Course review
Review each learning objective in this topic, then open its concept explanation or question set.
Learning objective
• Organelles are discrete cell subunits adapted for specific functions • Nuclei, chloroplasts, mitochondria, vesicles, ribosomes, and plasma membrane are organelles • Cell wall, cytoskeleton, and cytoplasm are not usually considered organelles
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Learning objective
• The nuclear envelope protects DNA and separates transcription from translation • Introns can be removed from pre-mRNA by RNA splicing before translation • Nuclear pores regulate mRNA export and protein import using selective transport
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Learning objective
• Compartmentalization concentrates enzymes, substrates, and suitable pH for specific reactions • It separates incompatible biochemical processes so they can be controlled • Lysosomes and phagolysosomes contain acidic hydrolytic digestion away from cytoplasm
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Learning objective
• The outer membrane contains transport proteins for pyruvate entry • Folded cristae increase surface area for electron transport chains and ATP synthase • The intermembrane space stores protons; the matrix contains Krebs cycle enzymes
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Learning objective
• Thylakoid membranes in grana hold photosystems, electron transport chains, and ATP synthase • Small thylakoid spaces allow rapid proton accumulation • The stroma contains enzymes and suitable pH for the Calvin cycle
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Learning objective
• The nuclear envelope is a double membrane continuous with the ER • Numerous nuclear pores allow rapid regulated exchange between nucleus and cytoplasm • The nuclear lamina supports the nucleus, and the envelope breaks into vesicles during division
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Learning objective
• Free ribosomes synthesize proteins retained and used in the cytoplasm • Polysomes allow many ribosomes to translate the same mRNA at once • RER-bound ribosomes synthesize proteins for secretion, membranes, or lysosomes
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Learning objective
• The Golgi is a stack of flattened cisternae receiving vesicles from the RER • Different cisternae modify proteins by glycosylation, sulfation, or phosphorylation • Vesicles from the Golgi deliver proteins to lysosomes, membranes, or secretion pathways
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Learning objective
• Vesicles move materials between organelles, plasma membrane, and extracellular space • Receptor-mediated endocytosis can form clathrin-coated pits and vesicles • Vesicle fusion is essential for secretion and neurotransmitter release
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