Study guides › B/B › Biology
Cell Structure & Organelles
Cells are the unit of life, and every organelle has a job the MCAT expects you to match to its structure. You will compare prokaryotes and eukaryotes, follow proteins through the endomembrane system, and link cytoskeleton, matrix, and junctions to tissue function.
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What this chapter covers
- Prokaryotes vs Eukaryotes. The MCAT loves the differences: ribosome size, cell walls, DNA organization, and why small cells work so well.
- Nucleus & the Endomembrane System. Follow a protein from ribosome to destination: this pathway shows up in passages about secretion, lysosomal disease, and drug trafficking.
- Mitochondria, Lysosomes & Peroxisomes. These organelles have specialized chemistry: expect questions on endosymbiosis, where ATP is made, and how the cell disposes of waste.
- The Cytoskeleton. Three filament types, three jobs. Know their subunits, polarity, and motors, plus the drugs that target them.
- Extracellular Matrix & Cell Junctions. Tissues are held together by matrix proteins and four junction types. Match each junction to its proteins and job.
Key points to know
- Prokaryotes: nucleoid, circular DNA, 70S ribosomes, binary fission
- Eukaryotes: nucleus, linear chromosomes with histones, 80S ribosomes
- Nucleolus assembles ribosomal subunits
- Rough ER: secretory, membrane, and lysosomal proteins; smooth ER: lipids, detox, Ca²⁺
- Mitochondria: double membrane, own circular DNA, ETC on inner membrane
- Endosymbiosis evidence: double membrane, circular DNA, 70S-like ribosomes, fission
- Actin (~7 nm): cortex, microvilli, cytokinesis, muscle
- Intermediate filaments (~10 nm): mechanical strength, no polarity, no motor
Try a practice question
Which structure is present in a typical bacterial cell but absent from human cells?
- Ribosomes
- A peptidoglycan cell wall
- A plasma membrane
- Cytoplasm
Show the answer
B. Every cell has ribosomes, a plasma membrane, and cytoplasm. Peptidoglycan is specific to bacterial walls, which is why penicillin-type drugs target bacteria and spare human cells.
Common questions
What does this chapter cover?
Cell Structure & Organelles covers Prokaryotes vs Eukaryotes, Nucleus & the Endomembrane System, Mitochondria, Lysosomes & Peroxisomes, The Cytoskeleton, Extracellular Matrix & Cell Junctions.
What should I know first?
Prokaryotes: nucleoid, circular DNA, 70S ribosomes, binary fission Eukaryotes: nucleus, linear chromosomes with histones, 80S ribosomes Nucleolus assembles ribosomal subunits
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.