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Compounds of the Cell Quiz: Can You Ace It?

Dive into water properties, protein shape and acid-base behavior - start the quiz now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration showing water molecule, acid base pH scale, protein helix, cell compounds on sky blue background

Calling all students, educators, and science buffs! The compounds of the cell quiz invites you to master cell chemistry by exploring water properties in cells, acid-base behavior in cells, and the diverse roles of organic compounds in cells. Test your understanding of macromolecules, ask yourself "the shape of a protein determines its ______?" and tackle fun cell questions that reinforce your grasp of hydrophilic interactions and lipid structures. You'll reinforce your knowledge of phospholipid bilayers, carbohydrate energy sources, stabilizing hydrogen bonds, and pH gradients vital to cell function. Ready to prep? Warm up with our cell structure quiz or go deeper in the chemical basis of life quiz , then dive in to prove you can ace it - start now!

What is the polarity of a water molecule?
Amphipathic molecule
Ionic molecule
Nonpolar molecule
Polar molecule
Water is polar because the oxygen atom attracts electrons more strongly than hydrogen, creating a dipole. This polarity allows water to form hydrogen bonds with other polar molecules. The resulting interactions underlie many of water's unique properties. Learn more
Which type of bond holds two water molecules together in liquid water?
Covalent bond
Ionic bond
Van der Waals force
Hydrogen bond
Hydrogen bonds form between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another. These bonds are weaker than covalent bonds but crucial for water's high cohesion and heat capacity. They constantly form and break in liquid water. Learn more
Which of the following properties of water contributes to its role as a universal solvent?
Lack of hydrogen bonding
High polarity
Low heat capacity
Hydrophobicity
Water's high polarity allows it to surround and separate ions or polar molecules, dissolving many substances. Its ability to form hydrogen bonds also helps stabilize dissolved solutes. This is why water is called the universal solvent. Learn more
What is the pH of pure water at 25°C?
0
14
7
1
At 25°C, pure water has equal concentrations of H? and OH? ions (10?? M), giving it a neutral pH of 7. This neutrality is a reference point for acid-base chemistry. Temperature changes can shift this balance slightly. Learn more
A solution with pH 4 is ______ times more acidic than a solution with pH 6.
10
20
100
2
Each pH unit represents a tenfold difference in hydrogen ion concentration. A pH of 4 has 10² (100) times more H? than a pH of 6. This logarithmic scale is fundamental to acid-base calculations. Learn more
Which is a characteristic of acids?
Accept electrons
Donate protons
Release OH? ions
Increase OH? concentration
Acids release protons (H?) in aqueous solution, increasing hydrogen ion concentration. This definition follows the Brønsted - Lowry theory. Acidic solutions have pH below 7. Learn more
Which is a characteristic of bases?
Increase H? concentration
Accept protons
Donate protons
Release H? ions
Bases accept protons (H?) or release hydroxide ions (OH?), reducing hydrogen ion concentration. They are defined by the Brønsted - Lowry and Arrhenius theories. Basic solutions have pH above 7. Learn more
What is the main functional group in amino acids that acts as a base?
Carboxyl group (-COOH)
Hydroxyl group (-OH)
Phosphate group (-PO?³?)
Amino group (-NH?)
The amino group (-NH?) can accept a proton, acting as a base in amino acids. It complements the acidic carboxyl group in the same molecule. This amphoteric behavior is key to protein structure. Learn more
Which monomer makes up proteins?
Monosaccharides
Nucleotides
Amino acids
Fatty acids
Proteins are polymers of amino acids linked by peptide bonds. There are 20 standard amino acids in most organisms. Sequence and chemistry of side chains determine protein function. Learn more
Which bond links amino acids in a protein?
Phosphodiester bond
Glycosidic bond
Hydrogen bond
Peptide bond
A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another. This linkage releases water in a condensation reaction. Peptide bonds form the protein backbone. Learn more
Which of the following sugars is a monosaccharide?
Cellulose
Starch
Glycogen
Glucose
Glucose is a simple sugar (monosaccharide) used as an energy source by cells. Starch, cellulose, and glycogen are polysaccharides made of glucose units. Monosaccharides cannot be hydrolyzed into simpler sugars. Learn more
What type of lipid is the main component of cell membranes?
Phospholipid
Wax
Steroid
Triglyceride
Phospholipids have hydrophilic heads and hydrophobic tails, forming bilayers in aqueous environments. This structure is fundamental to cell membrane integrity and function. Triglycerides store energy rather than form membranes. Learn more
What are the building blocks of nucleic acids?
Nucleotides
Monosaccharides
Fatty acids
Amino acids
Nucleic acids like DNA and RNA are polymers of nucleotides, each containing a sugar, phosphate, and nitrogenous base. The sequence of nucleotides encodes genetic information. Polymerization occurs via phosphodiester bonds. Learn more
ATP is primarily used in cells for what purpose?
Genetic information
Structural support
Insulation
Energy transfer
ATP (adenosine triphosphate) stores and transfers energy in cells by donating its terminal phosphate group. This drives many biochemical reactions. It is often called the energy currency of the cell. Learn more
Which element is most abundant in organic compounds of cells?
Sodium
Magnesium
Iron
Carbon
Carbon forms four covalent bonds, allowing complex and diverse organic molecules essential for life. It is the backbone of carbohydrates, lipids, proteins, and nucleic acids. No other element shows similar versatility. Learn more
What type of isomerism is exhibited by glucose and fructose?
Cis-trans isomers
Enantiomers
Structural isomers
Stereoisomers
Glucose and fructose share the same molecular formula (C?H??O?) but differ in atom connectivity, making them structural isomers. Their different arrangements lead to distinct chemical properties. Structural isomerism is common in carbohydrates. Learn more
Which functional group in a molecule is acidic?
Amino group (-NH?)
Carboxyl group (-COOH)
Hydroxyl group (-OH)
Methyl group (-CH?)
The carboxyl group can donate a proton (H?), acting as an acid in biological molecules. This release of H? lowers pH in solutions. Amino and hydroxyl groups are less acidic. Learn more
Which polysaccharide is the primary storage form of glucose in animals?
Starch
Glycogen
Cellulose
Chitin
Glycogen is a highly branched polymer of glucose that animals store primarily in liver and muscle cells. Its structure allows rapid release of glucose when needed. In plants, the analogous storage polymer is starch. Learn more
Which level of protein structure is determined by hydrogen bonding between backbone atoms?
Tertiary structure
Primary structure
Secondary structure
Quaternary structure
Secondary structure refers to ?-helices and ?-sheets stabilized by hydrogen bonds between amino and carbonyl groups of the peptide backbone. These regular patterns form before full folding. They differ from tertiary interactions of side chains. Learn more
The tertiary structure of a protein is primarily stabilized by which interactions?
Peptide bonds
Backbone hydrogen bonds
Phosphodiester bonds
R-group interactions
Tertiary structure involves folding driven by interactions among side chains, including hydrophobic effects, ionic bonds, hydrogen bonds, and disulfide bridges. These interactions define the three-dimensional shape. Peptide bonds maintain primary structure only. Learn more
Which compound acts as a buffer in human blood?
Bicarbonate
Glucose
Urea
Phosphate
The bicarbonate buffer system (H?CO?/HCO??) maintains blood pH around 7.4 by neutralizing excess acids or bases. It is the primary extracellular buffer. Phosphate plays a minor role in cells. Learn more
Which amino acid has a sulfur atom in its side chain?
Cysteine
Lysine
Glycine
Serine
Cysteine contains a thiol (-SH) group that can form disulfide bonds, stabilizing protein tertiary and quaternary structures. Methionine also contains sulfur but is less reactive. Glycine and serine lack sulfur. Learn more
Which type of lipid has four fused hydrocarbon rings?
Triglyceride
Steroid
Phospholipid
Glycolipid
Steroids have a core structure of four fused rings and include cholesterol and steroid hormones. This ring system distinguishes them from glycerol-based lipids. Their hydrophobic nature affects membrane fluidity. Learn more
DNA differs from RNA because DNA contains:
Additional hydroxyl group
Uracil
Deoxyribose sugar
Ribose sugar
DNA contains deoxyribose, missing an oxygen at the 2? carbon compared to ribose in RNA. This makes DNA more chemically stable. RNA has ribose and uses uracil instead of thymine. Learn more
Which base pairs are held together by three hydrogen bonds?
Adenine and thymine
Cytosine and guanine
Adenine and uracil
Guanine and thymine
C-G pairs form three hydrogen bonds, making them more stable than A-T (or A-U) pairs, which have two. This contributes to the higher melting temperature of GC-rich DNA. Stability affects replication and transcription. Learn more
What type of bond links nucleotides in a DNA strand?
Peptide bond
Phosphodiester bond
Hydrogen bond
Glycosidic bond
Phosphodiester bonds connect the 3? hydroxyl of one sugar to the 5? phosphate of the next, forming the sugar-phosphate backbone. These covalent bonds provide stability and directionality. Hydrogen bonds hold the two DNA strands together. Learn more
Which vitamin is a precursor for coenzyme NAD+?
Thiamine (Vitamin B1)
Biotin (Vitamin B7)
Niacin (Vitamin B3)
Riboflavin (Vitamin B2)
Niacin is used by cells to synthesize NAD+ and NADP+, essential cofactors in redox reactions. Deficiency leads to pellagra. Riboflavin is a precursor for FAD, not NAD+. Learn more
The molecule that carries amino acids to the ribosome is:
snRNA
rRNA
mRNA
tRNA
Transfer RNA (tRNA) matches its anticodon to mRNA codons and delivers specific amino acids during translation. Ribosomal RNA (rRNA) is part of the ribosome structure. mRNA carries the genetic code. Learn more
Which level of protein structure involves interactions between subunits?
Quaternary structure
Primary structure
Tertiary structure
Secondary structure
Quaternary structure refers to the assembly of multiple polypeptide chains (subunits) into a functional protein complex. Hemoglobin is a classic example. Interactions include hydrophobic contacts, hydrogen bonds, and ionic bonds. Learn more
A molecule that speeds up a chemical reaction without being consumed is:
Substrate
Enzyme
Nucleotide
Catalyst
Enzymes are biological catalysts that increase reaction rates by lowering activation energy without being consumed. While 'catalyst' is a general term, enzymes are the specific proteins in cells. Substrates are reactants enzymes act on. Learn more
Which amino acid is considered electrically neutral but polar?
Leucine
Tryptophan
Lysine
Serine
Serine has a polar hydroxyl side chain but no net charge at physiological pH, making it polar-neutral. Lysine is positively charged, leucine and tryptophan are nonpolar. Serine often participates in active sites. Learn more
The hydrophobic effect primarily drives which level of protein folding?
Tertiary structure
Quaternary structure
Secondary structure
Primary structure
Hydrophobic effect causes nonpolar side chains to cluster away from water, driving the tertiary folding of the entire polypeptide. Secondary structure is formed by backbone hydrogen bonds. Quaternary involves subunit assembly. Learn more
Which dietary lipid is unsaturated at every double bond?
Monounsaturated fat
Trans fat
Polyunsaturated fat
Saturated fat
Polyunsaturated fats contain multiple cis double bonds, preventing tight packing and remaining liquid at room temperature. Monounsaturated fats have a single double bond. Trans fats have trans-configured double bonds. Learn more
In aqueous solution, the phosphate group in phospholipids is oriented:
In the membrane core
Away from water
Toward the water
Attached to glycoproteins
Phospholipid phosphate heads are hydrophilic and face the aqueous environment, while hydrophobic fatty acid tails face inward. This arrangement forms stable bilayers. Core interactions involve tail packing. Learn more
What is the pKa of the carboxyl group of amino acids approximately?
Around 2
Around 9
Around 4.5
Around 7
Most amino acids have a carboxyl group pKa near 2.0, meaning it donates a proton at low pH. The amino group pKa is near 9.0. These values determine overall charge at different pH. Learn more
Glycosidic bonds are formed between which groups of monosaccharides?
Amino groups
Carboxyl groups
Hydroxyl groups
Phosphate groups
Glycosidic bonds form via condensation between the hydroxyl group of one sugar and the anomeric carbon of another, releasing water. This linkage joins monosaccharides into disaccharides and polysaccharides. Learn more
Which reaction involves water to break chemical bonds?
Dephosphorylation
Hydrolysis
Condensation
Phosphorylation
Hydrolysis reactions use water to cleave bonds, such as breaking polymers into monomers. Condensation (dehydration) reactions do the opposite by removing water. Hydrolysis is critical in digestion. Learn more
The isoelectric point of an amino acid is defined as the pH at which:
It carries no net charge
It is fully denatured
It has maximum positive charge
It has maximum negative charge
At its isoelectric point (pI), the amino acid's positive and negative charges balance, resulting in no net charge. This affects solubility and migration in electric fields. pI varies with side chain chemistry. Learn more
Which structure forms when fatty acids and detergents aggregate in water?
Liposome
Bilayer
Vesicle
Micelle
Micelles form when single-tailed amphipathic molecules pack into spherical structures, shielding hydrophobic tails from water. Phospholipids can form bilayers or liposomes instead. Detergents often form micelles. Learn more
Which group of lipids includes cholesterol?
Glycolipids
Sterols
Triglycerides
Phospholipids
Cholesterol is a sterol, a subclass of steroids characterized by the four-ring structure. Triglycerides store energy, phospholipids form membranes, and glycolipids have sugar headgroups. Sterols modulate membrane fluidity. Learn more
What is the primary structure of cellulose?
?-1,4 glycosidic bonds between glucose
?-1,6 glycosidic bonds between glucose
?-1,6 glycosidic bonds between glucose
?-1,4 glycosidic bonds between glucose
Cellulose is a linear polymer of glucose linked by ?-1,4 glycosidic bonds, allowing extensive hydrogen bonding between chains. This gives cellulose high tensile strength in plant cell walls. Starch uses ? linkages instead. Learn more
Which technique is used to determine the primary sequence of a protein?
Mass spectrometry
Edman degradation
NMR spectroscopy
X-ray crystallography
Edman degradation sequentially removes and identifies N-terminal amino acids one at a time, revealing the primary sequence. Mass spectrometry can also sequence peptides but Edman is classical. X-ray and NMR give structural information. Learn more
Which sugar phosphorylation is the first step in glycolysis?
Glucose to glucose-6-phosphate
Glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate
Fructose to fructose-6-phosphate
Pyruvate to phosphoenolpyruvate
Hexokinase catalyzes phosphorylation of glucose at the 6-position to form glucose-6-phosphate, trapping glucose in the cell and committing it to metabolism. This is the first irreversible step of glycolysis. Learn more
Which group of proteins accelerates the folding of other proteins?
Kinases
Proteases
Chaperones
Ribozymes
Molecular chaperones assist nascent or stress-denatured proteins to fold correctly without being part of the final structure. Proteases degrade proteins. Ribozymes are RNA enzymes. Kinases phosphorylate targets. Learn more
Which cellular component is rich in ribonucleotides and magnesium ions?
Lysosomes
Mitochondria
Ribosomes
Nucleus
Ribosomes consist of rRNA and proteins, requiring magnesium ions for structural stability and function during translation. The nucleus stores DNA but is not the site of ribonucleotide-rich complexes. Lysosomes degrade macromolecules. Learn more
In a peptide bond formation, which molecule is released?
Carbon dioxide
Ammonia
Water
Phosphate
Peptide bond formation is a condensation reaction releasing one molecule of water when the carboxyl group of one amino acid bonds to the amino group of another. This dehydration synthesis forms the backbone of proteins. Learn more
Which functional group on an amino acid participates in hydrogen bonding to stabilize alpha-helices?
Side chain thiol
Side chain methyl
Amide (peptide backbone NH)
Carboxyl side chain
Alpha-helices are stabilized by hydrogen bonds between the backbone amide hydrogen (NH) of one residue and the carbonyl oxygen four residues earlier. Side chains play less direct roles. This regular bonding pattern defines the helix. Learn more
The Bohr effect describes how:
Lipid bilayer fluidity
pH and CO? affect hemoglobin affinity for oxygen
Allosteric enzyme kinetics
Nucleic acid denaturation
The Bohr effect refers to the decrease in hemoglobin's oxygen affinity in response to lower pH and higher CO?, enhancing oxygen release in tissues. It is crucial for efficient gas exchange. Allosteric enzymes follow other regulatory principles. Learn more
Which nucleoside triphosphate is used in RNA transcription but not in DNA replication?
TTP
GTP
ATP
UTP
RNA polymerases use UTP (uridine triphosphate) to incorporate uracil into RNA, whereas DNA polymerases use TTP (thymidine triphosphate) for thymine in DNA. ATP and GTP are used by both processes. Learn more
In a phospholipid bilayer, which motion is most rapid?
Rotation
Migration
Lateral diffusion
Flip-flop
Lateral diffusion (side-to-side movement) of lipids within the same leaflet is very fast, occurring millions of times per second. Flip-flop (between leaflets) is rare without enzymes. Rotation is intermediate. Learn more
Zwitterionic form of amino acids predominates at:
High pH
Low pH
Physiological pH (~7)
Isoelectric point
At physiological pH (~7), most amino acids exist as zwitterions with protonated amino groups and deprotonated carboxyl groups. Below that pH they carry net positive charge; above, net negative. Zwitterionic form optimizes solubility. Learn more
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Study Outcomes

  1. Understand water properties in cells -

    Explain how water's polarity, cohesion and solvent capabilities support key cellular processes.

  2. Analyze acid-base behavior in cells -

    Describe how acids and bases interact in the intracellular environment to influence pH and drive biochemical reactions.

  3. Evaluate protein shape-function relationships -

    Assess how the shape of a protein determines its function and how structural changes can impact activity.

  4. Identify major organic compounds in cells -

    Recognize the structures and roles of carbohydrates, lipids, proteins and nucleic acids within living cells.

  5. Apply concepts to quiz scenarios -

    Use core cell chemistry principles to answer targeted quiz questions and measure your understanding.

  6. Differentiate between compound classes -

    Compare chemical properties and cellular roles to distinguish among different classes of cell compounds.

Cheat Sheet

  1. Mnemonic for Water Properties (CHAPS) -

    When studying for the compounds of the cell quiz, use the CHAPS mnemonic to master water properties in cells. Water's polarity enables it to dissolve polar substances and form hydrogen bonds that underlie cohesion, adhesion, and high specific heat (Source: Khan Academy).

  2. Acid-Base Behavior and Buffers -

    Acid-base behavior in cells is tightly regulated by buffer systems such as bicarbonate, which follows the Henderson-Hasselbalch equation (pH = pKa + log([A-]/[HA])). A slight shift in proton concentration can alter enzyme activity, so cells maintain a cytoplasmic pH around 7.2 for optimal metabolism (Source: National Institute of General Medical Sciences).

  3. Protein Structure and Function -

    The shape of a protein determines its function, with levels of structure from primary to quaternary dictating specific folding patterns. For example, the lock-and-key model shows how enzymes like catalase bind substrates precisely at their active site (Source: American Society for Biochemistry and Molecular Biology).

  4. Classes of Organic Compounds in Cells -

    Organic compounds in cells include four macromolecule classes: carbohydrates (monosaccharides), lipids (fatty acids/glycerol), proteins (amino acids), and nucleic acids (nucleotides). Recognizing each class's monomers and roles - energy storage, membrane structure, catalysis, and genetic coding - is foundational (Source: MIT OpenCourseWare).

  5. Dehydration Synthesis vs. Hydrolysis -

    Biological polymers form via dehydration synthesis, where monomers link and release water (e.g., amino acid + amino acid → dipeptide + H2O), and they break down through hydrolysis when water is added. Mastering these contrasting reactions is key to understanding metabolic pathways and enzymatic catalysis (Source: Lehninger Principles of Biochemistry).

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