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Bio exam questions > lipids > Flashcards

lipids Flashcards

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Biology 101 flashcards
1
Q

describe the test for lipids (2)

A
  • add ethanol and shake
  • add water and shake
  • forms a milky emulsion
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2
Q

why are lipids not polymers

A

they don’t have repeating monomer units

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3
Q

describe the structure of a triglyceride molecule (1)

A
  • glycerol molecule
  • 3 fatty acid chains
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4
Q

what is an ester bond

A

a covalent bond formed between the OH of a glycerol molecule and the OH of a fatty acid in a condensation reaction

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5
Q

how many ester bonds are in a triglyceride

A

3

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6
Q

are fats solid or liquid at room temperature

A

solid e.g. butter

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7
Q

are oils solid or liquid at room temperature

A

liquid e.g. olive oil

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8
Q

what is a saturated fatty acid

A

fatty acid chain with no double carbon bonds (doesn’t include the carboxyl group)

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9
Q

define monoUNsaturated

A

fatty acid with one double carbon bond

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10
Q

define polyUNsaturated

A

fatty acid with multiple double carbon bonds

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11
Q

why are unsaturated triglycerides liquids at room temperature?

A
  • they contain double carbon bonds
  • double carbon bonds cause fatty acid tails to bend
  • triglyceride molecules are further apart
  • intermolecular force of attraction decreases, molecule is less compact
  • less energy to overcome so it is liquid at room temperature
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12
Q

why are saturated triglycerides solid at room temperature?

A
  • no double carbon bonds
  • fatty acid tails don’t bend
  • less space between molecules so stronger intermolecular forces of attraction
  • more energy to overcome so solid at room temperature
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13
Q

why do triglycerides release lots of energy

A

there are lots of carbon-hydrogen bonds, these release energy when they break

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14
Q

why are triglycerides a good water source

A

they release water when they are broken down in respiration

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15
Q

are triglycerides polar or non-polar?

A

non-polar so they are insoluble
- don’t affect osmosis in cells

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16
Q

give 3 uses of lipids

A
  • aquatic animals produce oil to waterproof their fur
  • thermal & electrical insulation
  • buoyancy
17
Q

how are lipids like proteins?

A

they have a constant region (glycerol) and a variable region (fatty acid)

18
Q

Describe the structure of a phospholipid (1)

A
  • glycerol
  • 2 fatty acids
  • phosphate group
19
Q

how does a phosphate group join a glycerol molecule

A
  • condensation reaction
  • between OH on glycerol and OH on phosphoric acid
  • creates a phosphate ester bond
20
Q

is the phospholipid head hydrophobic or hydrophilic?

A

hydrophilic
- has a negative charge
- attracts H+ in water

21
Q

what are micelles

A

circular formations that are made up of phospholipid tails

22
Q

describe phospholipid bilayer

A
  • hydrophilic heads face outwards towards the water
  • hydrophobic tails face inwards away from water
23
Q

how are membranes fluid

A

because phospholipids can move around each other- allows the cell to change shape

24
Q

give 2 roles of the bilayer

A
  • controls what leaves/ enters the cell
  • electrical insulation- does not let ions or water in as the fatty acid tails are hydrophobic and non-polar
25
Q

give 5 functions of lipids

A
  • phospholipids provide flexibility to membranes

-thermal insulation- slow conductors of heat and retain body heat

-electrical insulation- in myelin sheath around nerve cells

-protection- fat around organs such as kidney

-insoluble- used for waterproofing, waxy lipid cuticle to prevent water loss

-energy source- when oxidised they release energy

26
Q

describe 2 features which make lipids suitable for their function

A
  • lots of energy stored in a small mass- good for animals as they can reduce the mass they carry around

-lots of energy stored in C-H bonds

  • they are large and non-polar so insoluble and dont affect water potential so no bursting

-release water when oxidised so act as a water source

27
Q

what is the difference between a phosphate molecule and a fatty acid molecule

A

phosphate is hydroPHILIC and attracts water

fatty acid is hydroPHOBIC and repels water

28
Q

describe the structure of a phospholipid

A
  • hydrophilic head- attracts water

-hydrophobic tail- repels water

29
Q

describe a control that could be used during a test for lipids

A
  • instead of adding ethanol and water to the sample, replace the sample with water
  • solution should stay clear
30
Q

list 2 differences between a triglyceride molecule and a phospholipid molecule (2)

A
  1. triglyceride has 3 fatty acids
  2. phospholipid has 2 fatty acids, 1 phosphate group

or

  1. triglyceride is non polar
  2. phospholipid is polar
31
Q

explain why phospholipids form a bilayer but triglycerides don’t (3)

A
  • phospholipids have both hydrophobic and hydrophilic regions
  • triglycerides are just hydrophobic- non-polar
  • phospholipid heads attract to water, fatty acid tails repel water
32
Q

compare and contrast the structure and properties of triglycerides and phospholipids (5)

A
  • both have glycerol
  • both have ester bonds
  • triglycerides have 3 fatty acids, phospholipids have 2 fatty acids and a phosphate group
  • both are insoluble in water
  • triglycerides are non-polar and phospholipids have hydrophilic and hydrophobic regions
  • both have C,H,O but phospholipids also have P

Bio exam questions (27 decks)

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