W1 summary + mc questions

Question 1

sugars

Answer 1

Key Families of Organic Molecules:

Monomers and Polymers: Monomers (e.g., sugars, amino acids) link to form polymers (e.g., polysaccharides, proteins).

Sugars: Energy sources and subunits of polysaccharides.
Monosaccharides (e.g., glucose) follow the formula (CH2O)n.
Covalent glycosidic bonds form polysaccharides like glycogen and starch.
Condensation Reactions: Bond formation by removing water; Hydrolysis: Breaking bonds by adding water.

Question 2

fatty acids

Answer 2

Components of membranes and energy storage.
Structure: Hydrophobic hydrocarbon tail + hydrophilic carboxyl group.
Saturated (no double bonds) vs. Unsaturated (one or more double bonds).
Stored as triacylglycerols (three fatty acids linked to glycerol).

Question 3

protein composition

Answer 3

Amino Acids: Building blocks of proteins, linked by peptide bonds.
Polypeptides: Chains of amino acids with specific 3D structures stabilized by noncovalent bonds.
Enzyme function depends on substrate binding through specific noncovalent interactions.

Question 4

nucleotides and nucleic acids

Answer 4

DNA and RNA Subunits:
-Nucleotides: Nitrogenous base + 5-carbon sugar (ribose or deoxyribose) + phosphate group.
Bases: Purines (adenine, guanine) and Pyrimidines (cytosine, thymine, uracil).

DNA: Long-term genetic information storage.
RNA: Short-term information carrier.
Linked by phosphodiester bonds between sugar and phosphate groups.

Question 5

Properties of Water:

Answer 5

Polar molecule with hydrogen bonding capabilities.
High boiling point, surface tension, and ability to dissolve hydrophilic substances.
Hydrophobic molecules cluster to minimize interaction with water (e.g., lipid bilayers).

Question 6

Explain why fatty acids are considered amphipathic.

Question 7

How do glycosidic bonds differ from peptide bonds?

Question 8

4. Which of the following reactions is energetically favorable?
   A. Condensation reaction
   B. Hydrolysis reaction
   C. Photosynthesis
   D. Protein synthesis

Answer 8

Answer: B

Question 9

why are G-C base pairs more stable than A-T base pairs?
A. They form covalent bonds
B. They involve van der Waals interactions
C. They form three hydrogen bonds instead of two
D. They are hydrophobic

Answer 9

Answer: C

Question 10

Which term describes molecules that have both hydrophobic and hydrophilic regions?
A. Amphipathic
B. Isomeric
C. Hydrophilic
D. Hydrophobic

Answer 10

Answer: A

Question 11

What kind of bond links amino acids in a protein?
A. Glycosidic bond
B. Hydrogen bond
C. Ionic bond
D. Peptide bond

Answer 11

Answer: D

Question 12

What is the role of buffers in biological systems?
A. Catalyzing chemical reactions
B. Stabilizing proton concentrations at around pH 7
C. Serving as energy storage molecules
D. Facilitating hydrolysis reactions

Answer 12

Answer: B

Question 13

What is the general formula for monosaccharides?
A. (CH3O)n
B. (CH2O)n
C. (C2HO)n
D. (C3H6O)n

Answer 13

Answer: B

Question 14

Why are phospholipids ideal for forming cell membranes?
A. They are hydrophilic
B. They are amphipathic, with hydrophilic heads and hydrophobic tails
C. They are hydrophobic
D. They contain only saturated fatty acids

Answer 14

Answer: B

Question 15

How do condensation and hydrolysis reactions differ?
A. Hydrolysis builds polymers; condensation breaks them down
B. Hydrolysis adds water to break bonds; condensation removes water to form bonds
C. Both require energy input
D. Both involve amino acids exclusively

Answer 15

Answer: B

Question 16

Which statement about fatty acids is true?
A. Saturated fatty acids have one or more double bonds
B. Unsaturated fatty acids are completely hydrogenated
C. Fatty acids are stored as triacylglycerols
D. Fatty acids only function as membrane components

Answer 16

Answer: C

Question 17

What property allows water to dissolve hydrophilic substances?
A. Its nonpolar nature
B. Hydrogen bonding and polarity
C. Its ability to form ionic bonds
D. Its amphipathic nature

Answer 17

Answer: B

Question 18

Which nitrogenous bases are pyrimidines?
A. Adenine and guanine
B. Cytosine, thymine, and uracil
C. Guanine and cytosine
D. Adenine and uracil

Answer 18

b

Question 19

What would likely happen if a buffer system in the blood failed?
A. Proteins would catalyze incorrect reactions
B. Blood pH would fluctuate drastically, affecting enzyme activity
C. Nucleotides would lose their phosphate groups
D. Hydrogen bonds in water would break

Answer 19

b

Question 20

If a sugar molecule undergoes condensation, what is the product?
A. A polysaccharide
B. A monosaccharide
C. A glycerol molecule
D. A nucleotide

Answer 20

Answer: A

Question 21

What feature of DNA allows it to replicate?
A. Its sugar-phosphate backbone
B. The antiparallel and complementary base pairing of its strands
C. Its hydrogen bonding alone
D. Its presence in the nucleus

Answer 21

b

Question 22

In a cell, which process uses ATP most directly?
A. Gene replication
B. Protein synthesis
C. Energy transfer in metabolic reactions
D. Membrane transport

Answer 22

c

Question 23

What makes enzymes specific to their substrates?
A. Their noncovalent bonds with other enzymes
B. Their 3D structure and the arrangement of binding sites
C. Their ability to form covalent bonds with any molecule
D. Their interaction with water molecules

Answer 23

b

Question 24

How does the amphipathic nature of fatty acids contribute to membrane structure?
A. Hydrophilic tails face the interior of the membrane, forming a bilayer.
B. Hydrophilic heads face outward, interacting with water, while hydrophobic tails form the bilayer interior.
C. Hydrophobic heads and tails alternate to create a semi-permeable structure.
D. Fatty acids remain in aqueous environments due to their hydrophilicity.

Answer 24

b

Question 25

What would happen if hydrogen bonds in DNA were significantly stronger? A. DNA replication would occur faster. B. The DNA strands would be harder to separate during replication. C. DNA would lose its ability to encode genetic information. D. RNA transcription would become more efficient.

Answer 25

b

Question 26

Why are glycoproteins and glycolipids important for cellular function? A. They provide energy storage for cells. B. They facilitate cell-cell recognition and communication. C. They store genetic information. D. They catalyze cellular reactions.

Answer 26

b

Question 27

How does an enzyme lower the activation energy of a reaction? A. By increasing the energy of the substrate. B. By forming covalent bonds with the product. C. By stabilizing the transition state of the reaction. D. By hydrolyzing ATP.

Answer 27

c

Question 28

What role does electronegativity play in bond polarity? A. It determines the atomic number of an element. B. It causes equal electron sharing in covalent bonds. C. It determines the unequal sharing of electrons, creating partial charges. D. It facilitates ionic bond formation.

Answer 28

c

Question 29

Why is ATP considered a high-energy molecule? A. It contains ribose, which stores energy. B. Its phosphoanhydride bonds release significant energy when hydrolyzed. C. It is amphipathic, making it reactive in both polar and nonpolar environments. D. Its nitrogenous base, adenine, is highly reactive.

Answer 29

b

Question 30

What would happen to a protein if its noncovalent interactions were disrupted? A. It would become a polysaccharide. B. It would lose its functional 3D structure. C. It would catalyze reactions more efficiently. D. It would form covalent bonds with other proteins.

Answer 30

b

Question 31

What is the consequence of a saturated fatty acid being replaced by an unsaturated one in a membrane? A. Increased membrane fluidity due to kinks from double bonds. B. Decreased membrane fluidity due to stronger interactions between chains. C. Membrane becomes impermeable to ions. D. The membrane forms vesicles more readily.

Answer 31

a

Question 32

Why is the 5' to 3' orientation of DNA strands critical for replication? A. It facilitates covalent bonding between sugars and phosphates. B. It aligns enzymes for accurate base pairing and synthesis. C. It prevents the DNA strands from separating. D. It allows for single-strand stability during replication.

Answer 32

b

Question 33

How do van der Waals interactions stabilize protein structure? A. They provide strong covalent bonds within polypeptides. B. They stabilize weak, temporary attractions between closely aligned atoms. C. They facilitate hydrogen bonding within amino acid residues. D. They enable peptide bond formation.

Answer 33

b

Question 34

What would happen if water’s polarity decreased significantly? A. Its boiling point would increase. B. It would no longer dissolve ionic or polar substances effectively. C. It would form more hydrogen bonds. D. Its hydrophobic properties would increase.

Answer 34

b

Question 35

If a cell could not perform hydrolysis, which process would be directly affected? A. Synthesis of polysaccharides B. Breakdown of proteins into amino acids C. Formation of nucleotides D. Assembly of lipid bilayers

Answer 35

b

Question 36

What makes the complementary base pairing in DNA crucial for genetic information? A. It provides chemical energy for replication. B. It ensures consistent and accurate replication of DNA sequences. C. It stabilizes the sugar-phosphate backbone. D. It prevents the DNA strands from separating.

Answer 36

b

Question 37

Why are amphipathic molecules critical in biological membranes? A. They enable active transport of molecules. B. They create distinct hydrophilic and hydrophobic regions, forming a bilayer. C. They prevent diffusion of polar molecules. D. They catalyze metabolic reactions.

Answer 37

b

Question 38

What would occur if the hydrogen bonding between water molecules weakened? A. Water would have a lower surface tension and boiling point. B. Ice would become denser than liquid water. C. Water’s polarity would increase. D. Hydrophilic molecules would dissolve more effectively.

Answer 38

a

Question 39

If phosphodiester bonds in nucleic acids were unstable, what process would be disrupted? A. Protein folding B. Energy transfer in metabolic reactions C. Stability and integrity of DNA and RNA D. Formation of lipid bilayers

Answer 39

c

Question 40

Why is RNA more reactive than DNA? A. RNA lacks a sugar-phosphate backbone. B. RNA has ribose, which contains a hydroxyl group, making it more chemically active. C. RNA contains uracil, which is highly unstable. D. RNA forms covalent bonds with proteins.

Answer 40

b

Question 41

If enzymes were unable to form noncovalent bonds with substrates, what would happen? A. Reaction rates would increase. B. Substrate specificity would decrease. C. Enzymes would hydrolyze ATP more efficiently. D. Products would not be released.

Answer 41

b

Question 42

What happens to a cell membrane’s permeability at high temperatures? A. It increases due to more fluidity from lipid movement. B. It decreases due to tighter packing of lipids. C. It remains constant due to the lipid bilayer structure. D. It becomes impermeable to all molecules.

Answer 42

a

Question 43

Why is the central dogma (DNA → RNA → protein) fundamental to life? A. It enables cell replication without genetic errors. B. It describes the flow of information essential for cellular function and replication. C. It allows for ATP synthesis during cellular respiration. D. It stabilizes cell membranes in harsh environments.

Answer 43

b