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Biology Topic 1A > Lipids > Flashcards

Lipids Flashcards

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1
Q

What are lipids?

A

a mixed group of hydrophobic compounds composed of the elements carbon, hydrogen and oxygen

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2
Q

How are triglycerides formed?

A

the condensation of one molecule of glycerol and 3 molecules of fatty acid

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3
Q

What kind of bond is formed by rection between glycerol and fatty acid?

A

ester bond

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4
Q

What is a saturated fatty acid?

A

the hydrocarbon chain has only single bonds between carbons

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5
Q

What is a unsaturated fatty acid?

A

hydrocarbon chain has at least one double bond between carbons

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6
Q

What are the properties of triglycerides?
How does structure relate to function?

A
  • energy storage molecule, insulation, protection in fatty tissue under skin or surrounding organs
  • the long hydrocarbon tails of the fatty acids contain lots of chemical energy so lots of energy is released when they’re broken down and due to large energy storing carbon-hydrogen bonds compared to number of carbon atoms
  • insoluble in water so they don’t affect the water potential so the cell cant swell by osmosis
  • triglycerides bundle together as insoluble droplets - hydrophobic fatty acid tails inwards
  • containing saturated fatty acids = high melting points - warm blooded animals - solid at room temp
  • containing unsaturated fatty acids = low melting points = cold blooded animals - liquid at room temp
  • lipids have a low mass = can be stored without increasing the mass and preventing movement
  • act as a metabolic water source = can release water if oxidised
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7
Q

How do triglycerides differ to phospholipids?

A

same structure but phospholipids have a phosphate group in place of a fatty acid chain

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8
Q

What are the properties of phospholipids?

A
  • phosphate group is hydrophilic
  • fatty acid tails hydrophobic
  • when mixed with water phospholipids form droplet spheres with hydrophilic heads facing water and hydrophobic tails facing eachother (a micelle)
  • form cell membrane bilayer = controls what enters and leaves - hydrophilic heads facing water hydrophobic tails facing inwards so water soluble substances cant easily pass through (membrane acts as a barrier)
  • more unsaturated fatty acid tails = fluid membrane
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9
Q

What is the test for lipids?

A
  • emulsion test
  • add sample and ethanol to test tube and shake for about one minute to dissolve
  • add water and shake gently
  • any lipid will show up as a milky emulsion
  • more lipid = more noticeable milky colour
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Biology Topic 1A (5 decks)

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