AP Biology Review Guide: Cells, Membranes, Transport, Organisms, and Calculations

Flashcards covering essential cell biology, microscope calculations, organelle functions, membrane transport mechanisms, action potentials, organism recognition, and basic statistical formulas from the AP Biology Review Guide.

Prokaryotic cells

Cells usually about $0.1\text{--}5\,\mu\text{m}$ in size that lack a nucleus or membrane-bound organelles, containing DNA in a nucleoid region (e.g., bacteria and archaea).

Eukaryotic cells

Cells usually about $10\text{--}100\,\mu\text{m}$ in size that possess a nucleus and membrane-bound organelles (e.g., animals, plants, fungi, and protists).

Total magnification

The overall magnification calculated by multiplying eyepiece magnification by objective magnification ($\text{eyepiece magnification} \times \text{objective magnification}$).

Field of view (FOV)

The diameter of the circular area visible through the microscope.

Nucleus

Organelle that contains DNA and helps regulate gene expression.

Nucleolus

Structure within the nucleus that makes rRNA and begins ribosomal subunit assembly.

Ribosome

Site of protein synthesis found free in the cytoplasm or attached to the rough endoplasmic reticulum.

Rough ER

Endoplasmic reticulum studded with ribosomes that processes and transports proteins.

Smooth ER

Endoplasmic reticulum that synthesizes lipids and is involved in detoxification and calcium storage in some cells.

Golgi complex

Organelle that modifies, sorts, and packages proteins and lipids into vesicles.

Mitochondrion

Organelle that produces much of the cell's ATP through cellular respiration.

Chloroplast

Organelle that performs photosynthesis; contains thylakoids, grana, and stroma.

Vacuole

Organelle that stores water, nutrients, and waste; in plant cells, the large central vacuole supports turgor pressure.

Lysosome

Organelle containing digestive enzymes inside an acidic compartment.

Peroxisome

Organelle that breaks down fatty acids and aids in the detoxification of substances.

Cytoskeleton

Structural network that maintains cell shape, moves materials, and assists with cell division.

Extracellular matrix

External network that supports animal cells and assists in receiving mechanical and chemical signals.

Microfilaments

Cytoskeletal fibers composed of actin with a diameter of about $7\,\text{nm}$.

Intermediate filaments

Cytoskeletal fibers with a diameter of about $8\text{--}12\,\text{nm}$.

Microtubules

Cytoskeletal fibers with a diameter of about $25\,\text{nm}$.

Plasmodesmata

Cell junctions that connect plant cells.

Gap junctions

Cell junctions that facilitate communication between animal cells.

Tight junctions

Cell junctions that seal spaces between adjacent cells.

Desmosomes

Cell junctions that anchor animal cells together.

Glyoxysomes

Specialized peroxisomes in certain plant tissues and seeds that convert stored fats into carbohydrates during germination.

Plasma membrane

A selectively permeable boundary that regulates the entrance and exit of materials.

Fluid mosaic model

Membrane structural model describing phospholipids and numerous proteins in lateral motion within the bilayer.

Integral protein

A membrane protein that penetrates the hydrophobic core of the lipid bilayer.

Transmembrane protein

An integral membrane protein that spans across the entire lipid bilayer.

Peripheral protein

A protein associated with only one surface of the membrane, often attached to an integral protein.

Cholesterol

A membrane lipid that buffers membrane fluidity across varying temperatures.

Simple diffusion

Passive net movement of solutes down a concentration gradient without requiring ATP.

Osmosis

The net diffusion of water across a selectively permeable membrane.

Facilitated diffusion

Passive movement of substances down a concentration gradient via a channel or carrier protein.

Channel protein

A transport protein that provides a continuous pathway across the membrane (e.g., aquaporins and ion channels).

Carrier protein

A transport protein that binds specific molecules and undergoes shape changes to shuttle them across the membrane.

Active transport

The energy-requiring movement of a substance against its concentration or electrochemical gradient.

Sodium-potassium pump

An active transport protein that consumes ATP to transport $3\,\text{Na}^+$ out of the cell and $2\,\text{K}^+$ into the cell per cycle.

Electrochemical gradient

The combined drive acting on an ion, incorporating both its concentration gradient and electrical charge effects.

Phagocytosis

Cellular eating; a type of endocytosis where pseudopodia engulf large particles to enclose them in a vesicle.

Pinocytosis

Cellular drinking; the nonspecific uptake of extracellular fluid and dissolved substances into vesicles.

Receptor-mediated endocytosis

Endocytic mechanism where specific ligands bind cell-surface receptor proteins, often in coated pits, triggering vesicle formation.

Exocytosis

Process in which internal vesicles fuse with the plasma membrane to release their contents outside the cell.

Cystinuria

A condition resulting from a missing or defective carrier for cystine reabsorption in kidney cells, potentially forming cystine kidney stones.

Plasmolysis

The phenomenon in which a plant cell's plasma membrane pulls away from the cell wall following excessive water loss in a hypertonic environment.

Water potential ($\Psi$)

A measure defined by $\Psi = \Psi_s + \Psi_p$ that dictates water movement from regions of higher water potential to regions of lower water potential.

Resting potential

The electrical potential across a resting neuronal membrane where the interior is negative relative to the outside, typically around $-70\,\text{mV}$.

Depolarization

The upstroke phase of an action potential when voltage-gated $\text{Na}^+$ channels open, allowing $\text{Na}^+$ to enter and make the membrane potential more positive.

Repolarization

The downstroke phase of an action potential during which voltage-gated $\text{K}^+$ channels allow $\text{K}^+$ to exit, returning the interior to a negative potential.

Hyperpolarization

The phase during which the membrane potential temporarily becomes more negative than the resting potential.

Refractory period

A brief timeframe following an action potential during which a neuron temporarily cannot fire another action potential normally.

Botulinum toxin

A toxin that blocks acetylcholine release at neuromuscular junctions, preventing muscle activation.

Surface-area-to-volume ratio ($\text{SA}/V$)

The ratio of surface area divided by volume ($\text{SA}/V$); smaller cells maintain a larger ratio, enabling more efficient exchange of materials relative to volume.

Euglena

A unicellular protist capable of both photosynthesis and heterotrophic nutrient acquisition.

Paramecium

A unicellular protist that feeds by ingesting food, employing cilia for both locomotion and feeding.

Stentor

A unicellular ciliate protist that is often trumpet-shaped.

Spirogyra

A filamentous, photosynthetic green alga.

Volvox

A colonial green alga characterized by cells arranged into a spherical colony.

Hydra

A multicellular freshwater cnidarian animal equipped with tentacles.

Water bear (tardigrade)

A microscopic multicellular animal featuring a segmented body and eight legs.

Daphnia magna

A small multicellular crustacean that filter-feeds on suspended particles in water.

Standard error of the mean (SEM)

A statistical value calculated as $\text{SEM} = \frac{s}{\sqrt{n}}$, where $s$ is the sample standard deviation and $n$ is the sample size.