AP Bio - Cell Structures Flashcards

What does Cell Theory state?

All living organisms are made of cells, they are the smallest unit of life, and that cells come other cells

Prokaryotes

Single-celled organisms without a nucleus or membrane bound organelles, either bacteria or archaea; DNA floats in the nucleoid

Eukaryotes

Larger organisms with complex organelles that are often membrane-bound, and that include plants, animals, fungi, and protists; has a full nucleus

Plasma Membrane

Selectively permeable phospholipid bilayer, with proteins controlling what enters and exits

Nucleus

Control center of eukaryotic cells that directs protein synthesis and contains the DNA of the cell

Nucleoid

Region in prokaryotes where DNA is concentrated (not membrane-bound)

Nucleolus

Dense structure inside the nucleus that makes ribosomal RNA (rRNA)  and assembles ribosome subunits

Cytoplasm

Entire region between the nucleus and plasma membrane, including organelles and cytosol.

Cytosol

The jelly-like fluid in which organelles float

Ribosomes

Molecular machines made of rRNA; proteins that build proteins from mRNA instructions, found free in the cytosol or on the rough ER

Cell Wall

Rigid outer layer in plants, fungi, and some prokaryotes that protects, supports, and shapes the cell; made of cellulose in plants.

Internal Membrane System

Network of membranes in eukaryotes that organizes reactions and transport (ER, Golgi, vesicles)

Flagella

Long whip-like structures used for movement

Pili

Short, hair-like projections in bacteria used for attachment or DNA exchange (conjugation)

Cytoskeleton

Dynamic protein network that provides support, shape, and movement inside cells.

Organelle

Specialized, membrane-bound compartment in eukaryotic cells with a unique function.

Mitochondria

Double-membrane organelles that generate ATP through cellular respiration; contain their own DNA and ribosomes.

Golgi Apparatus

Stack of flattened sacs that modifies, sorts, and ships proteins and lipids.

Endoplasmic Reticulum (rough)

Studded with ribosomes; site of protein synthesis and modification.

Endoplasmic Reticulum (smooth)

Lacks ribosomes; synthesizes lipids, detoxifies, stores calcium.

Lysosome

Enzyme-filled vesicles that digest macromolecules and recycle cellular components

Vacuole

Large vesicles for storage, digestion, and water balance; especially big in plant cells for turgor pressure.

Chloroplast

Double-membrane organelles with thylakoids where photosynthesis occurs; contain their own DNA.

Plastid

Plant organelles that store or synthesize compounds (chloroplasts, chromoplasts, amyloplasts)

Peroxisome

Organelles that break down fatty acids and detoxify harmful substances using peroxide

Thylakoid

Flattened sacs inside chloroplasts where the light reactions of photosynthesis occur (stacked into grana)

Glyoxysome

Specialized peroxisomes in plant seeds that convert fats into sugars for energy during germination

Microfilaments

Thin actin filaments involved in cell shape, movement, and muscle contraction

Intermediate Filaments

Rope-like fibers providing structural strength and anchoring organelles.

Microtubules

Hollow tubes of tubulin that form tracks for organelle movement, make spindle fibers, and build cilia/flagella

Surface Area - Volume Ratio

A measure that limits cell size; smaller cells have more surface area relative to volume, aiding efficient exchange

Endosymbiotic Theory

The idea that mitochondria and chloroplasts originated as prokaryotes engulfed by ancestral eukaryotic cells

Motor Protein Movement

Proteins like kinesin and dynein that “walk” along microtubules, hauling organelles/vesicles using ATP

Cell Fractionation

Lab technique that breaks cells and separates components by size/density using centrifugation

Nuclear Envelope

Double membrane with pores that surrounds the nucleus, regulating traffic of RNA and proteins; connected with the membrane of the rough ER

Integral Membrane Protein

Proteins embedded in membrane, involved in transport, signaling, or anchoring

Peripheral Membrane Protein

Proteins loosely attached to membrane surface (inside or outside), often for signaling or support.

Glycolipid

Lipid with carbohydrate chain attached; used for cell recognition, cell-to-cell communication, and cell membrane stability

Glycoprotein

Protein with carbohydrate chain attached; used for cell recognition, cell adhesion, acts as receptors*

Cell Recognition

The ability of cells to identify each other using carbohydrate “tags” on proteins/lipids

Cell Adhesion

Process of cells sticking together via proteins or carbs

Homotypic Bonding

Cells sticking via the same proteins on each cell surface.

Heterotypic Bonding

Cells sticking via different surface proteins that match like lock-and-key.

Cell Junction

Specialized structures that link cells together

Tight Junction

Seals cells together to prevent leakage (like in the intestine).

Desmosome

Anchoring junctions that hold cells together like rivets, connected to intermediate filaments

Gap Junction

Channels that connect animal cells for direct communication of ions/small molecules

Plasmodemata

Plant cell channels through cell walls that allow exchange of water and molecules

Extracellular Matrix

Network of proteins (like collagen) and carbs outside cells that provides support and regulates cell behavior

Selective Permeability

The plasma membrane’s ability to regulate what enters and leaves the cell

Diffusion

Movement of molecules from high to low concentration (no energy).

Isotonic Solution

Solute concentration equal inside and out → no net water movement.

Hypertonic Solution

Higher solute outside → water leaves cell → shrinks (plasmolysis in plants).

Hypotonic Solution

Lower solute outside → water enters cell → swells (plants = turgid; animals risk lysis)

Facilitated Diffusion

Passive transport using channel or carrier proteins

Channel Proteins

Membrane proteins forming tunnels for molecules to pass through.

Ion Channels

Proteins that allow ions to move down their concentration gradient.

Gated Channels

Ion channels that open/close in response to a stimulus (voltage, ligand, mechanical).

Membrane Potential

The voltage difference across a cell’s membrane, created by ion gradients.

Aquaporins

Channel proteins specifically for water transport.

Sodium Potassium Pump

Active transport protein that pumps 3 Na⁺ out and 2 K⁺ in, maintaining membrane potential. Requires ATP

Membrane Fluidity and Cholesterol

Phospholipids move laterally; cholesterol prevents too much rigidity (cold temps) or fluidity (hot temps).

Active Transport

Movement of molecules against their gradient, requiring energy (usually ATP).

Uniports

Transport proteins moving one molecule in one direction.

Symports

Transport proteins moving two molecules in the same direction

Antiports

Transport proteins moving two molecules in opposite directions

Phagocytosis

Cell eating; engulfing large particles into vesicles

Pinocytosis

“Cell drinking”; engulfing fluids and dissolved solutes

Receptor-mediated Endocytosis

Uptake of specific molecules using receptor proteins and clathrin-coated pits.

Receptor Proteins

Proteins that detect signals or bind specific molecules, triggering cellular responses

Clathrin Coated Pits

Specialized pits with a clathrin protein coat that form vesicles in receptor-mediated endocytosis.

Exocytosis

Vesicles fuse with the plasma membrane to release materials outside.

Membrane functions (other)

Communication – Receptors receive signals.

Compartmentalization – Separates reactions into organelles.

Transport – Regulates exchange of molecules.

Recognition/Identity – Glycoproteins & glycolipids serve as ID tags.

Anchoring – Connects to cytoskeleton & ECM.