STEM Readiness: Pre-Calculus Readiness - Vectors/Parametric: Vectors Component Form - Magnitude, Direction, Unit Vectors

Must?Know (20–25 detailed bullets)

• Prokaryotic cells range from 0.1–5.0 ?m in diameter; eukaryotic cells range from 10–100 ?m.
• Prokaryotes include bacteria and archaea; eukaryotes include animals, plants, fungi, and protists.
• DNA in prokaryotes is located in the nucleoid, a region without a membrane; eukaryotes house DNA within a membrane-bound nucleus.
• Prokaryotes lack membrane-bound organelles; eukaryotes have endoplasmic reticulum, Golgi apparatus, mitochondria, and lysosomes.
• Ribosomes in prokaryotes are 70S (50S + 30S subunits); eukaryotic cytoplasmic ribosomes are 80S (60S + 40S subunits).
• Mitochondria and chloroplasts in eukaryotes contain 70S ribosomes, similar to prokaryotes, supporting the endosymbiotic theory.
• Prokaryotic cell walls typically contain peptidoglycan (e.g., Escherichia coli); archaea lack peptidoglycan and have pseudopeptidoglycan or other polymers.
• Plant cell walls are composed of cellulose; fungal cell walls contain chitin; animal cells lack cell walls.
• Mycoplasma, a bacterium, lacks a cell wall and is resistant to antibiotics like penicillin that target peptidoglycan synthesis.
• Red blood cells in mammals lack a nucleus at maturity, limiting their lifespan and preventing cell division.
• Both prokaryotes and eukaryotes have a phospholipid bilayer plasma membrane that regulates transport and maintains electrochemical gradients.
• Eukaryotes have extensive internal membranes forming organelles; prokaryotes do not, though some have infoldings like mesosomes.
• Plasmids are small, circular DNA molecules found in many prokaryotes and can carry antibiotic resistance genes; rare in eukaryotes.
• Binary fission is the primary mode of reproduction in prokaryotes; eukaryotes divide by mitosis and cytokinesis.
• Eukaryotic nuclei are surrounded by a double membrane called the nuclear envelope, which contains nuclear pores for RNA export.
• Nucleolus within the nucleus is the site of ribosomal RNA synthesis and ribosome subunit assembly.
• Endosymbiotic theory is supported by mitochondria and chloroplasts having circular DNA, 70S ribosomes, and double membranes.
• Chloroplasts are found in plants and algae, perform photosynthesis, and are absent in animal and fungal cells.
• Lysosomes are membrane-bound organelles in animal cells containing hydrolytic enzymes for degradation; rare in plant cells (vacuoles perform similar function).
• Peroxisomes contain enzymes for fatty acid oxidation and detoxify hydrogen peroxide; present in both plant and animal eukaryotic cells.
• Cytoskeleton elements (microtubules, microfilaments, intermediate filaments) are present in eukaryotes; prokaryotes have homologs (e.g., FtsZ, MreB) but no true cytoskeleton.
• Flagella in prokaryotes are made of flagellin and rotate; eukaryotic flagella are composed of microtubules (9+2 arrangement) and bend.
• Gram-positive bacteria have thick peptidoglycan and no outer membrane; Gram-negative bacteria have thin peptidoglycan and an outer membrane with lipopolysaccharide.
• Archaea lack peptidoglycan, have ether-linked lipids in membranes, and often live in extreme environments (e.g., Methanogens in anaerobic conditions).
• Plant cells have a large central vacuole for turgor pressure and storage; animal cells have small or transient vacuoles.

Difficulty Level

Intermediate – requires distinguishing structural and functional differences across domains and organelle roles, commonly tested in first-semester biology.

Common Traps (3–5 factual traps)

Trap: All cells with cell walls have peptidoglycan – Fact: Only bacteria have peptidoglycan; plants (cellulose), fungi (chitin), and archaea (no peptidoglycan) differ.

Trap: Ribosome size correlates with organism complexity – Fact: Mitochondria and chloroplasts have 70S ribosomes despite being in eukaryotic cells.

Trap: The nucleus is the only organelle with a double membrane – Fact: Mitochondria and chloroplasts also have double membranes.

Trap: Prokaryotes have no internal structure – Fact: Prokaryotes have nucleoids, ribosomes, and some have protein-based cytoskeletal homologs.

Practice MCQs (5–7 questions)

Question: Which of the following is a defining feature of eukaryotic cells but absent in prokaryotes?
A) Plasma membrane
B) Ribosomes
C) Circular DNA
D) Membrane-bound nucleus
Answer: D
Explanation: The membrane-bound nucleus is exclusive to eukaryotes.
Why the top distractor is wrong: Circular DNA is present in prokaryotes and also in mitochondria and chloroplasts of eukaryotes.

Question: A cell is observed to have a cell wall, chloroplasts, and a large central vacuole. It is most likely:
A) Fungal cell
B) Animal cell
C) Bacterial cell
D) Plant cell
Answer: D
Explanation: Plant cells uniquely have all three structures listed.
Why the top distractor is wrong: Fungal cells have cell walls but lack chloroplasts and large central vacuoles.

Question: Which structure is found in both prokaryotes and eukaryotes?
A) Mitochondria
B) 80S ribosomes
C) Phospholipid bilayer membrane
D) Golgi apparatus
Answer: C
Explanation: The phospholipid bilayer is universal in cellular life.
Why the top distractor is wrong: Mitochondria are only in eukaryotes.

Question: Which of the following provides evidence for the endosymbiotic theory?
A) Eukaryotes have linear DNA
B) Mitochondria have 70S ribosomes and circular DNA
C) Prokaryotes divide by binary fission
D) Lysosomes contain digestive enzymes
Answer: B
Explanation: Mitochondrial 70S ribosomes and circular DNA resemble prokaryotic features.
Why the top distractor is wrong: Linear DNA is not evidence of endosymbiosis; it is a eukaryotic trait.

Question: Which organism lacks a cell wall and is therefore not affected by penicillin?
A) Escherichia coli
B) Saccharomyces cerevisiae
C) Mycoplasma pneumoniae
D) Bacillus subtilis
Answer: C
Explanation: Mycoplasma lacks a cell wall and is naturally resistant to cell wall-targeting antibiotics.
Why the top distractor is wrong: E. coli has a Gram-negative cell wall and is inhibited by penicillin in some cases.

Question: Where is ribosomal RNA synthesized in a eukaryotic cell?
A) Cytoplasm
B) Rough endoplasmic reticulum
C) Nucleolus
D) Mitochondria
Answer: C
Explanation: The nucleolus is the site of rRNA transcription and ribosome subunit assembly.
Why the top distractor is wrong: Rough ER is involved in protein synthesis, not rRNA production.

Question: Which of the following is true about prokaryotic flagella?
A) Composed of microtubules in a 9+2 arrangement
B) Powered by ATP hydrolysis in the cytoplasm
C) Rotate like a propeller using a basal motor
D) Grow by adding subunits at the tip
Answer: C
Explanation: Prokaryotic flagella rotate via a proton-driven motor embedded in the membrane.
Why the top distractor is wrong: 9+2 microtubule arrangement is found in eukaryotic flagella.

Last?Minute Revision (20–25 one?liners)

• Prokaryotic cell size: 0.1–5.0 ?m; eukaryotic: 10–100 ?m.
• Prokaryotes have nucleoid; eukaryotes have nucleus with nuclear envelope.
• Prokaryotic ribosome = 70S; eukaryotic cytoplasmic ribosome = 80S.
• Mitochondria and chloroplasts have 70S ribosomes and circular DNA – evidence of endosymbiosis.
• Bacterial cell walls contain peptidoglycan; archaea do not.
• Plant cell wall = cellulose; fungal = chitin; animal cells = no cell wall.
• Mycoplasma has no cell wall – naturally penicillin-resistant.
• Mature mammalian red blood cells lack a nucleus – cannot divide or repair DNA.
• Both domains have phospholipid bilayer plasma membranes.
• Eukaryotes have membrane-bound organelles; prokaryotes do not.
• Endoplasmic reticulum and Golgi apparatus are exclusive to eukaryotes.
• Lysosomes are common in animal cells; plants use vacuoles for degradation.
• Nucleolus = site of rRNA synthesis and ribosome assembly.
• Binary fission = prokaryotic division; mitosis = eukaryotic nuclear division.
• Plasmids = small circular DNA in bacteria; can carry antibiotic resistance.
• Archaea have ether-linked membrane lipids, not ester-linked like bacteria and eukaryotes.
• Eukaryotic flagella: 9+2 microtubule arrangement, bend via dynein.
• Prokaryotic flagella: made of flagellin, rotate using proton motive force.
• Gram-positive bacteria: thick peptidoglycan, no outer membrane.
• Gram-negative bacteria: thin peptidoglycan, outer membrane with LPS.
• Mitochondria have double membrane, produce ATP via oxidative phosphorylation.
• Chloroplasts perform photosynthesis, contain chlorophyll, found in plants and algae.
• Peroxisomes break down fatty acids and detoxify H?O?.
• Cytoskeleton (microtubules, actin) is eukaryotic; prokaryotes have FtsZ, MreB homologs.
• Verify from standard textbook: exact lipid composition in archaeal membranes varies by species.