cell biology exam #2
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114 Terms
What is the endomembrane system?
A group of organelles that modify, sort, package, and transport cellular materials.
What is the pathway of a secreted protein?
Ribosome → rough ER → transport vesicle → cis-Golgi → medial Golgi → trans-Golgi → secretory vesicle → plasma membrane.
What is the main function of rough ER?
Synthesis, folding, and modification of secreted and membrane proteins.
What is the main function of smooth ER?
Lipid synthesis, detoxification, and calcium storage.
What does SRP do?
It recognizes an ER signal sequence and directs the ribosome to the ER membrane.
What do ER chaperones do?
They help newly synthesized proteins fold correctly.
What is ER-associated degradation?
The removal and destruction of misfolded ER proteins.
What is the unfolded protein response?
A response that reduces ER stress caused by accumulated misfolded proteins.
What does PERK do?
It temporarily reduces protein translation.
What does IRE1 do?
It activates stress-response pathways that increase protein folding and degradation.
What does ATF6 do?
It activates gene expression for ER stress management.
What can chronic ER stress cause?
Apoptosis, partly through CHOP activation.
What does COPII transport?
Proteins from the ER to the Golgi.
What does COPI transport?
Proteins from the Golgi back to the ER and between Golgi compartments.
What does clathrin transport?
Cargo from the plasma membrane to endosomes and from the trans-Golgi to lysosomes.
What do Rab GTPases do?
They help vesicles recognize and reach the correct target membrane.
What do SNARE proteins do?
They help vesicles fuse with the correct target membrane.
What happens if vesicle fusion fails?
Vesicles accumulate near the target membrane and cargo is not delivered.
What are the three regions of the Golgi?
Cis, medial, and trans.
What does the cis-Golgi do?
It receives vesicles from the ER.
What does the trans-Golgi do?
It sorts cargo toward its final destination.
What is N-linked glycosylation?
Carbohydrate addition that begins in the ER and is refined in the Golgi.
What is O-linked glycosylation?
Carbohydrate addition that occurs mainly in the Golgi.
What does the KDEL signal do?
It returns escaped ER proteins from the Golgi to the ER.
What is the function of a lysosome?
To digest macromolecules and damaged organelles.
What is autophagy?
The delivery of cytoplasmic material or damaged organelles to lysosomes for degradation.
What is an early endosome?
A sorting compartment associated with Rab5.
What is a late endosome?
A more acidic sorting compartment associated with Rab7.
What does simple diffusion require?
No transport protein and no cellular energy; molecules move down their gradient.
What is facilitated diffusion?
Movement down an electrochemical gradient through a channel or carrier.
What is primary active transport?
Movement against a gradient using ATP directly.
What is secondary active transport?
Movement powered by the energy stored in an ion gradient.
What is a symporter?
A transporter that moves two substances in the same direction.
What is an antiporter?
A transporter that moves substances in opposite directions.
What does the Na⁺/K⁺ pump do?
It uses ATP to move Na⁺ out of the cell and K⁺ into the cell.
Why do carriers become saturated?
They have a limited number of binding sites that can all become occupied.
What causes a membrane potential?
Unequal ion distributions and selective membrane permeability.
What causes depolarization?
Opening of sodium channels and sodium entry.
What causes repolarization?
Opening of potassium channels and potassium exit.
Why is myelin important?
It insulates axons and increases action-potential conduction speed.
What is the endosymbiotic theory?
The theory that mitochondria and chloroplasts evolved from bacteria living inside ancestral eukaryotic cells.
What evidence supports endosymbiosis?
Circular DNA, bacterial-like ribosomes, double membranes, binary fission, and bacterial ancestry.
Why do mitochondria and chloroplasts have double membranes?
The inner membrane came from the original bacterium and the outer membrane came from the host cell.
Where are most mitochondrial and chloroplast proteins produced?
In the cytosol from genes located in the nucleus.
What are targeting peptides?
Sequences that direct proteins to the correct organelle.
What are TOM and TIM?
Protein-import complexes used by mitochondria.
What are TOC and TIC?
Protein-import complexes used by chloroplasts.
What is the function of mitochondrial cristae?
They increase inner-membrane surface area for ATP production.
Where is the mitochondrial ETC located?
In the inner mitochondrial membrane.
Where does the citric acid cycle occur?
In the mitochondrial matrix.
What do NADH and FADH₂ carry?
High-energy electrons to the electron transport chain.
What is the electron transport chain?
A series of protein complexes that transfer electrons and pump protons.
What is the final electron acceptor in respiration?
Oxygen.
What does oxygen become after accepting electrons?
Water.
What is chemiosmosis?
ATP production using energy stored in a proton gradient.
What does ATP synthase do?
It uses proton flow to produce ATP from ADP and phosphate.
What happens if oxygen is absent?
The mitochondrial ETC stops because electrons cannot be passed to a final acceptor.
What are the light reactions?
Reactions that use light to produce ATP and NADPH and release oxygen.
What happens in Photosystem II?
Water is split, releasing electrons, protons, and oxygen.
What happens in Photosystem I?
Light re-energizes electrons for NADPH production.
Where do the light reactions occur?
In the thylakoid membrane.
Where does the Calvin cycle occur?
In the chloroplast stroma.
What does the Calvin cycle use?
ATP, NADPH, and CO₂.
What are the three stages of the Calvin cycle?
Carboxylation, reduction, and regeneration.
What is RuBisCO?
The enzyme that catalyzes carbon fixation.
What is glycolysis?
The breakdown of glucose into two pyruvate molecules in the cytosol.
Does glycolysis require oxygen?
No.
What happens to pyruvate during aerobic metabolism?
It is converted into acetyl-CoA.
What is acetyl-CoA?
A central metabolic intermediate connecting carbohydrate, fat, and amino-acid metabolism.
What is the main purpose of the citric acid cycle?
To produce NADH and FADH₂ for the electron transport chain.
What is fermentation's purpose?
To regenerate NAD⁺ so glycolysis can continue without oxygen.
Why do fats yield large amounts of energy?
Fatty acids are highly reduced and produce many electron carriers.
What is mitophagy?
The selective removal of damaged mitochondria by autophagy.
What is retrograde signaling?
Communication from mitochondria or chloroplasts to the nucleus.
What are the three cytoskeletal systems?
Microtubules, actin filaments, and intermediate filaments.
What is the main function of microtubules?
Intracellular transport, chromosome movement, and cilia or flagella movement.
What is the main function of actin?
Cell movement, shape changes, adhesion, and contraction.
What is the main function of intermediate filaments?
Mechanical strength and resistance to stress.
What are microtubules made of?
α- and β-tubulin heterodimers.
What is dynamic instability?
The rapid growth and shrinkage of microtubules.
Why is dynamic instability useful?
It allows cells to reorganize quickly during mitosis, migration, and signaling.
What is the centrosome?
The main microtubule-organizing center in animal cells.
What does kinesin do?
It generally moves cargo toward microtubule plus ends.
What does dynein do?
It generally moves cargo toward microtubule minus ends.
What is the mitotic spindle?
A microtubule structure that separates chromosomes.
What is the contractile ring?
An actin-myosin structure that divides the cell during cytokinesis.
What is the 9+2 arrangement?
Nine outer microtubule doublets surrounding two central microtubules in cilia and flagella.
What does myosin do?
It uses ATP to generate force along actin filaments.
What are intermediate filaments?
Stable, rope-like fibers that resist mechanical stress.
What is the nuclear lamina?
A lamin-based network that supports the nucleus and anchors chromatin.
What is the first major signal after membrane damage?
Extracellular Ca²⁺ enters the cell.
Why is calcium important in membrane repair?
It activates repair signaling and recruits membrane-remodeling proteins.
What does ESCRT do?
It helps remove damaged membrane regions and reseal the membrane.
What does CHMP4B recruitment demonstrate?
That CHMP4B is associated with damaged membrane regions.
How can researchers show CHMP4B is required for repair?
Disrupt CHMP4B and test whether membrane resealing decreases.
What is a calcium wave?
A calcium signal that spreads from injured cells to neighboring cells.
What do gap junctions do?
They help transmit calcium signals between neighboring cells.
What does DUOX produce?
Hydrogen peroxide.
How does H₂O₂ help repair?
It acts as an early signal that recruits inflammatory cells.
What is actomyosin contractility?
Force generated by actin and myosin interactions.