BIOL 2210 Midterm Exam I: Key Concepts in Microbiology

Section 1: The Microbial World and You

Spontaneous Generation and Pasteur's Experiment

Understanding the historical context of microbiology is essential. Louis Pasteur's experiments disproved the theory of spontaneous generation, demonstrating that bacteria grow only when introduced from external sources.

• Spontaneous Generation: The outdated belief that life could arise from non-living matter.

• Pasteur's Experiment: Showed that bacteria do not grow in sterile media unless contaminated.

• Application: Foundation for aseptic techniques in microbiology.

Chemical Principles

Covalent Bonds and Molecular Interactions

Chemical bonds are fundamental to molecular structure and function in cells.

• Covalent Bond: A bond formed by the sharing of electrons between atoms.

• Resonance: Occurs when electrons are delocalized over two or more atoms, stabilizing the molecule.

• Example: Resonance in benzene ring structures.

Hydrogen Bonds

Hydrogen bonds are weak interactions crucial for the structure of water, proteins, and nucleic acids.

• Hydrogen Bond: Attraction between a hydrogen atom and an electronegative atom (e.g., N or O).

• Example: Hydrogen bonding in water molecules.

Polarity and Solubility

The polarity of molecules affects their solubility and interactions in aqueous environments.

• Polar Molecules: Dissolve well in water due to charge separation.

• Nonpolar Molecules: Do not dissolve well in water.

Observing Microorganisms Through a Microscope

Types of Microscopes

Microscopy is essential for visualizing microorganisms. Different types of microscopes offer various advantages.

• Bright Field: Uses light transmitted through the specimen.

• Dark Field: Uses scattered light to enhance contrast.

• Phase Contrast: Enhances differences in refractive index.

• Confocal Scanning Laser: Provides 3D images by scanning with a laser.

Differential Staining

Staining techniques differentiate between types of bacteria based on cell wall properties.

• Gram Stain: Distinguishes Gram-positive and Gram-negative bacteria.

• Acid-Fast Stain: Identifies bacteria with mycolic acid in their cell walls (e.g., Mycobacterium).

Functional Anatomy of Prokaryotic and Eukaryotic Cells

Cell Structures

Understanding cell structure is key to microbiology.

• Capsules and Slime Layers: Protect bacteria and aid in adherence.

• Cell Wall: Provides structural support and shape.

• Flagella: Enable motility.

• Pili: Facilitate attachment and genetic exchange.

Membrane Structure

The phospholipid bilayer is fundamental to cell membrane function.

• Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails.

• Fatty Acid Component: Hydrophobic region of the membrane.

Microbial Metabolism

Enzyme Function and Inhibition

Enzymes catalyze biochemical reactions and can be regulated by inhibitors.

• Competitive Inhibitor: Binds to the active site, blocking substrate access.

• Noncompetitive Inhibitor: Binds elsewhere, altering enzyme activity.

Metabolic Pathways

Cells use metabolic pathways to generate energy and synthesize biomolecules.

• TCA Cycle: Central pathway for energy production in aerobic organisms.

• Glycolysis: Converts glucose to pyruvate, generating ATP.

• Substrate-Level Phosphorylation: Direct transfer of phosphate to ADP to form ATP.

• Equation: $\text{ADP} + \text{P}_i \rightarrow \text{ATP}$

Microbial Growth

Culture Techniques

Microbiologists use various methods to grow and study bacteria.

• Batch Culture: Closed system with limited nutrients.

• Continuous Culture: Open system with constant nutrient supply.

• Chemostat: Device for maintaining continuous culture.

Growth Phases

Bacterial growth follows distinct phases.

• Lag Phase: Adaptation period.

• Log Phase: Exponential growth.

• Stationary Phase: Nutrient depletion slows growth.

• Death Phase: Decline in viable cells.

Chemical Composition of Media

Defined vs. Complex Media

Media composition affects bacterial growth and experimental outcomes.

• Defined Media: Exact chemical composition known.

• Complex Media: Contains extracts with unknown composition.

Ingredient	Amount
K2HPO4	1.0 g/liter
NaCl	5 g/liter
MgSO4	0.2 g/liter
Glucose	1 g/liter
Yeast extract	1 g/liter

Control of Microbial Growth

Antimicrobial Agents and Resistance

Understanding how to control microbial growth is essential for health and industry.

• Antibiotics: Target specific bacterial processes.

• Resistance: Bacteria can evolve mechanisms to evade antibiotics.

Additional Info

• Some questions reference advanced topics such as protein transport, endosymbiosis, and cell signaling, which are relevant to microbial cell biology.

• Highlighted answers indicate correct choices for exam review.