STEM Readiness: Pre-Calculus Readiness - Mathematical Reasoning: Absolute Value Equations - Inequalities Distance, Interpretation

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, an unenclosed region lacking a membrane; eukaryotes house DNA within a membrane-bound nucleus.
• Prokaryotes lack membrane-bound organelles; eukaryotes contain organelles such as mitochondria, lysosomes, and the Golgi apparatus.
• Prokaryotic ribosomes are 70S (composed of 50S and 30S subunits); eukaryotic cytoplasmic ribosomes are 80S (60S and 40S).
• Mitochondria and chloroplasts in eukaryotes contain 70S ribosomes, supporting their origin via endosymbiotic theory.
• Prokaryotic cell walls typically contain peptidoglycan (e.g., Escherichia coli); archaea lack peptidoglycan and have different cell wall chemistry.
• Plant cell walls are composed of cellulose; fungal cell walls contain chitin; animal cells lack cell walls.
• Both prokaryotes and eukaryotes have a phospholipid bilayer plasma membrane that regulates transport.
• Eukaryotes have internal membrane systems including the endoplasmic reticulum (ER) and Golgi apparatus; prokaryotes do not.
• The smooth ER synthesizes lipids and detoxifies drugs; the rough ER (with ribosomes) synthesizes proteins for secretion.
• The Golgi apparatus modifies, sorts, and packages proteins into vesicles for transport; absent in prokaryotes.
• Mitochondria generate ATP via aerobic respiration and have double membranes; they are absent in prokaryotes.
• Chloroplasts (in plants and algae) conduct photosynthesis, have double membranes and thylakoids, and are absent in prokaryotes.
• Lysosomes (in animal cells) contain hydrolytic enzymes for digestion; plant cells use vacuoles for similar functions.
• Centrioles (involved in spindle formation during mitosis) are found in animal cells but not in most plant cells.
• Mycoplasma species are bacteria without a cell wall, making them resistant to antibiotics like penicillin.
• Mature human red blood cells lack a nucleus and mitochondria, maximizing space for hemoglobin.
• Endosymbiotic theory is supported by mitochondria and chloroplasts having circular DNA, 70S ribosomes, and the ability to replicate independently.
• Nuclear pores in the nuclear envelope regulate the passage of RNA and proteins; prokaryotes lack such structures.
• Cytoskeleton elements (microtubules, actin filaments) are present in eukaryotes and aid in shape and transport; prokaryotes have simpler structural proteins.
• Flagella in prokaryotes are made of flagellin and rotate; eukaryotic flagella are composed of microtubules (9+2 arrangement) and bend.
• Plasmids are small, circular DNA molecules found in many prokaryotes; eukaryotes rarely have plasmid-like structures (e.g., in yeast).
• Binary fission is the method of asexual reproduction in prokaryotes; eukaryotes divide via mitosis and cytokinesis.
• Peptidoglycan thickness distinguishes Gram-positive (thick) and Gram-negative (thin, with outer membrane) bacteria.

Difficulty Level

Intermediate – requires distinguishing structural and functional differences across domains and recognizing exceptions.

Common Traps (3–5 factual traps)

Trap: All cells with cell walls have peptidoglycan – Fact: Only bacteria have peptidoglycan; plant (cellulose) and fungal (chitin) cell walls have different compositions.
Trap: Ribosome size is the same across all organisms – Fact: Prokaryotes have 70S ribosomes, eukaryotes have 80S (except in mitochondria and chloroplasts, which have 70S).
Trap: The nucleus is the only place DNA is found in eukaryotes – Fact: Mitochondria and chloroplasts contain their own DNA.
Trap: Prokaryotes have no internal structure – Fact: Prokaryotes have nucleoids, ribosomes, and sometimes inclusions or protein-based cytoskeletal elements.
Trap: Eukaryotic cells are always larger and more complex than prokaryotic cells – Fact: While generally true, some giant bacteria (e.g., Thiomargarita namibiensis, up to 750 ?m) exceed typical eukaryotic size.

Practice MCQs (5–7 questions)

Question: Which of the following is a feature found in eukaryotic cells but absent in prokaryotic cells?
A) Circular DNA
B) 70S ribosomes
C) Membrane-bound nucleus
D) Plasma membrane
Answer: C
Explanation: A 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: Which structure is responsible for protein modification and packaging in eukaryotic cells?
A) Nucleolus
B) Rough ER
C) Golgi apparatus
D) Lysosome
Answer: C
Explanation: The Golgi apparatus modifies, sorts, and packages proteins into vesicles.
Why the top distractor is wrong: The rough ER synthesizes proteins but does not modify or package them for secretion.

Question: A cell is observed to lack a nucleus and has 70S ribosomes. It also contains peptidoglycan in its cell wall. This cell is most likely:
A) A plant cell
B) A fungal cell
C) A bacterial cell
D) An animal cell
Answer: C
Explanation: Bacteria are prokaryotes with 70S ribosomes, peptidoglycan, and no nucleus.
Why the top distractor is wrong: Plant cells are eukaryotic, have 80S ribosomes, and cellulose walls.

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 reproduce by binary fission
D) Eukaryotes have a cytoskeleton
Answer: B
Explanation: Mitochondria resemble bacteria in ribosome type and DNA structure, supporting bacterial origin.
Why the top distractor is wrong: Linear DNA is common in eukaryotes but does not support endosymbiosis.

Question: Which of the following cells lacks mitochondria?
A) Yeast cell
B) Leaf cell
C) Mature human red blood cell
D) Liver cell
Answer: C
Explanation: Mature human red blood cells lack mitochondria and generate ATP via glycolysis.
Why the top distractor is wrong: Yeast cells are eukaryotic fungi and contain mitochondria.

Question: What is the primary component of the cell wall in fungi?
A) Peptidoglycan
B) Cellulose
C) Chitin
D) Lipopolysaccharide
Answer: C
Explanation: Fungal cell walls are composed of chitin, a nitrogen-containing polysaccharide.
Why the top distractor is wrong: Peptidoglycan is found in bacterial cell walls, not fungal.

Question: Which of the following structures is present in plant cells but not in animal cells?
A) Plasma membrane
B) Mitochondria
C) Central vacuole
D) Ribosomes
Answer: C
Explanation: A large central vacuole is a defining feature of plant cells.
Why the top distractor is wrong: Mitochondria are present in both plant and animal cells.

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

• Prokaryotic cell size: 0.1–5.0 ?m; eukaryotic: 10–100 ?m.
• Prokaryotes have no nucleus; DNA in nucleoid.
• Eukaryotes have membrane-bound nucleus with nuclear pores.
• Prokaryotic ribosome = 70S; eukaryotic cytoplasmic ribosome = 80S.
• Mitochondria and chloroplasts have 70S ribosomes and circular DNA – evidence of endosymbiosis.
• Bacteria cell wall contains peptidoglycan; archaea do not.
• Plant cell wall = cellulose; fungal = chitin; animal cells = no cell wall.
• Both cell types have phospholipid bilayer plasma membrane.
• Eukaryotes have internal membranes (ER, Golgi, nucleus); prokaryotes do not.
• Smooth ER: lipid synthesis; rough ER: protein synthesis (with ribosomes).
• Golgi apparatus: modifies, sorts, packages proteins into vesicles.
• Mitochondria: ATP production, double membrane, own DNA.
• Chloroplasts: photosynthesis, thylakoids, double membrane, own DNA.
• Lysosomes: contain hydrolytic enzymes, found in animal cells.
• Mature human red blood cells lack nucleus and mitochondria.
• Mycoplasma has no cell wall – smallest known bacteria.
• Flagella: prokaryotic = flagellin, rotating; eukaryotic = microtubules (9+2), bending.
• Centrioles present in animal cells, absent in most plant cells.
• Plasmids: small circular DNA in prokaryotes (common), yeast (rare).
• Binary fission = prokaryotic division; mitosis = eukaryotic nuclear division.
• Gram-positive bacteria: thick peptidoglycan; Gram-negative: thin peptidoglycan + outer membrane.
• Cytoskeleton in eukaryotes: microtubules, actin filaments; prokaryotes have analogous proteins.
• Nuclear envelope: double membrane with pores; regulates RNA/protein transport.
• Endosymbiotic theory supported by mitochondrial/chloroplast autonomy in replication and genetics.
• Verify from standard textbook: exact ribosomal subunit sizes (50S/30S for 70S; 60S/40S for 80S).
• Archaea lack peptidoglycan but are prokaryotic in structure.