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

Themes in Biology & The Scientific Method

Characteristics of Living Things

Biology is the study of living organisms, which share several defining characteristics.

• Organization: Living things are composed of one or more cells.

• Metabolism: They carry out chemical reactions to obtain and use energy.

• Homeostasis: Regulation of internal environment to maintain stable conditions.

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Reproduction: Ability to produce new individuals.

• Response to Stimuli: React to environmental changes.

• Evolution: Populations change over time through adaptation.

The Scientific Method

The scientific method is a systematic approach to investigating natural phenomena.

• Observation: Noticing and describing events in a careful, orderly way.

• Question: Formulating a question based on observations.

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

• Prediction: What you expect to happen if the hypothesis is correct.

• Experiment: Testing the hypothesis under controlled conditions.

• Analysis: Interpreting data and drawing conclusions.

• Communication: Sharing results with the scientific community.

Example: Testing whether fertilizer increases plant growth by comparing treated and untreated plants.

Hypothesis vs. Prediction

• Hypothesis: A proposed explanation (e.g., "Fertilizer increases plant growth").

• Prediction: A specific outcome expected (e.g., "Plants with fertilizer will grow taller than those without").

Experimental Design & Analysis

• Variables: Independent (manipulated), dependent (measured), and controlled (kept constant).

• Control Group: Group not receiving the experimental treatment.

• Data Presentation: Results are often shown in graphs or tables.

• Statistical Significance: Results are evaluated using statistical tests (e.g., p-values).

• Inference vs. Statement: A statement describes results; an inference interprets them.

Digestion & Absorption

Alimentary Canal & Accessory Organs

The digestive system consists of the alimentary canal and accessory organs, each with specific functions.

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

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

Digestion Processes

• Ingestion: Taking in food.

• Secretion: Release of digestive enzymes and fluids.

• Absorption: Uptake of nutrients into blood or lymph.

• Elimination: Removal of undigested material.

Digestive Tract Structure & Function

• Stomach: Protein digestion begins; acidic environment.

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

• Large Intestine: Water absorption and feces formation.

Enzymes & Biomolecules

• Enzymes: Biological catalysts (e.g., amylase, pepsin, lipase).

• Biomolecules: Carbohydrates, proteins, lipids, nucleic acids.

Absorption Mechanisms

• Passive Transport: Diffusion and osmosis; no energy required.

• Active Transport: Requires energy (ATP); moves substances against concentration gradient.

Fick's Law of Diffusion

Describes the rate of diffusion across a membrane.

• Equation:

$J = -D \frac{dC}{dx}$

• J: Rate of diffusion

• D: Diffusion coefficient

• dC/dx: Concentration gradient

Lipids & Cell Membranes

Types of Lipids

• Fats (Triglycerides): Energy storage; composed of glycerol and fatty acids.

• Phospholipids: Major component of cell membranes; amphipathic.

• 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 face inward.

• Proteins: Integral and peripheral; involved in transport, signaling, and structure.

• Cholesterol: Modulates membrane fluidity.

Membrane Transport

• Passive Transport: Diffusion, osmosis, facilitated diffusion.

• Active Transport: Requires ATP; e.g., Na+-K+ ATPase pump.

• Carrier Proteins: Transport specific molecules across membranes.

• Channel Proteins: Form pores for ions and water (e.g., aquaporins).

Osmosis & Diffusion

• Osmosis: Movement of water across a semipermeable membrane from low to high solute concentration.

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

Facilitated Diffusion vs. Active Transport

Feature	Facilitated Diffusion	Active Transport
Energy Requirement	No	Yes (ATP)
Direction	Down concentration gradient	Against concentration gradient
Proteins Involved	Carrier/channel proteins	Pumps (e.g., Na+-K+ ATPase)

Carbon Chemistry & Biomolecules

Carbon Skeletons

• Structural Diversity: Chains, branches, rings.

• Functional Groups: Hydroxyl, carboxyl, amino, phosphate, methyl.

Functional Groups in Biomolecules

• Polar: Hydroxyl, carboxyl, phosphate.

• Non-polar: Methyl.

• Acidic: Carboxyl.

• Basic: Amino.

Miller Experiment

• Purpose: Simulate early Earth conditions to test origin of organic molecules.

• Findings: Amino acids and other organic compounds formed.

Cells

Prokaryotic vs. Eukaryotic Cells

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

• Eukaryotic: Nucleus, membrane-bound organelles, larger (e.g., plants, animals).

Shared Characteristics

• Plasma membrane

• Cytoplasm

• DNA as genetic material

• Ribosomes

Graphing & Data Analysis

Variables in Experiments

• Independent Variable: Manipulated by the experimenter.

• Dependent Variable: Measured response.

• Graphing: Independent variable on x-axis, dependent on y-axis.

Example: Testing camouflage effectiveness by measuring predation rates in different environments.

Vocabulary

Key Terms

Term	Definition
Alimentary canal	Continuous tube from mouth to anus for digestion and absorption
Facilitated diffusion	Passive transport of molecules via membrane proteins
Osmosis	Diffusion of water across a semipermeable membrane
Phagocytosis	Cellular process of engulfing large particles
Prokaryote	Cell without a nucleus
Eukaryote	Cell with a nucleus and organelles
Phospholipid	Lipid with a phosphate group; major component of cell membranes
Endocytosis	Process of taking substances into a cell by engulfing them in a vesicle
Exocytosis	Process of expelling substances from a cell via vesicles
Microvilli	Small projections on cell surface that increase surface area
Tight junction	Cell junction that prevents leakage between cells
Carrier protein	Membrane protein that transports substances across the membrane

Additional info: Definitions and explanations have been expanded for clarity and completeness. Some examples and context have been inferred from standard biology curricula.