STEM Readiness: Pre-Calculus Readiness - Functions/Algebra: Transformations - Shifts, Reflections, Stretches

Must?Know (20–25 detailed bullets)

• Prokaryotic cells range from 0.1–5.0 ?m in diameter; eukaryotic cells range from 10–100 ?m.
• Prokaryotic DNA is located in the nucleoid, a region without a membrane; eukaryotic DNA is enclosed within a membrane-bound nucleus.
• Prokaryotes have 70S ribosomes (composed of 30S and 50S subunits); eukaryotes have 80S ribosomes (40S and 60S subunits).
• Mitochondria and chloroplasts in eukaryotes contain 70S ribosomes, supporting their origin via endosymbiosis.
• Bacterial cell walls contain peptidoglycan; archaea lack peptidoglycan and have pseudopeptidoglycan or other polymers.
• Plant cell walls are made of cellulose; fungal cell walls contain chitin; animal cells lack a cell wall.
• All cells have a plasma membrane composed of a phospholipid bilayer with embedded proteins.
• Eukaryotes have internal membrane systems including the endoplasmic reticulum (ER), Golgi apparatus, and lysosomes; prokaryotes lack these.
• Mitochondria are present in nearly all eukaryotic cells and are the site of aerobic respiration; absent in prokaryotes.
• Chloroplasts are found in plant and algal cells and conduct photosynthesis; not present in prokaryotes or animal cells.
• Prokaryotes include bacteria and archaea; eukaryotes include animals, plants, fungi, and protists.
• Binary fission is the primary method of reproduction in prokaryotes; mitosis and meiosis occur in eukaryotes.
• Prokaryotic DNA is typically a single, circular chromosome; eukaryotic DNA is organized into multiple linear chromosomes.
• Plasmids are small, circular DNA molecules commonly found in prokaryotes; rare in eukaryotes.
• Cytoskeleton is present in both cell types: prokaryotes have FtsZ, MreB, and CreS proteins; eukaryotes have microtubules, actin filaments, and intermediate filaments.
• Flagella in prokaryotes are made of flagellin and rotate; eukaryotic flagella are composed of microtubules (9+2 arrangement) and bend.
• Mycoplasma species are bacteria without a cell wall, making them resistant to antibiotics like penicillin.
• Human red blood cells lack a nucleus and mitochondria in maturity, limiting their lifespan and metabolic capacity.
• Endosymbiotic theory is supported by mitochondria and chloroplasts having their own DNA (circular), 70S ribosomes, and double membranes.
• Lysosomes are membrane-bound organelles in animal cells containing hydrolytic enzymes; rare in plant cells (vacuole performs similar function).
• The nuclear envelope in eukaryotes is a double membrane with nuclear pores that regulate transport; absent in prokaryotes.
• Smooth ER synthesizes lipids and detoxifies chemicals; rough ER has ribosomes and synthesizes proteins for secretion or membranes.
• Golgi apparatus modifies, sorts, and packages proteins into vesicles for transport to target destinations.
• Peroxisomes contain oxidative enzymes (e.g., catalase) and break down fatty acids and hydrogen peroxide; present in both plant and animal eukaryotic cells.
• Plant vacuoles are large, central, and maintain turgor pressure; animal cells have small or temporary vacuoles.

Difficulty Level

Intermediate – requires clear differentiation between structural and functional features across domains and kingdoms, with emphasis on exceptions and evolutionary implications.

Common Traps (3–5 factual traps)

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

Trap: Ribosome size is proportional to cell complexity – Fact: Mitochondria and chloroplasts have 70S ribosomes like prokaryotes, despite being in eukaryotic cells.

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

Trap: Eukaryotes evolved from prokaryotes directly – Fact: Eukaryotes likely arose from archaeal ancestors with endosymbiotic events; not direct descendants of modern bacteria.

Practice MCQs (5–7 questions)

Question: Which of the following is a defining feature of eukaryotic cells but absent in prokaryotic cells?
A) Plasma membrane
B) Ribosomes
C) Circular DNA
D) Membrane-bound nucleus
Answer: D
Explanation: The membrane-bound nucleus is unique to eukaryotes.
Why the top distractor is wrong: Circular DNA (C) is found in prokaryotes and also in mitochondria and chloroplasts, so it is not exclusive to prokaryotes.

Question: A cell is observed to have a cell wall, chloroplasts, and a large central vacuole. Which type of cell is it most likely?
A) Fungal cell
B) Animal cell
C) Bacterial cell
D) Plant cell
Answer: D
Explanation: Chloroplasts, cell wall (cellulose), and large central vacuole are characteristic of plant cells.
Why the top distractor is wrong: Fungal cells (A) have cell walls but made of chitin and lack chloroplasts and large vacuoles.

Question: Which structure is found in both prokaryotes and eukaryotes but differs in size and composition?
A) Mitochondria
B) Ribosome
C) Nucleus
D) Golgi apparatus
Answer: B
Explanation: Ribosomes are present in both, but 70S in prokaryotes, 80S in eukaryotes.
Why the top distractor is wrong: Mitochondria (A) are only in eukaryotes and some protists via endosymbiosis.

Question: Which of the following provides the strongest evidence for the endosymbiotic theory?
A) Mitochondria have a double membrane
B) Mitochondria have 70S ribosomes and circular DNA
C) Mitochondria divide by mitosis
D) Mitochondria are larger than ribosomes
Answer: B
Explanation: 70S ribosomes and circular DNA in mitochondria resemble those of bacteria, supporting bacterial origin.
Why the top distractor is wrong: Double membrane (A) is supportive but not as specific as genetic and ribosomal evidence.

Question: Which organism lacks a cell wall and is classified as a prokaryote?
A) Escherichia coli
B) Saccharomyces cerevisiae
C) Mycoplasma pneumoniae
D) Arabidopsis thaliana
Answer: C
Explanation: Mycoplasma is a bacterium without a cell wall, unlike most prokaryotes.
Why the top distractor is wrong: E. coli (A) has a peptidoglycan cell wall, typical of bacteria.

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 – supports endosymbiosis.
• Bacterial cell wall contains peptidoglycan; archaea do not.
• Plant cell wall = cellulose; fungal = chitin; animal = no cell wall.
• Mycoplasma – prokaryote without cell wall.
• Human mature red blood cells lack nucleus and mitochondria.
• All cells have phospholipid bilayer plasma membrane.
• Eukaryotes have internal membranes: ER, Golgi, lysosomes, nucleus.
• Prokaryotes reproduce by binary fission; eukaryotes by mitosis/meiosis.
• Prokaryotic DNA = single circular chromosome; eukaryotic = multiple linear chromosomes.
• Plasmids = small circular DNA, common in bacteria.
• Cytoskeleton in prokaryotes: FtsZ, MreB, CreS; eukaryotes: actin, microtubules, intermediate filaments.
• Prokaryotic flagellum = flagellin, rotates; eukaryotic = microtubules (9+2), bends.
• Mitochondria = site of aerobic respiration; absent in prokaryotes.
• Chloroplasts = site of photosynthesis; in plants and algae only.
• Lysosomes contain hydrolytic enzymes; mainly in animal cells.
• Smooth ER = lipid synthesis, detoxification; rough ER = protein synthesis.
• Golgi apparatus = modifies, sorts, packages proteins into vesicles.
• Peroxisomes break down fatty acids and H?O? using catalase.
• Plant vacuole maintains turgor pressure; animal vacuoles are small.
• Nuclear envelope = double membrane with nuclear pores.
• Endosymbiotic theory supported by: circular DNA, 70S ribosomes, double membrane, binary fission in mitochondria/chloroplasts.