STEM Readiness: Pre-Calculus Readiness - Functions/Algebra: Rational Functions - Asymptotes, Holes, End Behaviour

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 endoplasmic reticulum, Golgi apparatus, mitochondria, and lysosomes.
• Prokaryotic ribosomes 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 endosymbiotic theory.
• Prokaryotic cell walls typically contain peptidoglycan (e.g., Escherichia coli); archaea lack peptidoglycan but may have pseudopeptidoglycan.
• 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 penicillin.
• Red blood cells in mammals lack a nucleus and mitochondria in maturity, maximizing hemoglobin capacity.
• Both prokaryotes and eukaryotes have a phospholipid bilayer plasma membrane with embedded proteins.
• Eukaryotes have internal membranes forming organelles; prokaryotes do not, though some have infoldings like mesosomes.
• Nuclear envelope in eukaryotes is a double membrane with nuclear pores regulating transport; absent in prokaryotes.
• Chromosomes in prokaryotes are typically a single circular DNA molecule; eukaryotes have multiple linear chromosomes.
• Plasmids are small, circular extrachromosomal DNA commonly found in prokaryotes, rarely in eukaryotes (e.g., yeast 2-micron plasmid).
• Binary fission is the primary mode of prokaryotic cell division; eukaryotes divide via mitosis and meiosis.
• Flagella in prokaryotes are made of flagellin and rotate; eukaryotic flagella are composed of microtubules (9+2 arrangement) and undulate.
• Endosymbiotic theory is supported by mitochondria and chloroplasts having circular DNA, 70S ribosomes, and double membranes.
• Lysosomes are membrane-bound organelles containing hydrolytic enzymes; present in animal cells, rare in plant cells (vacuoles perform similar function).
• Plant cells contain a large central vacuole for turgor pressure; animal cells have small or transient vacuoles.
• Chloroplasts are photosynthetic organelles in plants and algae; absent in animals and fungi.
• Cytoskeleton (microtubules, microfilaments, intermediate filaments) is present in eukaryotes; prokaryotes have homologous proteins (e.g., FtsZ, MreB) but no true cytoskeleton.
• Pili and fimbriae are protein appendages in some prokaryotes for adhesion or conjugation; not found in eukaryotes.
• Gram-positive bacteria have thick peptidoglycan layers; Gram-negative bacteria have thin peptidoglycan and an outer membrane with lipopolysaccharide (LPS).
• Archaea lack peptidoglycan and have ether-linked lipids in membranes; bacteria and eukaryotes have ester-linked lipids.

Difficulty Level

Intermediate – routinely tested in first-semester biology with emphasis on comparative structure and functional implications.

Common Traps (3–5 factual traps)

Trap: All cells with cell walls have peptidoglycan – Fact: Only bacteria have peptidoglycan; plant cell walls are cellulose, fungal walls are chitin.

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

Trap: Prokaryotes have no internal structure – Fact: Prokaryotes have nucleoids, ribosomes, and some have protein compartments or membrane infoldings.

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

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: 70S ribosomes are found in prokaryotes and also in mitochondria/chloroplasts, so not exclusive to prokaryotes.

Question: A cell is observed to have a cell wall, no nucleus, and 70S ribosomes. Which of the following is the most likely identity?
A) Fungal cell
B) Plant cell
C) Bacterial cell
D) Animal cell
Answer: C
Explanation: Bacteria have cell walls (peptidoglycan), no nucleus, and 70S ribosomes.
Why the top distractor is wrong: Fungal cells have cell walls but are eukaryotic (80S ribosomes, nucleus present).

Question: Which structure provides evidence for the endosymbiotic origin of mitochondria?
A) Presence of a single membrane
B) Linear chromosomes
C) 80S ribosomes
D) Circular DNA and 70S ribosomes
Answer: D
Explanation: Mitochondria have circular DNA and 70S ribosomes, similar to bacteria.
Why the top distractor is wrong: 80S ribosomes are found in the eukaryotic cytoplasm, not in mitochondria.

Question: Which of the following cells lacks mitochondria?
A) Yeast cell
B) Leaf cell
C) Mature human red blood cell
D) Skin cell
Answer: C
Explanation: Mature human red blood cells lack mitochondria and nuclei.
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 Gram-positive bacteria?
A) Chitin
B) Cellulose
C) Peptidoglycan
D) Lipopolysaccharide
Answer: C
Explanation: Gram-positive bacteria have thick peptidoglycan layers.
Why the top distractor is wrong: Lipopolysaccharide is found in the outer membrane of Gram-negative bacteria, not Gram-positive.

Question: Which of the following is true of both prokaryotes and eukaryotes?
A) Presence of mitochondria
B) Use of 80S ribosomes
C) Phospholipid bilayer membrane
D) Linear chromosomes
Answer: C
Explanation: Both cell types have a plasma membrane made of phospholipid bilayer.
Why the top distractor is wrong: 80S ribosomes are only in eukaryotic cytoplasm; prokaryotes have 70S.

Question: Which organism lacks a cell wall entirely?
A) Streptococcus pneumoniae
B) Saccharomyces cerevisiae
C) Mycoplasma genitalium
D) Arabidopsis thaliana
Answer: C
Explanation: Mycoplasma is a bacterium without a cell wall.
Why the top distractor is wrong: Streptococcus is Gram-positive with a thick peptidoglycan wall.

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

• Prokaryotic cell size: 0.1–5.0 ?m; eukaryotic: 10–100 ?m.
• Prokaryotes: DNA in nucleoid; eukaryotes: DNA in nucleus.
• 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 wall.
• Mycoplasma – smallest known bacterium, no cell wall.
• Mature red blood cells lack a nucleus and mitochondria.
• Both cell types have phospholipid bilayer plasma membranes.
• Eukaryotes have internal membranes (ER, Golgi); prokaryotes do not.
• Nuclear envelope = double membrane with nuclear pores.
• Prokaryotic DNA = single circular chromosome; eukaryotes = multiple linear chromosomes.
• Plasmids = small, circular DNA; common in bacteria.
• Prokaryotes divide by binary fission; eukaryotes by mitosis/meiosis.
• Prokaryotic flagellum = flagellin, rotates; eukaryotic = microtubules (9+2), bends.
• Lysosomes present in animal cells, not typical in plant cells.
• Central vacuole in plant cells maintains turgor pressure.
• Chloroplasts perform photosynthesis; found in plants and algae.
• Cytoskeleton: microtubules, microfilaments, intermediate filaments – only in eukaryotes.
• Pili and fimbriae = prokaryotic surface structures for attachment.
• Gram-negative bacteria have LPS in outer membrane; triggers immune response.
• Archaea have ether-linked lipids; bacteria and eukaryotes have ester-linked.
• Endosymbiotic theory explains origin of mitochondria and chloroplasts.
• FtsZ protein in bacteria is homolog of eukaryotic tubulin.
• MreB protein in bacteria is homolog of eukaryotic actin.