Biology Lecture Review: Scientific Method, Biochemistry, Cell Biology, Cellular Respiration, and Health

Comprehensive vocabulary flashcards covering the scientific method, chemistry of water and biological macromolecules, cellular structure, enzyme kinetics, cellular respiration, and metabolism-related health conditions.

Hypothesis

A proposed explanation for a single observation that is testable and potentially falsifiable.

Scientific Theory

A powerful, broad explanation of a large set of observations that rests on many hypotheses that have been tested and generates additional hypotheses.

Inductive Reasoning

The logical process of combining a series of specific observations into a general summary or conclusion.

Deductive Reasoning

The logical process of using a general principle to make a specific prediction, typically formatted as an "if…then" statement.

Independent Variable

A factor in an experiment that can be manipulated by the researcher to test its effect.

Dependent Variable

A factor in an experiment that cannot be directly changed by the researcher and is measured to evaluate the effect of the independent variable.

Controlled Experiment

An experiment designed to test the effect of a single variable by comparing an experimental group to a control group.

Control

A subject in an experiment who is not exposed to the experimental treatment.

Placebo

An inactive or sham treatment administered to a control group in an experiment.

Blind Experiment

An experimental setup in which subjects do not know whether they are receiving the experimental treatment or a placebo to eliminate bias.

Double Blinding

An experimental procedure in which neither the subjects nor the person administering the treatments know which subjects are in the experimental or control group until after the experiment.

Correlation

A mutual relationship or connection between two variables, which does not necessarily prove that one variable causes the other.

Sampling Error

The effect of chance on experimental or observational results due to testing a sample rather than an entire population.

Statistically Significant

A mathematical result indicating that an observed difference between experimental groups is probably real and not due to sampling error.

Primary Source

A written paper describing original research results published in a professional journal after undergoing peer review.

Secondary Source

A media outlet, book, news report, advertisement, or internet site that summarizes or interprets primary scientific research.

Peer Review

The formal evaluation of submitted research papers by other scientific experts in the same field before publication.

Anecdotal Evidence

Information or claims based on an individual's personal experience or testimonial rather than on systematic experimental testing.

Polar Molecule

A molecule in which electrons are shared unequally between atoms, giving one end a partial negative charge and the other a partial positive charge.

Hydrogen Bond

A weak attraction between the slightly positive hydrogen atom of one polar molecule and a slightly negative atom of another polar molecule.

Cohesion

The tendency of like molecules, such as water molecules connected by hydrogen bonds, to stick together.

Hydrophilic

Polar or charged molecules that readily interact with and dissolve in water ("water-loving").

Hydrophobic

Nonpolar molecules that do not contain charged atoms and do not dissolve in water ("water-hating").

pH Scale

A measure of the relative concentration of hydrogen ions ($\text{H}^+$) and hydroxide ions ($\text{OH}^-$) in a solution, where values below $7$ are acidic, above $7$ are basic, and $7$ is neutral.

Organic Chemistry

The branch of chemistry focused on carbon-containing compounds, which form the structural basis of living organisms.

Covalent Bond

A strong chemical bond formed when two atoms share electrons.

Biological Macromolecules

Large organic molecules found in living organisms that are synthesized from smaller monomer subunits; includes carbohydrates, proteins, lipids, and nucleic acids.

Carbohydrates

Macromolecules composed of carbon, hydrogen, and oxygen ($\text{CH}_2\text{O}$) that serve as a major source of cellular energy.

Monosaccharide

A simple single-sugar monomer subunit, such as glucose.

Disaccharide

A carbohydrate composed of two sugar subunits bonded together, such as sucrose.

Polysaccharide

A complex carbohydrate composed of many linked sugar subunits, such as cellulose.

Proteins

Biological macromolecules made of carbon, oxygen, hydrogen, and nitrogen that are composed of repeating amino acid monomers.

Amino Acids

The monomer building blocks of proteins, consisting of an amino group, a carboxyl group, a central carbon, and a variable side group.

Lipids

Hydrophobic organic macromolecules composed primarily of carbon and hydrogen, divided into fats, steroids, and phospholipids.

Fats

Lipids composed of a glycerol molecule joined to three fatty acid tails, used primarily for energy storage.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings, such as cholesterol and sex hormones.

Phospholipids

Lipids consisting of a glycerol molecule linked to two fatty acid tails and a phosphate group, forming the major component of cell membranes.

Nucleic Acids

Polymers composed of nucleotide monomers that function in storing and transmitting genetic information, including DNA and RNA.

Nucleotide

The structural subunit of nucleic acids, consisting of a sugar, a phosphate group, and a nitrogenous base.

Purines

Nitrogenous bases containing a double-ring chemical structure, specifically Adenine ($\text{A}$) and Guanine ($\text{G}$).

Pyrimidines

Nitrogenous bases containing a single-ring chemical structure, specifically Thymine ($\text{T}$) and Cytosine ($\text{C}$).

Complementary Base-Pairing Rules

The pairing arrangement in DNA where purines hydrogen-bond with pyrimidines: Adenine ($\text{A}$) bonds with Thymine ($\text{T}$), and Guanine ($\text{G}$) bonds with Cytosine ($\text{C}$).

Prokaryotic Cells

Small, microscopic cells that lack a nucleus and membrane-bound organelles, containing unhoused genetic material in a nucleoid region.

Eukaryotic Cells

Larger, complex single-celled or multicellular cells that contain a membrane-bound nucleus housing genetic material and specialized organelles.

Homeostasis

The ability of an organism to maintain a constant internal environment despite changes in the external environment.

Theory of Evolution

The principle that all modern organisms descended from a common ancestor through natural selection and genetic change over time.

Enzymes

Specialized proteins that catalyze (speed up) chemical reactions in cells by lowering activation energy without being modified in the process.

Metabolism

The sum of all chemical reactions occurring within an organism.

Activation Energy

The amount of energy required to start a chemical reaction.

Substrate

The specific reactant substance that is catalyzed by binding to an enzyme.

Active Site

The region on an enzyme where the substrate binds.

Induced Fit

The structural change that occurs when a substrate binds to an enzyme's active site, causing the active site to shape itself more snugly around the substrate.

Calorie

The amount of energy required to raise the temperature of $1\text{ gram}$ of water by $1^\bullet\text{C}$; $1000\text{ calories} = 1\text{ kilocalorie}$ or $1\text{ Calorie}$.

Metabolic Rate

The rate at which the body uses energy.

Basal Metabolic Rate (BMR)

The resting energy expenditure of an awake, alert person at rest, which averages about $70\text{ Calories/hour}$ or $1680\text{ Calories/day}$.

Cellular Respiration

A series of enzymatic reactions that converts energy stored in food into energy stored in ATP.

Adenosine Triphosphate (ATP)

The primary energy currency of cells, consisting of adenine, a sugar, and three negatively charged phosphate groups.

Phosphorylation

The transfer of a phosphate group from ATP to another molecule, transferring energy and producing ADP.

Aerobic Cellular Respiration

The oxygen-requiring process in mitochondria that harvests energy from glucose ($\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$) to regenerate ATP.

Glycolysis

The initial anaerobic stage of cellular respiration in the cytosol, breaking down a $6\text{-carbon}$ glucose into two $3\text{-carbon}$ pyruvic acid molecules and yielding $2\text{ ATP}$ and $NADH$.

NAD+

A chemical electron carrier molecule that picks up electrons and hydrogen ions released during cellular respiration to become NADH.

Citric Acid Cycle

A series of chemical reactions catalyzed by 8 enzymes in the mitochondrial matrix that processes pyruvic acid derivatives, releasing $\text{CO}_2$ and producing $2\text{ ATP}$ and $NADH$.

Electron Transport Chain

A series of proteins in the inner mitochondrial membrane that transfers electrons from NADH, pumping $\text{H}^+$ ions into the intermembrane space.

ATP Synthase

A protein channel in the inner mitochondrial membrane that utilizes the flow of $\text{H}^+$ ions to generate $32$ or $34\text{ ATP}$ molecules.

Anaerobic Respiration

A cellular process that generates energy and ATP in the absence of oxygen.

Fermentation

An anaerobic process used to regenerate $\text{NAD}^+$ by converting pyruvic acid into lactic acid (in muscle cells and yogurt bacteria) or ethanol and $\text{CO}_2$ (in yeast).

Body Mass Index (BMI)

A calculation estimating body fat content based on height and weight to evaluate illness and mortality risk, with a healthy range of $20\text{--}25$.

Obesity

A health condition defined by a Body Mass Index (BMI) of $30$ or higher.

Diabetes

A metabolic disorder characterized by improper regulation of carbohydrate metabolism and blood glucose levels.

Insulin

A hormone produced by the beta cells of the pancreas that stimulates body cells to take up glucose from the blood.

Type 1 Diabetes

An autoimmune form of diabetes, typically arising in childhood, in which the pancreas lacks beta cells and cannot produce insulin.

Type 2 Diabetes

A form of diabetes usually arising in adulthood and linked to obesity, in which body cells fail to respond effectively to insulin.

Hypertension

Chronic high blood pressure, defined as blood pressure persistently over $140/90$.

Systolic Pressure

The force exerted by blood on vessel walls as the heart contracts.

Diastolic Pressure

The force exerted by blood on vessel walls while the heart is resting between contractions.

Low-Density Lipoproteins (LDLs)

Lipoproteins that transport cholesterol throughout the body and deposit excess cholesterol in blood vessel walls.

High-Density Lipoproteins (HDLs)

Lipoproteins that transport excess cholesterol back to the liver for excretion as bile.

Anorexia

An eating disorder characterized by self-starvation, which can lead to damaged heart muscle, altered heart rhythms, amenorrhea, and osteoporosis.

Amenorrhea

The cessation of menstruation resulting from low body fat, which can cause permanent sterility and increased risk of osteoporosis.

Bulimia

An eating disorder characterized by binge eating followed by purging, which can cause stomach rupture, dehydration, and dental erosion.

Photosynthesis

The biological process by which plants and photoautotrophic microorganisms trap light energy to convert carbon dioxide and water into glucose and oxygen ($6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$).

Chloroplast

The specialized membrane-bound organelle in plant cells where photosynthesis takes place.

Stroma

The thick fluid enclosed within a chloroplast that surrounds the thylakoids and serves as the site for the Calvin cycle.

Thylakoids

Disk-like membrane structures inside a chloroplast that house chlorophyll and host the light reactions of photosynthesis.

Chlorophyll

The primary light-absorbing pigment molecule embedded on the surface of thylakoid membranes.

Light Reactions

The initial stage of photosynthesis taking place in thylakoids, where absorbed sunlight splits water, releasing $\text{O}_2$ and producing $\text{ATP}$ and $\text{NADPH}$.

Calvin Cycle

The second stage of photosynthesis occurring in the stroma, which uses $\text{ATP}$ and $\text{NADPH}$ to synthesize glucose from $\text{CO}_2$.

Stomata

Microscopic pore openings on leaf surfaces that facilitate gas exchange by allowing $\text{CO}_2$ to enter while $\text{O}_2$ and water vapor exit.

Guard Cells

Specialized epidermal cells that flank stomatal pores and regulate their opening and closing to balance gas exchange and water loss.

Transpiration

The process by which water vapor moves out of a plant and evaporates through open stomata.

Photorespiration

A counterproductive pathway occurring when stomata close, causing oxygen to react with $\text{RuBP}$ instead of $\text{CO}_2$, thereby releasing $\text{CO}_2$ and slowing photosynthesis.

C3 Plants

Standard plants that close their stomata in hot conditions to conserve water, making them susceptible to photorespiration.

C4 Plants

Plants equipped with an additional enzyme that allows efficient carbon fixation and sugar production even when stomata are nearly closed, avoiding photorespiration.

CAM Plants

Desert-adapted plants that open their stomata only at night to fix carbon into an organic acid, which is broken down into $\text{CO}_2$ during the day for photosynthesis.

Deforestation

The large-scale clearing of forests for agriculture or settlement, contributing approximately $25\%$ of human-added atmospheric carbon dioxide.

Carbon Footprint

The total amount of greenhouse gases produced directly and indirectly by human activities.