STEM Readiness: Pre-Calculus Readiness - Polar Coordinates: Polar Coordinates - Conversion, Multiple Representations, Graphing

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; eukaryotes house DNA within a membrane-bound nucleus.
• Prokaryotes lack membrane-bound organelles; eukaryotes contain organelles such as mitochondria, ER, and Golgi.
• Prokaryotic ribosomes are 70S (50S + 30S subunits); eukaryotic cytoplasmic ribosomes are 80S (60S + 40S).
• Mitochondria and chloroplasts contain 70S ribosomes, supporting their origin via endosymbiotic theory.
• Bacterial cell walls contain peptidoglycan; archaea lack peptidoglycan but may have pseudopeptidoglycan.
• Plant cell walls are made of cellulose; fungal cell walls are composed of chitin.
• Animal cells lack a cell wall; some protists (e.g., algae) have cell walls, others (e.g., amoeba) do not.
• Both prokaryotes and eukaryotes have a phospholipid bilayer plasma membrane with embedded proteins.
• Eukaryotes have internal membranes forming organelles (e.g., nuclear envelope, ER, lysosomes); prokaryotes do not.
• The nuclear envelope in eukaryotes is a double membrane with nuclear pores that regulate molecule transport.
• Nucleolus is located within the nucleus and is the site of ribosomal RNA synthesis and ribosome assembly.
• Endoplasmic reticulum (ER): rough ER has ribosomes and synthesizes proteins; smooth ER lacks ribosomes and synthesizes lipids.
• Golgi apparatus modifies, sorts, and packages proteins for secretion or delivery to other organelles.
• Mitochondria are the site of aerobic respiration; they have double membranes, cristae, and their own circular DNA.
• Chloroplasts (in plants and algae) perform photosynthesis; they contain thylakoids, grana, and their own circular DNA.
• Lysosomes (in animal cells) contain hydrolytic enzymes for intracellular digestion; absent in most plant cells.
• Peroxisomes break down fatty acids and detoxify hydrogen peroxide; present in both plant and animal cells.
• Mycoplasma species are bacteria that lack a cell wall; they are the smallest known prokaryotes (~0.2 ?m).
• Human red blood cells lack a nucleus and mitochondria in maturity, maximizing hemoglobin capacity.
• Archaea may live in extreme environments (e.g., thermophiles in hot springs) but share 70S ribosomes with bacteria.
• Endosymbiotic theory is supported by mitochondria and chloroplasts having 70S ribosomes, circular DNA, and ability to replicate independently.
• Cytoskeleton (microtubules, microfilaments, intermediate filaments) is present in eukaryotes; prokaryotes have homologous proteins (e.g., FtsZ) but no true cytoskeleton.
• Flagella differ: bacterial flagella are made of flagellin and rotate; eukaryotic flagella are made of microtubules (9+2 array) and bend.

Difficulty Level

Intermediate – expected foundational knowledge for first-semester biology but includes nuanced distinctions often tested in detail.

Common Traps (3–5 factual traps)

Trap: All cells with cell walls have peptidoglycan – Fact: Only bacteria have peptidoglycan; plants have cellulose, fungi have chitin, and archaea lack peptidoglycan.

Trap: Ribosome size is the same across all organisms – Fact: Prokaryotes have 70S ribosomes; eukaryotes have 80S in cytoplasm, but mitochondria and chloroplasts have 70S.

Trap: The nucleus is the only organelle with a double membrane – Fact: Mitochondria and chloroplasts also have double membranes; nucleus, mitochondria, and chloroplasts all have two lipid bilayers.

Trap: Prokaryotes have no internal structure – Fact: Prokaryotes have nucleoids, ribosomes, inclusions, and some have protein-based cytoskeletal elements (e.g., FtsZ, MreB).

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.

Question: Which structure is present in plant cells but not in animal cells?
A) Mitochondria
B) Golgi apparatus
C) Chloroplasts
D) Lysosomes
Answer: C
Explanation: Chloroplasts are found in plants and algae for photosynthesis; animal cells lack them.
Why the top distractor is wrong: Mitochondria are present in both plant and animal cells.

Question: A bacterial cell and a human liver cell are compared. Which component is smaller in size?
A) Human ribosome (80S)
B) Bacterial ribosome (70S)
C) Human nucleus
D) Bacterial nucleoid
Answer: B
Explanation: 70S ribosomes in bacteria are smaller than 80S ribosomes in human cells.
Why the top distractor is wrong: The 80S ribosome is larger than the 70S, so A is incorrect.

Question: Which of the following provides the strongest evidence for the endosymbiotic origin of mitochondria?
A) Presence of a double membrane
B) Ability to synthesize proteins using 80S ribosomes
C) Linear DNA attached to histones
D) Independent replication and 70S ribosomes
Answer: D
Explanation: Mitochondria replicate independently and have 70S ribosomes and circular DNA, like bacteria.
Why the top distractor is wrong: Double membranes are not unique to mitochondria and do not alone prove endosymbiosis.

Question: Which organism lacks a cell wall?
A) Escherichia coli
B) Saccharomyces cerevisiae
C) Mycoplasma pneumoniae
D) Arabidopsis thaliana
Answer: C
Explanation: Mycoplasma is a bacterium that naturally lacks a cell wall.
Why the top distractor is wrong: E. coli has a peptidoglycan cell wall; yeast (B) has chitin; Arabidopsis (D) has cellulose.

Question: Where is DNA located in a eukaryotic animal cell?
A) Nucleoid only
B) Nucleus and mitochondria
C) Nucleus only
D) Cytoplasm and nucleus
Answer: B
Explanation: Eukaryotic nuclear DNA is in the nucleus; mitochondrial DNA is in the mitochondria.
Why the top distractor is wrong: Nucleoid is a prokaryotic structure; DNA is not free in the cytoplasm.

Question: Which of the following organelles is responsible for lipid synthesis and detoxification in liver cells?
A) Rough endoplasmic reticulum
B) Golgi apparatus
C) Smooth endoplasmic reticulum
D) Lysosome
Answer: C
Explanation: Smooth ER synthesizes lipids and detoxifies drugs and poisons in hepatocytes.
Why the top distractor is wrong: Rough ER synthesizes proteins, not lipids.

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.
• Bacterial cell wall contains peptidoglycan; archaea do not.
• Plant cell wall = cellulose; fungal = chitin; animal cells = no cell wall.
• Mycoplasma – smallest prokaryote, no cell wall.
• Mature human red blood cells lack nucleus and mitochondria.
• Both cell types have phospholipid bilayer plasma membrane.
• Eukaryotes have internal membranes (ER, Golgi, lysosomes); prokaryotes do not.
• Nucleolus = site of rRNA synthesis and ribosome assembly.
• Rough ER has ribosomes; synthesizes proteins for secretion/membranes.
• Smooth ER = lipid synthesis, detoxification, calcium storage.
• Golgi apparatus = modifies, sorts, packages proteins into vesicles.
• Mitochondria = site of ATP production; double membrane; cristae increase surface area.
• Chloroplasts = site of photosynthesis; contain thylakoids and grana.
• Lysosomes contain acid hydrolases; break down macromolecules; mainly in animal cells.
• Peroxisomes break down fatty acids and detoxify H?O?.
• Cytoskeleton components: microtubules (tubulin), microfilaments (actin), intermediate filaments.
• Prokaryotes have FtsZ (tubulin homolog) and MreB (actin homolog).
• Archaea lack peptidoglycan but may have similar cell wall structures.
• Bacterial flagellum = flagellin, rotates; eukaryotic flagellum = 9+2 microtubules, bends.
• Endosymbiotic theory supported by organelle size similarity to bacteria, binary fission, independent DNA.
• Verify from standard textbook: exact protein composition of nuclear pore complex.
• Verify from standard textbook: proportion of 70S ribosomes in mitochondrial vs. chloroplast comparison.