biology semester 1

Independent Variable

The variable that is deliberately changed by the experimenter.

Dependent Variable

The variable that is measured or observed in an experiment.

Controlled Variable (Constant)

Variables kept the same to ensure a fair test.

Experimental Control

A baseline setup used for comparison in an experiment.

Organization

Living things are composed of one or more cells, the basic unit of life.

Metabolism

All chemical reactions that maintain life and require energy.

Homeostasis

Ability to maintain a stable internal environment despite external changes.

Growth and Development

Organisms grow and develop according to instructions in their DNA.

Reproduction

Ability to produce new organisms, sexually or asexually.

Response to Stimuli

Ability to respond to environmental changes.

Evolution

Change in populations over time through natural selection and adaptation.

Spontaneous Generation

Disproven idea that life arises from nonliving matter.

Biogenesis

Theory stating that all living things come from pre-existing living things.

Abiogenesis

Hypothesis that life originated from nonliving matter through chemical processes.

Macromolecule

Large biological molecule formed from smaller repeating units called monomers.

Monomer

Small molecule that serves as a building block for polymers.

Polymerization

Process of joining monomers through condensation reactions.

Condensation (Dehydration Synthesis)

Reaction that forms polymers by removing water.

Hydrolysis

Reaction that breaks polymers into monomers by adding water.

Four Biological Macromolecules

Carbohydrates, lipids, proteins, nucleic acids.

CHNOPS

Elements that make up biological macromolecules (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur).

Carbohydrate Structure

Composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio.

Monosaccharide

Single sugar molecule (e.g., glucose, fructose).

Disaccharide

Two monosaccharides bonded together (e.g., sucrose, lactose).

Polysaccharide

Long chain of monosaccharides (e.g., starch, glycogen, cellulose).

Carbohydrate Function

Primary source of energy and structural support.

Plant Energy Storage

Starch.

Animal Energy Storage

Glycogen.

Structural Carbohydrates

Cellulose (plants), chitin (fungi and insects).

Glycosidic Bond

Bond that links monosaccharides together.

Lipid Structure

Mostly carbon and hydrogen; hydrophobic.

Triglyceride

Glycerol bonded to three fatty acids.

Phospholipid

Glycerol, two fatty acids, and a phosphate group.

Steroid

Lipid with four fused carbon rings (e.g., cholesterol).

Lipid Function

Long-term energy storage, insulation, cell membranes, signaling.

Saturated Fat

Fatty acids with no double bonds; solid at room temperature.

Unsaturated Fat

Fatty acids with one or more double bonds; liquid at room temperature.

Ester Bond

Bond linking fatty acids to glycerol.

Phospholipid Bilayer

Structure forming cell membranes.

Protein Structure

Composed of carbon, hydrogen, oxygen, and nitrogen.

Amino Acid

Monomer of proteins.

Peptide Bond

Bond linking amino acids together.

Enzyme

Protein that catalyzes chemical reactions.

Structural Protein

Protein that provides support (e.g., collagen, keratin).

Transport Protein

Protein that carries substances (e.g., hemoglobin).

Defense Protein

Protein involved in immune response (e.g., antibodies).

Hormonal Protein

Protein that regulates body processes (e.g., insulin).

Essential Amino Acids

Amino acids that must be obtained from diet.

Protease

Enzyme that breaks down proteins.

Nucleic Acid Structure

Composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Nucleotide

Monomer of nucleic acids consisting of sugar, phosphate, and nitrogenous base.

DNA

Double-stranded nucleic acid that stores genetic information.

RNA

Single-stranded nucleic acid involved in protein synthesis.

DNA Bases

Adenine, Thymine, Cytosine, Guanine.

RNA Bases

Adenine, Uracil, Cytosine, Guanine.

Phosphodiester Bond

Bond linking nucleotides together.

Genetic Information

Instructions for protein synthesis and inheritance.

Polarity

Unequal sharing of electrons causing partial charges.

Hydrogen Bond

Weak attraction between polar molecules.

Cohesion

Attraction between water molecules.

Adhesion

Attraction between water and other substances.

High Heat Capacity

Water resists temperature change.

Universal Solvent

Water dissolves many substances.

Capillary Action

Movement of water through narrow spaces.

Density of Ice

Solid water is less dense than liquid water.

Cellular Respiration

Process by which organisms convert glucose into ATP.

Overall Respiration Equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.

Aerobic Respiration

Requires oxygen; occurs in mitochondria.

Anaerobic Respiration

Does not require oxygen; occurs in cytoplasm.

Electron Carriers

NAD⁺, NADH, FAD, FADH₂ transport electrons.

Glycolysis

Anaerobic breakdown of glucose into two pyruvate molecules.

Glycolysis ATP Yield

Net gain of 2 ATP and 2 NADH.

Pyruvate Oxidation

Converts pyruvate into acetyl-CoA.

Krebs Cycle

Aerobic cycle producing CO₂, NADH, FADH₂, and ATP.

Electron Transport Chain

Uses electron carriers to create a proton gradient for ATP synthesis.

ATP Synthase

Enzyme that produces ATP using proton flow.

Oxidative Phosphorylation

ATP production driven by the electron transport chain.

Alcoholic Fermentation

Anaerobic pathway producing ethanol and CO₂.

Lactic Acid Fermentation

Anaerobic pathway producing lactic acid.

Photosynthesis

Process by which plants convert light energy into chemical energy.

Overall Photosynthesis Equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Chloroplast

Organelle where photosynthesis occurs.

Thylakoid

Membrane sacs where light-dependent reactions occur.

Stroma

Fluid-filled space where Calvin cycle occurs.

Light-Dependent Reactions

Use light to produce ATP and NADPH.

Photosystem II

Absorbs light and splits water molecules.

Photolysis

Splitting of water into oxygen, protons, and electrons.

Photosystem I

Re-energizes electrons to produce NADPH.

Calvin Cycle

Light-independent reactions that produce sugar.

Carbon Fixation

CO₂ binds to RuBP via Rubisco.

Reduction Phase

3-PGA converted to G3P using ATP and NADPH.

Regeneration

RuBP is regenerated to continue the Calvin cycle.

G3P

Three-carbon sugar used to make glucose.

Anabolic Reactions

Build complex molecules and require energy.

Catabolic Reactions

Break down molecules and release energy.

ATP

Primary energy molecule of cells.

ATP to ADP

Releases energy by breaking a phosphate bond.

High-Energy Phosphate Bond

Bond between the 2nd and 3rd phosphate groups.

Activation Energy

Energy required to start a reaction.

Substrate

Reactant that binds to an enzyme.