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BIOL 112 > L5: Membrane Lipids - Membrane Structure and Self-Assembly > Flashcards

L5: Membrane Lipids - Membrane Structure and Self-Assembly Flashcards

1
Q

What is the primary subunit of the cell membrane?

A

phospholipid

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2
Q

What is the purpose of the cell membrane?

A
  • defines the cell’s boundary
  • barrier to the environment
  • wall to hold stuff in
  • gateway for things that need to move in and out of the cell
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3
Q

What are the two important regions of a phospholipid

A
  • head

- tails

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4
Q

Describe the phospholipid’s head

A
  • contains a number of polar bonds and ionic charges

- polar head

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5
Q

Describe the phospholipid’s tails

A
  • carbon and hydrogen bonds

- non-polar tails

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6
Q

What is an amphipathic molecule?

A

a molecule that contains both polar (hydrophilic) and non-polar (hydrophobic) components.

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7
Q

What happens to phospholipids when added to water?

A

They spontaneously form a bilayer

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8
Q

Describe the non-covalent interactions in terms of the non-polar tails

A

interact with each other with ID-ID interactions

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9
Q

Describe the non-covalent interactions in terms of the polar heads

A

interact with each other and surrounding water with:

  • PD-PD interactions
  • PD-ion interactions
  • H-bond interactions
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10
Q

What is an important aspect of the cell membrane?

A

It is largely held together by non-covalent interactions

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11
Q

Describe the concept of the fluid mosaic model

A
  • “fluid”: membranes are dynamic. the lipids and proteins are not covalently linked and can move freely in the plane of the membrane
  • mosaic: diverse components. Membranes are made up of phospholipids embedded with proteins.
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12
Q

Which molecules can easily pass through the membrane?

A
  • small, non-polar molecules

- CO2, O2, and H2O (even though they’re polar)

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13
Q

What does the direction of net movement depend on?

A

the concentration gradient

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14
Q

Which molecules CANNOT easily pass through the membrane?

A
  • large, polar molecules

- ex: glucose

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15
Q

What are non-covalent interactions?

A
  • weak bonds that are less permanent

- interactions between other molecules

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16
Q

What is macromolecular assembly?

A

When macromolecules assemble into higher-order structures.

- ex: DNA Helix, Lipid Bilayer

17
Q

What are some examples of an INTRAmoleculer interaction?

A

Covalent, Ionic interactions

18
Q

What are the TWO key ideas in regards to phospholipids/membrane structure?

A
  • Phospholipid structure interact via non-covalent interactions
  • Membrane formation is spontaneous due to thermodynamics and hydrophobic effect
19
Q

Define and explain “hydrophilic”

A
  • molecules (or molecular groups that are part of that molecule) that interact with water
  • typically, polar, charged, make H-bonds and ionic interactions
20
Q

Define and explain “hydrophobic”

A
  • molecules (or molecular groups that are part of a larger molecule) that tend to have weak or little interactions with water
  • typically non-polar bonds
21
Q

What type of bond is present between water and water

A

PD-PD

22
Q

What types of bond(s) are present between water and a lipid head group?

A
  • PD-PD
  • PD-Ion
  • PD-ID
23
Q

What types of bond(s) are present between water and lipid tails?

A
  • PD-ID
24
Q

What types of bond(s) are present between lipid tails and lipid tails?

A
  • ID-ID
25
Q

What contributes to the enthalpy of the system?

A

Covalent (between atoms in the phospholipids) and non-covalent interactions contribute to the enthalpy (bondedness) of the system

26
Q

In an aqueous environment, what happens when a lipid bilayer forms?

A
  • Hydrophobic part of lipid molecules make many non-covalent interactions between each other
  • hydrophilic part of lipid molecules make many non-covalent interactions with water
  • water molecules make many non-covalent interactions with the hydrophilic parts and between themselves
27
Q

What does a system’s stability depend on?

A
  • enthalpy

- entropy

28
Q

In regards to phospholipid assembly in water, what happens to the stability of the system?

A
  • it moves from less stable to more stable
29
Q

Describe phospholipid assembly in water in terms of spontaneity

A
  • spontaneous and energetically favourable (delta g < 0)
30
Q

What is the hydrophobic effect?

A
  • The observation that burying non-polar groups away from water increases the system stability
  • Water molecules have increased entropy (motional freedom) when tails come together
31
Q

Describe SPONTANEOUS state of thermodynamics.

A
  • Energetically favourable
  • likely to happen in this direction
  • less stable to more stable
32
Q

Describe NON-SPONTANEOUS state of thermodynamics.

A
  • Energetically unfavourable
  • requires energy to happen in this direction
  • more stable to less stable

BIOL 112 (23 decks)

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