Rucete ✏ Campbell Biology In a Nutshell
Unit 1 THE CHEMISTRY OF LIFE — Concept 5.3 Lipids Are a Diverse Group of Hydrophobic Molecules — Practice Questions
(Multiple Choice — Click to Reveal Answer)
1. What is the defining feature of lipids?
- They contain nitrogen
- They are hydrophilic
- They are hydrophobic
- They are polymers
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3. They are hydrophobic
2. Which of the following is NOT a lipid?
- Fats
- Phospholipids
- Steroids
- Starch
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4. Starch
3. What type of molecules make up fats?
- Glycerol and fatty acids
- Glucose and fructose
- Nucleotides
- Amino acids
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1. Glycerol and fatty acids
4. What kind of bond links fatty acids to glycerol in fats?
- Glycosidic linkage
- Ester linkage
- Peptide bond
- Hydrogen bond
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2. Ester linkage
5. What is a fat molecule also called?
- Triglyceride
- Monosaccharide
- Phospholipid
- Steroid
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1. Triglyceride
6. How many fatty acids are typically joined to one glycerol in a fat?
- 1
- 2
- 3
- 4
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3. 3
7. What is the main function of fats in animals?
- Catalyze reactions
- Store genetic information
- Store energy
- Provide structure to DNA
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3. Store energy
8. What is the physical state of saturated fats at room temperature?
- Gas
- Liquid
- Solid
- Plasma
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3. Solid
9. Which type of fat contains no double bonds?
- Unsaturated fats
- Saturated fats
- Trans fats
- Hydrogenated oils
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2. Saturated fats
10. Which fat is considered healthier for the human body?
- Trans fat
- Saturated fat
- Unsaturated fat
- Animal fat
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3. Unsaturated fat
11. What creates the kink in unsaturated fatty acids?
- Hydrogen bonds
- Double bonds
- Carbonyl groups
- Triple bonds
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2. Double bonds
12. What makes phospholipids unique compared to fats?
- They are completely hydrophobic
- They have four fatty acid chains
- They have both hydrophilic and hydrophobic regions
- They are made of amino acids
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3. They have both hydrophilic and hydrophobic regions
13. What is the function of phospholipids in cells?
- Store energy
- Build DNA
- Form cell membranes
- Transport oxygen
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3. Form cell membranes
14. Which lipid type includes hormones like testosterone?
- Fats
- Phospholipids
- Steroids
- Carbohydrates
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3. Steroids
15. What structure do steroids share?
- Chain of fatty acids
- Four fused carbon rings
- Hexose sugars
- Phosphate group tails
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2. Four fused carbon rings
16. What is the most well-known steroid in animals?
- Testosterone
- Cholesterol
- Estrogen
- Insulin
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2. Cholesterol
17. What role does cholesterol play in animal cell membranes?
- Provides energy
- Maintains fluidity
- Breaks down fatty acids
- Causes rigidity
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2. Maintains fluidity
18. What type of fat is produced by hydrogenating unsaturated fats?
- Saturated fat
- Trans fat
- Phospholipid
- Omega-3 fat
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2. Trans fat
19. What is one danger of consuming trans fats?
- Weight gain only
- Improved digestion
- Increased heart disease risk
- Muscle loss
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3. Increased heart disease risk
20. Which part of a phospholipid is hydrophobic?
- The phosphate group
- The fatty acid tails
- The glycerol backbone
- The ring structure
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2. The fatty acid tails
21. Which part of a phospholipid is hydrophilic?
- The fatty acid tails
- The carbon rings
- The phosphate group
- The ester linkage
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3. The phosphate group
22. What arrangement do phospholipids form in water?
- Micelles
- Bilayers
- Triple helices
- Sheets with no order
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2. Bilayers
23. Which lipid type serves as precursors to hormones?
- Fats
- Carbohydrates
- Steroids
- Proteins
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3. Steroids
24. What does it mean that lipids are "not true polymers"?
- They are inorganic
- They don’t contain carbon
- They are not made of repeating monomers
- They dissolve in water
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3. They are not made of repeating monomers
25. Which property allows lipids to serve as long-term energy storage?
- High water content
- Dense molecular weight
- Many C-H bonds storing energy
- Fast breakdown by enzymes
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3. Many C-H bonds storing energy
26. Why are lipids insoluble in water?
- They have polar side chains
- They contain charged groups
- They are mostly nonpolar hydrocarbons
- They dissolve too quickly
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3. They are mostly nonpolar hydrocarbons
27. How does the structure of saturated and unsaturated fats affect their physical properties?
- Saturated fats are liquid due to branching
- Unsaturated fats pack tightly due to double bonds
- Double bonds in unsaturated fats create kinks, making them liquid
- Saturated fats have double bonds that break easily
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3. Double bonds in unsaturated fats create kinks, making them liquid
28. What makes phospholipids amphipathic?
- They have only hydrophobic regions
- They contain both hydrophilic and hydrophobic parts
- They form steroids
- They are fully soluble in water
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2. They contain both hydrophilic and hydrophobic parts
29. Which part of the phospholipid interacts with the aqueous environment inside and outside the cell?
- Fatty acid tails
- Hydrocarbon center
- Phosphate head group
- Glycerol backbone
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3. Phosphate head group
30. What effect do trans fats have on the human body?
- Lower LDL and increase HDL
- Raise LDL and lower HDL
- Improve membrane fluidity
- Aid in digestion of carbohydrates
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2. Raise LDL and lower HDL
31. How do steroid hormones differ from peptide hormones in transport?
- They dissolve freely in blood
- They are stored in vesicles
- They pass through membranes due to lipid solubility
- They are made of amino acids
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3. They pass through membranes due to lipid solubility
32. Which lipid helps maintain fluidity in animal cell membranes?
- Cholesterol
- Phospholipid
- Triglyceride
- Estrogen
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1. Cholesterol
33. What determines whether a fatty acid is classified as omega-3?
- The number of double bonds
- The location of the first double bond from the methyl end
- The presence of a phosphate group
- Its saturation level
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2. The location of the first double bond from the methyl end
34. How do phospholipids behave in water?
- They dissolve completely
- They form single-layer micelles
- They self-assemble into bilayers
- They form ionic crystals
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3. They self-assemble into bilayers
35. What property of lipids makes them suitable for long-term energy storage?
- They have polar bonds
- They can form polymers
- They contain many high-energy C-H bonds
- They are easily digested
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3. They contain many high-energy C-H bonds
36. Why are lipids not considered true polymers?
Show Answer
Because they are not made of repeating monomer units; instead, they are assembled from smaller components like glycerol and fatty acids.
37. Describe the structure of a fat molecule.
Show Answer
A fat molecule consists of one glycerol molecule joined to three fatty acid chains via ester linkages, forming a triglyceride.
38. How does the presence of double bonds affect the structure and fluidity of unsaturated fats?
Show Answer
Double bonds create kinks in the hydrocarbon chains, preventing tight packing and making the fat more fluid at room temperature.
39. What distinguishes a saturated fat from an unsaturated fat?
Show Answer
Saturated fats have no double bonds between carbon atoms and are straight; unsaturated fats have one or more double bonds, causing bends in the chain.
40. Explain why phospholipids are essential for cell membrane structure.
Show Answer
Phospholipids form bilayers with hydrophilic heads facing outward and hydrophobic tails inward, creating a selective barrier for cells.
41. What makes phospholipids amphipathic molecules?
Show Answer
They contain both hydrophilic (phosphate head) and hydrophobic (fatty acid tails) regions.
42. How does cholesterol influence membrane fluidity?
Show Answer
Cholesterol stabilizes membranes by preventing them from becoming too fluid at high temperatures or too rigid at low temperatures.
43. Describe the basic structure shared by all steroids.
Show Answer
All steroids share a carbon skeleton made of four fused rings (three six-membered and one five-membered).
44. What role do steroids play in animal physiology?
Show Answer
Steroids act as hormones, such as testosterone and estrogen, regulating various physiological processes including metabolism and reproduction.
45. How do trans fats form, and why are they considered harmful?
Show Answer
They are formed by hydrogenating unsaturated fats, which can raise LDL cholesterol and increase risk of heart disease.
46. What is the energy storage advantage of fats over carbohydrates?
Show Answer
Fats store more than twice the energy per gram due to their many nonpolar C-H bonds, making them efficient for long-term storage.
47. Explain how the structure of phospholipids contributes to membrane self-assembly in water.
Show Answer
Their amphipathic nature causes them to spontaneously arrange into bilayers in aqueous environments, shielding hydrophobic tails from water.
48. What structural characteristic of unsaturated fats prevents them from solidifying at room temperature?
Show Answer
They have cis-double bonds that introduce kinks, preventing close packing of molecules.
49. How do omega-3 fatty acids benefit human health?
Show Answer
They reduce inflammation, lower blood pressure, and may help prevent heart disease.
50. Why are lipids crucial for biological membranes and energy metabolism?
Show Answer
Lipids form the structural basis of membranes and store high amounts of energy for cellular processes.