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Medical Biochemistry > 3-Lipids > Flashcards

3-Lipids Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the functions of Lipids?

A

They provide:
Energy
-provide the proper amount of calories in order to meet body’s needs

Structure

  1. Source of essential fatty acids are needed for cell membranes, skins, cardiovasular and brain health
  2. Phospholipids form the mberane of lipoproteins in order to make the transort of lipids to blood possible

Cell signalling

Other functions:

Provide insulation and help maintain the body temperature

Help in the absorption of the fat-soluble vitamins A,D,E,K

Form the adipose tissue where is the site of fat storage on the body were excess triglycerides are stored until they are nedded for energy when fasting

Cholesterol (a class of lipids) is used to produce;

Steroid hormones(e.g androgens)
Bile acids
Vitamin D
Glucocortinoids (e.g. cortisol)

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2
Q

Which are the type of lipids?Are they the ONLY lipids

A

Phospholipids Triglycerides Sterols. NO they are not the only lipids, but they are the most relevant lipids that are found in food and nutrition

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3
Q

Which are the charasteristics of a fatty acid that determine how the fat affects the body

A
  • Saturation

- Length

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4
Q

How many carbons can a fatty acid have?

A

A fatty acid usually has an even number of carbons (from 2 to 26)

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5
Q

When can a fatty acid be characterised as a short,medium,long chain fatty acid?

A

small=2 -6
medium=8-14
long= more than 14
7 is not mentioned because it isn’t an even number

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6
Q

In what do the fatty acids differ to and what these characteristics determine

A

un/saturation(no.of double bonds) =melting point
Lentgh(o. of carbons)= melting point
Position of gemoetry(cis or trans)=health effects

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7
Q

Define the 18:1 w-9 fatty acid

A

18= number of carbons
1=number of double/triple bonds
w-9=umber of carbon atom from the last double/triple bond to the methyl end

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8
Q

Why saturated fatty acids form solid forms in room temperature?

A

Due to the fact that there is no double/triple bond, the fatty acids are lineal, meaning that they are well stacked together

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9
Q

Why unsaturated fatty acids form liquid forms in room temperature?

A

Due to the fact that unsaturated fatty acids consists of AT LEAST one double/triple bond, they carbon ‘tai’ is not liner so they cannot be perfectly stacked together

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10
Q

What is the main characteristic of a monounsaturated fatty acid

A

It has ONE double bond (triple?)

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11
Q

What is the main characteristic of a polyusaturated fatty acid

A

It has at least TWO double bonds (triple?)

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12
Q

Which form is most common trans or cis unsaturated fatty acids?

A

Cis form is the most common

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13
Q

Where do the trans unsaaturated fatty acids come from?

A

Ruminants(cow, sheep)
During bacterial Fermentation
During partial hydrogenation of fats( used ny food industries to harden fats)

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14
Q

What is the difference between the cis and trans unsaturated fatty acids and wthats the consequence in its melting point?

A

On the cis form the hydrogens in double bond are in the same ‘‘side’’. On the trans form the hydrogens are in differet sides.

The cis form lowers the melting point( as they are bent)

The trans form bhave similar to saturated fatty acids as they are linear!

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15
Q

Which form of fatty acid increases the LDL cholesterol and which the HDL cholesterol?

A

Trans fatty acids increase LDL (bad cholesterol)

Cis fatty acids increase HDL(good cholesterol)

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16
Q

Which fatty acids are characterized as ‘‘essential’’?

A

Essential fatty acids are the fatty acids that cannot be synthesized by human bosy and must be taken through diet.

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17
Q

What is the function of Linoleic acid(w-6)?

A

It is a component for membrane structural lipids

It is important for cell signalling

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18
Q

What is the function of Alpha-linleic acid (w-3)?

A

It is a precursor for eicosapentanoic acid(EPA) and docosahexanoic acid (DHA)

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19
Q

Why EPA and DPA acids are important?

A

They are important structural membrane lipids

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20
Q

What kind of fatty acids are EPA and DPA w-3 or w-6?From which acid are derived from?

A

They are w-3 fatty acids and derive from Alpha-linoleic acid

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21
Q

What is the role of w-6 fatty acids?

A
  • They form structural lipids and support normal growth
  • Reproduction
  • Maintainace of skin (water permeability)
  • Haemostasis( the opposite of haemorrhage) and -Immune function
  • Eicosanoid formation (derived from w-6)

(Eicosanoids are cell signalling molecules)

22
Q

What is the role of w-3 fatty acids?

A

-Vision
-Brain Function
-Cardiac Function (protection of arrythmias)
-Anti-inflammatory function
Eicosanoid formation(derived from w-3)

(Eicosanoids are cell signalling molecules)

23
Q

What type of fatty acid is the Arachidonic Acid (AA)…….w-6 or w-3?

A

w-6

24
Q

What are the pharmacological effects of changing the Arachidonic Acid/EPA/DPA ratio due to a diet that is based on fish?

            westerns diet           High fish diet AA: from       8           to               22 EPA: from     8           to               0.5 DPA from      6          to                1
A

-Increased bleeding time (which automatically means increased clotting time)
-Mild improvements in inflammatory disease( psoriasis, arthritis
-Lower blood pressure in high intakes(3 grams/day)
-10 timew lower incidence of hearrt attack and strokes
-Lower total cholesterol, LDL-Cholesterol,triglycerides
Higher HDL-Cholesterol

25
Q

Which is the sterol in humans?

A

Cholesterol

26
Q

Some main characteristics about fat? (3)

A
  • It is the most calorie dense macronutrient providing 9 kcal/g
  • 98% of the fat is in the form of triglycerides
  • Most food contains fat
27
Q

Some foods high in saturated fat?

A

meat
eggs
dairy products

28
Q

Foods that contain w-3 polyunsaturated fats?

A

oily fish

  • Nuts
  • Rapeseed/flaxseed oil
29
Q

Foods that contain w-6 polyunsaturated fatty acids?

A
  • Nuts
  • Seeds
  • Vegetable oils
30
Q

Whats the procedure of digestion and what are the final products?

A
  • Begins in the mouth by lingual lipase
  • Continues in the gastric lipase
  • Bile acids, along with the peristalsis of the intestine, emulsify the fat to allow pancreatic lipases to digest the lipid further
  • The final products of lipid digestion are fatty acids, bile salts, and monoglycerides
31
Q

What is the ending for the products of lipid digestion productlong chain fatty acids)?

A
  • Short chain fatty acids directly enter the bloodstream

- Long chain fatty acids need special carriers called chylomicrons

32
Q

How much dietary fat is absorbed?

A

Around 90-95%

33
Q

Which molecules that derive from lipid digestion are absorbed directly in bloodstream?

A
  • Glycerol

- Short and medium-fatty acids chains

34
Q

Which molecules that derive from lipid digestion are absorbed by enterocytes?

A
  • Long chain fatty acids
  • holesterol
  • monoglycerides
35
Q

What are enterocytes?

A

They are cells lining the small intestine that absorb nutrients

36
Q

Inside the enterocyte, which are the 4 possible fates of fatty acids? Which path does the majority of fatty acids follow?

A
  1. Storage within the enterocytes
  2. Formation of cholesterol esters or phospholipids
  3. Oxidation of energy
  4. Packaged into triglycerides to be transported to the rest of the body

The majority follows the 4th

37
Q

What is the function of chylomicrons?

A

They transport triglycerides from the enterocyte to the muscles and adipose tissue.

38
Q

Which is the fate of triglycerides packaged in chylomicrons?

A

It depends on the needs of the body after consuming the meal:

  • If the body is at rest, triglycerides are taken up by adipose tissue for storage
  • If the body is active, muscle tissue will oxidize fatty acids to provide energy, in a process called β-oxidation.
39
Q

Are there more lipoproteins that can carry lipids(except from chylomicrons)?If yes which ones? Which is their function?

A

Yes there are:

  1. Very Low density lipoproteins(VLDL)
  2. Low density Lipoproteins(LDL)
  3. High density Lipoproteins(HDL)
  • VLDL transports triglycerides from the liver to muscle and adipose tissue
  • LDL transports cholesterol from liver to the other body tissues
  • HDL transports cholesterol form the tissues back to the liver
40
Q

In which areas is the fat being stored in adipose tissue

A

1) Under the skin, called subcutaneous adipose tissue

2) Around organs in the abdomen, called viscelar adipose tissue(VAT)

41
Q

What are the VAT percentages for women and men?What about Metabolic Syndrome?

A

VAT accounts for ¬10-20% of total fat in men and ¬5-8% in women
VAT adipocytes are more insulin resistant, which
increase the risk of Metabolic Syndrome .

42
Q

How much calories should come from fat?What is the recommended saturated fat intake?

A
  • For adults: 30-33% of total calories should come from fat

- Saturated fat intake should be <10%

43
Q

Canculate daily total fat intake and saturated fat intake, If you consume 2500 calories a day:

A

83g daily= fat

28=saturated fat

44
Q

How many calories is a gram of fat?

A

9 calories

45
Q

What are the effects when fat intake is small, (essential fatty acids)?

A

Symptoms of this are:

  • Poor wound healing
  • Visual problems
  • Neuropathy
  • Susceptibility to infection
  • Decreased growth in children etc.
46
Q

Are w-6 and w-3 essential or non-essential?

A

They are essential, they cannot be synthesized by human body so they need to be taken through diet

47
Q

What are the effects of excess fat intake?Are the findings absolutely true?

A
  • Obesity is the most prevalent outcome of excess calorie intake from fat
  • Various cancers(e.g. colorectal & breast cancer) with high fat intake and high saturated fat intake

However the findings might be complicated by the confounding of obesity in this study ( The people that were examined were all obese)

48
Q

What does a systematic review indicates about the reduction in saturated fat intake?

A

14% reduction in cardiovascular risk

49
Q

Name 4 lipoproteins

A
  • Chylomicrons
  • VLDL
  • LDL
  • HDL
50
Q

What kind of fatty acids are the linoleic and Alpha-linoleic acid, essential or non-essential

A

essential

51
Q

What do the chylomicrons consist of?

A

triglycerides, phospholipids, cholesterol, proteins

52
Q

What are the possible fates of triglycerides that are packed on chylomicrons?

A

The fate of the triglycerides packaged in chylomicrons depends on the needs of the body after consuming the meal:

  • If the body is at rest, triglycerides are taken up by adipose tissue for storage
  • If the body is active, muscle tissue will oxidize fatty acids to provide energy, in a process called β-oxidation.

Medical Biochemistry (7 decks)

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