STEM Readiness: Pre-Calculus Readiness - Trigonometry: Trig Functions Graphs - Amplitude, Period, Phase Shift, y = A sin(Bx + C) + D

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 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, similar to prokaryotes, supporting endosymbiotic theory.
• Prokaryotic cell walls (in bacteria) contain peptidoglycan; archaea lack peptidoglycan and have different wall chemistries.
• Plant cell walls are made 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.
• Both prokaryotes and eukaryotes have a phospholipid bilayer plasma membrane with embedded proteins.
• Eukaryotes have internal membrane systems including the endoplasmic reticulum (ER), nuclear envelope, and Golgi apparatus; prokaryotes do not.
• The nuclear envelope in eukaryotes is a double membrane with nuclear pores that regulate transport; prokaryotes lack this structure.
• Chromosomes in prokaryotes are typically a single circular DNA molecule; eukaryotes have multiple linear chromosomes.
• Plasmids are small, circular DNA molecules commonly found in prokaryotes; they are rare in eukaryotes.
• Binary fission is the method of asexual reproduction in prokaryotes; eukaryotes divide via mitosis and meiosis.
• Eukaryotic mitochondria generate ATP via oxidative phosphorylation and have cristae (inner membrane folds); prokaryotes perform respiration on the plasma membrane.
• Chloroplasts are found in plant and algal cells and perform photosynthesis; no prokaryote has chloroplasts, though cyanobacteria perform photosynthesis on thylakoid membranes.
• Lysosomes (containing hydrolytic enzymes) are present in animal cells, absent in most plant cells; both are eukaryotic.
• Centrioles involved in spindle formation during mitosis are found in animal cells, not in most plant cells.
• Red blood cells in mammals lack a nucleus and organelles, maximizing space for hemoglobin; this is a eukaryotic cell without a nucleus.
• Cilia and flagella in eukaryotes have a 9+2 microtubule arrangement; prokaryotic flagella are composed of flagellin and lack microtubules.
• Endosymbiotic theory proposes that mitochondria and chloroplasts originated from engulfed prokaryotes; evidence includes their own DNA, 70S ribosomes, and ability to replicate independently.
• Mitochondrial DNA is circular and lacks histones, resembling bacterial chromosomes.
• Archaea lack peptidoglycan and have ether-linked lipids in their membranes; bacteria and eukaryotes have ester-linked phospholipids.
• Gram-positive bacteria have thick peptidoglycan layers; Gram-negative have thin layers and an outer membrane with lipopolysaccharide.

Difficulty Level

Intermediate – routinely tested in first-year 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 (cellulose), fungal (chitin), and archaeal (pseudopeptidoglycan or other) walls differ chemically.

Trap: Ribosome size directly correlates with cell complexity – Fact: Mitochondria and chloroplasts in eukaryotes have 70S ribosomes, like prokaryotes, due to evolutionary origin.

Trap: The nucleus is the only organelle that contains DNA in eukaryotes – Fact: Mitochondria and chloroplasts also contain DNA, separate from nuclear DNA.

Trap: Prokaryotes have no internal structure – Fact: Prokaryotes have cytoskeletal proteins (e.g., FtsZ), ribosomes, and nucleoids, though not membrane-bound organelles.

Trap: Eukaryotic flagella evolved from prokaryotic flagella – Fact: Eukaryotic flagella (9+2 microtubules) are structurally and evolutionarily distinct from prokaryotic flagella (flagellin filaments).

Practice MCQs (5–7 questions)

Question: Which of the following is a feature shared by both prokaryotic and eukaryotic cells?
A) Membrane-bound nucleus
B) Mitochondria
C) Phospholipid bilayer plasma membrane
D) 80S ribosomes
Answer: C
Explanation: Both cell types have a phospholipid bilayer as the plasma membrane.
Why the top distractor is wrong: D is incorrect because 80S ribosomes are only in eukaryotic cytoplasm; prokaryotes have 70S.

Question: Which structure is found in plant cells but not in animal cells?
A) Mitochondria
B) Lysosomes
C) Cellulose cell wall
D) Plasma membrane
Answer: C
Explanation: Plant cells have a cellulose-based cell wall; animal cells lack a cell wall.
Why the top distractor is wrong: B is incorrect because lysosomes are typically present in animal cells but rare or absent in plant cells.

Question: Which of the following provides evidence for the endosymbiotic theory?
A) Eukaryotes have linear chromosomes
B) Mitochondria have 70S ribosomes and circular DNA
C) Prokaryotes divide by binary fission
D) Eukaryotic ribosomes are larger
Answer: B
Explanation: Mitochondria resemble bacteria in ribosome type and DNA structure, supporting bacterial origin.
Why the top distractor is wrong: A is a general eukaryotic trait but not evidence for endosymbiosis.

Question: A bacterial cell is placed in a hypotonic solution. Which component prevents lysis?
A) Plasma membrane
B) Capsule
C) Peptidoglycan cell wall
D) Nucleoid
Answer: C
Explanation: The peptidoglycan wall provides structural strength to resist osmotic pressure.
Why the top distractor is wrong: A is incorrect because the plasma membrane alone cannot prevent bursting in hypotonic conditions.

Question: Which of the following cells lacks a nucleus?
A) Yeast cell
B) Human skin cell
C) Escherichia coli
D) Onion root cell
Answer: C
Explanation: E. coli is a prokaryote and lacks a membrane-bound nucleus.
Why the top distractor is wrong: A is incorrect because yeast is a eukaryotic fungus with a nucleus.

Question: What is the primary component of fungal cell walls?
A) Peptidoglycan
B) Cellulose
C) Chitin
D) Lipopolysaccharide
Answer: C
Explanation: Fungi have cell walls made of chitin, a nitrogen-containing polysaccharide.
Why the top distractor is wrong: A is incorrect because peptidoglycan is found only in bacteria.

Question: Which organelle is responsible for protein modification and sorting in eukaryotic cells?
A) Nucleus
B) Rough endoplasmic reticulum
C) Golgi apparatus
D) Lysosome
Answer: C
Explanation: The Golgi apparatus modifies, sorts, and packages proteins for secretion or delivery.
Why the top distractor is wrong: B is incorrect because the rough ER synthesizes proteins but does not sort or modify them for final destination.

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.
• Bacteria: peptidoglycan cell wall; Archaea: no peptidoglycan.
• Plant cell wall = cellulose; fungal = chitin; animal = no cell wall.
• Mycoplasma lacks a cell wall – resistant to penicillin.
• Both cell types have phospholipid bilayer membranes.
• Eukaryotes have internal membranes (ER, Golgi, nucleus); prokaryotes do not.
• Nuclear envelope has nuclear pores for RNA/protein transport.
• Prokaryotes have circular chromosome; eukaryotes have linear chromosomes with histones.
• Plasmids are common in prokaryotes, rare in eukaryotes.
• Prokaryotes reproduce by binary fission; eukaryotes by mitosis/meiosis.
• Mitochondria have cristae; no prokaryote has mitochondria.
• Chloroplasts only in plants and algae; perform photosynthesis.
• Lysosomes: in animal cells, not in most plant cells.
• Centrioles: in animal cells, absent in most plants.
• Mammalian red blood cells lack a nucleus and organelles.
• Eukaryotic flagella: 9+2 microtubule arrangement; prokaryotic: flagellin filament, no microtubules.
• Endosymbiotic theory supported by mitochondrial DNA (circular, no histones).
• Mitochondria replicate independently of the host cell.
• Archaea have ether-linked lipids; bacteria and eukaryotes have ester-linked.
• Gram-positive: thick peptidoglycan; Gram-negative: thin peptidoglycan + outer LPS membrane.
• FtsZ protein in prokaryotes is homologous to eukaryotic tubulin.
• Verify from standard textbook: exact lipid composition in archaeal membranes varies widely.