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A-level Biology - 3.1.1 Biological Molecules Part 3

Biology25 CardsCreated about 2 months ago

This deck covers the roles, structures, and properties of lipids, including triglycerides and phospholipids, as well as their functions in biological systems.

Elaborate on lipids' role in plasma membranes

Phospholipids contribute to flexibility of membranes & transfer of lipid-soluble substances across them
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Key Terms

Term
Definition
Elaborate on lipids' role in plasma membranes
Phospholipids contribute to flexibility of membranes & transfer of lipid-soluble substances across them
Elaborate on lipids' role in protection
Stored around delicate organs
Elaborate on lipids' role in insulation
Fats = slow conductors of heat = help retain body heat
Elaborate on lipids' role in waterproofing
Lipids are insoluble in water ∴ waterproof material In plants & insects: waxy cuticle to conserve water In mammals: produce oil secretion from sebaceo...

Describe the structure of a triglyceride

One molecule of glycerol with 3 fatty acids attached to it

What do fatty acids have?
Have long 'tails' made from hydrocarbons

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TermDefinition
Elaborate on lipids' role in plasma membranes
Phospholipids contribute to flexibility of membranes & transfer of lipid-soluble substances across them
Elaborate on lipids' role in protection
Stored around delicate organs
Elaborate on lipids' role in insulation
Fats = slow conductors of heat = help retain body heat
Elaborate on lipids' role in waterproofing
Lipids are insoluble in water ∴ waterproof material In plants & insects: waxy cuticle to conserve water In mammals: produce oil secretion from sebaceous glands in skin

Describe the structure of a triglyceride

One molecule of glycerol with 3 fatty acids attached to it

What do fatty acids have?
Have long 'tails' made from hydrocarbons
Properties in triglycerides differ due to variations in ___ __
fatty acids
Name 2 kinds of fatty acids
Saturated Unsaturated

Draw a saturated fatty acid

Draw a unsaturated fatty acid

What does the double carbon bond causes the chain to do?
Causes it to kink
Define mono-unsaturated
Single double bond
Define polyunsaturated
More than one double bond
Describe how a triglycerides forms
A fatty acid joins to a glycerol molecule When ester bond is formed = molecule of water is released - condensation reaction Process happens twice more = form a triglyceride
Why are triglycerides good energy storage molecules?
Long hydrocarbon tails of fatty acids contains lots of chemical energy = lot of energy released when they're broken down ∴ contain twice as much energy per gram as carbohydrates

Describe how the structure of a triglyceride makes them insouble

Triglycerides clump together as insoluble droplets in cells ∵ fatty acid tails = hydrophobic = tails face inwards = shielding themselves from water with their glycerol heads

Where are phospholipids found?
In cell membranes

Describe the structure of a phospholipid

One molecule of glycerol with 2 fatty acids + a phosphate group attached to it

Draw glycerol

Draw the basic structure of a fatty acid

Draw a triglyceride

Phospholipids:
Phosphate group (the 'head') is _______ hydrophilic (attracts water)

hydrophilic (attracts water)

Phospholipids: Fatty acid tails is _______

hydrophobic (repel water)

Describe how phospholipids' structures relates to its function

Phospholipids make up the bilayer of cell membranes Heads are hydrophilic & tails are hydrophobic = form double layer with their heads facing out towards the water on either side Centre of bilayer = hydrophobic = water-soluble substances can't easily pass through Membrane acts as a barrier to those substances

Describe the emulison test for lipids

Shake test substance with ethanol for few minutes so that it dissolves & then pour solution into water Any lipid will show up as a milky emulsion More lipid there is = more noticeable milky colour will be