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Ansc 301 > Lipids in Lactation > Flashcards

Lipids in Lactation Flashcards

1
Q

Define lipids

A

A diverse range of compounds that have nonpolar groups that make them relatively insoluble in water

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2
Q

What are the functions of lipids in the cell?

A

Structure (ex. phospholipid membranes, FA)

Signaling

Storage (of energy)

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3
Q

How are lipids sub-classified?

A

By their chemical structure

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4
Q

Describe triglycerides

A

Triglycerides are used to store energy in plants and animals

They are the most energy dense of the lipids

Characteristics:
- glycerol backbone, 3 fatty acids
- major lipid class in concentrate feeds
- main lipid store in animal tissues
- diverse because they may contain different fatty acids
- the fatty acid is the energy dense part

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5
Q

Describe glycolipids

A

Glycolipids are “complex” structural lipids that contain a carbohydrate (therefore they are less energy dense than a TAG)

Characteristics:
- glycerol backbone, 2 fatty acids, and one or two sugars
- major lipid class in forages

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6
Q

Describe phospholipids

A

Phospholipids are “complex” structural lipids that contain a phosphate group (also less energy dense than TAG)

Characterisitics:
- glycerol backbone
- 2 fatty acids
- one phosphate group
- a base

Important biological roles:
1. cell membrane structure, integrity, and transport
2. second messenger in intracellular transduction (signaling) of hormone actions

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7
Q

Describe steroids

A

Steroids are also lipids and include cholesterol, vitamin D, and steroid hormones

They have a cyclopentane ring as a shared common structure

They are important to membrane structure and endocrine functions (steroid hormones)

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8
Q

Describe fatty acids

A

Fatty acids are long carbon chains with a methyl group (CH3) at one end and a carboxyl group (COOH) at the other

Characterized by:
1. Number of carbons (chain length)
2. Number of double bonds (unsaturation)
3. Location and orientation of these bonds (position relative to methyl end is nutritionally important, ex. Omega 3 and Omega 6; cis and trans bonds are different)

The structure of a fatty acid is important to how it is metabolized, how it is used, and if it is bioactive

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9
Q

Describe trans fats

A

Trans fats are only found in industrial processed oils and ruminant fat (meat and milk too).

The industrial sources ones are bad for people, while the ruminant ones are likely more healthy.

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10
Q

How can we characterize fatty acids?

A

By number of double bonds

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11
Q

Describe the composition of palm oil

A

high in palmitic fatty acid (C16:0)

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12
Q

Describe the composition of flax oil

A

high in omega 3 (18:3)

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13
Q

Describe the composition of corn and soybean oil

A

high in omega 6 (18:2)

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14
Q

Describe the composition of canola oil

A

balance of a higher ratio of omega 9 and 3 to a lower ratio of omega 6

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15
Q

What type of feeds are generally high in omega-3?

A

forages

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16
Q

What types of feeds are high in omega-6?

A

Soy and corn

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17
Q

What types of feeds are high in saturated fatty acids or 18:1?

A

animal fats and palm oil

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18
Q

Why are fatty acids somewhat different today?

A

We have selected for different fatty acid profiles.

For instance, canola oil was selected to be low in erucic acid.

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19
Q

What are two simple methods to characterize an oil?

A

Saponification number and iodine numbers

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20
Q

Discuss saponification number

A

This is an indicator of the average chain length of a fatty acid

The longer the average chain length, the lower the number

Saponification number is not used very often because many FA are similar in length

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21
Q

Discuss iodine number

A

This is a measure of the unsaturation of fat

The more unsaturated bonds, the higher the iodine number

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22
Q

Discuss fatty acid profile

A

This determines the actual concentration of each fatty acid in the oil via gas chromatography

It is expensive and time consuming

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23
Q

What are the two ways oils can spoil or become rancid?

A

Hydrolytic rancidity and oxidative rancidity

24
Q

Discuss hydrolytic rancidity

A

Triglycerides are broken down to free fatty acids, which may lead to odors.

The nutritional value of the fatty acid is not affected, and this is not toxic to the animal.

25
Q

Discuss oxidative rancidity

A

Double bonds of the unsaturated fatty acids (PUFA) are attacked by oxygen. This causes off flavors and odors.

Peroxides (free radicals) are formed and perpetuate, eventually attacking gut tissue.

This may reduce performance in animals and may damage tissues, so it is potentially dangerous and can be considered an issue for health or safety.

26
Q

How can oxidative rancidity be prevented?

A

With antioxidants like Vitamin E

They prevent formation of free radicals or dispose of them before they can attack the gut tissue.

27
Q

What can increase the risk of oxidation?

A

exposure to air, sunlight, and high temperatures

28
Q

Where are lipids absorbed and how must they be broken down?

A

Lipids are digested and absorbed in the small intestine (80% in jejunum)

They must be broken down into free FA and monoglycerides and emulsified into small droplets

Short-chain FA (VFAs) are absorbed in the rumen, omasum, and hindgut

The 2 main agents of breakdown are bile salts and lipase

29
Q

How do bile salts and lipase help breakdown lipids?

A

Bile salts increase the solubility

Lipase breaks down triglycerides

30
Q

Describe lipase

A

Lipase is the enzyme that breaks down triglycerides to monoglycerides and fatty acids

Lipase comes from saliva and gastric secretions (mammals only), pancreas, and intestinal cells

Lipase also breaks down phospholipids and cleaves FA from cholesterol in the pancreas

31
Q

Describe bile salts

A

Bile salts are important to emulsify lipids into small droplets and micelles.

Na and K are the salts of bile acids
Bile salts are secreted through the bile duct
They are activated by pancreatic lipase
Emulsify fats to micelles (tiny droplets of mixed lipids and bile salts)
- recycled to the liver via the portal vein

32
Q

Why is the breakdown of fat droplets important?

A

Fat droplets are broken apart into smaller droplets, which makes it easier to lipase to attach and work to breakdown the droplets to micelles

33
Q

Describe the absorption of micelles

A

Micelles are coated in bile and free FA and monoglycerides that are absorbed by the epithelial cells. This is ultimately a futile cycle because once absorbed, the MG and free FA are reformed as triglycerides.

These triglycerides are then packaged into chylomicrons and absorbed by lymph vessels (run to heart first, then rest of body)

34
Q

What is the function of chylomicron

A

Chylomicrons are lipoproteins coated in protein and carbs, which allow them to be absorbed in the lymph vessels and move through the body

Chylomicrons are molecules used to transport FA in plasma, and they are transported through lymph vessels

35
Q

Describe micelle formation

A

Micelles are composed of fatty acids, bile salts, and monoglycerides

They have long-chain saturated FA solubilized in the hydrophobic interior of the micelle (micelles have a hydrophobic core and a hydrophilic exterior)

Ruminants use lysolecithin in place of monoglycerides since they don’t have monoglycerides

36
Q

Describe bile salt synthesis

A

Bile salts are synthesized from cholesterol in the liver. They aid in digestion and are efficiently absorbed and recycled (95% reabsorbed in the portal vein)

37
Q

How can plasma cholesterol be reduced?

A

If forced to make bile salts, plasma cholesterol will decrease. This can be forced by preventing the reabsorption of bile salts

38
Q

What are required for transport of FA in the blood?

A

lipoproteins

39
Q

Describe lipoproteins in general

A

Lipoproteins come from different tissues and have different compositions because of what they are doing

They differ in their density because of differences in fat to protein composition

40
Q

Discuss VLDLy

A

VLDLy is a special lipoprotein made by birds in the liver and deposited in the egg yolk; it transports fats to the oocyte

Its synthesis is increased by giving the bird estrogen

41
Q

How do cells intake triglycerides

A

Cells DO NOT take in triglycerides; lipoprotein lipase breaks down triglycerides into free FA and glycerol, then the FA are absorbed by the cell

42
Q

What is the function of lipoprotein lipase

A

They break down trigylcerides into glycerol and FA in the blood so that the FA can be taken up by cells

43
Q

What is the purpose of triglycerides in the body?

A

storage of energy and insulation

44
Q

What is the purpose of phospholipids, glycolipids, and steroids in the body?

A

make up cell membranes and regulate cell function

45
Q

What is the purpose of essential fatty acids in the cell?

A

comprise cell membranes and work in synthesis of eicosanoids

46
Q

How do lipids act as transporters?

A

They can be carriers of fat soluble vitamines

47
Q

What are the two essential fatty acids?

A

Linoleic (C18:2) and linolenic (C18:3) are essential because they cannot be synthesized by animals

They are important to cell membranes and important in the synthesis of regulatory compounds like eicosanoids

48
Q

What fatty acids are “conditionally essential?”

A

arachidonic acid can be synthesized from C18:2

EPA and DHA can be synthesized from C18:3

49
Q

What are signs of essential fatty acid deficiencies?

A

skin lesions, reproductive failure, edema, subcutaneous hemorrhage

50
Q

What type of fat synthesis is limited in most animals?

A

Synthesis of very long chain n-3 polyunsaturate fats (PUFA) from linolenic acid

51
Q

What are eicosanoids?

A

These are signaling molecules made from arachidonic acids (Omega 6) or EPA (Omega 3).

They can form prostaglandins, thrombaxones, and leukotrienes.

52
Q

How does the activity of an eicosanoid differ?

A

They differ based on if they are made from omega 3 or omega 6.

Omega 3 are more anti-inflammatory
Omega 6 are more pro-inflammatory

53
Q

Where is EPA not found?

A

plant sources

54
Q

What are EPA and DHA and why are they important?

A

EPA and DHA are very long chain omega-3 fatty acids that are bioactive.

They are essential to brain and nerve development.
They reduce inflammation, benefit heart disease, arthritis, blood cholesterol, retinal degeneration, etc.

They are found only in cold water fish and algae

18:1 and 18:3 n-3 may be key to “Mediterranean diet” that has lower obesity and heart disease

55
Q

How do the fatty acids consumed by a ruminant differ from the fatty acids they absorb?

A

Rumen microbes saturate fatty acids in a process known as biohydrogenation, so they absorb saturated FA

56
Q

Describe biohydrogenation

A

First, esterified fatty acids are hydrolyzed by bacterial lipases in the rumen to release free FA

Then, biohydrogenation converts cis bonds to trans bonds before removing the double bond entirely

Biohydrogenation is done because unsaturated fatty acids are toxic to the rumen microbes

Ansc 301 (15 decks)

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