Question 1

Cell Membrane Fluidity

Accepted Answer

The flexibility of the plasma membrane is influenced by temperature, fatty acid saturation, and cholesterol.

Question 2

Unsaturated Fatty Acids

Accepted Answer

In phospholipids, these have double bonds that increase membrane fluidity.

Question 3

Saturated Fatty Acids

Accepted Answer

In phospholipids, these lack double bonds and make membranes more rigid.

Question 4

Amphipathic Molecule

Accepted Answer

A molecule with both hydrophilic and hydrophobic regions, like a phospholipid.

Question 5

Lipid Rafts

Accepted Answer

Specialized membrane microdomains rich in cholesterol that organize cell signaling molecules.

Question 6

Transport Proteins

Accepted Answer

Membrane proteins that help move substances across the membrane.

Question 7

Channel Proteins

Accepted Answer

Provide hydrophilic passageways for specific molecules or ions.

Question 8

Carrier Proteins

Accepted Answer

Bind specific molecules, undergo shape change, and transport them across the membrane.

Question 9

Ion Channels

Accepted Answer

Protein channels allowing specific ions to pass; can be gated by voltage or ligands.

Question 10

Membrane Potential

Accepted Answer

The voltage across a cell’s plasma membrane created by ion distribution.

Question 11

Electrochemical Gradient

Accepted Answer

Combined force of electrical and concentration gradients driving ion movement.

Question 12

Proton Pump

Accepted Answer

Active transport mechanism that moves protons across membranes to create potential energy.

Question 13

ATP Synthase

Accepted Answer

Enzyme that synthesizes ATP using a proton gradient across a membrane.

Question 14

Endomembrane System

Accepted Answer

System of membranes including ER, Golgi, lysosomes, and vesicles for transport and processing.

Question 15

Vesicle

Accepted Answer

Small membrane sac that transports materials between organelles or to the plasma membrane.

Question 16

Secretory Pathway

Accepted Answer

Pathway for proteins destined for secretion or membranes (Rough ER → Golgi → vesicle → membrane).

Question 17

Glycoprotein

Accepted Answer

Protein with carbohydrate chains attached; important for cell recognition.

Question 18

Glycolipid

Accepted Answer

Lipid with a carbohydrate chain that aids in cell identification.

Question 19

Cell Recognition

Accepted Answer

The ability of a cell to distinguish one type of cell from another, often via surface molecules.

Question 20

Signal Transduction Pathway

Accepted Answer

Process by which a cell converts an external signal into a specific response.

Question 21

Ligand

Accepted Answer

A molecule that binds to a receptor and triggers a cellular response.

Question 22

Receptor Protein

Accepted Answer

Protein that receives and binds signaling molecules, initiating a signal transduction cascade.

Question 23

G Protein-Coupled Receptor (GPCR)

Accepted Answer

Membrane receptor that activates a G protein when bound by a ligand.

Question 24

G Protein

Accepted Answer

A molecular switch that relays signals from GPCRs to other signaling proteins.

Question 25

Second Messenger

Accepted Answer

Small molecule (like cAMP or Ca²⁺) that relays and amplifies intracellular signals.

Question 26

cAMP (Cyclic AMP)

Accepted Answer

A common second messenger involved in many signal transduction pathways.

Question 27

Protein Kinase

Accepted Answer

Enzyme that transfers phosphate groups to proteins, activating or deactivating them.

Question 28

Protein Phosphatase

Accepted Answer

Enzyme that removes phosphate groups from proteins, turning off signaling pathways.

Question 29

Signal Amplification

Accepted Answer

Each step in a signal transduction cascade activates multiple downstream molecules.

Question 30

Phosphorylation Cascade

Accepted Answer

Series of protein activations through phosphorylation events in cell signaling.

Question 31

Cell Communication

Accepted Answer

The process of cells detecting and responding to signals in their environment.

Question 32

Local Signaling

Accepted Answer

Communication between nearby cells through direct contact or short-distance signaling.

Question 33

Paracrine Signaling

Accepted Answer

Type of local signaling where cells release molecules that act on nearby cells.

Question 34

Synaptic Signaling

Accepted Answer

Nerve cell releases neurotransmitters that cross synapse to target cell.

Question 35

Endocrine Signaling

Accepted Answer

Long-distance signaling where hormones travel through the bloodstream to target cells.

Question 36

Hormone

Accepted Answer

Chemical messenger secreted into body fluids that affects target cells at distant sites.

Question 37

Reception

Accepted Answer

First step of cell signaling where the signal molecule binds to a receptor.

Question 38

Transduction

Accepted Answer

Series of molecular events that convert the signal into a cellular response.

Question 39

Response

Accepted Answer

Final stage of cell signaling where the cell changes behavior or gene expression.

Question 40

Feedback Mechanisms

Accepted Answer

Biological processes that regulate systems by increasing or decreasing activity.

Question 41

Negative Feedback

Accepted Answer

Process that reduces the output of a system, maintaining homeostasis.

Question 42

Positive Feedback

Accepted Answer

Process that amplifies a response, driving it to completion (e.g., childbirth contractions).

Question 43

Apoptosis

Accepted Answer

Programmed cell death that removes damaged or unnecessary cells.

Question 44

Autophagy

Accepted Answer

Process in which lysosomes digest damaged organelles or cell components.

Question 45

Cell Junctions

Accepted Answer

Structures that connect cells and facilitate communication or adhesion.

Question 46

Desmosome Proteins

Accepted Answer

Cadherins that anchor cells together in tissues under mechanical stress.

Question 47

Gap Junction Proteins

Accepted Answer

Connexins that form pores connecting animal cells’ cytoplasms.

Question 48

Plasmodesmata Proteins

Accepted Answer

Callose-lined channels allowing small molecules to pass between plant cells.

Question 49

Surface Receptor

Accepted Answer

Receptor located in the plasma membrane that binds polar signaling molecules.

Question 50

Intracellular Receptor

Accepted Answer

Receptor inside the cell that binds nonpolar, lipid-soluble molecules like steroid hormones.

Question 51

Steroid Hormones

Accepted Answer

Lipid-based hormones that pass through membranes and bind to intracellular receptors.

Question 52

Gene Expression Response

Accepted Answer

Type of cell response that changes transcription or translation of specific genes.

Question 53

Homeostasis

Accepted Answer

Stable internal condition maintained through feedback and cell signaling.

Question 54

Osmoregulation

Accepted Answer

Process by which cells or organisms maintain water balance.

Question 55

Turgor Pressure

Accepted Answer

The pressure exerted by water inside the plant cell against its wall.

Question 56

Plasmolysis

Accepted Answer

When a plant cell loses water in a hypertonic solution, causing the membrane to pull away from the wall.

Question 57

Cotransport Example

Accepted Answer

The uptake of sucrose into plant cells powered by proton gradients established by proton pumps.

Question 58

Membrane Potential Example

Accepted Answer

Resting potential in neurons where the inside is negatively charged relative to outside.

Question 59

Endocytosis Example

Accepted Answer

White blood cell engulfing bacteria.

Question 60

Exocytosis Example

Accepted Answer

Neurons releasing neurotransmitters into a synapse.

Question 61

Mitochondria Function

Accepted Answer

Convert energy from organic molecules into ATP through cellular respiration.

Question 62

Chloroplast Function

Accepted Answer

Convert solar energy into chemical energy through photosynthesis.

Question 63

Lysosome Function

Accepted Answer

Break down waste and damaged organelles using hydrolytic enzymes.

Question 64

Golgi Function

Accepted Answer

Modify, sort, and package proteins for secretion or delivery to organelles.

Term	Definition
Cell Membrane Fluidity	The flexibility of the plasma membrane is influenced by temperature, fatty acid saturation, and cholesterol.
Unsaturated Fatty Acids	In phospholipids, these have double bonds that increase membrane fluidity.
Saturated Fatty Acids	In phospholipids, these lack double bonds and make membranes more rigid.
Amphipathic Molecule	A molecule with both hydrophilic and hydrophobic regions, like a phospholipid.
Lipid Rafts	Specialized membrane microdomains rich in cholesterol that organize cell signaling molecules.
Transport Proteins	Membrane proteins that help move substances across the membrane.
Channel Proteins	Provide hydrophilic passageways for specific molecules or ions.
Carrier Proteins	Bind specific molecules, undergo shape change, and transport them across the membrane.
Ion Channels	Protein channels allowing specific ions to pass; can be gated by voltage or ligands.
Membrane Potential	The voltage across a cell’s plasma membrane created by ion distribution.
Electrochemical Gradient	Combined force of electrical and concentration gradients driving ion movement.
Proton Pump	Active transport mechanism that moves protons across membranes to create potential energy.
ATP Synthase	Enzyme that synthesizes ATP using a proton gradient across a membrane.
Endomembrane System	System of membranes including ER, Golgi, lysosomes, and vesicles for transport and processing.
Vesicle	Small membrane sac that transports materials between organelles or to the plasma membrane.
Secretory Pathway	Pathway for proteins destined for secretion or membranes (Rough ER → Golgi → vesicle → membrane).
Glycoprotein	Protein with carbohydrate chains attached; important for cell recognition.
Glycolipid	Lipid with a carbohydrate chain that aids in cell identification.
Cell Recognition	The ability of a cell to distinguish one type of cell from another, often via surface molecules.
Signal Transduction Pathway	Process by which a cell converts an external signal into a specific response.
Ligand	A molecule that binds to a receptor and triggers a cellular response.
Receptor Protein	Protein that receives and binds signaling molecules, initiating a signal transduction cascade.
G Protein-Coupled Receptor (GPCR)	Membrane receptor that activates a G protein when bound by a ligand.
G Protein	A molecular switch that relays signals from GPCRs to other signaling proteins.
Second Messenger	Small molecule (like cAMP or Ca²⁺) that relays and amplifies intracellular signals.
cAMP (Cyclic AMP)	A common second messenger involved in many signal transduction pathways.
Protein Kinase	Enzyme that transfers phosphate groups to proteins, activating or deactivating them.
Protein Phosphatase	Enzyme that removes phosphate groups from proteins, turning off signaling pathways.
Signal Amplification	Each step in a signal transduction cascade activates multiple downstream molecules.
Phosphorylation Cascade	Series of protein activations through phosphorylation events in cell signaling.
Cell Communication	The process of cells detecting and responding to signals in their environment.
Local Signaling	Communication between nearby cells through direct contact or short-distance signaling.
Paracrine Signaling	Type of local signaling where cells release molecules that act on nearby cells.
Synaptic Signaling	Nerve cell releases neurotransmitters that cross synapse to target cell.
Endocrine Signaling	Long-distance signaling where hormones travel through the bloodstream to target cells.
Hormone	Chemical messenger secreted into body fluids that affects target cells at distant sites.
Reception	First step of cell signaling where the signal molecule binds to a receptor.
Transduction	Series of molecular events that convert the signal into a cellular response.
Response	Final stage of cell signaling where the cell changes behavior or gene expression.
Feedback Mechanisms	Biological processes that regulate systems by increasing or decreasing activity.
Negative Feedback	Process that reduces the output of a system, maintaining homeostasis.
Positive Feedback	Process that amplifies a response, driving it to completion (e.g., childbirth contractions).
Apoptosis	Programmed cell death that removes damaged or unnecessary cells.
Autophagy	Process in which lysosomes digest damaged organelles or cell components.
Cell Junctions	Structures that connect cells and facilitate communication or adhesion.
Desmosome Proteins	Cadherins that anchor cells together in tissues under mechanical stress.
Gap Junction Proteins	Connexins that form pores connecting animal cells’ cytoplasms.
Plasmodesmata Proteins	Callose-lined channels allowing small molecules to pass between plant cells.
Surface Receptor	Receptor located in the plasma membrane that binds polar signaling molecules.
Intracellular Receptor	Receptor inside the cell that binds nonpolar, lipid-soluble molecules like steroid hormones.
Steroid Hormones	Lipid-based hormones that pass through membranes and bind to intracellular receptors.
Gene Expression Response	Type of cell response that changes transcription or translation of specific genes.
Homeostasis	Stable internal condition maintained through feedback and cell signaling.
Osmoregulation	Process by which cells or organisms maintain water balance.
Turgor Pressure	The pressure exerted by water inside the plant cell against its wall.
Plasmolysis	When a plant cell loses water in a hypertonic solution, causing the membrane to pull away from the wall.
Cotransport Example	The uptake of sucrose into plant cells powered by proton gradients established by proton pumps.
Membrane Potential Example	Resting potential in neurons where the inside is negatively charged relative to outside.
Endocytosis Example	White blood cell engulfing bacteria.
Exocytosis Example	Neurons releasing neurotransmitters into a synapse.
Mitochondria Function	Convert energy from organic molecules into ATP through cellular respiration.
Chloroplast Function	Convert solar energy into chemical energy through photosynthesis.
Lysosome Function	Break down waste and damaged organelles using hydrolytic enzymes.
Golgi Function	Modify, sort, and package proteins for secretion or delivery to organelles.
Smooth ER Function	Synthesize lipids, metabolize carbohydrates, and detoxify drugs.
Rough ER Function	Produce and fold proteins for secretion or for use in membranes.
Peroxisome Function	Oxidize fatty acids and detoxify harmful compounds.
Cytoskeleton Function	Provide structural support, movement, and intracellular transport.
Microtubule Motor Proteins	Dynein and kinesin proteins that move vesicles along microtubules.
Dynamic Equilibrium	State in which molecules continue to move but overall concentration remains constant.
Water Potential	The potential energy of water in a system; drives osmosis (Ψ = Ψs + Ψp).
Solute Potential	Component of water potential determined by solute concentration (always negative).
Pressure Potential	Component of water potential caused by physical pressure on a solution.
Cell Theory	The cell is the basic unit of life; all living things are made of cells, and all cells come from pre-existing cells.
Prokaryotic Cell	A cell lacking a nucleus and membrane-bound organelles; includes bacteria and archaea.
Eukaryotic Cell	A cell containing a true nucleus and membrane-bound organelles; includes plants, animals, fungi, and protists.
Plasma Membrane	A selectively permeable phospholipid bilayer that regulates the entry and exit of substances.
Phospholipid Bilayer	The main structural component of membranes; hydrophilic heads and hydrophobic tails create a semi-permeable barrier.
Selective Permeability	Property of biological membranes allowing some substances to pass while restricting others.
Cytoplasm	The region between the nucleus and plasma membrane containing organelles and cytosol.
Nucleus	Membrane-bound organelle that contains the cell’s DNA and controls gene expression.
Nuclear Envelope	Double membrane surrounding the nucleus, containing pores for RNA and protein exchange.
Nucleolus	Region inside the nucleus responsible for ribosome synthesis.
Ribosome	Structure made of rRNA and proteins; the site of protein synthesis.
Free Ribosomes	Ribosomes floating in cytosol; produce proteins for use within the cell.
Bound Ribosomes	Ribosomes attached to rough ER; produce proteins for export or for membranes.
Endoplasmic Reticulum (ER)	Network of membranes involved in protein and lipid synthesis.
Rough ER	ER studded with ribosomes; synthesizes and modifies proteins.
Smooth ER	ER without ribosomes; synthesizes lipids, detoxifies toxins, and stores calcium ions.
Golgi Apparatus	Stack of flattened membranes that modifies, sorts, and packages proteins for secretion or delivery.
Lysosome	Membrane-bound sac of digestive enzymes that breaks down macromolecules and old organelles.
Peroxisome	Organelle that breaks down fatty acids and detoxifies harmful substances, producing hydrogen peroxide.
Vacuole	Storage organelle; large central vacuole in plants stores water and maintains turgor pressure.
Mitochondrion	Organelle that generates ATP through cellular respiration; has its own DNA and double membrane.
Chloroplast	Plant organelle where photosynthesis occurs; contains chlorophyll and its own DNA.
Endosymbiotic	Theory Idea that mitochondria and chloroplasts originated from prokaryotic cells engulfed by ancestors of eukaryotes.
Cytoskeleton	Network of fibers that maintains cell shape, secures organelles, and enables cell movement.
Microtubules	Hollow protein tubes made of tubulin; form spindle fibers and cilia/flagella.
Microfilaments	Fine protein threads made of actin; involved in cell movement and muscle contraction.
Intermediate	Filaments Rope-like filaments that provide structural support and anchor organelles.
Centrosome	Region near the nucleus that organizes microtubules; contains centrioles in animal cells.
Centriole	Cylindrical structure in animal cells that helps organize cell division.
Cilia	Short, hair-like projections used for movement or moving fluids over a cell surface.
Flagella	Long, whip-like tail used for locomotion in some cells.
Cell Wall	Rigid structure outside the plasma membrane in plants, fungi, and bacteria providing support and protection.
Extracellular Matrix (ECM)	Collection of proteins and carbohydrates outside animal cells providing structural and biochemical support.
Plasmodesmata	Channels between plant cell walls that allow for communication and transport.
Tight Junctions	Connections between animal cells forming a watertight seal.
Desmosomes	Anchoring junctions that hold animal cells together through intermediate filaments.
Gap Junctions	Channels between adjacent animal cells allowing ions and small molecules to pass.
Passive Transport	Movement of molecules across the membrane without energy input.
Diffusion	Movement of molecules from high to low concentration until equilibrium is reached.
Facilitated Diffusion	Passive transport aided by membrane proteins.
Osmosis	Diffusion of water through a selectively permeable membrane.
Tonicity	The ability of a surrounding solution to cause a cell to gain or lose water.
Isotonic Solution	Solution with equal solute concentration inside and outside the cell; no net water movement.
Hypotonic Solution	Solution with lower solute concentration outside the cell; water enters, cell swells.
Hypertonic Solution	Solution with higher solute concentration outside the cell; water leaves, cell shrinks.
Active Transport	Movement of molecules against the concentration gradient requiring energy (ATP).
Sodium-Potassium Pump	Transport protein that pumps Na+ out and K+ into the cell, maintaining membrane potential.
Endocytosis	Process by which cells take in materials via vesicles formed from the plasma membrane.
Exocytosis	Process of vesicles fusing with the plasma membrane to release contents outside the cell.
Phagocytosis	“Cell eating”; a type of endocytosis where large particles are engulfed.
Pinocytosis	“Cell drinking”; a type of endocytosis that brings in fluids and dissolved substances.
Receptor-Mediated Endocytosis	Selective uptake of molecules based on receptor-ligand interactions.
Surface Area-to-Volume Ratio	Ratio affecting cell efficiency; smaller cells have higher ratios for better material exchange.
Compartmentalization	Organization of cellular functions into membrane-bound organelles for efficiency.
Fluid Mosaic Model	Model describing the plasma membrane as a fluid combination of lipids and proteins.
Cholesterol	Inserts into the phospholipid bilayer to regulate membrane fluidity.
Integral Protein	Protein embedded within the lipid bilayer, often spanning the membrane.
Peripheral Protein	Protein attached to the surface of the membrane, not embedded.
Aquaporin	Protein channel that facilitates water diffusion across membranes.
ATP (Adenosine Triphosphate)	Main energy currency of the cell produced by mitochondria.
Cell Fractionation	Laboratory technique to separate organelles for study based on size and density.
Proton Gradient	Difference in proton concentration across a membrane driving ATP synthesis.
Cotransport	Active transport of one substance indirectly driving the transport of another.
Signal Transduction	Pathway by which a signal is converted into a cellular response.

AP Bio Unit 2

AP Biology

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