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Cell biology > Lipids and cellular membrane structure and function > Flashcards

Lipids and cellular membrane structure and function Flashcards

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1
Q

What are sphingolipids?

A

Sphingolipids are lipids that do not contain glycerol. Instead they contain the long chain amino alcohol sphingosine, from which this class of compounds takes its name.

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2
Q

Where are sphingolipids most abundant?

A

They are most abundant in the nervous system

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3
Q

What are the simplest compounds of the class of sphingolipids? Describe this compound

A

Ceramides

They consist of one fatty acid linked to the amino group of sphingosine by an amide bond.

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4
Q

How are sphingomyelins structured?

A

In sphingomyelins, the primary alcohol group of sphingosine is esterified to phosphoric acid, which, in turn, is esterified to another amino alcohol, choline

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5
Q

What are the functions of complex sphingolipids?

A

Complex sphingolipids in cell membranes are thought to serve several functions, including protection from harmful environmental factors, signal transmission, and adhesion sites for extracellular proteins

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6
Q

What are the functions of lipids (name a function for each of the three types of lipids)

A

Triglycerides: Storage form of lipids
Sphingolipids: Signaling, protein targets
Phospholipids: make up biological membranes

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7
Q

What are phospholipids derived from?

A

phosphatidic acid

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8
Q

Give an example of simple lipids?

A

Triglycerides

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9
Q

Give an example of complex lipids

A

Sphingolipids and glucerophospholipids

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10
Q

Give an example of a polar lipid

A

Phospholipid

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11
Q

What is the cell membrane composed of? (name all the molecules)

A 
Phospholipids
Cholesterol
Proteins
Other lipids
Carbohydrates
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12
Q

Which substances are impermeable to the phospholipid bilayer of the cell membrane?

A

Water soluble molecules such as ions, glucose and urea

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13
Q

Which substances are permeable to the phospholipid bilayer?

A

Oxygen, carbon dioxide, and alcohol

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14
Q

What are the functions four functions of cholesterol in the cell membrane?

A
  • It immobilizes the outer surface of the membrane, reducing fluidity.
  • Reduces permeability to very small water-soluble molecules that would otherwise freely cross.
  • Separate phospholipid tails thus preventing crystallization of the membrane.
  • Secures peripheral proteins by forming high density lipid rafts capable of anchoring the proteins
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15
Q

What are sphingomyelins made up of?

A

Ceramide + choline

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16
Q

Where are sphingomyelins mostly found?

A

Nerve tissues, red blood cells, and other ocular lenses

17
Q

True or false:

Sphingomyelins are incapable of forming hydrogen bonds

A

FALSE

Sphiingomyelins have hydrogen bonding capabilities

18
Q

True or false:

Hydrophobic chains of sphingomyelin are more saturated than other phospholipids

A

True

19
Q

Why are omega 3 and omega 6 considered essential?

A

Omega 3 (DHA) and Omega 6 (AA) are polyunsaturated fatty acids that are most prominent in brain cells

20
Q

What is optimum ratio between Omega 3 and 6?

A

1:1 to 4:1

20
Q

What is optimum ratio between Omega 3 and 6?

A

1:1 to 4:1

21
Q

Describe integral glycoproteins

A 
Protrude all the way through the membrane
Structural channels (or pores)
Carrier proteins (active transport)
22
Q

Describe peripheral glycoproteins

A

Attached only to one surface
Receptors for water soluble chemicals
Enzymatically activate the intracellular part of the protein

23
Q

List 4 functions of the cell membrane

A

Identification
Communication
Transport
Isolation of cytoplasm from the external environment

24
Q

What are the chemical characteristics of the cell membrane?

A
  • Amphiphilic
  • Semipermeable
  • Fluid
25
Q

Define fluidity

A

Ability or ease of molecules to move in the membrane. It refers to the viscosity of the cell membrane

26
Q

What factors influence fluidity of the membrane?

A
  • Alcohol consumption: increase fluidity
  • Cholesterol composition: less fluidity
  • Phospholipid (unsaturated, saturated)
  • Temperature
27
Q

Why do unsaturated fatty acids increase membrane permeability?

A

Unsaturated FAs have kinks that lead to lesser van de Waals interaction with other lipids

28
Q

Why do short chain FAs increase the membrane’s permeability?

A

Less surface area because the interaction between hydrocarbons is reduced

29
Q

Define permeability

A

Permeability of a membrane is the rate of passive diffusion of molecules across the membrane. It’s the ease with which molecules pass through the membrane barrier.

30
Q

List factors influencing permeability

A
  1. Temp
  2. Solvent concentration
  3. Chain length
  4. Whether the membrane lipids are saturated/unsaturated
31
Q

List and explain the factors affecting drug delivery

A

-Physicochemical properties of the drug:
Molecular size
Concentration gradient
pKa

-Properties of the membrane
Thickness
Surface area
Permeability (drug-specific)
Solution pH on either side of the membrane

-Type of transport
Paracellular, in which case it diffuses through extracellular fluid
Diffusion through membranes
Active transport by facilitated diffusion or transport proteins

32
Q

What are the considerations for drug delivery?

A

Small molecule cargo – conjugate to known carrier
Peptide cargo – cyclizing peptides, methylating nitorogen
Protein cargo – membrane disruption, pores/channels, virus based, lipid/polymer carriers, nano-carriers

33
Q

How does pH affect drug solubility?

A

The lipid solubility of drugs is determined by the degree to which they are ionised in the body fluid, which in turn depends on their pKa and on the pH of the body fluid

34
Q

Nme the lipid-soluble vitamins

A

Vitamin A (Retinol, retinoic acid): vision, growth, cell division, reproduction, antioxidant and immunity
Vitamin D : help the body absorb and retain calcium and phosphorus
Vitamin E (Alpha-tocopherol): Antioxidant, immune protection, works with vit K
Vitamin K: blood clotting and wound healing

Cell biology (7 decks)

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