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MCAT > Biochemistry: C6 - Lipids > Flashcards

Biochemistry: C6 - Lipids Flashcards

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MCAT flashcards
1
Q

Three primary roles of fat

A
  1. In adipose tissue, TRIGYLCERIDES (fats) store energy.
  2. in cellular membranes, PHOPHOLIPIDS maintain and intra and extracellular environment
  3. CHOLESTEROL is the building block for steroid hormone.
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2
Q

syn for hydrophobic

A

lipophilic

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3
Q

syn for hydrophilic

A

lipophobic

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4
Q

structure of fatty acids

A

unsub alkane with carboxylic acid end

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5
Q

define saturated

A

no c-c double bonds BC every C is covalently bonded to the maximum number of hydrogens

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6
Q

define unsaturated

A

FA have one or more double bonds –> Z (cis) config

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7
Q

If FA is in water….

A

then the long hydrophobic chains will INTERACT with each other to MINIMIZE contact with each other. ** Charged carboxyl end will be exposed to the aqueous environment

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8
Q

define micelle

A

a structure fatty acids form in an aqueous solution

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9
Q

how is a micelle formed?

A

through hydrophobic interactions

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10
Q

define solvation shell

A

is the solvent interface of any chemical compound or biomolecule that constitutes the solute

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11
Q

solvation shell of water molecule is called?

A

hydration shell

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12
Q

function of a solvation shell

A

since water molecules has a dipole in which it likes to share its charges with other polar molecules, this shell will allow the MOST water-water interaction and LEAST water-lipid interaction

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13
Q

What faces out and in of a micelle?

A

out are the carboxylic acid head groups and inside are the hydrophobic lipid tails

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14
Q

explain the process in which soap removes grease

A

grease is not soluble in water, it is hydrophobic (lipophilic). Soap forms a micelle around a grease particle. **image if the hyrophilic heads of soap facing out, hydrophobic tails facing inwards with a hydrophobic grease particle in the center, caved in.

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15
Q

How is a triglyceride formed?

A

gylcerol + 3 fatty acids undergo a base catalyzed ester hydrolysis

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16
Q

what is amphipathic and is a fatty acid this?

A

def: when a molecule had both hydrophobic and hydrophilic regions
yes: heads (polar) and tails (nonpolar)

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17
Q

function of lipases

A

enzymes that hydrolyze fats, which means they break down fats with the addition of water.

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18
Q

Which is a more efficient energy storage molecule: fats or carbs? why?

A

fats because of 2 reasons: (1) packing and (2) energy content

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19
Q

packing

A

fats pack more closely than carbs because of their hydrophobicity. carbs’s have hydroxyl groups that interact with water, carrying high water-of-solvation. So basically, the amount of carbon in unit area of fat is far greater than carbs.

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20
Q

energy content

A

fat molecules are reduced, meaning it has an H, while carbs are less reduced, more oxidized. Metabolism process requires oxidation of foods to release energy. Fats, being more reduced, have more capability to be oxidized. Carbs can be also be oxidized but less.

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21
Q

Animal and plant energy content

A

animals use fat and less glycogen to store energy

plants (potatoes) use carbs to store most of their energy

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22
Q

what lipid makes up a membrane?

A

phospholipid –> derived from diacylglycerol phosphate or DG-P.

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23
Q

DG-P structure

A

a glyercol, with 2 fatty acids, and a phosphate group.

The P group usually has an even bigger polar group added to it.

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24
Q

DG-P + choline (function)

A

phosphatidylcholine: lipid component of lung surfacant ==> reduces surface tension inside lung alveoli

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25
Q

DG-P + ethanolamine (function)

A

phosphatidylethanolamine: involved in signal transmission across cell membrane

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26
Q

what do FA form and what do phospholipids form?

A

FA - micelle

Phospholipids - lipid bilayer

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27
Q

What characteristics of a phospholipid bilayer increase its membrane fluidity

A
  • degree of saturation: more double bonds, or more unsaturated –> more fluid
  • tail length: shorter tail length of fatty acid –> more fluid
  • amount of cholesterol:
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28
Q

How does cholesterol play a role?

A

Cholesterol keeps fluidity at optimal level

  • at low temperatures, it increase fluidity (same way as kinks in FA)
  • at high temp, it decrease fluidity
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29
Q

What can’t pass through the PM?

A 
certain hormones (peptides)
charged particles (Na+)
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30
Q

Terpenes

A

built of isoprene units with a general formula of (C5H8)n

can be cyclic or linear

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31
Q

isoprene unit

A

(C5H8). Units of these make up an terpene

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32
Q

name terpenes of 1, 2, 3, and 6 isoprene units

A

1 - monoterpene
2 - sesquiterpene
3 - diterpene
6 - squalene

33
Q

squalene

A

important in ear wax

34
Q

trepenoid

A

isoprene skeleton + other elements (O, N, S etc.)

ex. Vitamin A (C20H30O)

35
Q

steroid characteristics:

A
  1. tetracyclic ring system

2.

36
Q

cholesterol characteristics:

A
  1. polycyclic amphipath
37
Q

lipoprotein

A

when cholesterol is packaged with protein and fats when traveling in the blood

38
Q

atheroscleortic vascular disease

A

build-up of plaques on the inside of the blood vessel

39
Q

what is a steroid

A

a molecule made up of cholesterol

40
Q

examples of steroid

A

estradiol (estrogen or female sex hormone)

testosterone (androgen or male sex hormone)

41
Q

What molecules have intracellular receptors?

A

steroid hormones because they are hydrophobic and can travel through the lipid membrane

42
Q

What molecules have extracellular receptors?

A

peptide hormones (hydrophilic), ex. insulin

43
Q

Name other lipids (4):

A

sphingolipids, waxes, fat-soluble vitamins, and prosagladins

44
Q

sphingolipids

A

same as phospholipid except has sphingosine backbone instead of glycerol

45
Q

Where is sphingolipids found?

A

sphingomyelin (important component of myelin sheath around axons)

46
Q

Waxes

A

long chain fats esterified to long chain alcohol.

47
Q

define esterify

A

to combine with an alcohol with elimination of a molecule of water, forming an ester.

  • highly hydrophobic
  • ex. ear wax (animals) and water barrier (cuticle in plants)
48
Q

Fat-Soluble vitamins

A
  • absorbed with dietary fat
  • stored in adipose tissue and in liver
  • ex. A, D E, K.
49
Q

Vitamin A

A

terpenoid -> vision, growth, epithelial maintenance, and immune function

50
Q

Vitamin D

A
  • dervied from cholesterol (a steroid)

- regulates blood levels of Ca2+ and phosphate

51
Q

Vitamin E

A

group of compounds called tocopherols (methylated pehnols) that are important antioxidants
- alpha tocopherol is most active

52
Q

Vitamin K

A

important clotting enzyme in clotting proteins

53
Q

Prostaglandins

A

belong to eicosanoid (20 carbon fatty acid) + has a 5 membered ring

  • regulate smooth muchle contraction in intestines
  • regulate blood vessel diamete
  • maintain gastric integrity (by decreasing acid secretion and increasing mucus secretion)
54
Q

Fatty Acid metabolism steps

A

the triglyceride is hydrolyzed to release the free fatty acid and then undergoes beta-oxidation (mito membrane)

55
Q

Chylomicrons

A

are lipo-proteins (transporters) that transport dietary fats from the intestine to liver, lungs, heart, and other organs in the body via the lymphatic and blood stream

56
Q

dietary fat is what kind of fat?

A

triglyceride

57
Q

more detailed steps of fatty acid metabolism

A
  1. acyl-CoA synthetase synthesizes a fatty acyl-CoA which gets transported into the mito
  2. fatty acyl-CoA undergoes 4 rxns that involve the cleaving of the alpha and beta carbons to liberate an acetyl CoA (side carbons are getting cut off
    - each round 2 Acetyl CoA get cleaved
    - final round 4 carbon Acetyl CoA get cleaved
58
Q

Math for 12 carbon saturated fatty acid (rounds)

A 
y is number of 2C rounds
x is number of 4C rounds = 1
x(4 c) + y(2c) = 12
4 + 2y = 12
2y =8
y = 4
Total of 5 rounds of beta oxidation
59
Q

How are # of Acetyl-CoA groups calculated?

A

1 round of beta oxidation –>

  • 1 NADH
  • 1 FADH2
  • 1 acetyl CoA for 1st round and 2 for last
60
Q

Math for 12 carbon saturated fatty acid (Acetyl-CoA groups)

A

5 total rounds

  • 5 NADH
  • 5 FADH2
  • 6 Acetyl-CoA
61
Q

TOTAL through KREBS of the 12C saturated FA

A
  • Each krebs cycle produces 3 NADH, 1 FADH2, and 1 GTP.

everything x 6

62
Q

define Ketogenesis

A

During periods of long starvation, glycogen stores become exhausted and blood glucose falls significantly. To help supply the CNS with energy when glucose supply is short, the liver generates ketone bodies in a process called ketogenesis

63
Q

ketone bodies

A
  • generated from acetyl-CoA
  • include acetone, acetoacetate and beta hydroxybutyrate
  • acidic
64
Q

What is special about acetone, acetoacetate and beta hydroxybutyrate

A

can be carried across the BBB and then be converted back to acetyl-CoA once they arrive at target organ –> enters krebs

65
Q

what is another time ketogenesis takes place?

A

when enough glucose is present in the blood BUT it is not able to enter the cell. Happens in patients suffering type 1 diabetes and do not take a insulin injection for a prolonged period of time. They opt to fatty acid oxidation or ketogenesis

66
Q

What happens when there is a lot of acetyl-CoA in the body?

A

you store them as ketone bodies

67
Q

diabetic ketoacidosis

A

when the patient produces a lot of blood acids (ketones). experiences fatigue, confusion and fruity breath (due to acetone which is very volatile present in the blood), can be mistaken for driving under the influence

68
Q

What are the ketone bodies present in the body?

A

acetone, acetoacetate and beta hydroxybutyrate

69
Q

A deleption of what might cause ketogenesis to take place?

A

OAA

70
Q

fatty acid synthesis

A

a de novo synthesis of FA

71
Q

location of FA synthesis and catabolism

A

synthesis/anabolism: cytoplasm

catabolism: Mito matric

72
Q

what is the committed step of FA anabolism?

A

carboxylation of acetyl-CoA

73
Q

overall steps of the committed step

A

acetyla-CoA —-> malonyla-CoA

74
Q

details of committed step

A

Occurs on the FA synthase enzyme (has domains on it)

  1. A-CoA binds to the acyl carrier protein (ACP)
  2. acetyl-CoA is then shifted to a cysteine residue domain
  3. malonyl-CoA binds to ACP
  4. acetyl group condenses with malonyl as the malonyl is decarboxylated
  5. 2 reductions (gets rid of carbonyl)
  6. shifts back to cysteine residue and new malonyl-CoA gets added to the ACP site.
  7. cys piece shifts up and combines with the new piece and then returns back down.
75
Q

Why are we adding a carbon and then removing?

A

this allows for an unfavorable reaction to take place

76
Q

Where do humans absorb aa from?

A

proteins from diets

77
Q

list all the ways proteins can be digested

A
  1. proteins from diet is digested into AA by proteases.
    a. the free individ AA can used to make cellular proteins
    b. amine groups of the AA can be used to synthesize nitrogenous compounds OR urea
    c. the carbon skeleton (alpa keto acid) can be used to either broken down into water and co2 OR coverted to glucose (glucogenic AA) OR acetyl CoA (ketogenic AA)
78
Q

3 main points about Terpenes

A

They are polymers of the isoprene monomer (C5H8)

The names of the first few polymer lengths (i.e., 2 isoprene units is a monoterpene, 3 isoprene units is sesquiterpene, and 4 isoprene units is a diterpene)

They are the monomers that comprise Vitamin A (terpenoid [OH] - general name given to terpenes with other elements)

MCAT (4 decks)

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