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z biology: module 2 > 3.5 Lipids > Flashcards

3.5 Lipids Flashcards

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1
Q

What state are fats, normally? (1 mark)

A

Solid

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2
Q

What state are oils, normally? (1 mark)

A

Liquid

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3
Q

Are lipids polar? (1 mark)

A

No.

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4
Q

Why are lipids non-polar, what does this mean for its interaction with water? (2 marks)

A

The electrons in the outer orbitals are more evenly distributed.
This means lipids are not soluble in water.

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5
Q

What is a macromolecule? (1 mark)

A

Large, complex molecules built from repeating units (monomers).

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6
Q

What is a triglyceride made up of? (1 mark)

A

One glycerol molecule bonded to three fatty acids.

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7
Q

What type of molecule is glycerol, what does this mean? (1 mark)

A

An alcohol, it has an OH group(s) (in this case 3)

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8
Q

What type of molecule is a fatty acid, what does this mean? (1 mark)

A

Carboxylic acid, contains a COOH group

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9
Q

How do the bonds between fatty acids and glycerol form? (1 mark)

A

Condensation reaction (or esterification), interaction between the hydroxyl groups.

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10
Q

What are the bonds between fatty acids and glycerol called? (1 mark)

A

Ester bonds

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11
Q

What is a fatty acid with double bonds between the carbons called? (1 mark)

A

Unsaturated

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12
Q

What is a saturated fatty acid? (1 mark)

A

A fatty acid with only single bonds between the carbons.

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13
Q

What is a fatty acid with one double bond linking two carbons called? (1 mark)

A

Monounsaturated

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14
Q

What is a fatty acid with two or more double bonds linking carbons called? (1 mark)

A

Polyunsaturated

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15
Q

Why are unsaturated fatty acids oils? (3 marks)

A

The double bonds cause the molecule to bend, so they do cannot pack as closely together, making them liquid at room temperature.

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16
Q

What elements do phospholipids contain? (2 marks)

A

Carbon, oxygen, hydrogen, phosphorus

17
Q

What components does a phospholipid contain? (2 marks)

A

A glycerol, two fatty acids, and a phosphate group.

17
Q

Are fatty acids polar? (1 mark)

A

No, they are non-polar

17
Q

Where are inorganic phosphate ions found? (1 mark)

A

In the cytoplasm of every cell.

18
Q

Is a phosphate group hydrophobic or hydrophilic? (1 mark)

A

Hydrophilic

19
Q

Phospholipids either form a layer on the surface of water or form bilayer structures in water, explain why this happens. (4 marks)

A

The ‘heads’ of the phospholipids are hydrophilic.
The ‘tails’ of the phospholipids are hydrophobic.
This means on the surface of water, the ‘heads’ are pointing downward into the water and the tails avoid it.
It also means, they form bilayers when in water, where there are two layers of phospholipids, so the tails can point inwards away from the water.

20
Q

Why is the dual hydrophobic/hydrophilic structure of phospholipids so important? (1 mark)

A

They form cell membranes, separating environments.

21
Q

What type of molecule is a sterol? (1 mark)

A

An alcohol

22
Q

Describe the structure of a sterol. (2 marks)

A

They are a four carbon ring structure, with an OH group at one end and a hydrocarbon chain at the other end.

23
Q

Explain why steroid alcohols (sterols) have dual hydrophobic/hydrophilic characteristics. (1 mark)

A

Only the OH group is polar (hydrophilic), the rest of the molecule is non-polar (hydrophobic).

24
Q

Give an example of a sterol. (1 mark)

A

Cholesterol

25
Q

What is the role of cholesterol in cell membranes? (2 marks)

A

To provide stability and regulate the fluidity of them.

26
Q

How does cholesterol regulate the fluidity of cell membranes? (1 mark)

A

Keeps them fluid at low temperatures and prevents them from becoming too fluid at high temperatures.

27
Q

State three biological roles of lipids. (3 marks)

A

Membrane formation
Hormone production
Electrical insulation (necessary for impulse transmission)
Waterproofing (e.g. bird’s feathers/plant’s leaves)

28
Q

State three functions of lipids stored under the skin and around vital organs. (3 marks)

A

Thermal insulation
Cushioning to protect vital organs
Buoyancy (for aquatic animals like whales)

29
Q

What is the test for lipids called? (1 mar)

A

Emulsion test

30
Q

Describe how the test for lipids is conducted. (2 marks)

A
  1. The sample is mixed with ethanol
  2. Then mixed with water and shaken
31
Q

What is the positive result for the test for lipids? (1 mark)

A

A white emulsion/ cloudy

z biology: module 2 (28 decks)

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