Lesson 3.1.3.2
3.1.3.2 Properties of lipids and the emulsion test: AQA Biology, Unit 1
20 questions
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Lesson 3.1.3.2, Properties of lipids and the emulsion test: 20 multiple choice questions for the AQA Biology (7402), Unit 1: Biological molecules, written with Revision Ninja.
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The 20 questions
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Which two liquids are added in sequence during the emulsion test for lipids?
- Ethanol then iodine
- Water then ethanol
- Ethanol then water
- Biuret then water
-
What observation indicates a positive result in the emulsion test for lipids?
- Milky white emulsion
- Blue-black solution
- Lilac purple solution
- Brick red precipitate
-
What is the role of ethanol in the emulsion test for lipids?
- To hydrolyse lipids
- To dissolve lipids
- To stain lipids
- To oxidise lipids
-
Which property of triglycerides makes them suitable as a waterproofing layer in animals?
- Insoluble in water
- Soluble in ethanol
- High specific heat
- Low density
-
Why do triglycerides release more energy per gram than carbohydrates when oxidised?
- More oxygen atoms
- More carbon-hydrogen bonds
- Higher water solubility
- More ester bonds
-
What main structure in cells is formed by phospholipids?
- Storage granules
- Cell membranes
- Cell walls
- Ribosomes
-
Which property of triglycerides makes them effective thermal insulators in animals?
- High heat capacity
- High solubility
- High density
- Low thermal conductivity
-
A sample remains clear after shaking with ethanol and water. What does this indicate?
- Reducing sugar present
- No lipid present
- Protein present
- Lipid present
-
What is the control in an emulsion test used to show?
- Water stays clear
- Lipids dissolve
- Proteins precipitate
- Ethanol is pure
-
Why does plant oil separate from water without dissolving when shaken?
- Oil is hydrophobic
- Oil is hydrophilic
- Oil is polar
- Oil is dense
-
Why does a cloudy white emulsion form when water is added to ethanol containing lipid?
- Lipid dissolves completely
- Ester bonds break
- Droplets scatter light
- Ethanol evaporates rapidly
-
A fat releases about 37 kJ of energy per gram on complete oxidation. How much energy is released from 25 g of this fat?
- 925 kJ
- 740 kJ
- 370 kJ
- 1480 kJ
-
What term describes a phospholipid molecule having both hydrophilic and hydrophobic regions?
- Amphipathic
- Non-polar
- Hydrophobic
- Hydrophilic
-
Which property of fat increases buoyancy in aquatic animals?
- High conductivity
- Higher density
- High viscosity
- Lower density
-
Why must apparatus be dry before performing an emulsion test?
- Increases lipid solubility
- Stops ethanol evaporating
- Prevents premature emulsion
- Prevents lipid oxidation
-
Why does a positive emulsion test not prove a sample is pure lipid?
- Test detects carbohydrates
- Test measures concentration
- Test is quantitative
- Test is qualitative
-
Why do lipids dissolve easily in ethanol but not in water?
- Lipids are polar
- Water is non-polar
- Ethanol is ionic
- Ethanol is non-polar
-
Why do lipids produce more metabolic water than carbohydrates during aerobic respiration?
- More hydrogen atoms
- More nitrogen atoms
- More oxygen atoms
- Fewer carbon atoms
-
Which variable must be kept constant to ensure a valid emulsion test comparison?
- Volume of ethanol
- pH of solution
- Temperature of water
- Concentration of enzyme
-
What prevents water-soluble ions from easily crossing a phospholipid bilayer?
- Glycoprotein receptors
- Hydrophobic centre
- Hydrophilic heads
- Channel proteins
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