Origins of Cell Compartmentalization - AP Biology

What is a characteristic of ribosomes in eukaryotic cells?

They can be free or bound to the ER. Location determines protein destination.
Which compartment is involved in digestion of macromolecules?

Lysosomes. Contain digestive enzymes in acidic environment.
What is the endomembrane system hypothesized to have originated from?

Plasma membrane invaginations and vesicle formation. Internal membrane system evolved from cell membrane extensions.
Which option identifies an organelle NOT derived from the endomembrane system?

Mitochondrion. Originated through endosymbiosis, not membrane infolding.
What evidence supports the endosymbiotic theory?

Mitochondria have their own DNA. Independent genetic material suggests bacterial origin.
What key structural feature of mitochondria supports endosymbiotic theory?

A double membrane. Outer membrane from host cell, inner from engulfed bacterium.
Which organelles are part of the endomembrane system?

Nuclear envelope, ER, Golgi, lysosomes, vesicles, plasma membrane. Connected membrane system excluding mitochondria and chloroplasts.
Name an organelle thought to have originated via endosymbiosis.

Mitochondria. Originally a free-living bacterium that was engulfed.
Which option best explains why mitochondria have a double membrane?

Engulfment produced an inner bacterial membrane plus an outer host-derived membrane. Engulfment preserves both bacterial and host membranes.
What is the purpose of the nuclear pore complex?

Regulates transport between the nucleus and cytoplasm. Selective gateway for nuclear-cytoplasmic exchange.
What is the serial endosymbiosis model of eukaryotic evolution?

Multiple endosymbiotic events produced mitochondria first, then plastids in some lineages. Mitochondria first, then chloroplasts in photosynthetic lineages.
Identify a function of the cell wall.

Provides structural support and protection. Rigid structure maintains plant cell shape.
Identify the evidence: an organelle divides by binary fission; what origin does this support?

Endosymbiotic origin. Binary fission is how prokaryotes reproduce.
Which structure is involved in the endomembrane system?

Endoplasmic reticulum. Network of interconnected membranes for transport.
What is the selective advantage of internal membranes for early cells?

Increased surface area for metabolic reactions and transport. More membrane area allows greater biochemical activity.
Which cellular structure is primarily responsible for compartmentalization?

Membranes. Create physical barriers that separate cellular compartments.
Which cellular structure is responsible for detoxification?

Smooth endoplasmic reticulum. Lacks ribosomes and processes lipids and toxins.
Choose the word that completes the claim: mitochondria are most closely related to ______.

$b^1$ -proteobacteria. Phylogenetic analysis shows closest relationship to this group.
What is the role of signal transduction in cells?

Transmission of signals from the cell surface to its interior. Coordinates cellular responses to environmental changes.
What is the selective advantage of separating transcription and translation?

Allows RNA processing and regulation before translation. Nuclear compartment enables complex gene regulation.
What is the nucleus thought to have originated from, according to the infolding model?

Infolding of the plasma membrane around DNA. Nuclear envelope continuous with endoplasmic reticulum.
Identify the evidence: an organelle has its own circular genome; what origin does this support?

Endosymbiotic origin from bacteria. Circular genomes are characteristic of prokaryotes.
What is a defining feature of eukaryotic cells?

Presence of membrane-bound organelles. Unlike prokaryotes, organelles are membrane-enclosed.
What is the significance of membrane fluidity?

Allows cell movement and growth. Maintains membrane integrity during cellular processes.
What is the role of the nuclear envelope?

It separates the nucleus from the cytoplasm. Controls molecular traffic between nuclear and cytoplasmic compartments.
Identify a structural feature of chloroplasts.

Thylakoid membranes. Flattened sacs that contain chlorophyll.
What is the function of the Golgi apparatus?

Modifying, sorting, and packaging proteins. Acts as the cell's shipping and receiving center.
What is the primary benefit of cell compartmentalization?

Increased efficiency of cellular processes. Each compartment can optimize conditions for specific reactions.
Identify a process that vesicles are involved in.

Endocytosis. Vesicles transport materials into the cell.
What is cell compartmentalization?

The separation of cellular processes into distinct areas within the cell. Allows specialized functions to occur in dedicated spaces.
Which organelle is involved in ATP production?

Mitochondria. Double membrane structure houses cellular respiration.
What is the significance of thylakoid membranes?

Site of the light reactions in photosynthesis. Chlorophyll captures light for photosystem reactions.
What is the main energetic benefit of acquiring mitochondria by endosymbiosis?

Greatly increased ATP production via aerobic respiration. Aerobic respiration produces much more ATP than fermentation.
What function do intermediate filaments serve?

Provide mechanical support to cells. Rope-like structures resist tension forces.
Which option best distinguishes endomembrane origin from endosymbiotic origin?

Endomembranes: invagination; mitochondria/chloroplasts: engulfed cells. Different mechanisms produced different organelle types.
Identify a function of the endoplasmic reticulum.

Protein and lipid synthesis. Rough ER makes proteins, smooth ER synthesizes lipids.
What are ribosomes responsible for?

Protein synthesis. Translate mRNA into polypeptide chains.
Choose the word that completes the claim: chloroplasts are most closely related to ______.

Cyanobacteria. Phylogenetic analysis shows closest relationship to this group.
Which option best describes why many mitochondrial proteins are made in the cytosol?

Most mitochondrial genes were transferred to the nuclear genome. Nuclear-encoded proteins are imported into mitochondria.
What is the predicted membrane count around plastids from secondary endosymbiosis?

More than $2$ membranes (often $3$ or $4$ ). Additional membranes from the engulfed eukaryotic host cell.
What is the primary component of cell membranes?

Phospholipids. Amphipathic molecules form bilayer structure.
Which organelle is believed to be a descendant of prokaryotic cells?

Chloroplasts. Evolved from cyanobacteria through endosymbiosis.
What is the most widely accepted prokaryotic ancestor of chloroplasts?

A photosynthetic cyanobacterium. Explains chloroplasts' photosynthetic abilities.
What role do membranes play in compartmentalization?

They create distinct environments within cells. Selective permeability maintains different internal conditions.
Which option best explains why chloroplasts have a double membrane?

Engulfment produced an inner cyanobacterial membrane plus an outer host-derived membrane. Engulfment preserves both cyanobacterial and host membranes.
Which process is facilitated by compartmentalization in mitochondria?

Cellular respiration. Inner membrane provides space for electron transport chain.
What key structural feature of chloroplasts supports endosymbiotic theory?

A double membrane. Outer membrane from host cell, inner from engulfed cyanobacterium.
Which ribosome type in mitochondria and chloroplasts supports endosymbiosis?

$70S$ -like ribosomes (bacterial-type). Unlike eukaryotic $80S$ ribosomes, matches bacterial ribosomes.
Which two organelles are best explained by endosymbiotic origin?

Mitochondria and chloroplasts. Both have double membranes and bacterial-like DNA and ribosomes.
What is gene transfer to the nucleus in the context of endosymbiosis?

Movement of endosymbiont genes into the host nuclear genome. Explains why organelles have reduced genomes over time.
What is the primary function of the cytoskeleton?

Maintaining cell shape and facilitating movement. Protein framework determines cell structure.
Identify the process that led to the origin of eukaryotic cells.

Endosymbiosis. One organism engulfing another led to organelle evolution.
What is cell compartmentalization in the context of eukaryotic cell evolution?

Division of cellular functions into membrane-bound organelles. Separates distinct cellular processes for increased efficiency.
Identify the correct statement about the nuclear envelope and its proposed origin.

It likely formed from plasma membrane infolding around genetic material. Nuclear envelope evolved from endomembrane system infolding.
Identify the role of microtubules in cells.

They provide structural support and facilitate transport. Hollow tubes that organize cellular transport.
Identify the correct statement about the age of mitochondria relative to plastids in eukaryotes.

Mitochondria evolved earlier; plastids evolved later in some lineages. All eukaryotes have mitochondria; only some have plastids.
Which option best explains why compartmentalization can increase metabolic efficiency?

It concentrates enzymes and substrates in specific microenvironments. Local concentration gradients optimize reaction rates.
Identify a factor that affects membrane fluidity.

Cholesterol content. Higher cholesterol reduces fluidity.
Identify the prediction: if plastids arose by secondary endosymbiosis, what membrane trait is expected?

Plastids surrounded by more than $2$ membranes. Multiple engulfment events add extra membrane layers.
What is the endosymbiotic theory proposed to explain about eukaryotic cells?

Some organelles originated as free-living prokaryotes engulfed by a host. Explains double membranes and bacterial-like features of organelles.
Describe the fluid mosaic model.

A model of the cell membrane with proteins floating in a lipid bilayer. Describes membrane structure and protein mobility.
What mode of division in mitochondria and chloroplasts supports endosymbiotic origin?

Binary fission. Reproduces like bacteria, not through mitosis.
What is the main ecological benefit of acquiring chloroplasts by endosymbiosis?

Ability to perform photosynthesis and produce organic carbon. Photosynthesis provides energy independence and primary production.
What is a centrosome?

A structure that organizes microtubules in cells. Microtubule organizing center near nucleus.
What is the selective advantage of compartmentalization for enzyme pathways?

Localization increases efficiency and reduces interfering side reactions. Spatial separation optimizes metabolic pathway efficiency.
Identify the evidence: an organelle contains $70S$ -like ribosomes; what origin does this support?

Endosymbiotic origin from prokaryotes. $70S$ ribosomes are found in prokaryotes, not eukaryotes.
Name a function of membrane proteins.

Transport of molecules across the membrane. Enable selective transport and communication.
What is a vesicle?

A small membrane-bound sac used for transport. Moves materials between cellular compartments.
Describe one feature of mitochondrial DNA.

Circular DNA similar to bacteria. Lacks histones and resembles prokaryotic genomes.
What is endosymbiosis?

A symbiotic relationship where one organism lives inside another. The host benefits while the endosymbiont gains protection.
What is primary endosymbiosis?

Engulfment of a cyanobacterium by a eukaryotic host to form a plastid. First acquisition creates organelles with two membranes.
What observation about organelle gene expression supports endosymbiotic theory?

Some proteins are encoded by organelle genomes and transcribed/translated inside. Maintains some independence like free-living bacteria.
Identify the correct statement about lysosomes and their evolutionary origin.

They arose from the endomembrane system, not endosymbiosis. Lysosomes are endomembrane derivatives, not endosymbionts.
What is the primary role of chloroplasts?

Photosynthesis. Converts light energy into chemical energy.
What type of DNA do mitochondria and chloroplasts contain that supports endosymbiosis?

Circular DNA similar to bacterial chromosomes. Resembles prokaryotic genomes rather than eukaryotic nuclear DNA.
What is the most widely accepted prokaryotic ancestor of mitochondria?

An aerobic $b^1$ -proteobacterium. Explains mitochondria's aerobic respiration capabilities.
What is secondary endosymbiosis?

Engulfment of a photosynthetic eukaryote, yielding plastids with extra membranes. Engulfing a eukaryote adds additional membrane layers.
What is the role of actin filaments?

Support cell shape and enable movement. Thin filaments involved in muscle contraction.
What is the purpose of peroxisomes?

Break down fatty acids and detoxify harmful substances. Use catalase enzyme to neutralize hydrogen peroxide.

Study these flashcards