Biology Chapter on Cells and Prokaryotes

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Questions and Answers

What is the significance of the surface area to volume ratio in cells?

It increases the rate of cell division.

It allows cells to grow larger without restrictions.

It affects the speed of genetic information transfer.

It ensures efficient material exchange as a cell grows. (correct)

Which of the following correctly describes a feature of prokaryotic cells?

They have a single circular chromosome. (correct)

They do not have a cell wall.

They have a nucleus and linear chromosomes.

They contain membrane-bound organelles.

In which kingdom would you classify a simple eukaryotic organism?

Animalia

Fungi

Monera

Protista (correct)

What role does the capsule play in prokaryotic cells?

It protects against host immune systems. Signup and view all the answers

Which structure in prokaryotic cells is primarily responsible for movement?

Flagella Signup and view all the answers

What is the primary function of the Glycocalyx in bacterial cells?

Offers protection and aids in adhesion Signup and view all the answers

Which flagella arrangement consists of a tuft of flagella at one or both ends?

Lophotrichous Signup and view all the answers

How does facilitated diffusion differ from simple diffusion?

Facilitated diffusion requires transport proteins Signup and view all the answers

What distinguishes endospores from regular cellular forms of bacteria?

Endospores can survive harsh conditions Signup and view all the answers

What do phospholipids in the plasma membrane primarily form?

A bilayer with hydrophobic tails inside Signup and view all the answers

Which type of movement across the plasma membrane involves molecules moving from low to high solute concentration?

Active transport Signup and view all the answers

What is the main role of cholesterol in eukaryotic cell membranes?

To maintain membrane fluidity and stability Signup and view all the answers

Which statement about bacterial and archaeal cell walls is accurate?

Archaeal cell walls lack peptidoglycan Signup and view all the answers

What component is present in the cell walls of Gram-negative bacteria?

Outer membrane with lipopolysaccharides Signup and view all the answers

Which step in the Gram staining procedure causes the stain to be washed out of Gram-negative bacteria?

Alcohol/Acetone Signup and view all the answers

What is the primary purpose of using a basic dye in staining bacterial cells?

Enhances cell shape contrast Signup and view all the answers

Which of the following bacterial arrangements describes clusters of cocci?

Staphylo- Signup and view all the answers

What type of stain is specifically used to visualize the protective outer layer surrounding certain bacteria?

Capsule Stain Signup and view all the answers

What is the role of iodine in the Gram staining process?

It forms a complex with crystal violet. Signup and view all the answers

Why is the Gram stain procedure essential for bacterial classification?

It guides treatment options and identifies cell wall structure. Signup and view all the answers

Study Notes

Cell Theory and Surface Area to Volume Ratio

Cell Theory: All living organisms are comprised of cells, which are the fundamental units of life, and all cells originate from pre-existing cells.
Surface Area to Volume Ratio: As cell size increases, volume grows faster than surface area, inhibiting efficient transport of nutrients and waste. Small cells facilitate better material exchange.

Differences Between Prokaryotic and Eukaryotic Cells

Prokaryotic Cells: Do not have a nucleus or membrane-bound organelles; contain a single, circular chromosome in the nucleoid.
Examples include Bacteria and Archaea; their cell walls are made of peptidoglycan.
Eukaryotic Cells: Feature a nucleus and membrane-bound organelles, with linear chromosomes in DNA.
Examples include animal cells, plant cells, fungal cells, and protists; plant cells have a cellulose cell wall, while fungi have chitin.

Evolution of the 5 Kingdoms of Life

Historical classification includes five kingdoms:
- Monera (prokaryotes),
- Protista (simple eukaryotes),
- Fungi,
- Plantae,
- Animalia.

Structure and Function of Prokaryotic Features

Plasma Membrane: Controls substance passage and nutrient transport.
Cell Wall: Provides structural integrity and protection, primarily through peptidoglycan in bacteria.
Flagella: Enables movement via motor at the base; axial filament found in spirochetes facilitates corkscrew movement.
Fimbriae and Pili: Hair-like structures aiding in attachment and genetic exchange.
Capsule: Protects against immune defenses and assists in adhesion. Glycocalyx offers additional protection and contributes to virulence.
Endospore: A resilient, dormant bacterial form that can endure extreme conditions.

Four Flagella Arrangements

Monotrichous: Single flagellum at one end.
Lophotrichous: Cluster of flagella at one or both ends.
Amphitrichous: One flagellum at each end.
Peritrichous: Flagella distributed across the entire surface.

Four Components of the Plasma Membrane

Fluid Mosaic Model: Membrane structure held together by hydrogen bonds.
Phospholipids: Form a bilayer with hydrophobic tails inward and hydrophilic heads outward.
Proteins: Integral and peripheral proteins assist in transport, signaling, and structural integrity.
Carbohydrates: Attached to proteins or lipids for cell recognition and communication.
Cholesterol (in eukaryotic cells): Reinforces membrane fluidity and stability.

Four Types of Movement Across the Plasma Membrane

Simple Diffusion: Molecules move from high to low concentration without energy, ideal for small hydrophobic substances.
Facilitated Diffusion: Involves transport proteins for larger hydrophilic molecules to move down their concentration gradient.
Active Transport: Movement against concentration gradients using ATP for energy.
Osmosis: Water movement from a low to high solute concentration through a selectively permeable membrane.

Bacterial and Archaeal Cell Walls; Gram-Positive vs. Gram-Negative

Gram-Positive Bacterial Cell Walls: Characterized by a thick peptidoglycan layer and stains purple; contains teichoic acids.
Gram-Negative Bacterial Cell Walls: Feature a thin peptidoglycan layer with an outer membrane containing lipopolysaccharides, staining pink/red.
Archaeal Cell Walls: Do not contain peptidoglycan; use polymers like pseudopeptidoglycan.

Gram Stain Procedure

Purpose: Differentiates Gram-positive and Gram-negative bacteria.
Steps include staining with crystal violet, forming a complex with iodine, washing with alcohol/acetone, and counterstaining with safranin.

Cell Shapes and Arrangements of Bacteria

Shapes:
- Cocci: Spherical
- Bacilli: Rod-shaped
- Spirilla: Spiral-shaped
Arrangements:
- Diplo-: pairs
- Strepto-: chains
- Staphylo-: clusters

Bacterial Smear

Defined as a thin layer of bacteria on a slide for staining and microscopic evaluation.
Preparation involves spreading bacteria on a slide, air-drying, and heat-fixing over a flame.

Acidic vs. Basic Dye & Simple Staining

Acidic Dye: Negatively charged, stains background (e.g., nigrosin).
Basic Dye: Positively charged and binds to negatively charged bacterial cells (e.g., crystal violet).
Simple Staining elevates contrast to enhance observation of cell morphology.

Staining Techniques

Gram Stain: Differentiates bacteria by cell wall structure.
Acid-Fast Stain: Identifies mycobacteria with waxy walls.
Capsule Stain: Visualizes the protective capsule around bacteria.
Endospore Stain: Detects spores resilient to extreme conditions.

Importance of Staining

Gram Stain: Essential for classifying bacteria, guiding treatment decisions.
Acid-Fast Stain is critical for identifying mycobacteria due to their resistant cell walls.

Negative Stain & Fixing

Negative Stain: Colors the background, leaving the cell clear due to repulsion by negative charge.
Fixation: Destroys bacteria and secures them to the slide for staining.

Appearance of Unstained vs. Stained Endospores

Unstained endospores: Clear or refractile areas under a microscope.
Stained endospores: Appear green when using keratin-specific stains like malachite green.

Evolution of Eukaryotic Cells & Endosymbiotic Theory

Eukaryotic cells likely evolved from prokaryotes through endosymbiosis, where larger cells engulf smaller cells that became organelles (e.g., mitochondria and chloroplasts).

Structure and Function of Eukaryotic Organelles

Plasma Membrane: Governs substance movement.
Cell Wall: Provides support in plants and fungi.
Nucleus: Houses DNA and regulates cell activities.
Rough ER: Synthesizes proteins.
Smooth ER: Produces lipids and detoxifies chemicals.
Golgi Complex: Modifies and packages proteins.
Mitochondria: Site of ATP production.
Lysosomes: Break down waste and cellular debris.

Prokaryotes vs. Eukaryotes

Prokaryotes: Simple structure, absence of membrane-bound organelles, generally smaller (e.g., bacteria).
Eukaryotes: Complex structure with membrane-bound organelles, larger in size (e.g., plants, animals, fungi).

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Description

Explore the essential features of cells in this quiz focusing on the surface area to volume ratio, characteristics of prokaryotic cells, and their functions within different kingdoms. Test your knowledge on the importance of structures such as the capsule and Glycocalyx in bacterial cells. Get ready to dive into the fascinating world of cellular biology!