (asexual reproduction).