Unit 2: Cell Structure and Function Flashcard Set

A set of 200 vocabulary flashcards covering cell structure and function, organelles, endomembrane trafficking, energy conversion, membrane permeability, passive/active transport, and water potential calculations.

Plasma membrane

A phospholipid-based membrane found in every type of cell that encloses the cytoplasm and forms a selective barrier.

Cytoplasm

The internal fluid and cellular contents found in every type of cell, both prokaryotic and eukaryotic.

DNA

The genetic material present in all cells, residing within a nucleus in eukaryotes or a nucleoid in prokaryotes.

Ribosomes

Non-membrane-bound complexes composed of ribosomal RNA (rRNA) and proteins that translate mRNA to synthesize polypeptides.

Universal cellular components

Four structures found in every type of cell: a plasma membrane, cytoplasm, DNA, and ribosomes.

Organelles in both plant and animal cells

Nucleus, ribosomes, rough and smooth ER, Golgi apparatus, mitochondria, cytoskeleton, plasma membrane, and cytoplasm.

Plant-specific structures

Structures found in plant cells but not animal cells: cell wall, chloroplasts (in photosynthetic cells), and typically one large central vacuole.

Animal-specific structures

Structures typically found in animal cells: lysosomes and centrosomes with centrioles.

Prokaryotic cells

Cells that lack a nucleus and membrane-bound organelles, and are generally smaller than eukaryotic cells.

Eukaryotic cells

Cells that contain a nucleus and membrane-bound organelles, compartmentalizing metabolic processes.

Relative cell size comparison

Prokaryotic cells are generally smaller in size compared to eukaryotic cells.

Nucleoid

The non-membrane-enclosed region where DNA is localized within a prokaryotic cell.

Prokaryotic cell wall

A rigid outer protective layer present outside the plasma membrane in prokaryotes (when present).

Bacterial capsule

An optional outer protective layer found surrounding the cell wall in some prokaryotes.

Pili

Optional surface hair-like projections found on some prokaryotic cells used for attachment or interactions.

Prokaryotic flagellum

An optional cellular appendage found on some prokaryotic cells used for propulsion and locomotion.

Membrane-bound eukaryotic structures

Structures enclosed by membranes: nucleus/nuclear envelope, ER, Golgi, vesicles, lysosomes, vacuoles, mitochondria, and chloroplasts.

Non-membrane-bound eukaryotic structures

Cell structures lacking membranes: ribosomes, nucleolus, cytoskeletal elements, and centrosomes/centrioles.

Surface area to volume ratio (SA:V)

The mathematical quotient calculated as surface area divided by volume ($\text{SA:V} = \text{surface area} \div \text{volume}$).

High SA:V ratio advantage

Cells are more efficient with a higher SA:V because more membrane surface area is available per unit volume for exchange of materials.

Mitochondrial cristae and SA:V

Folds of the inner mitochondrial membrane that maximize surface area for reactions and protein complexes, increasing ATP production capacity.

Thylakoid membranes and SA:V

Numerous internal chloroplast membranes that maximize surface area for photosynthetic complexes, boosting energy conversion.

Cellular compartmentalization

The creation of separate internal environments by membranes to concentrate needed molecules and prevent incompatible reactions from interfering.

Thylakoid membrane proteins

Membrane-bound photosynthetic components including chlorophyll, photosystems, electron carriers, and ATP synthase.

Origin of the endomembrane system

Evolved likely from inward foldings (infoldings) of the ancestral cell membrane.

Endosymbiosis

The evolutionary process where an ancestral cell engulfed bacteria that survived internally, establishing a mutually beneficial relationship.

Mitochondrial endosymbiotic origin

Descended from engulfed aerobic bacteria that formed a mutualistic partnership within an ancestral host cell.

Chloroplast endosymbiotic origin

Descended from engulfed photosynthetic bacteria that were later integrated into specific eukaryotic lineages.

Circular DNA evidence for endosymbiosis

Mitochondria and chloroplasts contain their own circular DNA molecules similar to bacterial genomes.

Bacterial-like ribosome evidence

Mitochondria and chloroplasts possess their own ribosomes that structurally resemble bacterial ribosomes rather than eukaryotic cytosolic ribosomes.

Binary fission in organelles

Mitochondria and chloroplasts replicate independently inside host cells via binary fission, the method used by bacteria.

Double membrane evidence for endosymbiosis

Mitochondria and chloroplasts are enclosed by two membranes, consistent with engulfment by an ancestral host.

Size evidence for endosymbiosis

Mitochondria and chloroplasts are approximately the same size as typical bacterial cells.

Structures for genetic information storage and transmission

The nucleus stores DNA, and ribosomes use instructions carried by mRNA to build proteins.

Nuclear envelope

A double membrane surrounding the nucleus, separated by a space and perforated by nuclear pore complexes.

Nuclear pore complexes

Channel structures that regulate the traffic of RNA, proteins, and macromolecules between the nucleus and cytoplasm.

Nuclear confinement of DNA

Normally, DNA does not exit through nuclear pores and stays in the nucleus; mRNA carries instructions to the cytoplasm.

Nucleolus

A dense nuclear subcompartment where ribosomal RNA (rRNA) is synthesized and ribosomal subunits are assembled.

Chromatin

DNA wrapped around proteins forming an uncoiled, dispersed complex inside the nucleus.

Chromosome

One organized DNA molecule with associated proteins that condenses into a visible structure during cell division.

Chromatin condensation

The coiling and packing of loose chromatin into visible chromosomes during the onset of cell division.

Macromolecular composition of ribosomes

Ribosomes are composed of ribosomal RNA (rRNA) and proteins.

Ribosome function

Translates mRNA transcripts to assemble amino acids into a polypeptide chain during protein synthesis.

Nuclear-ribosomal collaboration

DNA is transcribed into mRNA inside the nucleus; mRNA exits through a pore, and ribosomes translate its sequence into protein.

Intracellular locations of ribosomes

Free in the cytosol, attached to the rough ER and outer nuclear envelope, or inside mitochondria and chloroplasts.

Free ribosomes

Ribosomes floating unattached in the cytosol that typically make proteins used in the cytosol or internal sites.

ER-bound ribosomes

Ribosomes attached to the rough ER that make proteins destined for secretion, membrane insertion, or the endomembrane system.

Endomembrane system

A connected internal membrane system that makes, modifies, sorts, transports, and recycles cellular proteins and lipids.

Components of the endomembrane system

Nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, vesicles, lysosomes, vacuoles, and the plasma membrane.

Vesicles

Small membrane-bound sacs that store or transport substances between cellular compartments.

Vesicular transport mechanism

Vesicles bud from one membrane, travel through the cell (often along cytoskeletal tracks), and fuse with a target membrane.

Rough endoplasmic reticulum structure

A network of flattened membrane sacs with ribosomes attached to the cytosolic surface.

Rough endoplasmic reticulum function

Synthesizes and begins folding and modifying proteins destined for secretion, membranes, or specific organelles.

Smooth endoplasmic reticulum structure

A branching tubular membrane network lacking attached ribosomes.

Smooth endoplasmic reticulum functions

Synthesizes lipids, detoxifies drugs and chemicals, and stores calcium ions.

Smooth ER in hepatocytes (liver cells)

Abundantly present in liver cells because they are specialized to detoxify drugs and metabolic waste chemicals.

Detoxification

The chemical breakdown and neutralization of drugs and chemicals carried out by enzymes in the smooth ER.

Calcium ion storage organelle

The smooth endoplasmic reticulum, which sequesters calcium ions for cellular signaling events.

Golgi apparatus structure

Stacks of flattened membrane-bound sacs called cisternae, featuring distinct receiving (cis) and shipping (trans) faces.

Cisternae

The individual flattened membrane sacs that make up the stacks of the Golgi apparatus.

Golgi apparatus function

Modifies, sorts, and packages proteins and lipids received from the ER into transport or secretory vesicles.

Receiving side of Golgi

The face of the Golgi apparatus (cis face) where transport vesicles from the rough ER fuse to deliver contents.

Shipping side of Golgi

The face of the Golgi apparatus (trans face) from which sorted vesicles bud off toward destinations.

Lysosome structure

A membrane-bound compartment containing digestive hydrolytic enzymes with an acidic internal lumen.

Lysosome interior pH

Acidic, providing the optimal low-pH environment for hydrolytic enzymes to degrade materials.

Lysosome function

Breaks down macromolecules, engulfed pathogens, and worn-out cell parts, recycling their components.

Hydrolytic enzymes

Digestive enzymes located within lysosomes that catalyze hydrolysis reactions to break chemical bonds.

Hydrolysis reaction

A chemical reaction that cleaves bonds between molecular subunits by adding water molecules.

Recycling cellular components

The breakdown of old or damaged organelles by lysosomes into basic molecular building blocks for reuse.

Vacuole structure

A membrane-bound storage compartment; plant cells typically have one large central vacuole.

Vacuole general functions

Stores water, ions, nutrients, pigments, and metabolic wastes inside eukaryotic cells.

Plant central vacuole function

Stores essential materials and holds water to generate internal turgor pressure against the cell wall.

Contractile vacuole

A specialized organelle in some freshwater protists that collects and expels excess incoming water.

Protein secretion pathway step 1 (Transcription)

DNA in the nucleus is transcribed into messenger RNA (mRNA).

Protein secretion pathway step 2 (Translation)

mRNA exits a nuclear pore and attaches to a ribosome on the rough ER, where the polypeptide is synthesized.

Protein secretion pathway step 3 (ER processing)

The synthesized protein enters the lumen of the rough ER to undergo initial folding and chemical modification.

Protein secretion pathway step 4 (Vesicle transport)

A transport vesicle buds from the rough ER carrying the protein and delivers it to the receiving face of the Golgi.

Protein secretion pathway step 5 (Golgi processing)

The Golgi apparatus modifies, sorts, and packages the protein into a secretory vesicle at its shipping face.

Protein secretion pathway step 6 (Exocytosis)

A secretory vesicle travels to and fuses with the plasma membrane, releasing the protein outside via exocytosis.

Plasma-membrane glycolipid synthesis

Lipid is made in the smooth ER; sugars are attached in ER/Golgi; vesicles transport it to the plasma membrane.

Lysosomal enzyme trafficking pathway

Enzymes synthesized on rough ER ribosomes are transported to the Golgi, sorted, tagged, and delivered to lysosomes in vesicles.

Consequence of blocked Golgi vesicle budding

Protein and lipid sorting halts; secretion declines, lysosomal enzymes fail to arrive, and membrane renewal stops, causing dysfunction.

Primary cell energy structures

Mitochondria and chloroplasts.

Mitochondrion outer membrane

The smooth phospholipid bilayer forming the exterior boundary of the mitochondrion.

Mitochondrion inner membrane

The highly folded internal membrane of the mitochondrion containing cristae, electron transport complexes, and ATP synthase.

Mitochondrial cristae

Inward folds of the inner mitochondrial membrane that expand the surface area available for cellular respiration.

Mitochondrial intermembrane space

The narrow region situated between the outer and inner membranes of the mitochondrion.

Mitochondrial matrix

The fluid-filled space enclosed by the inner membrane holding pyruvate oxidation and citric acid cycle enzymes, DNA, and ribosomes.

Pyruvate oxidation location

Occurs within the mitochondrial matrix catalyzed by resident enzymes.

Citric acid cycle location

Occurs in the mitochondrial matrix driven by soluble matrix enzymes.

Chloroplast outer envelope membrane

The outermost lipid bilayer enclosing the chloroplast structure.

Chloroplast inner envelope membrane

The inner lipid membrane situated directly beneath the outer envelope of the chloroplast.

Stroma

The fluid surrounding thylakoids containing enzymes for the Calvin cycle, chloroplast circular DNA, and ribosomes.

Thylakoid

A flattened, internal membrane sac inside chloroplasts where light-dependent photosynthetic reactions occur.

Grana

Stacks of individual thylakoid discs inside a chloroplast.

Role of thylakoids in glucose production

Provide surface area for light-dependent reactions to generate ATP and NADPH, which power the Calvin cycle in the stroma.

Calvin cycle location

Occurs in the stroma of the chloroplast, utilizing ATP and NADPH to synthesize sugars.

Cellular structural integrity components

Maintained by the cytoskeleton, supported by the plasma membrane and (in some cells) the cell wall or extracellular matrix.

Cytoskeleton

A network of protein fibers in the cytoplasm supporting cell shape, internal organization, and movement.

Three main cytoskeletal structures

Microfilaments (actin filaments), intermediate filaments, and microtubules.