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nutr 2150 > lec 5 > Flashcards

lec 5 Flashcards

1
Q

What are lipids?

A

Non-polar organic compounds, including fats, oils, waxes, sterols, and fat-soluble vitamins (A, D, E, and K).

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2
Q

What forms do lipids exist in?

A

Liquids (oils) or solids (fats).

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3
Q

What are the types of glycerides based on fatty acid esters?

A

Monoglycerides, diglycerides, and triglycerides.

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4
Q

What are fatty acids?

A

Straight-chain aliphatic carboxylic acids that vary in length, saturation, and type of saturation.

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5
Q

What are the three main types of fatty acids?

A

Saturated fats, cis unsaturated fats, and trans unsaturated fats.

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6
Q

What does “cis” mean in fatty acids?

A

“on the same side,” naturally occurring.

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7
Q

What does “trans” mean in fatty acids?

A

“across,” typically industrially produced but also found naturally in dairy.

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8
Q

hat is the difference between even and random fatty acid distribution?

A

Even distribution: Fatty acids are as evenly spread as possible across triglycerides.
Random distribution: Fatty acids are randomly placed with no preferences.

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9
Q

What is restricted random fatty acid distribution?

A

Fatty acids are randomly distributed, but some positions on the triglyceride are preferred.

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10
Q

What are semi-crystalline solids?

A

Solids with ordered polycrystalline structures but also contain amorphous oil phases.

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11
Q

What are the two stages of crystallization in fats?

A

Nucleation (formation of initial crystals) and crystal growth (enlargement of nuclei).

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12
Q

What is supersaturation in lipids?

A

The temperature difference between melting and crystallization, driven by undercooling.

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13
Q

What are the two types of nucleation in lipids

A

Homogeneous (large undercooling, nuclei form at once) and heterogeneous (low undercooling, nuclei form around other nuclei).

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14
Q

How does nucleation and growth rate affect crystal size?

A

High nucleation rate = More, smaller crystals.
High growth rate = Fewer, larger crystals.

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15
Q

What is polymorphism in lipids?

A

The ability of identical TAGs to have different crystal packing, affecting fat properties.

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16
Q

What happens during polymorphic transformations?

A

They move towards more stable forms, with higher melting points.

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17
Q

What are the crystal sizes of different polymorphs?

A

α and β’ = Small crystals (< 5 μm).
β = Large crystals (~50 μm), often gritty.

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18
Q

What is the tempering process for chocolate?

A

Melt TAGs → Cool to form β-V nuclei → Heat to melt β’ but not β-V → Allow β-V nuclei to grow.

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19
Q

What is hydrolytic rancidity in lipids?

A

Lipid breakdown by water or enzymes, causing smells, foaming, and smoke.

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20
Q

What is lipid oxidation?

A

Oxygen reacts with unsaturated lipids, leading to spoilage and reduced shelf life.

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21
Q

How does the number of double bonds affect oxidation?

A

More double bonds = Faster oxidation rate.

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22
Q

What are common initiators of lipid oxidation?

A

Metals (Fe, Cu, Mn), heat, light, and radicals.

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23
Q

What happens during the initiation stage of lipid oxidation?

A

A hydrogen atom is removed, forming a fatty acid radical stabilized by resonance.

24
Q

What is the propagation stage in lipid oxidation?

A

Free radicals transfer, forming unstable lipid hydroperoxides (LOOH).

25
Q

What happens during hydroperoxide breakdown?

A

Hydroperoxides decompose into alkoxy and hydroxyl radicals, which are highly reactive.

26
Q

What is termination in lipid oxidation?

A

Free radicals stabilize by recombining or reacting with water, slowing oxidation and causing rancidity.

27
Q

What happens during lipid oxidation termination

A

Free radicals break down into small compounds like ketones and aldehydes, causing off flavors, odors, and increased oil viscosity.

28
Q

What are the two classes of antioxidants?

A

Primary antioxidants: React with radicals to stop chain reactions.
Secondary antioxidants: Deactivate pro-oxidants and quench UV light.

29
Q

What are the requirements for primary antioxidants?

A

They must donate hydrogen, stabilize free radicals, have conjugation, and provide steric hindrance.

30
Q

How do primary antioxidants work?

A

They donate hydrogen, stabilize unpaired electrons via resonance, and terminate radicals through reactions.

31
Q

What is hydrogenation in lipids?

A

A process that stabilizes oils by removing double bonds, converting unsaturated fats to saturated or trans fats.

32
Q

What are the steps in hydrogenation?

A

1.Double bond interacts with the metal catalyst.
2.Hydrogen adsorbs to the catalyst surface.
3.Hydrogen attaches to one carbon of the double bond.
4.Another hydrogen attaches, releasing the fatty acid.

33
Q

What is partial hydrogenation?

A

A process that causes cis-trans and positional isomerization of double bonds, now banned in Canada.

34
Q

What is full hydrogenation?

A

It completely saturates the fat, leaving no double bonds and is used for stability in products like frying oils.

35
Q

What is interesterification in lipids?

A

A process that randomizes the position of fatty acids in triglycerides.

36
Q

How do fatty acids affect cardiovascular health?

A

Oxidized LDLs and foam cells form plaques in arteries, leading to atherosclerosis and hardened vessels.

37
Q

What are plaques made of in atherosclerosis?

A

Foam cells (oxidized LDL + macrophages) and calcium, forming hard and insoluble deposits.

38
Q

What are aliphatic side chains in amino acids?

A

AVLIGP (Alanine, Valine, Leucine, Isoleucine, Glycine, Proline).

39
Q

What are polar neutral side chains in amino acids?

A

STNQ (Serine, Threonine, Asparagine, Glutamine).

40
Q

What are sulfur-containing side chains in amino acids?

A

CM (Cysteine, Methionine).

41
Q

What are aromatic side chains in amino acids?

A

FWY (Phenylalanine, Tryptophan, Tyrosine).

42
Q

What are cationic side chains in amino acids?

A

HKR (Histidine, Lysine, Arginine).

43
Q

What are anionic side chains in amino acids?

A

DE (Aspartic acid, Glutamic acid).

44
Q

How are amino acids linked in proteins?

A

By peptide bonds formed via a dehydration reaction, making the bond rigid and planar.

45
Q

What is the primary structure of a protein?

A

The sequence of amino acids modified only by hydrolysis or chemical modifications like phosphorylation or glycosylation.

46
Q

What is the secondary structure of a protein?

A

Local conformations like β-sheets and α-helices formed by the polypeptide backbone.

47
Q

What stabilizes protein tertiary structure?

A

Covalent (disulfide bridges) and non-covalent (salt bridges, hydrogen bonds, van der Waals forces) interactions.

48
Q

What is the quaternary structure of a protein?

A

A structure formed by more than one polypeptide chain, e.g., myoglobin.

49
Q

What is the difference between parallel and antiparallel β-sheets?

A

Parallel sheets have angled H-bonds, while antiparallel sheets have straight H-bonds.

50
Q

What is protein denaturation?

A

The unfolding of secondary, tertiary, and quaternary structures due to environmental changes.

51
Q

What agents cause protein denaturation?

A

Heat, pH changes, ionic strength, solvent polarity, and shear.

52
Q

What are the effects of protein denaturation?

A

Decreased solubility, increased digestibility, reduced activity, increased viscosity, and higher water-binding.

53
Q

How does collagen form gelatin and jello?

A

Heat denatures collagen, and cooling allows partial refolding, creating a gel network.

54
Q

What is intraesterification?

A

Rearranges fatty acids within the same triglyceride molecule, changing their positions on the glycerol backbone without altering chemical composition.

55
Q

How does intraesterification differ from interesterification?

A

Intraesterification occurs within one molecule, while interesterification involves fatty acid exchange between different triglycerides.

nutr 2150 (3 decks)

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