Intro Biology Study Guide - Chapters 1 to 4

Vocabulary flashcards covering fundamental concepts in introductory biology including experimental design, chemistry of life, biological macromolecules, and cell structures and processes.

Scientific literacy

A general, evidence-based understanding of the basics of science, essential for making good personal and societal decisions.

Null hypothesis ($H_0$)

A hypothesis stating that there is no relationship or effect between two factors; usually what is directly tested in an experiment.

Independent variable

The factor that the experimenter deliberately changes or controls in an experiment, plotted on the $x\text{-axis}$.

Dependent variable

The measured outcome expected to respond to changes in the independent variable, plotted on the $y\text{-axis}$.

Control variable

Any factor kept constant during an experiment so that it does not confound results.

Confounding variable

A hidden third factor that could explain an apparent relationship between two variables.

Scientific theory

An explanatory hypothesis exceptionally well-supported by data, repeatedly tested, broad in scope, and unlikely to be overturned by new evidence.

Scientific Method Cycle

An ongoing cycle used to investigate natural phenomena involving observation, question, hypothesis, experiment, data analysis, and conclusion.

"Big Four" elements

The four elements—Oxygen ($65\%$), Carbon ($18.5\%$), Hydrogen ($9.5\%$), and Nitrogen ($3\%$)—that make up approximately $96\%$ of human body mass.

Covalent bond

A strong chemical bond formed when atoms share electrons to fill their outer electron shells.

Ionic bond

A strong chemical bond created when one atom fully transfers electron(s) to another, forming oppositely charged ions that attract.

Hydrogen bond

A weak attraction between a slightly positive hydrogen atom on one molecule and a slightly negative atom (often oxygen or nitrogen) on another molecule.

Three Types of Chemical Bonds

Chemical attractions categorized as covalent bonds (sharing electrons), ionic bonds (transferring electrons), and hydrogen bonds (weak partial-charge attraction).

Cohesion

The property of water molecules sticking to each other via hydrogen bonds, creating surface tension and allowing water transport in tall trees.

Condensation reaction

A chemical reaction that builds a polymer from monomers by joining them together and releasing a water molecule; also called a dehydration reaction.

Hydrolysis

An enzyme-catalyzed reaction that breaks a polymer into its constituent monomers using a water molecule.

Four Macromolecules of Life

The major biological macromolecules: Carbohydrates (monosaccharides), Lipids (glycerol + fatty acids), Proteins (amino acids), and Nucleic Acids (nucleotides).

Saturated fat

A lipid with no double bonds in its fatty acid tails, causing straight chains that pack tightly and remain solid at room temperature.

Unsaturated fat

A lipid with one or more double bonds in its fatty acid tails, causing kinked chains that do not pack tightly and remain liquid at room temperature.

Amphipathic

Describing a molecule, such as a phospholipid, that possesses both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.

Peptide bond

The covalent bond linking amino acid monomers into a polypeptide chain.

Denaturation

The loss of a protein's three-dimensional shape and function caused by extreme conditions such as heat or pH changes.

Enzyme

An organic protein molecule that speeds up chemical reactions by lowering activation energy without being consumed by the reaction.

Endosymbiotic theory

The theory stating that mitochondria and chloroplasts likely evolved from free-living bacteria-like organisms engulfed by an ancestral eukaryotic cell.

Fluid mosaic model

A structural description of the plasma membrane as an ever-shifting, fluid bilayer of phospholipids embedded with diverse proteins.

Transport Across the Cell Membrane

Processes for moving substances across the plasma membrane, including Simple Diffusion, Facilitated Diffusion, Osmosis, and Active Transport.

Simple diffusion

Passive movement of small nonpolar molecules (such as $O_2$ and $CO_2$) directly through the lipid bilayer from high to low concentration.

Facilitated diffusion

Passive movement of polar or charged molecules across a membrane through a channel or carrier protein from high to low concentration.

Osmosis

The passive diffusion of water across a membrane through aquaporin channel proteins from high to low water concentration.

Active transport

The movement of molecules against their concentration gradient (from low to high concentration) using protein pumps and requiring ATP.

Hypotonic solution

A solution with a lower solute concentration than the inside of a cell, causing water to flow into the cell and making it swell or burst.

Hypertonic solution

A solution with a higher solute concentration than the inside of a cell, causing water to flow out of the cell and making it shrivel.

Generalized Animal Cell Organelles

Structures contained within an animal cell, including the Nucleus, Mitochondrion, Rough ER, Smooth ER, Golgi apparatus, Lysosome, Ribosomes, and Cytoskeleton.

Mitochondrion

An organelle that converts nutrients and $O_2$ into ATP via cellular respiration; possesses its own circular DNA inherited from the mother.

Rough ER

A ribosome-studded organelle that folds and modifies proteins destined for export or membrane insertion.

Smooth ER

An organelle without ribosomes that synthesizes lipids and detoxifies drugs and metabolic waste; abundant in liver cells.

Golgi apparatus

An organelle that modifies, sorts, tags, and packages proteins and lipids into vesicles for shipping.

Lysosome

An acidic organelle that functions as cellular garbage disposal, digesting waste, worn-out organelles, and engulfed particles.

Chloroplast

An organelle found in plants and algae that converts light energy into chemical energy (glucose) via photosynthesis.

Plasmodesmata

Microscopic channels that pass through cell walls to connect adjacent plant cells.