APBIO

What is polarity in water?

Water is polar because oxygen is more electronegative than hydrogen, creating partial charges (δ− on O, δ+ on H).

What are hydrogen bonds in water?

Weak attractions between the δ+ hydrogen of one water molecule and the δ− oxygen of another.

Why are hydrogen bonds important in water?

They give water cohesion, adhesion, high heat capacity, and high heat of vaporization.

What are ribosomes?

Structures that synthesize proteins by translating mRNA.

What is the rough ER?

Organelle studded with ribosomes that modifies and transports proteins.

What is the smooth ER?

Organelle that synthesizes lipids and detoxifies chemicals.

What is the Golgi apparatus?

Modifies, sorts, and ships proteins and lipids.

What is the function of mitochondria?

Produces ATP through cellular respiration.

What are lysosomes?

Contain enzymes that break down macromolecules and waste.

What is a vacuole?

Stores water, nutrients, and waste; central vacuole maintains plant cell turgor.

What is a chloroplast?

Site of photosynthesis; converts light energy into chemical energy.

What are membrane convolutions and why are they important?

Folds in membranes that increase surface area for more reactions.

What are phospholipids?

Molecules with hydrophilic heads and hydrophobic tails forming a bilayer.

What are the 6 types of membrane proteins?

Transport, enzymatic, signal transduction, recognition, intercellular joining, anchorage.

What is osmosis?

Diffusion of water across a selectively permeable membrane.

What is selective permeability?

The membrane allows some substances to pass while restricting others.

What is passive transport?

Movement of molecules without energy (down concentration gradient).

What is active transport?

Movement of molecules using ATP (against gradient).

What is exocytosis?

Vesicles fuse with membrane to release materials out of the cell.

What is endocytosis?

Cell takes in materials by forming vesicles.

What is facilitated diffusion?

Movement of molecules through protein channels without energy.

What is a hypertonic solution?

Higher solute concentration outside → water leaves cell.

What is a hypotonic solution?

Lower solute concentration outside → water enters cell.

What is an isotonic solution?

Equal solute concentration → no net water movement.

What is osmoregulation?

Control of water balance in an organism.

What is water potential?

Measure of potential energy of water; predicts direction of water movement.

What is the endosymbiotic theory?

Mitochondria and chloroplasts originated from engulfed prokaryotes.

What are ideal conditions for enzyme activity?

Optimal temperature, pH, and substrate concentration.

What is denaturation?

Loss of enzyme shape and function due to extreme conditions.

What is an active site?

Region where substrate binds on an enzyme.

What is a competitive inhibitor?

Molecule that competes with substrate for active site.

What is a noncompetitive inhibitor?

Binds elsewhere and changes enzyme shape.

What is an allosteric site?

Site where regulators bind to change enzyme activity.

What happens in the light reactions?

Light energy splits water, produces ATP and NADPH.

What happens in the Calvin cycle?

Uses ATP and NADPH to fix CO₂ into glucose.

What is fermentation?

Anaerobic process that regenerates NAD⁺ to keep glycolysis running.

What is glycolysis?

Breaks glucose into pyruvate, producing ATP and NADH.

What happens in the Krebs cycle?

Breaks down acetyl-CoA, releasing CO₂ and producing NADH/FADH₂.

What is the electron transport chain?

Uses electrons to create a proton gradient for ATP production.

What is chemiosmosis?

Movement of protons through ATP synthase to make ATP.

What is transpiration?

Loss of water vapor from plant leaves.

What is cell-to-cell signaling?

Communication between nearby cells using direct contact or local signals.

What is long-distance signaling?

Hormones travel through bloodstream to target cells.

What is signal transduction?

Process of converting external signal into cellular response.

What are G protein pathways?

Signal pathways using G proteins to relay signals inside the cell.

What are relay molecules?

Proteins that pass signals inside the cell.

What are secondary messengers?

Small molecules (like cAMP) that amplify signals.

What is apoptosis?

Programmed cell death.

What is positive feedback?

Response amplifies the original stimulus.

What is negative feedback?

Response reduces the original stimulus.

What happens in G1 phase?

The cell grows larger, copies organelles, and synthesizes mRNA and proteins required for DNA replication

What happens in S phase?

DNA is replicated.

What happens in G2 phase?

Cell prepares for division by increasing in size and duplicating organelles,

What happens in mitosis?

Division of nucleus into two identical nuclei.

What happens in cytokinesis?

Division of cytoplasm.

What is RNA interference (RNAi)?

Process where RNA molecules silence gene expression.

What are internal controls of the cell cycle?

Checkpoints that ensure proper division (e.g., DNA integrity).

What are external controls of the cell cycle?

Signals like growth factors from other cells.

What are cyclins and CDKs?

Proteins that regulate progression through the cell cycle.

What is haploid?

One set of chromosomes (n).

What is diploid?

Two sets of chromosomes (2n).

How many cells are produced in meiosis?

Four haploid cells.

How many cells are produced in mitosis?

Two diploid cells.

What is crossing over?

Exchange of DNA between homologous chromosomes.

What is independent assortment?

Random alignment of chromosome pairs in meiosis.

What is random fertilization?

Any sperm can fertilize any egg → genetic variation.

What is the law of multiplication?

Probability of two events = multiply their probabilities.

What are sex-linked traits?

Traits carried on sex chromosomes (usually X).

What are linked genes?

Genes located close together on the same chromosome.

What is epigenetics?

Changes in gene expression without altering DNA sequence.

What is a gene mutation?

Change in DNA sequence.

What is nondisjunction?

Failure of chromosomes to separate properly.

What is DNA synthesis?

Process of copying DNA before cell division.

What is semi-conservative replication?

Each new DNA has one old strand and one new strand.

What does 5’→3’ directionality mean?

DNA and RNA polymerase synthesize new nucleic acid strands, adding nucleotides only to the 3’ end.

What does helicase do?

Unwinds the DNA double helix.

What does topoisomerase do?

Relieves tension in DNA during DNA replication and transcription.

What does DNA polymerase do?

Adds nucleotides to build DNA.

What does ligase do?

Joins Okazaki fragments on the lagging strand in replication.

What does RNA polymerase do?

Synthesizes RNA from DNA.

What is a codon?

Three-nucleotide sequence that codes for an amino acid.

What are exons?

Coding regions of genes.

What are introns?

Noncoding regions removed during processing.

What is mRNA processing?

Addition of cap, poly-A tail, and splicing of introns.

What is transcription?

DNA → mRNA.

What is translation?

Ribosomes in the cytoplasm or rough ER read mRNA (produced via transcription) to synthesize polypeptides.

What is the ribosome’s role?

Reads mRNA and builds proteins.

What is RNAi?

Silences gene expression using small RNA molecules.

What are transcription factors?

Proteins that regulate gene expression.

What is a promoter?

DNA sequence where transcription begins.

What are operons?

prokaryotic gene regulation systems that cluster functionally related genes under a single promoter, allowing bacteria to turn entire metabolic pathways on or off.

What is activation energy?

Energy required to start a chemical reaction.

How do enzymes lower activation energy?

They stabilize the transition state and bring substrates together.

What is the fluid mosaic model?

Membrane is flexible with embedded proteins moving within lipid bilayer.