General Biology Exam 1 Study Guide: Scientific Method, Digestion, Membranes, and Cells

Exam 1 Preparation: Overview

This study guide covers foundational topics in General Biology, including the scientific method, digestion and absorption, membrane structure and function, and cell biology. The guide is organized by major themes and provides definitions, explanations, and examples to support exam preparation.

Themes in Biology & The Scientific Method

Scientific Method and Experimental Design

The scientific method is a systematic approach to investigating natural phenomena. It involves making observations, forming hypotheses, conducting experiments, and analyzing results.

• Hypothesis: A testable explanation for an observation or question.

• Prediction: A statement about what will happen if the hypothesis is correct.

• Experiment: A procedure to test the hypothesis, often involving control and experimental groups.

• Variables: Factors that can change in an experiment. Independent variable is manipulated; dependent variable is measured.

• Control group: The group not exposed to the experimental variable, used for comparison.

• Data analysis: Involves interpreting results, often using graphs and statistical tests.

Example: Testing whether light affects mouse activity by comparing activity in light vs. dark conditions.

Hypothesis vs. Prediction

• Hypothesis: A proposed explanation (e.g., "Light increases mouse activity").

• Prediction: What you expect to observe if the hypothesis is true (e.g., "Mice will be more active in light").

Analyzing Results

• Write a sentence describing results shown in a graph.

• Identify the major theme in biology illustrated by a research study.

• Describe controlled and independent variables in an experiment.

• Determine the trend in a graph (e.g., increasing, decreasing, no change).

• Evaluate whether results are statistically significant (often using p-values).

• Distinguish between a result (what is observed) and an inference (interpretation of the result).

Digestion & Absorption

Digestive System Structure and Function

The digestive system breaks down food into nutrients that can be absorbed and used by the body. It includes the alimentary canal and accessory organs.

• Alimentary canal: Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.

• Accessory organs: Salivary glands, liver, gallbladder, pancreas.

• Digestion: Mechanical and chemical breakdown of food.

• Absorption: Uptake of nutrients by cells lining the digestive tract.

Regions and Functions

• Mouth: Mechanical breakdown, saliva begins starch digestion.

• Stomach: Protein digestion begins, acidic environment.

• Small intestine: Major site of digestion and absorption; villi and microvilli increase surface area.

• Large intestine: Water absorption, formation of feces.

Key Digestive Processes

• List enzymes and their substrates (e.g., pepsin digests proteins in the stomach).

• Trace the path of food and absorption of nutrients.

• Explain the function of epithelial cells in absorption.

• Relate structure (e.g., villi, microvilli) to function (increased surface area for absorption).

Fick's Law of Diffusion

• Describes the rate of diffusion across a membrane.

$J = -D \frac{dC}{dx}$ Where: J = flux (rate of diffusion) D = diffusion coefficient dC/dx = concentration gradient

Lipids & Cell Membranes

Types of Lipids

• Fats (triglycerides): Energy storage, insulation.

• Phospholipids: Major component of cell membranes.

• Steroids: Hormones and membrane components (e.g., cholesterol).

Saturated vs. Unsaturated Fatty Acids

• Saturated: No double bonds, solid at room temperature.

• Unsaturated: One or more double bonds, liquid at room temperature.

Cell Membrane Structure

• Phospholipid bilayer: Hydrophilic heads face outward, hydrophobic tails inward.

• Proteins: Embedded in the membrane, serve as channels, carriers, or receptors.

• Cholesterol: Modulates membrane fluidity.

Membrane Transport

• Passive transport: Movement of substances down their concentration gradient (no energy required).

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Facilitated diffusion: Passive transport via membrane proteins.

• Active transport: Movement against the concentration gradient, requires energy (ATP).

• Carrier proteins: Bind and transport specific molecules.

• Channel proteins: Form pores for specific ions or molecules.

Examples of Membrane Proteins

• GLUT1: Glucose transporter.

• Aquaporin: Water channel protein.

• Na+/K+ pump: Active transport of sodium and potassium ions.

Cells

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: No nucleus, smaller, simpler (e.g., bacteria).

• Eukaryotes: Nucleus, membrane-bound organelles (e.g., plants, animals, fungi, protists).

Shared Characteristics of All Cells

• Plasma membrane

• Cytoplasm

• Genetic material (DNA)

• Ribosomes

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	No	Yes
Membrane-bound organelles	No	Yes
Size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Vocabulary and Key Terms

• Adaptation: A trait that increases an organism's fitness in a particular environment.

• Alimentary canal: The digestive tract from mouth to anus.

• Bile: A digestive fluid produced by the liver, stored in the gallbladder.

• Cholesterol: A lipid that is an essential component of cell membranes.

• Diffusion: Movement of molecules from high to low concentration.

• Facilitated diffusion: Passive transport of molecules via membrane proteins.

• Osmosis: Diffusion of water across a membrane.

• Phagocytosis: Cellular "eating"; engulfing large particles.

• Phospholipid: A lipid with a phosphate group, major component of membranes.

• Prokaryote: Cell without a nucleus.

• Eukaryote: Cell with a nucleus.

• Endocytosis: Uptake of materials into the cell by engulfing them in a membrane.

• Exocytosis: Release of materials from the cell by fusion of a vesicle with the membrane.

Practice: Graphs and Diagrams

• Draw and label a saturated and unsaturated hydrocarbon.

• Draw a phospholipid bilayer, label hydrophilic and hydrophobic regions.

• Given a table or graph, identify independent and dependent variables and describe the relationship.

• Practice writing experimental descriptions and interpreting results.

Additional info:

• Some content was expanded for clarity and completeness, including definitions and examples of key terms, and a summary table comparing cell types.