Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biochemistry 441B > Lipid Structure and Function > Flashcards

Lipid Structure and Function Flashcards

1
Q

What three important roles do lipids serve?

A

Energy storage

Cell membranes

Signaling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the common and defining feature of lipids?

A

Hydrophobicity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are most lipids derived from?

A

Fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are fatty acids?

A

Consist of a carboxylic acid and a hydrocarbon tail (4 - 36 carbons)

Can covalently bond to proteins to (lipid) tether proteins to biological membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the most abundant natural fatty acids?

A

unbranched

contain 12-20 carbons

even-numbered
- acetyl CoA (2 carbons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are saturated fatty acids?

A

Contain fully reduced methylene groups

  • no double bonds
  • all single bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are unsaturated fatty acids?

A

Contain at least 1 double bond

Monounsaturated
- 1 double bond

OR

Polyunsaturated
- more than 1 double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What affects the structure of fatty acids?

A

The degree of saturation and the configuration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the structure of saturated fatty acids?

A

Free rotation about every C-C bond and are largely linear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the structure of unsaturated fatty acids?

A

Rotation is restricted about the C=C bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

In the structure of unsaturated fatty acids, the cis configuration of the C=C bond introduces what?

A

Cis of C=C bond introduces a bend (kink) in the fatty acid

Whereas a trans C=C bond is more linear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe standard fatty acid nomenclature.

A

Assigns number 1 to the carboxyl carbon (C-1), and a (alpha) or number 2 to the carbon next to it

Each line segment of the zigzag represents a single bond between adjacent carbons

The position of any double bond(s) is indicated by △ followed by a superscript number indicating the lower-numbered carbon in the double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are PUFAs?

A

Alternative Nomenclature for Polyunsaturated Fatty Acids - Omega Fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe Alternative Nomenclature for Polyunsaturated Fatty Acids.

A

Carbons are numbered in the opposite direction, assigning number 1 to the methyl carbon (also designated ω) at the other end of the chain

The positions of the double bonds are indicted relative to the ω carbon

PUFAs with a double bond between C3 and C4 are called Omega-3 fatty acids and those with a double bond between C6 and C7 Omega-6 fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe structure of an omega-3 fatty acid.

A

First relation with omega carbon (where the first double bond is from the omega carbon 1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What configuration are the majority of fatty acids?

A

Cis configuration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which 2 Omega fatty acids are needed in our diet?

A

a-linolenic acid, Omega-3 fatty acids

Linoleic acid, Omega-6 fatty acids

(opposite sides of double bond placement)

We have enzymes needed to convert linoleic acid into arachidonic acid, and a-linolenic acid to EPA and DHA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does unsaturation cause in lipids?

A

Causes a physical change

The length and degree of saturation of the fatty acid affects the melting point of lipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does length of the fatty acid affect the melting point of lipids?

A

Increases as the chain length increases

Decreases as the number of bonds increases

Summary: The more kinks, the less tightly packed (not as many favorable reactions) which is why melting point is lower
- i.e. butter in fridge (oily when left out)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does degree of saturation of the fatty acid affect the melting point of lipids?

A

Saturated fatty acids pack in a fairly orderly way
- extensive favorable interactions

Unsaturated cis fatty acid pack less orderly due to the kink

  • less-extensive favorable interactions
  • it takes less thermal energy to disrupt disordered packing of unsaturated fatty acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Do saturated or unsaturated fatty acids take less thermal energy to disrupt disordered packing of them?

A

Unsaturated fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the other names for fats?

A

Triacylglycerides (TG)

Tricacylglycerols (TAG)

Fats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the main function for triacylglycerols and what do they contain?

A

energy storage in animals

contains 3 fatty acids esterified to a glycerol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does 3 unsaturated fatty acids usually make?

A

oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Compare the complete oxidation of glycogen and TAG.
Glycogen results in ~6kJ/g TAG results in ~38kJ/g
26
What are TAGs derived from?
Dietary sources Liver biosynthesis Adipocytes
27
How are dietary triacylglycerols transported to the circulatory system?
By chlomicrons
28
How are triacylglycerols synthesized in the liver exported and packaged?
exported in lipoproteins packaged in VLDL Particles
29
Triacylglycerols stored in adipose tissue are hydrolyzed and released as what? How are they transported?
hydrolyzed and released as free fatty acids and glycerols by hormone signaling transported by albumin, a carrier protein.
30
What are essentially insoluble in water in this section?
Triacylglycerols and Cholesteryl esters Yet must be moved from tissue of origin to the tissues where they will be stored or consumed
31
To facilitate their transport, triacylglycerols and cholesteryl esters are carried in the blood plasma as ____.
Lipoprotein particles (entire particles)
32
What are apolipoproteins?
Specific carrier proteins that combine with lipids to form several class of lipoprotein particles Function to promote lipoprotein particle formation in endomembrane systems of cells and also serve as molecular tags for lipoprotein metabolism in the body "Apolipoproteins" refers to the protein part of the lipoprotein particle
33
What are lipoprotein particles?
Spherical complexes with hydrophobic lipids in the core and hydrophilic amino acid side chains at the surface
34
What are the four major classes of lipoprotein particles? (include densities as well)
Smaller particles = more dense --------------------------------------- Chylomicrons (50-200 nm) - largest and least dense Very low-density lipoproteins (VLDL) - 28-70 nm Low-density lipoproteins (LDL) - 20-25 nm - bad cholesterol High-density lipoproteins (HDL) - 8-11 nm - smallest, most dense - good cholesterol
35
What is the specific function of chylomicrons?
Transport TAG and cholesterol from intestinal epithelia to tissues
36
What is the specific function of VLDL?
Transport excess TAG and cholesterol from liver to adipose tissue
37
What is the specific function of LDL?
Transport cholesterol to non-hepatic tissues
38
What is the specific function of HDL?
Transport cholesterol from blood to liver (for excretion) and steroidogenic tissues (for steroid hormone synthesis)
39
Dietary TAGs are transported by ____.
Chylomicrons
40
What is the largest of all lipoprotein particles?
Chylomicrons
41
What kind of membrane does chylomicrons consist of?
Monolayer of phospholipid membrane containing free cholesterol The phospholipid membrane is embedded with up to 6 different apolipoproteins
42
What does the interior of the chylomicron particle contain?
Large amounts of TAGs and cholesterol esters, which are destined for delivery to peripheral tissues Cholesterol has to be hydrophobic so it is esterified
43
What enzymes metabolize dietary TAGs in the intestine before being exported to the circulatory system as components of Chylomicrons?
1. Bile acid which will break down the TAGs - dietary TAGs emulsified by bile acids 2. Lipase cleavage which will break the bond of glycerol and fatty acid 3. Fatty acids resynthesized into triacylglycerols 4. Triacylglycerols packed into chylomicrons 5. Chylomicron export to lymphatic system 6. Enters circulatory system through the left subclavian vein
44
What is ApoC-II?
On the surface of chylomicrons Binds to and activates lipoprotein lipase on endothelial cells, leading to the release of fatty acids and glycerol
45
What does lipoprotein lipase do?
Cleaves acyl ester bonds and releases fatty acids and glycerols
46
What is albumin?
Carrier protein for free fatty acids in blood plasma - binds to fatty acids Most abundant plasma protein Protects cell membranes from the detergent effect of free fatty acids
47
What are the fatty acids synthesized in the liver from and used for?
From acetyl-CoA in the cytosol Used to generate TAGs in the endomembrane system before being packaged into VLDL particles THIS IS IN THE ER
48
Where do VLDL particles that are secreted transported to?
Peripheral tissues
49
What stores TAGs in lipid droplets?
Adipocytes
50
What are lipid droplets?
Storage sites for newly formed TAGs in adipocytes
51
What is liposuction?
Surgical procedure that removes adipocytes from fat deposits in the body
52
What are lipid droplets surrounded by?
Phospholipid monolayer containing large amounts of the protein Perilipin which protects them from the lipases Once perilipin is phosphorylated, lipases can then attach
53
What kind of hormonal signaling in adipocytes stimulate release of free fatty acids (FFAs) from TAGs stored in lipid droplets?
Gluacgon signaling
54
How are free fatty acids released by lipase cleavage?
Sequestered by fatty acid binding protein 4 and then exported to the circulatory system Where they are transported to peripheral tissues by the carrier protein albumin
55
What are cell membranes made of?
Lipids and proteins
56
What are the 3 major types of membrane lipids?
Glycerophospholipids (major component) Sphingolipids Cholesterol
57
What are glycerophospholipids?
Most abundant membrane lipids Addition of a polar head group to phosphatidate 2 fatty acids here with a phosphate group at C3
58
What is the substrate for glycerophospholipid synthesis?
Phosphatidate
59
What is a phosphatidate?
2 FAs and a phosphate group attached to a glycerol
60
What are examples of glycerophospholipids? (just be able to identify them)
Phosphatidyl-serine Phosphatidyl-ethanolamine Phosphatidyl-choline Phosphatidyl-inositol
61
What are sphingolipids?
Addition of a polar head group to sphingosine Derived from Ceramide (Sphingosine and one fatty acid) No glycerol compared to glycerophospholipid
62
What is spingosine?
Synthesized by linking serine to the carboxyl group of palmitate
63
What are the two most common types of sphingolipids?
Sphingophospholipids Sphingoglycolipids
64
How much does cholesterol constitute for lipids in the plasma membrane?
25-40%
65
What affects the fluidity of the membrane?
Cholesterol
66
Cholesterol is a metabolic precursor to?
Steroid hormone for cell signaling (Progesterone) Bile acid biosynthesis for digestion (Glycocholate)
67
What are two sources of cholesterol?
diet biosynthesis
68
What is the structure of cholesterol?
4 rings C27 tetracyclic molecule of a planar ring system with a polar -OH group on one end and a hydrophobic alkyl side chain on the other end
69
How are glycerophospholipids and sphingolipids differentially distributed in the membrane?
two monolayers
70
Is the overall cholesterol content of the inner and outer monolayers of the erythrocyte plasma membrane similar?
Yes they are similar
71
What are lipid rafts?
Discrete membrane regions that contain high concentrations of cholesterol and an aggregation of transmembrane receptor proteins and glycoproteins involved in cell signaling
72
Is the membrane thicker or thinner in the region of the lipid raft?
Thicker because transmembrane glycoproteins are thicker
73
What does the hydrophobic property of lipids contribute to in cell signaling?
Function as high-affinity ligands that bind to hydrophobic properties in receptor proteins
74
What is arachidonate?
precursor for immune regulatory molecules called "Eicosanoids"
75
What is a precursor to vitamin D (cholecalciferol)?
7-Dehydrocholesterol
76
What are the functions of steroid hormones?
Endocrine signaling Half life of hours
77
What are eicosanoids?
a group of signaling molecules derived from C20 PUFAs such as Arachidonate
78
How is arachidonate used as a response to GPCR signaling?
Arachidonate is released from the membrane by phospholipases and further modified
79
What is paracrine's half-lives?
Half-lives of only a few minutes
80
What are the cyclooxygenase enzymes?
COX-1 and COX-2 and are differentially inhibited by aspirin and ibuprofen. COX-2 is also inhibinited by rofecoxib and celecoxib
81
What are non-steroidal anti-inflammatory drugs (NSAIDs)?
Nonselective COX-1/COX-2 inhibitors such as aspirin and ibuprofen are small molecules that bind to the active site of both COX-1 and COX-2
82
What is the function of COX-1?
protects against stomach ulcers but COX-1 inhibition can lead to the development of ulcers
83
What is the function of COX-2?
mediates joint inflammation but COX-2 inhibition reduces join inflammation
84
What are selective COX-2 inhibitors?
Rofecoxib (Vioxx) and Celecoxib (Celebrex)
85
What happens when Selective COX-2 inhibitors inhibit COX-2?
It won't fit COX-1, making it not inhibited and no stomach ulcers It will inhibit COX-2 and reduce inflammation, pain and fever BUT creates a new problem where the Selective COX-2 inhibitors do not fit prostacyclin synthase perfectly and only partially inhibits it resulting in increased platelet aggregation, formation of blood clots

Biochemistry 441B (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions