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Knowledge Check: Unit 1 — Chapters 1–3

Knowledge Check: Unit 1 — Chapters 1–3

Test yourself on Unit 1: The Chemistry of Life (Chapters 1–3). Every question below was written from the chapters’ own text — their summaries, key terms, explanations, and tables — and none repeats a question from the section pages. There are no hints: treat it like a test. Questions are grouped by the section they come from, so a miss tells you exactly which section to review.

Chapter 1: The Study of Life

1.1 The Science of Biology

Which pair of disciplines builds on both the life and the physical sciences and is described as interdisciplinary?

A hypothesis that experimental results can potentially disprove is described as ________.

Why do life scientists carry a particular ethical obligation, and what is the field that has grown to address such obligations?

Show model answer
All scientists—and many people in other fields—have ethical obligations, but those in the life sciences have a particular obligation because their research may involve people or other living things. Bioethics is thus an important and continually evolving field, in which researchers collaborate with other thinkers and organizations to define guidelines for current practice and to consider new developments and emerging technologies.

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1.2 Themes and Concepts of Biology

Which of the following examples illustrates adaptation, an organism’s fit to its environment?

The process of gradual change in a population or species over time is called ________.

Compare what molecular biology and neurobiology each study.

Show model answer
Molecular biology studies biological processes at the molecular level, including interactions among molecules such as DNA, RNA, and proteins, and the way they are regulated. Neurobiology studies the biology of the nervous system; because of its interdisciplinary nature it is also known as neuroscience, and it studies nervous system functions using molecular, cellular, developmental, medical, and computational approaches.

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Chapter 2: The Chemical Foundation of Life

2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks

Together, the number of protons and neutrons in an atom determine its ________.

An ion necessary for nerve impulse conduction, muscle contractions, and water balance is called a(n) ________.

Why does nitrogen’s triple covalent bond make it hard for living organisms to use nitrogen gas from the atmosphere?

Show model answer
Molecular nitrogen (N₂) consists of two nitrogen atoms joined by a triple covalent bond, and the more covalent bonds between two atoms, the stronger their connection, so triple bonds are the strongest. This strong triple bond makes it difficult for living systems to break apart the nitrogen for use as a constituent of proteins and DNA.

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2.2 Water

What is the approximate pH of human blood?

The process in which atoms or groups of atoms break off a molecule and form ions is called ________.

Why does water’s oxygen atom carry a partial negative charge while its hydrogen atoms carry a partial positive charge?

Show model answer
Water is polar because oxygen is more electronegative than hydrogen, so the electrons shared in its covalent bonds spend more time near the oxygen nucleus than near the hydrogen nuclei. This generates a partial negative charge near the oxygen and a partial positive charge near the hydrogens.

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2.3 Carbon

In hydrocarbon names, the suffix “-ene” indicates a carbon-to-carbon ________ bond.

A molecule consisting of closed rings of carbon atoms with alternating single and double bonds is called a(n) ________.

Why can’t a molecule’s D and L enantiomers be superimposed on each other?

Show model answer
Enantiomers share the same chemical structure and chemical bonds, but they differ in the three-dimensional placement of their atoms, so the two forms are non-superimposable mirror images of each other.

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Chapter 3: Biological Macromolecules

3.1 Synthesis of Biological Macromolecules

Which enzyme breaks down lipids into smaller molecules?

The smallest unit of a larger molecule that is a polymer is called a ________.

How can one kind of monomer combine to form several different polymers, and what example illustrates this?

Show model answer
Different monomer types can combine in many configurations, giving rise to a diverse group of macromolecules. Even one kind of monomer can combine in a variety of ways to form several different polymers. For example, glucose monomers are the constituents of starch, glycogen, and cellulose.

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3.2 Carbohydrates

The nitrogen-containing polysaccharide that forms the exoskeleton of arthropods and the cell walls of fungi is called ________.

How does dietary fiber help remove excess cholesterol from the body?

Show model answer
Fiber binds to the cholesterol in the small intestine, then attaches to the cholesterol and prevents the cholesterol particles from entering the bloodstream. Cholesterol then exits the body via the feces.

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Which disaccharide forms from a dehydration reaction between two glucose molecules?

3.3 Lipids

A lipid made of long-chain fatty acids esterified to long-chain alcohols, which forms a protective coating on some feathers and leaf surfaces, is called a ________.

What health benefits are associated with omega-3 fatty acids?

Show model answer
Research indicates that omega-3 fatty acids reduce the risk of sudden death from heart attacks, lower triglycerides in the blood, decrease blood pressure, and prevent thrombosis by inhibiting blood clotting. They also reduce inflammation, and may help lower the risk of some cancers in animals.

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Cholesterol is the precursor of ________.

3.4 Proteins

A protein that assists another protein during the folding process is called a ________.

Which type of protein provides nourishment in early embryo development and the seedling?

How does comparing cytochrome c’s amino acid sequence across species provide evidence of evolutionary kinship?

Show model answer
Protein sequencing has shown that there is a considerable amount of cytochrome c amino acid sequence homology among different species. In other words, we can assess evolutionary kinship by measuring the similarities or differences among various species’ DNA or protein sequences. Human cytochrome c contains 104 amino acids. For each cytochrome c molecule from different organisms that scientists have sequenced to date, 37 of these amino acids appear in the same position in all cytochrome c samples.

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3.5 Nucleic Acids

What is chromatin, and how does it form?

Show model answer
In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes.

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The process through which messenger RNA forms on a template of DNA is called ________.

Sort each feature into the nucleic acid it describes.

DNA

    RNA

      This knowledge check is written for Unit 1 (Chapters 1–3) of Biology 2e by Mary Ann Clark, Jung Choi, Matthew Douglas, and OpenStax, © OpenStax, licensed under CC BY-NC-SA 4.0. Access the original for free at openstax.org. Changes: every question is locally written from the pinned text of the chapters’ own modules — their section summaries, glossary definitions, body passages, and comparison tables — and none is transcribed from the book’s exercise sets, which the section pages already carry; no question carries a hint, and every self-check carries a rubric that decomposes a model answer made of the module’s own sentences.

      Nucleic AcidsCell Structure