Question 1

Which property of tetrodotoxin (TTX) prevents it from freely diffusing across a cell's lipid bilayer?

Accepted Answer

Its polar structure with multiple charged and hydroxyl groups

Question 2

TTX causes death by impacting protein channels that allow $$\mathrm{Na^+} to $$diffuse into a cell. Based on the graph showing channel activity before and after TTX exposure, what is the most likely mechanism of TTX toxicity?

Accepted Answer

It acts as a plug, binding to residues in the protein tunnel so $$\mathrm{Na^+}$$ cannot get through.

Question 3

Which of the following accurately describes what establishes the polarity of nucleic acid molecules?

Accepted Answer

Whether or not the 3' or the 5' carbon of the sugar is linked to another nucleotide.

Question 4

What can you deduce from a diagram of a linear carbohydrate polymer with repeating monomer units and $$\beta-1$$,4 glycosidic linkages?

Accepted Answer

It is likely used for structure in an organism.

Question 5

The plasma membrane of the prokaryote *Thermus aquaticus* remains stable at high temperatures due to which adaptation?

Accepted Answer

Increasing the proportion of phospholipids with saturated fatty acid tails and increasing the length of the tails.

Question 6

Which component of the plasma membrane acts as the primary barrier to ions and charged molecules?

Accepted Answer

The hydrophobic core of the phospholipid bilayer

Question 7

Which of the following is an accurate comparison of facilitated diffusion and active transport?

Accepted Answer

Both processes use integral membrane proteins to move substances across the membrane.

Question 8

You drop human red blood cells into a solution of pure water. Which of the following best explains what will occur?

Accepted Answer

The cells will swell because water will enter the cells by osmosis.

Question 9

Which of the following is NOT a tenet of modern cell theory?

Accepted Answer

All cells contain a nucleus.

Question 10

Which experiment provided evidence for the chemical evolution hypothesis by demonstrating that organic molecules could be synthesized under early Earth conditions?

Accepted Answer

The Miller-Urey experiment

Question 11

According to the RNA-world hypothesis, why is RNA considered a likely candidate for the first molecular replicator?

Accepted Answer

RNA can both store genetic information and catalyze chemical reactions.

Question 12

Which of the following best explains why phospholipid bilayers are critical for the formation of the first cells?

Accepted Answer

They create a selective barrier, allowing an internal environment distinct from the external environment.

Question 13

Which of the following features is found in both prokaryotic and eukaryotic cells?

Accepted Answer

Ribosomes

Question 14

Which adaptation would you expect to find in the plasma membrane of a bacterium living in a cold environment?

Accepted Answer

Increased proportion of phospholipids with unsaturated fatty acid tails

Question 15

Which of the following statements about the Last Universal Common Ancestor (LUCA) is correct?

Accepted Answer

LUCA is the ancestor of all current biological life on Earth.

Question 16

Which of the following best describes the sequence of events in chemical evolution leading to the first cell?

Accepted Answer

Inorganic molecules → complex organic molecules → RNA replicators and lipid structures → cells

Question 17

Which of the following is a key structural difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.

Question 18

Which property of water is most important for the formation of the cell membrane?

Accepted Answer

Water's polarity, which drives the formation of hydrophobic and hydrophilic regions

Question 19

Which of the following best explains why cells are relatively small?

Accepted Answer

A high surface area-to-volume ratio allows efficient exchange of materials with the environment.

Foundations of Cells: Chemical Evolution, Cell Theory, and Cell Types

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