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LSM2106 : Fundamental Biochemistry > 11. Lipids > Flashcards

11. Lipids Flashcards

1
Q

How many carbon and C=C bonds does palmitic acid have?

A

16 C, 0 C=C

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2
Q

How many carbon and C=C bonds does oleic acid have?

A

18 C, 1 C=C

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3
Q

How are fatty acids metabolised after digestion?

A
  1. carbon backbone oxidised in acetyl-CoA

in the presence of oxaloacetate : acetyl-CoA combines with oxaloacetate to undergo TCA cycle to produce 3 NADH, 1 FADH2, 2 CO2, 1 ATP and regenerated as oxalacetate

in the absence of oxaloacetate (due to low carb diet etc): acetyl-CoA forms ketone bodies.

Oxaloacetate is synthesised from sugars. In a low carb diet / fasting –> oxaloacetate is consumed to form glucose via gluconeogenic pathway, unavailable for reaction with acetyl CoA

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4
Q

What are the names of 2 of the ketone bodies that can be formed in fatty acid metabolism?

A

acetoacetate, D-3-hydroxybutyrate

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5
Q

What is the main function of lipoproteins?

A

To transport cholesterol and triacylglycerols/triglycerides

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6
Q

What are the 6 types of lipoproteins, in ascending order of density?

A
  1. Chylomicrons
  2. Chylomicron remnants
  3. Very low density lipoproteins (VLDL)
  4. Intermediate-density lipoproteins (IDL)
  5. Low-density lipoproteins (LDL)
  6. High-density lipoproteins (HDL)
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7
Q

What do chylomicrons transport?

A

Triglycerides,cholesterol and other lipids (from the diet) away from the samll intestine

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8
Q

What do chylomicron remnants transport?

A

Carry cholesterol-rich residues to liver (for liver to absorb)

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9
Q

What do Very low density lipoproteins (VLDL) transport?

A

Exports excess triacylglycerols and cholesterol from liver into bloodstream.

  • cholesterol + fatty acids from triacylglycerols / triglycerides combine and carried as cholesteryl esters
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10
Q

What do Intermediate-density lipoproteins (IDL) transport?

A
  • Breaks down remnant cholesteryl esters into cholesterol and fatty acids
  • fatty acids are uptaken by tissues (normal tissues)
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11
Q

What do Low-density lipoproteins (LDL) transport?

A

LDL carry cholesterol in bloodstream (bad cholesterol)

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12
Q

What do High-density lipoproteins (HDL) transport?

A

It packs up cholesterol released into the plasma and delivers to liver for excretion (good cholesterol)

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13
Q

Biological cell membranes have several functions. 2 of the functions are:
- Prevent molecules from leaking out of the cell
- Prevent unwanted molecules from diffusing in

This function is performed by which part of the cell membrane?

A

Lipid bilayer

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14
Q

Another function of biological cell membranes is that they contain transport systems to take up or remove molecules – selective permeability.

which part of the cell membrane performs this function?

A

Protein components which act as pumps/channels in cell

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15
Q

Although the biological cell membrane is mainly lipid and proteins, what do they contain also/

A

carbohydrates linked to lipid and proteins (glycolipid and glycoprotein)

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16
Q

Why might most unsaturated fatty acids in phospholipids be in the cis rather than the trans conformation?

A

Phospholipid bilayer – cell membrane
- Cis double bond introduces a kink that prevents packing of the fatty acid chains. Cis double bonds maintain fluidity of the cell membrane.

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17
Q

What are the components of phospholipids?

A
  • Glycerol backbone
  • 2 fatty acids bonded to glycerol backbone
  • 1 phosphate attached to glycerol backbone
  • 1 alcohol group bonded to phosphate group

Can refer to notes for better visualisation

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18
Q

Phospholipids are synthesised from diacylglercol (glycerol + 2 fatty acids) and phosphate-alcohol group. In this synthesis, either the diacylglucerol molecule or the alcohol group must be ____ by ____________________________

A

Activated, addition of phosphate group (phosphorylation)

19
Q

Glycolipids are sugar-containing lipids, where sugar residues are always on the ____ side of the membrane

A

extracellular

20
Q

What are glycolipids made of ?

A
  • Sphingosine backbone
  • 1/2 fatty acid groups
  • 1 sugar group
21
Q

What is the name of the simplest glycolipid?

A

Cereboside

  • 1 sphingosine, 1 fatty acid, 1 sugar
22
Q

A sphingosine molecule is made of ___ and __

A

amino acid, alcohol (amino-alcohol)

23
Q
A
24
Q

what is the most complex sphingolipid and what do they do?

A

Gangliosides
- binding immune cells to sites of injury in inflammatory response

25
Q

What is cholesterol made of?

A
  • Steroid nucleus (4 hydrocarbn chains linked together)
  • Long hydrocarbon tail
26
Q

What are 2 functions of cholesterol?

A

1) modulates the fluidity of animal cell membranes (cholesterol is embedded in lipid bilayer)
- During low temp, Cholesterol prevents phospholipids from packing too tightly, maintaining fluidity

2) Precursor of steroid hormones such as progesterone and testosterone

27
Q

What are the 3 derivatives of cholesterol?

A
  1. Bile – breakdown product of cholesterol
  2. Vitamin D
  3. Steroid hormones
28
Q

Other than phospholipid bilayer, what other structure can phospholipids form, under what condition?

A

Micelle
- Only forms when there is only 1 fatty acid chain (salts of fatty acids)
- When there are 2 fatty acid chains, too bulky to fit into interior of micelle → steric hindrance

29
Q
A
30
Q

Membrane proteins

Myelin contains ____% of protein.
What does myelin do?

A

18%
- It is high in fat, and acts as an insulator of electrical signals

in the dendron (nerve cell), myelin sheath over the main part –> electrical signals cannot be passed through in areas with myelin over it, electrical signals “jump” → effective transfer

31
Q

Typical plasma membranes contain ____% of protein

A

50%

32
Q

Mitochondria membranes consist of ____% protein.

A

75%
- Electron transport chain –> channel proteins to pump protons and electrons

33
Q

Association of proteins with lipid bilayer

What are peripheral proteins?

A

Proteins that are bound to cell membrane by electrostatic and hydrogen-bond interactions
- interact with hydrophilic head of phospholipid bilayer, on the surface of membrane

34
Q

Association of proteins with lipid bilayer

What are integral proteins?

A

Proteins that form extensive interaction with hydrocarbon chains (hydrophobic part) of membrane lipids
- are embedded within membrane

35
Q

The fluidity of phospholipid bilayer of cell membranes are determined by? [2]

A
  1. Fatty acid composition (cis vs trans)
  2. Cholesterol content
36
Q
A
37
Q

The outer and inner surfaces of the biological membrane are structurally and functionally symmetric. True or False?

A

False
- Outer and inner surfaces of biological membranes have different components and different enzymatic activities

38
Q

How is the assymetry of biological membranes preserved?

A

Insertion of membrane proteins + assymetrical distribution of lipids

39
Q

What are the 3 types of membrane proteins associated with the phospholipid bilayer?

A
  1. Pumps
  2. Carrier proteins
  3. Channels
40
Q

Pumps use what kind of transport? (active transport/diffusion/facilitated diffusion etc)

A

Primary active transport involving use of ATP

41
Q

Pumps use what kind of transport? (active transport/diffusion/facilitated diffusion etc)

A

Secondary active transport
with no use of ATP

  • utilises gradient of one ion to drive transport of another against its gradient.
42
Q

Carrier proteins

Carrier proteins can be classified into antiporters, symports and uniporters. What is an antiporter?

A

It is a carrier protein that transports 2 different ions in opposite directions at the same time

43
Q

Carrier proteins

What is a symporter?

A

(membrane) carrier proteins which carry 2 species of ions in the same direction at the same time.

44
Q

What is a uniporter?

A

(membrane) carrier proteins which carry 1 species of ions in either directions based on the concentration of the species on either side of the membrane.

LSM2106 : Fundamental Biochemistry (10 decks)

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