AP Biology Semester 1 Final

Why does water have a high specific heat and why is this biologically important?

Water forms hydrogen bonds due to polarity, which absorb heat before breaking. This stabilizes temperature and helps maintain homeostasis.

How does water’s heat of vaporization support thermoregulation?

Evaporation breaks hydrogen bonds, removing heat from surfaces (e.g., sweating cools the body)

Difference between dehydration synthesis and hydrolysis?

Dehydration synthesis removes water to form polymers; hydrolysis adds water to break polymers into monomers.

How does carbohydrate structure relate to function?

Monosaccharides provide quick energy; polysaccharides (starch, glycogen) store energy; cellulose provides structural support due to β-linkages.

Why are lipids hydrophobic and how does that affect membranes?

Lipids are nonpolar; phospholipids form bilayers with hydrophilic heads outward and hydrophobic tails inward, creating selective permeability.

Why do smaller cells exchange materials more efficiently than larger cells?

Smaller cells have a higher surface area–to–volume ratio, increasing diffusion efficiency.

Describe the fluid mosaic model.

A dynamic phospholipid bilayer with embedded, movable proteins, cholesterol, and carbohydrates.

Difference between passive and active transport?

Passive transport moves substances down their concentration gradient without energy; active transport moves substances against the gradient using ATP.

What role do aquaporins play in membranes?

Channel proteins that facilitate rapid water movement across membranes.

What happens to an animal cell in a hypertonic solution?

Water leaves the cell, causing it to shrink (crenation).

Why is compartmentalization important in eukaryotic cells?

Separates incompatible reactions and increases efficiency by localizing processes.

Evidence supporting the endosymbiotic theory?

Mitochondria and chloroplasts have their own circular DNA, ribosomes, double membranes, and replicate independently.

How can I tell if something is hypotonic?

• Lower solute outside

• Higher water outside

• ➜ Water moves into the cell

• Plant cell becomes turgid

How can I tell if something is hypertonic

• Higher solute outside

• Lower water outside

• ➜ Water moves out of the cell

• Plant cell → plasmolysis

How can I tell if something is isotonic

• Equal solute

• ➜ No net water movement

Water moves in which direction relative to solute concentration?

Toward higher solute (less free water). Hypotonic → in, hypertonic → out, isotonic → none.

Why can’t cells get too big?

SA:V ratio decreases → inefficient material exchange.

What do channel vs carrier proteins do?

Channel = pore, fast; carrier = binds, slow. Both aid selective permeability.

How do enzymes affect reaction rates?

Lower activation energy; substrate binds at active site; do not change ΔG.

What happens if pH or temperature changes too much?

Enzyme denatures → active site changes → reaction slows or stops.

Competitive vs noncompetitive inhibitors?

Competitive binds active site; can be overcome by substrate. Noncompetitive binds elsewhere; changes enzyme shape → reduces activity.

Light reactions vs Calvin cycle — where and what?

Light reactions: thylakoid, produce ATP & NADPH. Calvin cycle: stroma, uses ATP & NADPH to fix CO₂ → G3P.

Function of Photosystems I & II?

PSII absorbs light → electrons → ETC → ATP. PSI absorbs light → electrons → NADPH.

What drives photophosphorylation?

Proton gradient across thylakoid → ATP synthase → ATP.

Glycolysis inputs/outputs & location?

Cytosol; glucose → 2 pyruvate + 2 ATP + 2 NADH.

Krebs cycle location & outputs?

Mitochondrial matrix; acetyl-CoA → 2 CO₂, 1 ATP, 3 NADH, 1 FADH₂ per cycle.

ETC & oxidative phosphorylation?

Inner mitochondrial membrane; electrons from NADH/FADH₂ → proton gradient → ATP via ATP synthase; O₂ final electron acceptor → H₂O.

Fermentation — when and why?

No O₂; pyruvate → lactate (animals) or ethanol + CO₂ (yeast); regenerates NAD⁺ for glycolysis.

What does the Calvin cycle produce?

G3P (sugar). CO₂ is the input, not the product.

What does one turn of the Krebs cycle produce per acetyl-CoA?

3 NADH, 1 FADH₂, 1 ATP, 2 CO₂

Where does the electron transport chain occur?

Inner mitochondrial membrane; O₂ is the final electron acceptor → H₂O formed.

How do cells communicate?

Direct contact (gap junctions) or chemical signaling (local = paracrine, long-distance = endocrine).

What are the 3 steps of a signal transduction pathway?

Reception → Transduction → Response

What can mutations in receptors or signaling proteins cause?

Altered or absent response; can lead to disease or cancer.

Difference between negative and positive feedback?

Negative feedback returns system to set point; positive feedback amplifies response.

Main phases of the cell cycle?

Interphase (G₁, S, G₂), Mitosis (prophase, metaphase, anaphase, telophase), Cytokinesis

Function of checkpoints in the cell cycle?

Cyclin-CDK complexes ensure proper progression; prevent DNA damage, errors.

What happens if checkpoints fail?

Can lead to cancer or apoptosis.

Direction of DNA replication and key enzymes?

5′ → 3′; helicase, primase, DNA polymerase, ligase

Leading vs lagging strand?

Leading = continuous synthesis; lagging = Okazaki fragments, discontinuous

How can you tell if something is autocrine

cell signals itself

How can you tell if something is paracrine

signals nearby cells (local)

How can you tell if something is endocrine

1. Endocrine – signals distant cells via blood (long-distance)

What is a G-protein coupled receptor (GPCR)?

Membrane receptor; ligand binds → activates G-protein → triggers intracellular cascade.

What is a ligand-gated ion channel?

Ligand binds → channel opens → ions flow → changes membrane potential or triggers response.

What is a hormone in cell signaling?

Chemical messenger secreted by endocrine cells → travels through blood → binds target cell receptor → triggers response.

Intracellular vs membrane receptors?

• Intracellular: ligand (e.g., steroid hormone) crosses membrane → binds receptor inside → alters gene expression.

• Membrane: ligand binds receptor on surface → triggers signal transduction cascade.