Prokaryotic Structures Quiz

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Questions and Answers

What happens to the frequency of tumbles in bacteria when exposed to a negative chemotactic signal?

It causes a complete cessation of movement.

It remains the same regardless of the stimulus.

It decreases as the bacteria become more attracted to the stimulus.

It increases as the bacteria move away from the stimulus. (correct)

What protein do fimbriae in gram-negative bacteria primarily consist of?

Pilina

Pilins (correct)

Flagellin

Archaellin

What is the primary function of archaella in motile archaeal cells?

To anchor the cell to surfaces.

To provide genetic material transfer.

To rotate and propel the cell through water. (correct)

To form biofilms with other cells.

Which structures do spirochetes use for their unique mode of movement?

Axial filaments Signup and view all the answers

How do fimbriae enhance bacterial adherence in their environment?

By adhering to biotic and abiotic surfaces. Signup and view all the answers

What is the primary function of gas vacuoles in aquatic prokaryotes?

To maintain buoyancy for optimal positioning in the water Signup and view all the answers

Which mineral is primarily found in magnetosomes?

Iron oxide Signup and view all the answers

What process leads to the formation of endospores in certain bacteria?

Sporulation Signup and view all the answers

What is dipicolinic acid's role in endospores?

It protects DNA from damage Signup and view all the answers

Which of the following statements about endospores is accurate?

Endospores can thrive in extreme environmental conditions. Signup and view all the answers

What are magnetotactic bacteria known for?

Having magnetosomes for directional movement Signup and view all the answers

Where within a vegetative cell can endospores be located?

Terminally, subterminally, or centrally Signup and view all the answers

What does the core of an endospore primarily consist of?

DNA, RNA, ribosomes, and enzymes Signup and view all the answers

What primary component is found in the cell walls of fungi?

Chitin Signup and view all the answers

Which of the following statements is true regarding the plasma membrane of eukaryotic cells?

Sterols are present, which are absent in prokaryotic plasma membranes. Signup and view all the answers

What is the role of the glycocalyx in eukaryotic cells?

Contains sticky carbohydrates for cell interaction. Signup and view all the answers

Which mechanism is NOT a form of endocytosis in eukaryotic cells?

Transcytosis Signup and view all the answers

How do protozoa differ from many eukaryotic cells regarding their outer covering?

They have a flexible outer protein covering called a pellicle. Signup and view all the answers

What role do integral membrane proteins play in facilitated diffusion?

They facilitate the movement of ions or large molecules across the plasma membrane. Signup and view all the answers

What is an isotonic solution?

A solution where the concentration of solutes equals that found inside a cell. Signup and view all the answers

What is the direction of water movement during osmosis?

From an area of low solute concentration to high solute concentration. Signup and view all the answers

What is the function of aquaporins in cellular osmosis?

They serve as channels specifically for water molecules. Signup and view all the answers

Which statement describes a hypotonic solution?

The solution has a lower concentration of solutes than the cells. Signup and view all the answers

What describes osmotic pressure?

The pressure required to prevent the movement of pure water into a solution with solutes. Signup and view all the answers

What type of diffusion specifically involves the use of transporter proteins?

Facilitated diffusion Signup and view all the answers

What happens during the equilibrium phase of osmotic pressure in a closed system?

Water molecules move equally in both directions with no net change in volume. Signup and view all the answers

What occurs when lysozyme is applied to gram-positive cells?

The cell wall is almost completely destroyed. Signup and view all the answers

Which structure is formed when a gram-negative cell reacts to lysozyme?

Spheroplast Signup and view all the answers

What is the primary function of peripheral proteins in the plasma membrane?

To catalyze chemical reactions and provide membrane support. Signup and view all the answers

The phospholipid bilayer of the plasma membrane consists of which of the following?

Hydrophilic polar heads on the surface and hydrophobic tails in the interior. Signup and view all the answers

What distinguishes integral proteins from peripheral proteins?

Integral proteins typically span the whole membrane. Signup and view all the answers

Which of the following statements is true regarding L forms of bacteria?

L forms can revert back to the walled state. Signup and view all the answers

Which component is a major part of the plasma membrane's composition?

Phospholipids as the most abundant chemicals. Signup and view all the answers

What can trigger the formation of L forms in bacteria?

Exposure to penicillin or lysozyme Signup and view all the answers

Study Notes

Nitrifying Bacteria and Acidithiobacilli

Nitrifying bacteria are essential for the nitrogen cycle, converting ammonia into nitrites and nitrates.
Acidithiobacilli are acidophilic bacteria involved in the oxidation of sulfide minerals, playing a crucial role in bioleaching.

Gas Vacuoles

Hollow cavities in aquatic prokaryotes, such as cyanobacteria, enable buoyancy for optimal light and nutrient access.
Essential for maintaining proper depth in water environments.

Magnetosomes

Inclusions of iron oxide (Fe3O4) encapsulated by plasma membrane invaginations assist in orientation and movement in aquatic environments.
Found in species like Magnetospirillum magnetotacticum, typically discovered in shallow freshwater sediment.

Endospores

Formed by certain gram-positive bacteria (e.g., Clostridium, Bacillus) under nutrient depletion as highly durable "resting" cells.
Feature thick protective walls and layers, allowing survival under extreme conditions such as heat and radiation.
Process of endospore formation takes several hours and is called sporulation.

Endospore Characteristics

Location can vary: terminal, subterminal, or centrally within the vegetative cell.
Composed of dipicolinic acid (DPA) and calcium ions to protect DNA.
Germination returns endospores to a vegetative state.

Bacterial Motility

Flagella: Structure for movement, with rotation propelling bacteria through media.
Archaella: Unique to archaeal cells, serve a similar function, using ATP and lacking a core.
Axial Filaments: Present in spirochetes, facilitate spiral movement by rotating beneath an outer sheath.

Fimbriae and Pili

Hairlike appendages in many gram-negative bacteria, composed of pilin protein.
Vital for adherence to surfaces and biofilm formation, can range from a few to hundreds per cell.

Protoplasts and L-forms

Protoplasts are wall-less cells capable of metabolism, formed when lysozyme affects gram-positive bacteria.
L-forms can occur in various genera, losing cell walls in response to antibiotics and retaining the ability to divide.

Plasma Membrane Structure

Comprises a lipid bilayer with phospholipids and proteins, lacking sterols compared to eukaryotic membranes.
Contains peripheral proteins (easy to remove) and integral proteins (only removable by disrupting the bilayer).

Facilitated Diffusion

Involves integral proteins that serve as channels for ion or large molecule movement across the plasma membrane.
Can be specific for certain larger molecules, aiding in nutrient absorption.

Osmosis

Water movement occurs from high to low concentration areas across selectively permeable membranes.
Defined terms include isotonic (equal solute concentration), hypotonic (lower outside), and hypertonic (higher outside).

Cell Wall and Glycocalyx

Most eukaryotic cells have simpler cell walls than prokaryotes, with algae walls primarily composed of cellulose and fungi walls made of chitin.
Yeast cell walls contain glucan and mannan, while protozoa have flexible pellicles instead of typical walls.

Eukaryotic Plasma Membrane

Eukaryotic membranes feature carbohydrates for bacterial attachment and receptors for cell recognition.
Unique to eukaryotic cells, endocytosis processes include phagocytosis, pinocytosis, and receptor-mediated endocytosis for nutrient uptake.

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Description

Test your knowledge on various prokaryotic structures such as gas vacuoles, magnetosomes, and other unique features of bacteria. This quiz covers the functionality and significance of these adaptations in aquatic environments. Challenge yourself with questions about nitrifying bacteria and cyanobacteria!