Biology Final (Amayra Evans HCC)

Everything you need to PASS the Biology Comprehensive Final Exam. From Basic terms, the study guide, to all the Chapter Quiz questions and answers. Good luck scholar! This took me 5 hours to make.

Which molecule in the ATP cycle contains the most energy for cellular work?

ATP

Rank ATP, ADP, AMP from highest to lowest energy.

ATP > ADP > AMP

Do H⁺ ions directly provide usable energy for cell work?

No — they store potential energy in a gradient used to make ATP.

The part of an enzyme where the substrate binds is called what?

The active site

Which process most commonly regulates enzymes in metabolic pathways?

Feedback inhibition

Why is simple diffusion considered a form of passive transport?

It requires no cellular energy and moves molecules down their gradient.

Does simple diffusion require energy from the cell?

No

Molecules moving from high to low concentration through a carrier protein occurs by what process?

Facilitated diffusion

If cells appear crenated in an osmosis experiment, what solution are they in?

A hypertonic solution

If solute concentration inside a cell equals outside the cell, the cell is in what environment?

Isotonic

Which should be classified separately: osmosis, diffusion, passive transport, active transport, or facilitated diffusion?

Active transport

What process allows water to move across a cell membrane?

Osmosis (through aquaporins)

Neurons releasing neurotransmitters via vesicle fusion with the membrane is what type of transport?

Exocytosis

Which process can occur without ATP energy?

Passive transport

Why do metabolic pathways require many different enzymes?

Each step needs a specific enzyme; pathways are sequential and highly regulated.

Enzymes are named for the substrate they bind because…

Enzymes exhibit substrate specificity (their active site fits only certain substrates).

Cell

The basic structural and functional unit of life; can be prokaryotic (no nucleus, no membrane-bound organelles) or eukaryotic (nucleus and membrane-bound organelles).

Cell theory

The scientific theory that (1) all living things are made of cells, (2) the cell is the basic unit of life, and (3) all cells arise from preexisting cells.

Characteristics of life

The shared properties of living organisms: organization, acquire materials & energy, homeostasis, respond to stimuli, growth & development, reproduction, and evolution.

Homeostasis

Maintenance of a stable internal environment despite external change (e.g., temperature regulation, ion balance).

Evolution by natural selection

Process where heritable variation in a population leads to differential survival and reproduction, causing change in trait frequencies across generations.

Scientific method

Iterative process: observation → question → hypothesis → experiment → data analysis → conclusion → peer review & replication.

Hypothesis

A testable, falsifiable proposed explanation for an observation or set of observations.

Variable (independent vs dependent)

Independent = factor you change experimentally; dependent = factor you measure as a response.

Control

A standard for comparison in an experiment; a treatment with known or baseline conditions.

Atom

Smallest unit of an element that retains chemical properties; composed of protons (+), neutrons (neutral), and electrons (−).

Covalent bond

Chemical bond formed when atoms share electron pairs; strong and common in biological molecules.

Ionic bond

Chemical attraction between oppositely charged ions formed by electron transfer.

Hydrogen bond

Weak electrostatic attraction between a hydrogen covalently bonded to an electronegative atom (O, N) and another electronegative atom; critical for water properties, DNA base pairing, and protein folding.

Water’s cohesion

Water molecules stick to each other via hydrogen bonds; contributes to surface tension and transport in plants.

Water’s high specific heat

Water resists temperature change because hydrogen bonds absorb heat; stabilizes organism and environmental temperatures.

Water as a solvent

Water’s polarity allows it to dissolve many ionic and polar substances, making it the universal biological solvent.

Hydrophobic vs hydrophilic

Hydrophobic = water-fearing (nonpolar); hydrophilic = water-loving (polar/charged).

pH

A measure of hydrogen ion concentration; pH = −log[H⁺]; biological systems tightly regulated (buffers).

Monomer vs polymer

Monomer = single subunit (e.g., glucose, amino acid); polymer = chain of monomers (e.g., polysaccharide, protein).

Carbohydrate

Organic molecules made of C, H, O often with formula (CH2O)n; functions: energy (glucose), storage (starch/glycogen), structure (cellulose).

Monosaccharide

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

Disaccharide

Two monosaccharides joined by glycosidic bond (e.g., sucrose, lactose).

Polysaccharide

Long chain of monosaccharides (starch, glycogen, cellulose) used for storage or structure.

Lipid

Hydrophobic molecules: fats/triglycerides (energy storage), phospholipids (membranes), steroids (hormones).

Phospholipid bilayer

Membrane structure with hydrophilic heads facing aqueous environments and hydrophobic tails facing inward; basis of cell membranes.

Protein

Polymer of amino acids that folds into a specific 3D shape to perform functions: enzymes, structural components, transporters, receptors.

Amino acid

Building block of proteins; has an amino group, carboxyl group, hydrogen, and variable R group.

Primary/secondary/tertiary/quaternary protein structure

Primary = amino acid sequence; secondary = local folding (α-helix, β-sheet via H-bonds); tertiary = overall 3D fold; quaternary = assembly of multiple polypeptide subunits.

Enzyme

Biological catalyst (usually protein) that lowers activation energy and increases reaction rate without being consumed.

Active site

Region of an enzyme where substrate binds and reaction proceeds; specificity arises from shape and chemical properties.

Induced fit model

Enzyme active site undergoes conformational change upon substrate binding to optimize interaction and catalysis.

Cofactor / coenzyme

Nonprotein helper (ion or organic molecule like NAD⁺, FAD, NADP⁺) required for enzyme activity.

Feedback inhibition

Regulation mechanism where the end product of a metabolic pathway inhibits an enzyme (often the first enzyme) in that pathway to prevent overproduction.

Competitive vs noncompetitive inhibitor

Competitive inhibitor binds active site competing with substrate; noncompetitive binds elsewhere changing enzyme shape and activity.

Activation energy (Ea)

The energy barrier that reactants must overcome to be converted to products; enzymes reduce Ea.

ATP (adenosine triphosphate)

Universal energy currency: adenine + ribose + three phosphate groups; hydrolysis (ATP → ADP + Pi) releases usable energy.

Structure of ATP

Adenine (nitrogenous base) + ribose (5-carbon sugar) + three phosphate groups; repulsion between phosphates stores potential energy.

ATP cycle

Continuous breakdown (ATP → ADP + Pi → energy release) and regeneration (ADP + Pi → ATP) powered by cellular metabolism (mostly mitochondria).

Coupled reactions

Energy-releasing reaction (e.g., ATP hydrolysis) is paired with an energy-requiring reaction so the net reaction is energetically favorable.

Basal metabolic rate (BMR)

Minimum energy per day to sustain life (heartbeat, temperature, nervous function); typically ~1200–2000 kcal/day and ~60–70% of total calorie needs.

First law of thermodynamics

Energy cannot be created or destroyed, only transferred or transformed (conservation of energy).

Second law of thermodynamics

Every energy transfer increases entropy (disorder); some usable energy is lost as heat during conversions.

Entropy

Measure of disorder; living systems must expend energy to maintain low internal entropy.

Redox reaction

Reaction where electrons (and often hydrogen ions) are transferred between molecules; oxidation = loss of electrons/H⁺, reduction = gain.

NAD⁺ / NADH and FAD / FADH₂

Electron carrier coenzymes: NAD⁺ accepts electrons → NADH, FAD accepts electrons → FADH₂; used in respiration and photosynthesis to shuttle electrons.

Photosynthesis overall equation

6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂ (CO₂ reduced to sugar; H₂O oxidized to O₂).

Chloroplast structure

Double membrane organelle with stroma (fluid) and thylakoids (membrane sacs); thylakoids stacked into grana; site of photosynthesis.

Thylakoid membrane

Location of pigment complexes (PSII, PSI), electron transport chain, and ATP synthase; creates proton gradient for ATP production.

Light reactions (photosynthesis)

Occur in thylakoid membranes: light excites electrons (PSII → ETC → PSI), water split (O₂ released), proton gradient formed, ATP and NADPH produced.

Noncyclic electron flow

Electrons move from water → PSII → ETC → PSI → NADP⁺ → NADPH; produces ATP and NADPH and releases O₂.

Photolysis

Light-driven splitting of water in PSII that provides replacement electrons and releases O₂ and H⁺.

Proton motive force (photosynthesis)

H⁺ gradient across thylakoid membrane used by ATP synthase to synthesize ATP from ADP + Pi.

NADP⁺ → NADPH

NADP⁺ accepts two electrons and one H⁺ at the end of photosynthetic electron transport to form NADPH for Calvin cycle.

Calvin cycle overview

Light-independent reactions in stroma that use ATP and NADPH to fix CO₂ into G3P through three stages: fixation, reduction, regeneration of RuBP.

RuBP (ribulose-1,5-bisphosphate)

5-carbon acceptor molecule in the Calvin cycle that combines with CO₂ via rubisco to form two 3-carbon molecules.

Rubisco (RuBP carboxylase)

Enzyme that catalyzes CO₂ fixation in the Calvin cycle; can also fix O₂ (photorespiration).

G3P (glyceraldehyde-3-phosphate)

3-carbon sugar produced by the Calvin cycle; two G3P combine to form glucose; precursor for many biomolecules.

C3 photosynthesis

Standard pathway where first detectable product is 3-carbon compound and Calvin cycle occurs in mesophyll cells; susceptible to photorespiration under heat/drought.

Photorespiration

Wasteful process when rubisco fixes O₂ instead of CO₂, producing no sugar and consuming energy; prevalent when stomata are closed.

C4 photosynthesis

Spatial partitioning: CO₂ initially fixed into 4-carbon compounds in mesophyll, transported to bundle sheath where Calvin cycle occurs; reduces photorespiration—advantage in hot/dry climates.

CAM photosynthesis

Temporal partitioning: CO₂ fixed at night into 4-carbon acids stored in vacuoles; CO₂ released during day for Calvin cycle—adaptation to arid environments.

Photosynthetic pigments

Molecules (chlorophyll a & b, carotenoids) that absorb specific wavelengths; chlorophyll absorbs red & blue best, reflects green.

Electromagnetic spectrum (visible light)

Range of wavelengths visible to humans (violet shortest wavelength/higher energy → red longest wavelength/lower energy); plants use mainly red and blue.

Engelmann’s experiment (1882)

Demonstrated that oxygen production (photosynthesis) is highest in blue and red light by observing aerobic bacteria aggregating near algal segments illuminated through a prism.

Endosymbiotic theory evidence

Mitochondria and chloroplasts have double membranes, their own circular DNA, and ribosomes similar to bacteria — evidence they arose from engulfed prokaryotes.

Mitochondrion structure

Double membrane organelle with inner folded membrane (cristae) and matrix; site of aerobic respiration and ATP production.

Cristae function

Inner membrane folds that increase surface area for the electron transport chain and ATP synthase complexes.

Cellular respiration overall equation

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ATP (energy released via oxidation of glucose).

Four phases of cellular respiration

Glycolysis (cytoplasm), prep reaction (pyruvate → acetyl-CoA in mitochondrial matrix), citric acid (Krebs) cycle (matrix), electron transport chain & oxidative phosphorylation (cristae).

Glycolysis inputs & outputs

Input: glucose + 2 ATP invested; Output: 2 pyruvate + 2 net ATP + 2 NADH (occurs in cytoplasm; anaerobic possible).

Substrate-level phosphorylation

ATP formed directly by transferring a phosphate from an intermediate substrate to ADP (occurs in glycolysis and Krebs cycle).

Preparatory reaction (pyruvate oxidation)

Pyruvate (3C) oxidized → acetyl group (2C) + CO₂; acetyl combined with CoA → acetyl-CoA; NAD⁺ reduced to NADH; occurs in mitochondrial matrix (twice per glucose).

Citric acid (Krebs) cycle outputs per glucose

Net per glucose (2 turns): 6 NADH, 2 FADH₂, 2 ATP (substrate-level), and 4 CO₂ (numbers may vary slightly by cell type).

Electron transport chain (ETC)

Series of protein carriers in inner mitochondrial membrane that accept electrons from NADH/FADH₂ and pump protons to create an electrochemical gradient used by ATP synthase.

ATP yield estimates

Typical maximum = ~38 ATP per glucose (2 from glycolysis + 2 from Krebs + ~34 from ETC), but many cells get 36 or fewer due to shuttles/leakage.

Chemiosmosis

Movement of protons down their electrochemical gradient through ATP synthase driving ATP production (both in mitochondria and chloroplasts).

Oxygen’s role in respiration

Final electron acceptor in the ETC; accepts electrons and H⁺ to form water, enabling continuous electron flow and ATP production.

NADH vs FADH₂ ATP yield difference

NADH donates electrons earlier in the ETC → typically yields ~3 ATP; FADH₂ donates later → yields ~2 ATP (historical textbook values).

Fermentation purpose

Regenerate NAD⁺ from NADH under anaerobic conditions so glycolysis can continue producing ATP; yields lactate (animals) or ethanol + CO₂ (yeast).

Lactic acid fermentation

Pyruvate reduced by NADH to lactate (recycles NAD⁺), occurs in muscle cells and some bacteria; contributes to temporary oxygen debt.

Alcohol fermentation

Pyruvate → acetaldehyde → ethanol + CO₂; regenerates NAD⁺; used by yeast in brewing/baking.

Anaerobic vs aerobic yields

Anaerobic (fermentation) yields 2 ATP per glucose (glycolysis only); aerobic respiration yields much more (~36–38 ATP) using mitochondria.

Metabolic fate of macromolecules

Carbs → glycolysis; Fats → glycerol + fatty acids (β-oxidation → acetyl-CoA); Proteins → deaminated, carbon skeletons enter glycolysis, acetyl-CoA, or Krebs cycle.

β-oxidation

Process by which fatty acids are broken into acetyl-CoA units that enter the citric acid cycle, yielding large amounts of ATP.