Question 1

Which of the following best describes a microbe, and when did microbes first appear on Earth?

Accepted Answer

A microscopic organism, including bacteria, archaea, and some eukaryotes, that first appeared over 3.5 billion years ago.

Question 2

Which equation represents oxygenic photosynthesis performed by phytoplankton, and what is its significance for atmospheric CO$_2$ and O$_2$?

Accepted Answer

$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$

Question 3

Which cellular structures are common to all cells, regardless of being prokaryotic or eukaryotic?

Accepted Answer

Plasma membrane, cytoplasm, ribosomes, DNA

Question 4

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

Accepted Answer

Eukaryotes have a nucleus, prokaryotes lack a nucleus.

Question 5

Which molecule is most commonly used to investigate evolutionary relationships among microbes, and why?

Accepted Answer

16S rRNA, because it is highly conserved, universally present, and contains variable regions for differentiation.

Question 6

Which equation represents aerobic respiration of glucose, and what is the main redox reaction involved?

Accepted Answer

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$

Question 7

Which of the following best explains the endosymbiont hypothesis for mitochondria?

Accepted Answer

Mitochondria originated from an engulfed aerobic bacterium by an ancestral eukaryotic cell.

Question 8

Which of the following is a major difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and lack an outer membrane.

Question 9

Which of the following best describes the biological pump created by phytoplankton metabolism?

Accepted Answer

Phytoplankton remove CO$_2$ from the atmosphere and transfer it to deep ocean sediments, helping regulate climate.

Question 10

Which of the following is a plausible outcome if you repeat Woese & Fox’s experiment but forget to add T1RNase to your extracted 16S rRNA?

Accepted Answer

The 16S rRNA will remain intact, leading to inaccurate evolutionary comparisons due to lack of fragmentation.

Question 11

Which of the following is a function of the prokaryotic cell wall?

Accepted Answer

Protection against osmotic lysis

Question 12

Which of the following best describes the difference between peptidoglycan and pseudomurein?

Accepted Answer

Peptidoglycan contains N-acetylmuramic acid, while pseudomurein contains N-acetyltalosaminuronic acid.

Question 13

Which of the following best describes the nutritional needs of an autotroph?

Accepted Answer

Uses inorganic carbon (CO$_2$) as the source for cellular material.

Question 14

Which of the following is a reason to use an electron microscope instead of a light microscope when studying microbes?

Accepted Answer

To achieve higher resolution and visualize ultrastructural details.

Question 15

Which of the following equations represents fermentation by lactic acid bacteria?

Accepted Answer

$C_6H_{12}O_6 \rightarrow 2C_3H_6O_3$

Question 16

Which of the following best describes the role of NADH in microbial metabolism?

Accepted Answer

NADH acts as an electron shuttle, transferring electrons to the electron transport chain during respiration.

Question 17

Which of the following is a difference between replication in eukaryotes and bacteria?

Accepted Answer

Bacteria have a single origin of replication, eukaryotes have multiple origins.

Question 18

Which of the following antibiotics targets translation, and what is its mechanism?

Accepted Answer

Tetracycline, binds to the 30S ribosomal subunit and prevents tRNA attachment.

Question 19

Which of the following best describes the process of substrate-level phosphorylation?

Accepted Answer

ATP is produced directly from ADP and inorganic phosphate during glycolysis or fermentation.

Microbiology Exam 1 Study Guide: Step-by-Step Guidance

Study Guide - Practice Questions