Which two major groups of biological lipids are required in the AQA specification?
Triglycerides and phospholipids
Both are important biological lipids but have different structures and functions in organisms.
What type of molecule combines with fatty acids to form triglycerides?
Glycerol
Glycerol is a three-carbon alcohol that forms the backbone of triglycerides.
How many fatty acid molecules are present in one triglyceride molecule?
Three
Each fatty acid attaches to glycerol via an ester bond.
Fill in the blank:
A triglyceride forms when one glycerol molecule reacts with three _______ molecules.
Fatty acid
This occurs through condensation reactions.
What type of chemical bond forms between glycerol and fatty acids in triglycerides?
Ester bond
Each ester bond forms during a condensation reaction that releases water.
Fill in the blank:
An ester bond forms between glycerol and a fatty acid during a _______ reaction.
Condensation
Water is released when the ester bond forms.
What term describes a fatty acid that contains no carbon–carbon double bonds?
Saturated
Saturated fatty acids contain the maximum number of hydrogen atoms.
What term describes a fatty acid that contains one or more carbon–carbon double bonds?
Unsaturated
Double bonds introduce bends in the fatty acid chain.
True or False:
Unsaturated fatty acids contain at least one carbon–carbon double bond.
True
These double bonds affect the shape and physical properties of the lipid.
In phospholipids, what group replaces one of the fatty acids found in a triglyceride?
Phosphate group
This substitution creates a molecule with different chemical properties.
Which lipid type is a major component of cell membranes?
Phospholipids
Their structure allows them to form bilayers in aqueous environments.
Which lipid type is primarily used for long-term energy storage in organisms?
Triglycerides
They have a high energy content and are stored in adipose tissue in animals.
Why are triglycerides good energy storage molecules?
They have high energy content.
They contain many C–H bonds and are insoluble, so they do not affect water potential.
Why are phospholipids suited to forming cell membranes?
They are amphipathic.
They have a hydrophilic phosphate head and hydrophobic fatty acid tails.
What qualitative test is used to detect lipids in a food sample?
Emulsion test
The test uses ethanol and water to detect lipids.
Fill in the blank:
A positive emulsion test for lipids produces a _______ white emulsion.
Milky
Lipids dissolve in ethanol and form a cloudy emulsion when water is added.
What reagent is first added to a sample during the emulsion test for lipids?
Ethanol
The mixture is shaken and then water is added to observe the emulsion.
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3.1.1 Monomers & Polymers9
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3.1.2 Carbohydrates22
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3.1.3 Lipids17
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3.1.4 Proteins39
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3.1.5 Nucleic Acids32
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3.1.6 ATP11
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3.1.7 Water11
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3.1.8 Inorganic ions8
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3.2.1 Cell structure52
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3.2.2 Cell division20
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3.2.3 Transport across cell membranes20
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3.2.4 Cell recognition & the immune system36
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3.3.1 Surface area to volume ratio13
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3.3.2 Gas exchange24
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3.3.3 Digestion & absorption16
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3.3.4 Mass transport39
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3.4.1 DNA, genes & chromosomes13
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3.4.2 DNA & protein synthesis14
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3.4.3 Genetic diversity & meiosis14
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3.4.4 Genetic diversity & adaptation20
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3.4.5 Species & taxonomy20
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3.4.6 Biodiversity within a community12
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3.4.7 Investigating diversity12
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3.5.1 Photosynthesis23
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3.5.2 Respiration17
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3.5.3 Energy & ecosystems20
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3.5.4 Nutrient cycles15
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3.6.1 Stimuli & Response62
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3.6.2 Nervous coordination53
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3.6.3 Skeletal muscles14
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3.6.4 Homeostasis57
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3.7.1 Inheritance12
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3.7.2 Populations15
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3.7.3 Evolution may lead to speciation22
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3.7.4 Populations in ecosystems24
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3.8.1 Gene Mutations and Protein Structure14
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3.8.2 Control of Gene Expression44
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3.8.3 Applications of Genome Projects10
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3.8.4 Gene Technologies and Their Applications46
