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BIOCHEM 405 > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

are lipids water soluble?

A

no because of the increase in hydrocarbons

they do not form covalent polymers –> there are noncovalent interactions

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2
Q

structure of lipids

A

polar, hydrophilic head
&
larger, nonpolor hydrophobic tail

tail driven by entropy effect
2nd stabilizing force: van der waals @ HC

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3
Q

amphiapatic

A

causes formation of micelles and membrane bilayers.

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4
Q

fatty acids

A

carboxylic acid with a long HC chain– usually 12-24 carbons

  • weak acid with pka of ~4.5
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5
Q

saturated

A

all carbons saturated with hydrogens (no double bonds)

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6
Q

unsaturated

A

1+ double bonds, naturally occurring, (cis)

as bonds insert and bend into HC, still have freedom of rotation–> many conformations

there are even # of C’s b/c of 2C precursor

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7
Q

monolayers in air

A

water interface with carboxylate group immersed in water and HC tail out of water

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8
Q

micelles

A

if shaken with water, HC tail cluster together

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9
Q

Triacylglycerols: Fats

A

long HC= ^ energy storage b/c carbon is in reduced form so it yields a large amount of energy on oxidation.

this is why it’s used for storage of metabolic energy.

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10
Q

Triacylglycerols structure

A

triester of fatty acids and glycerols; major long term energy storage molecules in many organisms.

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11
Q

simple fats

A

same fatty acid esterified, mixed= more common

fats rich in unsat EA = liquid at room temp

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12
Q

fat storage functions

A

E production: most fat in animals is oxidized for the generation og ATP, to drive metabolic processes

heat prod: some specialized cells oxidized triglycs for heat prod rather than to make ATP

insulation: layers of fat cells under the skin serve as thermal insulation

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13
Q

membrane lipids

A

amphipathic- form surface monolayers, bilayers or vesicles when in contact with h2o

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14
Q

Boundary – defines cells and organelles

A

But - must be selectively permeable & allow for transmission of molecules and information

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15
Q

Membranes can be used to store and utilize energy

A

Must maintain concentration gradients
(eg. H+, Na+, K+, Ca+2, small molecules)
(used for transport and signaling)

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16
Q

membrane must be

A

flexible- adopt various shapes and be self sealing

  • Must accommodate proteins of various types and shapes
  • Must allow for diffusion (both Lipids and Proteins)
  • Must allow for vesicle formation and membrane fusion

• Must be adaptable to varying cellular conditions and functions

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17
Q

Glycerophospholipids :

A

Important building blocks of biological membranes

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18
Q

ion gradient

A

way to store energy

  • transport molecules
  • signaling
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19
Q

Fatty Acids:

A

Important building blocks of glycerophospholipids and many other lipids like sphingolipids, and fats

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20
Q

Fatty Acids- four key biological roles

A
  1. Essential components of biological
    membranes

2.Post-translational modifications –
localization of proteins to membranes

3.Intra- and Inter-cellular signaling molecules

4.Energy storage: Main component of
Fats

21
Q

Fatty Acids - starting point for understanding Cellular Membranes and Lipid Metabolism

A

Carboxylic Acids with long hydrocarbon chains

Most commonly have 12-24 carbons

Typically linear

Can have one or more double bonds

(cis-double bonds: 30° kink in the hydrocarbon chain)

22
Q

n-Octadecanoate

A

18:0

23
Q

Oleate cis-9-Octadecanoate

A

18:1(Δ9)

24
Q

9,12,15- Octadecanoate

Linolenate

A

18:3(Δ9,12,15)
18:3 n-3
ω3 fatty acid

Double bonds in Fatty Acids are not conjugated

25
Q

Laurate

A

12:0 44.2

26
Q

Myristate

A

14:0 53.9

27
Q

Palimitate

A

16:0 63.1

28
Q

Stearate

A

18:0 69.6

29
Q

Arachidate

A

20:0 76.5

30
Q

Palmitoleate

A

16:1Δ9 -0.5

31
Q

Oleate

A

18:1Δ9 16.0

32
Q

Linoleneate

A

18:3Δ9,12,15 -11.0

33
Q

Arachidonate

A

20:4Δ5,8,11,14 -50.0

34
Q

diff between 18 carbon fatty acids

stearate
oleate
elaidate

A

stearate 18:0 69.6°C
oleate 18:1Δ9 12.0 °C
elaidate 18:1Δ9 45.0 °C

(oleate= cis, elaidate= trans)

Note: Elaidate is the major trans fat found in hydrogenated vegetable oils. Some is found naturally in cow milk.

35
Q

Lipid

A

A Lipid is: “any of various substances that are soluble in nonpolar organic solvents (such as chloroform and ether), that are usually insoluble in water, that with proteins and carbohydrates constitute the principal structural components of living cells”

36
Q

Triacylglycerols (Fats or Triglycerides)

A

Stored in Lipid Droplets in Adipocytes (below) and other cell types

Fats are very hydrophobic

Fats pack closely together excluding water

Efficient form of stored energy.

37
Q

Membrane Lipids – Cardiolipins

A
  • Cardiolipin - “double” phospholipid that has four fatty acid tails
  • Important component of the inner mitochondrial membrane. Constitutes about 20% of the total lipid.
  • Serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain
38
Q

Ceramides

A

the parent compounds of more abundant sphingolipids

39
Q

Sphingomyelins

A

Conformationally similar to phosphoglycerides.

Found in Myelin sheath that surrounds neuronal cells

40
Q

Cerebrosides

A

Head group is a single

sugar (non-ionic)

41
Q

Gangliosides

A

Complex oligosaccharide head group with at least one sialic acid

42
Q

Complex carbohydrate head group:

A
  • Can specifically bind proteins
  • Certain pituitary hormones
  • Attachment site for Cholera Toxin
  • Cell-cell recognition
  • Growth and Differentiation

• Altered metabolism can lead to severe neurological disorders
• Tay-Sachs disease
• Defect in a lysosomal
enzyme needed to degrade Gangliosides

43
Q

Membrane Lipids - Cholesterol

A

Steroids have four fused, non-planar rings
(Sterols are a subgroup of steroid alcohols)

Parent compound to other steroids

44
Q

Lipids self-associate into larger complexes in aqueous solutions

A

Lipid self-association is driven by the Hydrophobic Effect

• Minimize contact of hydrocarbon chains with water
– maximize entropy (ΔS) (ΔG=ΔH-TΔS)
• Favorable van der Waals Interactions

Amphipathic Lipids like Glycerophospholipids & Sphingolipids

  • Hydrophilic head group is highly hydrated
  • Spontaneously form a bilayer
  • No exposed edges – self-sealing
  • Self-assembly is a highly cooperative process
45
Q

Amphipathic properties of phospholipids

promote self-assembly of lipid bilayers

A

Shape matters – Phosphoglycerides spontaneously form bilayers.
Single Fatty-Acyl chains, like detergents, tend to form micelles.

What would you expect from the self-assembly of fats in aqueous solutions?

46
Q

Amphipathic properties of phospholipids promote self-assembly of lipid bilayers

A

Shape matters – Phosphoglycerides spontaneously form bilayers.

Single Fatty-Acyl chains, like detergents, tend to form micelles.

47
Q

Biological Membranes

The Fluid Mosaic Model of membrane organization

A
  • The Lipid Bilayer – a thin two-dimensional fluid
  • Membrane is assembled by non-covalent interactions
  • Membrane is Asymmetric
  • Lipids, Peripheral and Integral Proteins, Glycosylation
48
Q

Summary

A
  • Structures, nomenclature, and properties of fatty acids
  • Fatty acids are an important component of many biological lipids
  • Properties of many lipids are determined by their component fatty acids

• Types of Membrane Lipids
• Triacylglycerols (fats) - energy storage
• Glycerophospholipids, sphigolipids, sterols –
Membrane lipids (amphipathic molecules)

  • Self-Assembly into larger structures
  • Globules, micelles, bilayers

BIOCHEM 405 (25 decks)

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