Metric System and pH

Metric System Conversions

The metric system is a decimal-based system of measurement used in science. Understanding metric prefixes and conversion is essential for laboratory work.

• Metric Prefixes: Common prefixes include milli (10-3), centi (10-2), kilo (103), etc.

• Conversion Example: To convert liters to milliliters, multiply by 1,000 (since 1 L = 1,000 mL).

• Formula:

pH Scale

The pH scale measures the concentration of hydrogen ions (H+) in a solution, ranging from 0 (most acidic) to 14 (most basic).

• Acidic: pH < 7; high H+ concentration

• Neutral: pH = 7; equal H+ and OH- concentrations

• Basic (Alkaline): pH > 7; low H+ concentration

• Relationship:

• Example: A solution with pH 2 has 100 times more H+ than a solution with pH 4.

Microscope

Types and Parts of Microscopes

Microscopes are essential tools for observing cells and tissues. There are two main types used in biology labs: compound and dissecting microscopes.

• Compound Microscope: Used for viewing small, thin specimens; has multiple objective lenses.

• Dissecting Microscope: Used for larger, three-dimensional specimens; has two types of lights: transmitted (from below) and reflected (from above).

• Parts: Eyepiece, objective lenses, stage, coarse/fine focus, light source, arm, base.

• Total Magnification:

Microscope Use and Care

• Cleaning: Use alcohol, ammonia-free Windex, and lens paper only.

• Wet Mount Preparation: Place specimen in water, cover with coverslip, draw chemical under coverslip using capillary action.

• Salt Solution Purpose: Used to observe osmosis in aquatic plant cells.

• Storage: Set microscope to lowest objective, stage down, light off, cord wrapped.

• Do NOT: Use rough materials to clean lenses, force focus knobs, leave slides on stage.

Plant Slide Characteristics

• Cell Wall: Provides structure and support.

• Chloroplasts: Site of photosynthesis.

• Example: Aquatic plant cells show plasmolysis when exposed to salt solution.

Cells

Cell Types and Structures

Cells are the basic units of life. They can be classified as prokaryotic or eukaryotic, and may have specialized structures.

• Prokaryotes: No nucleus, simple structure (e.g., bacteria).

• Eukaryotes: Have nucleus and organelles (e.g., plant, animal, fungal cells).

• Cell Wall vs Cell Membrane: Plant, fungal, and some prokaryotic cells have cell walls; animal cells have only cell membranes.

• Specialized Parts: Nucleus, mitochondria, chloroplasts, vacuoles, etc.

• Iodine Use: Stains starch in potato and banana cells, making structures visible.

Scientific Method

Steps of the Scientific Method

The scientific method is a systematic approach to investigation in biology.

• Observation: Noticing phenomena.

• Question: Formulating a research question.

• Hypothesis: Proposed explanation; testable and falsifiable.

• Experiment: Testing the hypothesis.

• Data Collection: Gathering results.

• Analysis: Interpreting data.

• Conclusion: Accept or reject hypothesis.

Variables

• Independent Variable: Changed by the experimenter.

• Dependent Variable: Measured outcome.

• Controlled Variables: Kept constant.

Hypothesis and Null Hypothesis

• Hypothesis: Predicts a relationship (e.g., "If plants are given more light, they will grow faster.")

• Null Hypothesis: States no effect or relationship (e.g., "Light does not affect plant growth.")

• Probability Value (p-value): Cutoff is usually 0.05; if p < 0.05, reject null hypothesis.

• Interpretation: Rejecting null means evidence for effect; failing to reject means insufficient evidence.

Enzymes

Enzyme Function and Characteristics

Enzymes are biological catalysts that speed up chemical reactions without being consumed.

• Specificity: Each enzyme acts on a specific substrate.

• Active Site: Region where substrate binds.

• Enzyme-Substrate Complex: Temporary association during reaction.

• Product: Result of enzyme action on substrate.

• Example: Amylase (enzyme) acts on starch (substrate) to produce maltose (product).

Experimental Variables Affecting Enzymes

• pH: Extreme pH can denature enzymes.

• Temperature: Icing slows, boiling denatures enzymes.

• Enzyme Treatment Results: Different treatments yield varying reaction rates.

Enzyme Reaction Equation

Summary Table: Cell Types and Structures

Additional info: Academic context and examples were added to clarify and expand brief points from the original notes.