L3 - Lipids Flashcards

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1
Q

What are the 2 groups of lipids?

A

Triglycerides and phospholipids

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2
Q

How are triglycerides formed?

A

By the condensation of one molecule of glycerol and three molecules of fatty acid

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3
Q

What forms an ester bond?

A

A condensation reaction between glycerol and a fatty acid (RCOOH)

One water molecules is released per ester bond

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4
Q

What 2 forms can the R-group of a fatty acid be?

A

saturated or unsaturated

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5
Q

What happens in phospholipids?

A

In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group

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6
Q

What are triglycerides mainly used as?

A

As energy store molecules

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7
Q

What type of bond forms beteren glycerol and the fatty acid chains?

A

Ester bonds

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8
Q

How many molecules of water are released per 1 triglyceride bond?

A

3 molecules of water

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9
Q

What is the structure of fatty acids?

A

Long ‘tails’ made of a chain of hydrocarbon with 4-36 carbon atoms
(Most have 12-18)

Glycerol links to the central carbon atom on fatty acids

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10
Q

What are triglycerides function in energy release?

A

Chemical energy is stored in the fatty acid hydrocarbon tails

So lots of energy is released when triglycerides are broken down

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11
Q

How does the amount of energy contained in lipids compare to carbs?

A

Carbs contain half the amount of energy per gram lipids do

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12
Q

Why do triglycerides repel water?

A

They are insoluble in water because the fatty acid tails are hydrophobic

Meaning the cell’s water potential isn’t affected by triglycerides

If they didn’t repel water, water would enter the cell through osmosis causing the cell to swell up

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13
Q

Why do the insoluble triglycerides crowd together at droplets in cells?

A

Because the hydrophobic fatty acid tails face inwards

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14
Q

What do phospholipids do?

A

Form a bilayer which controls what comes in and out of the cell

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15
Q

What is the structure of phospholipids?

A

Composed of fatty acid chains attached to glycerol

Has 2 hydrophobic fatty acid tails and 1 hydrophilic phosphate group
Making it an amphipathic molecule

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16
Q

What do the hydrophobic tails of phospholipids do?

A

They can’t interact with water

In membranes, they face inwards in the bilayer

This means water-soluble substances can’t easily pass through the membrane

17
Q

What does the hydrophilic head of phospholipids do?

A

It can interact with water

In membranes, it faces outwards

18
Q

What is the structure of saturated fatty acids?

A

Carbon atoms have single bonds in between them in the hydrocarbon chain

The number of hydrogen atoms attached to the carbon skeleton is maximised

19
Q

What are saturated fatty acids like at room temperature?

What are they also linked to?

A

Solid at room temp and usually of animal origin

Linked to increased risk of cardiovascular disease in humans

20
Q

What foods contain a high proportion of saturated fat?

5

A
Cream
Cheese
Butter
Other whole dairy products
Fatty meats
21
Q

What is the structure of unsaturated fatty acids?

A

Have one or more double bonds between carbon atoms in the hydrocarbon chain

22
Q

What is an example of an unsaturated fat?

A

Cooking oils

23
Q

What are unsaturated fats like at room temperature?

A

Double bonds ‘kink’ the carbon chain so unsaturated fats can’t pack tightly together

Causing them to remain liquid at room temperature

24
Q

Is the phosphate head of phospholipids positively or negatively charged?

A

Negatively charged

25
Q

What are the 3 main functions that lipids serve in plants and/or animals?

A

Storage of energy

A structural component of hormones

As signalling molecules

26
Q

How do phospholipids contribute to cell membrane structure?

A

Phospholipids orient their heads towards the polar molecules and tails in the interior of the membrane, forming a bilayer