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LQB186 > Lipids and membranes > Flashcards

Lipids and membranes Flashcards

1
Q

What are triacylglycerols formed from?

A

Esters of glycerol and fatty acids

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2
Q

What shows a double bond in a hydrocarbon zig-zag line?

A

Two short parallel lines

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3
Q

What are the functions of fat in the body? There are three possible answers

A
  • Long term food storage in adipose cells
  • Cushioning in vital organs
  • Insulation
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4
Q

What is the function of glycolipids being in the outer leaflets with carbohydrate portions exposed on the cell surface?

A

These have important roles in cell identity/blood group identification etc

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5
Q

Cholesterols are not found in which types of organisms?

A

Bacteria and plants

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6
Q

What three elements are in basic lipids?

A

Carbon, hydrogen, and some oxygen

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7
Q

Where is the first double bond in omega-6?

A

After the sixth carbon from the methyl group

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8
Q

How is a hydrocarbon chain often abbreviated in structural drawings?

A

The hydrocarbon chain is often represented by a zig-zag line

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9
Q

True or false: large polar and charged molecules can rapidly cross the plasma membrane

A

False

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10
Q

Phospholipids consist of a ____ ____ attached to a glycerol or serine, attached to a phosphate group, attached to a polar head group

A

Fatty acid

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11
Q

What is the common trait of lipids?

A

They are hydrophobic

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12
Q

Do plants contain cholesterols?

A

No, there are no cholesterols in plants

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13
Q

Which type of fatty acids are inflexible, saturated on unsaturated?

A

Saturated

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14
Q

Where is cholesterol found in the plasma membrane?

A

In both inner and outer leaflets

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15
Q

What is the purpose of the cholesterol raft?

A

The raft can secure proteins in membrane

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16
Q

Are all fatty acids with identical functional groups the same?

A

No, the length of the hydrocarbon chain and presence/absence of double bonds means there could be different substances despite the same functional groups

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17
Q

Are lipids true polyers?

A

No

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18
Q

What is the name for unsaturated fats that are artifically converted to saturated fats through addition of hydrogen?

A

Hydrogenated fats

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19
Q

Why can’t unsaturated fatty acids be packed together?

A

The double bonds cause bending in their structures which prevents packing

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20
Q

What substances combine to form waxes?

A

Esters of fatty acids and long chain alcohols

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21
Q

Which type of fatty acids can be packed together?

A

Saturated fatty acids

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22
Q

What type of fats are solid at room temperature?

A

Saturated fats

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23
Q

Where are glycolipids found in the cell?

A

Exclusively in the outer leaflets with carbohydrate portions exposed on the cell surface

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24
Q

What property of lipids is important for their role as barriers for cells?

A

They are hydrophobic

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25
Q

A faatty acid with two H atoms attached to each C on the carbon chain is what type of fatty acid?

A

Saturated fatty acid

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26
Q

How much of the plasma membrane is comprised of phospholipids?

A

Approximately 50%

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27
Q

What are carotenoids?

A

Accessory pigments for light harvesting, prevention of photo-oxidative damage, and pigmentation attracting insects

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28
Q

What reaction synthesises fats?

A

Dehydration reactions

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29
Q

What is the common lay term for unsaturated fats?

A

Oils

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30
Q

Fatty acids are comprised of a ____ end, a ____ chain, and an ____ group

A

Methyl; hydrocarbon, acid

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31
Q

A methyl end, hydrocarbon chain, and an acid end is what kind of molecule?

A

Fatty acid

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32
Q

Fats are assembled from which two molecules?

A

Glycerol and fatty acids

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33
Q

Fats are synthesised through what kind of reaction?

A

Dehydration reactions

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34
Q

A fatty acid with the maximum amount of hydrogens attached is what type of fatty acid?

A

Saturated

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35
Q

Phospholipids consist of a fatty acid attached to a glycerol or serine, attached to a phosphate group, attached to a ____ ____ group

A

Polar head

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36
Q

Are unsaturated fats flexible or inflexible?

A

Flexible

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37
Q

At what tonicity is there no net movement of water?

A

Isotonic

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38
Q

The fatty acid is what component of a phospholipid?

A

The hydrophobic tail

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39
Q

A three carbon chain structure with OH groups on one side and H on the other forms what molecule?

A

Glycerol

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40
Q

Fats, phospholipids, steroids, waxes, and pigments are all examples of what type of organic molecule?

A

Lipids

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41
Q

What is the name of an unsaturated fat where the hydrogen atoms on either side of the double bond are on opposite sides of the carbon chain?

A

Trans fat

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42
Q

What is a poly-unsaturated fatty acid?

A

An unsaturated fatty acid with more than one double bond in the carbon chain

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43
Q

What is hypotonic?

A

Lower concentration of solutes outside the membrane; cell will gain water

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44
Q

What is the name of the functional group in which a carbon on an end of a carbon chain has one double bonded oxygen and a single bonded OH

A

Carboxylic acid

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45
Q

What is an unsaturated fatty acid?

A

A fatty acid with a double bond between two carbons in the chain

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46
Q

Where is the first double bond in omega-3?

A

After the third carbon from the methyl group

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47
Q

When identifying double bond location for naming fatty acids, where does the count along the carbon chain begin?

A

The carbons are counted beginning from the methyl group

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48
Q

Glycerol and fatty acids combine to form what?

A

Fats

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49
Q

What is tonicity?

A

The ability of a solution that surrounds a cell to cause the cell to gain or lose water

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50
Q

How are proteins directed to their appropriate place in membranes?

A

Fatty acids acting as targeting molecules

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51
Q

What is the role of cholesterol in cell membranes?

A

Adds structural stability and reduces permeability to some molecules which allows the membranes to function as barriers

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52
Q

Hydrophobic molecules are ____ soluble

A

Lipid

53
Q

Movement of a substance across a semipermeable membrane without using energy is what kind of transport?

A

Passive transport

54
Q

What are hydrogenated fats?

A

Unsaturated fats that have been artifically converted to saturated fats by adding hydrogen

55
Q

At what tonicity will the cell gain water?

A

Hypotonic

56
Q

What is the name of an unsaturated fat where the hydrogen atoms on either side of the double bond are on the same side of the carbon chain?

A

Cis fat

57
Q

Describe the structure of a glycerol molecule

A

A three carbon chain structure with OH groups on one side and H on the other

58
Q

Which can pass through the plasma membrane rapidly, hydrophilic or hydrophobic molecules?

A

Hydrophobic molecules

59
Q

How do phospholipids orient themselves in water?

A

So the hydrophilic head is closest to the water and the hydrophobic tail is as far from the water as possible

60
Q

How do fatty acids function as targeting molecules in a cell?

A

Fatty acids are attached to many proteins, and through this direct proteins to their appropriate place in membranes

61
Q

What is at each point in the zig-zag line in chemical structures?

A

A carbon attached to two hydrogen atoms

62
Q

Phospholipids consist of a fatty acid attached to a ____ or ____, attached to a phosphate group, attached to a polar head group

A

Glycerol; serine

63
Q

How do fatty acids act as messenger molecules?

A

Products of fatty acids function as hormones and intracellular messenger molecules (messengers)

64
Q

Movement of water from a solution of low concentration through a semipermeable membrane to a solution of high concentration is what kind of transport?

A

Osmosis

65
Q

What is osmosis?

A

Movement of water from a solution of low concentration through a semipermeable membrane to a solution of high concentration

66
Q

What determines how the hydrocarbon chain bends in unsaturated fats?

A

The orientation of the H atoms on either side of the double bond

67
Q

What is a mono-unsaturated fatty acid?

A

An unsaturated fatty acid with one double bond in the carbon chain

68
Q

Describe the structure of micelle

A

Spherical with a single phospholipid layer - hydrophilic heads on the outer surface and tails pointed inward towards the centre

69
Q

Is cholesterol hydrophilic, amphipathic, or hydrophobic?

A

Amphipathic

70
Q

Describe the structure of liposomes

A

Spherical with a bilayer; one layer with hydrophilic heads on the outer surface and tails pointed inward, the second layer with tails beside those of the first layer and heads lining an aqueous spherical compartment in the centre

71
Q

What controls osmoregulation?

A

The hypothalamus

72
Q

When is osmosis important regarding plasma membranes?

A

When a molecule alone cannot pass through a membrane - rather than the molecules moving across, the water molecules move. This results in an uneven volume of water but an equal concentration of solutes on either side of the membrane

73
Q

Cholesterol confers structural ____

A

Stability

74
Q

What organisms contain carotenoids?

A

Plants, bacteria, and algae. Humans cannot synthesise carotenoids, so any present are obtained through food

75
Q

What is meant by a cholesterol ‘raft’?

A

Cholesterol can move together to form a higher concentration ‘raft’ which can secure proteins in membrane

76
Q

What is a byproduct of fat synthesis?

A

Water

77
Q

Are phospholipids hydrophilic, amphipathic, or hydrophobic?

A

Amphipathic - they have both hydrophilic and hydrophobic parts (the head and tail, respectively)

78
Q

Name two components of cell membranes for which fatty acids are the building blocks

A

Phospholipids and glycolipids

79
Q

What is hypertonic?

A

Higher concentration of solutes inside the membrane; cell will lose water

80
Q

What is the structure of phospholipids?

A

A fatty acid attached to a glycerol or serine, attached to a phosphate group, attached to a polar head group

81
Q

Esters of glycerol and fatty acids form what molecule?

A

Triacylglycerols

82
Q

Can unsaturated fats be packed together?

A

No

83
Q

What are liposomes important for?

A

The separation of one part of a cell from another

84
Q

Describe diffusion

A

The tendency for molecules of a particular substance to spread out evenly into the available space and easily across the membrane to achieve equilibrium

85
Q

A fatty acid with a double bond in the carbon chain is what type of fatty acid?

A

Unsaturated

86
Q

What prevents unsaturated fats being packed together?

A

The double bonds causing bends in their structures

87
Q

Are lipids mostly stationary in the plasma membrane?

A

No, their movement is constant and dynamic

88
Q

What is often drawn as a zig-zag line in chemical structures?

A

A hydrocarbon chain

89
Q

What is the structure of a fatty acid?

A

A methyl end, hydrocarbon chain, and an acid end

90
Q

How are lipids distributed in the plasma membrane?

A

Asymmetrically in inner and outer leaflets of the membrane

91
Q

Describe concentration gradients in relation to diffusion

A

The difference in concentration of a substance from one area to another - substances diffuse down their concentration gradient

92
Q

What phospholipid structure is important for the separation of one part of a cell from another?

A

Liposome

93
Q

What is passive transport?

A

Movement of a substance across a semipermeable membrane without using energy

94
Q

What is determined by the orientation of the H atoms on either side of the double bonded carbons of an unsaturated fat?

A

How the chain bends

95
Q

What is the name of the model used to describe the plasma membrane?

A

Fluid mosaic model

96
Q

Is tonicity a description of the concentration of solutes, or of the water?

A

Concentration of solutes

97
Q

How does synthesis of fats produce water?

A

The OH on the end of the fatty acid and a H from one of the OH groups on the glycerol combine to form H₂O

98
Q

A carbon on the end of a carbon chain with three hydrogen atoms attached is what kind of group?

A

A methyl group

99
Q

Are unsaturated fats fluid or solid at room temperature?

A

Fluid

100
Q

Can essential fatty acids be synthesised by humans?

A

No

101
Q

The methyl group in hydrocarbons is often referred to as the ____

A

Tail

102
Q

Phospholipids consist of a fatty acid attached to a glycerol or serine, attached to a ____ ____, attached to a polar head group

A

Phosphate group

103
Q

At what tonicity will the cell lose water?

A

Hypertonic

104
Q

What is controlled by osmoregulation?

A

Water levels, therefore tonicity

105
Q

How do lipids move through the plasma membrane?

A

Lipids can drift laterally, but rarely ‘flip-flop’ from one leaflet to another

106
Q

Tonicity is controlled by what process?

A

Osmoregulation

107
Q

Which are lipid soluble, hydrophobic or hydrophilic molecules?

A

Hydrophobic

108
Q

What are phospholipid bilayer sheets?

A

Two layers of phospholipids with hydrophilic heads on the outside and hydrophobic tails on the inside

109
Q

Are saturated fatty acids flexible or inflexible?

A

Inflexible

110
Q

A carbon on the end of a carbon chain that has a double bond to an oxygen and a single bond to an OH is what kind of group?

A

An acid group

111
Q

Are saturated fats liquid or solid at room temperature?

A

Solid

112
Q

What is the meaning of ‘saturation’ of fatty acids?

A

A saturated fatty acid has two H atoms attached to each carbon on the carbon chain

113
Q

What do double bonds do to the structures of unsaturated fatty acids?

A

They bend the hydrocarbon chain

114
Q

What is isotonic?

A

Concentrations of solutes either side of the membrane are the same; no net movement of water

115
Q

What is the role of cholesterol in a general cell?

A

Cholesterol binds lipids together, which firms cell membranes and provides integrity

116
Q

What other substance is produced in the creation of hydrogenated fats?

A

Unsaturated fats with trans double bonds

117
Q

What is a trans fat?

A

An unsaturated fat where the hydrogen atoms on either side of the double bond are on opposite sides of the carbon chain

118
Q

How many hydrogens does a saturated fatty acid have?

A

The maximum amount (actual number depends on length of the carbon chain)

119
Q

What is cholesterol a precursor of? There are three possible answers

A

Sex hormones such as testosterone and oestrogen, fat soluble vitamins, and bile acids

120
Q

Can large polar molecules rapidly cross the plasma membrane?

A

No

121
Q

Which fat soluble vitamins is cholesterol a precursor of?

A

Vitamins A, E, D, and K

122
Q

Osmosis can result in an uneven volume of water on either side of a membrane, but an equal concentration of what?

A

An equal concentration of solutes on either side of the membrane

123
Q

What maintains osmoregulation?

A

The exact amount of water and salt removed from blood by the kidneys.

Note the kidneys alter the concentration of substances, but osmoregulation is controlled by the hypothalamus

124
Q

Can charged molecules rapidly cross the plasma membrane?

A

No

125
Q

Esters of fatty acids and long chain alcohols form what type of substance?

A

Waxes

126
Q

What is a cis fat?

A

An unsaturated fat where the hydrogen atoms on either side of the double bond are on the same side of the carbon chain

127
Q

Tonicity depends on the concentration of what?

A

The concentration of solutes that cannot cross the cell membrane

128
Q

What is beta-carotene?

A

A carotenoid that is a precursor for vitamin A - substances include retinol, retinal (visual pigment), and retinoic acid (regulation of gene expression)

LQB186 (5 decks)

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