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BIO112 > Unit 1 Chapter 6: Lipids and Membranes > Flashcards

Unit 1 Chapter 6: Lipids and Membranes Flashcards

1
Q

What are the 7 main functions of lipids

A
  1. energy storage
  2. cell membranes
  3. capture of light energy
  4. hormones and vitamins
  5. insulation
  6. electrical insulation of nerves
  7. water repellency
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2
Q

Are lipids soluble or insoluble in H2O, why?

A

insoluble, because they are hydrocarbons, and therefore are non-polar

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3
Q

What is the structure of a fatty acid

A

a hydrocarbon chain bonded to a hydroxyl

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4
Q

What are the 3 types of lipids found in cells

A

fats, steroids, phospholipids

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5
Q

What are fats

A

composed of 3 fatty acids, bonded to glycerol(3C)/ therefore, also called triglycerides

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6
Q

How do fats form

A

via dehydration between hydroxyl of the glycerol and the caroxyl of a fatty acid

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7
Q

What bond joins glycerol and fatty acids

A

ester linkage

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8
Q

True/False: fats are polymers and fatty acids are monomers

A

false

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9
Q

What are steroids

A

a family of lipids distinguished by their bulky 4 ring structure (differ based on side chain)

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10
Q

What are phospholipids

A

a glycerol, linked to a phosphate and either 2 chains of isoprene(archaea) or 2 fatty acids(bacteria/eukarya)/phosphate is also bonded to a small charged/polar group
-hydrophilic head/hydrophobic tail

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11
Q

Why are vitamins A and D added to milk

A

they are lipid soluble

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12
Q

What does amphipathic mean and which lipids have this quality

A
  • to have both hydrophilic and hydrophobic elements

- phospholipids (steroids can also be)

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13
Q

What is the main role of fats

A

store energy

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14
Q

Which lipids are key components of plasma membranes

A

phospholipids and steroids

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15
Q

Why do bilayers seal/form an enclosed space

A

it is energetically favourable

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16
Q

What is a micelle

A

tiny droplets that form when phospholipid tails are forced together (in a circle)

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17
Q

What is a lipid bilayer

A

forms when 2 sheets of phospholipids align

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18
Q

Do micelles and lipid bilayers require energy to form

A

no they form spontaneously

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19
Q

Describe the permeability of the lipid bilayer and what does it mean

A

highly selectively permeable/ some substances cross the membrane much easier than others

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20
Q

Rank the permeability of substances across the lipid bilayer

A

small NP molecs> large NP molecs>small polar molecs>large polar molecs>ions

21
Q

How to phospholipids behave in the bilayer (movement)

A

in constant lateral motion, very rarely flip to other side of bilayer

22
Q

What is the difference between sat. and unsat. fats

A

sat fats are straight chains that stack nicely (max H-atoms), unsat fats have a double bond which creates a kink and prevents them from stacking nicely

23
Q

How does saturation vs unsaturation affect the lipid bilayr

A

unsat fats create gaps which increase permeability, sat fats stack and therefore reduce permeability

24
Q

How are hydrophobic interactions between phospholips tails affected by saturation and length of hydrocarbon chain

A

interactions weaken in unsat fats (due to gaps)

interactions strengthen in sat fats as length increases

25
Q

What does adding cholesterol do to membrane permeability

A

reduces it by increasing density of the hydrophobic section due to its bulky ring structure

26
Q

How does temperature affect membrane permeability

A

permeability decreases as temp decreases, as temps drop molecs in the bilayer move more slowly as a result the phospholipid tails pack together more tightly and eventually begin to solidify

27
Q

Can proteins be amphipathic

A

yes due to the versatility of their side chains (polar and non-polar)

28
Q

What is diffusion

A

the passive mixing of substances ALONG a concentration gradient(high to low), driven by an increase in entropy

29
Q

Why does diffusion happen

A

Brownian motion (random walk) due to thermal motions and collisions

30
Q

What determines rate of diffusion

A

distance, temp,size of molecule, steepness of conc.gradient

31
Q

What is osmosis

A

diffusion of H2O across a semi permeable membrane driven by an increase in entropy

32
Q

What is a hypertonic solution

A

higher concentration of solute outside of cell, water flows out, results in cell shrivelling/shrinking

33
Q

What is a hypotonic solution

A

higher concentration of solute inside cell, water flows in, results in cell swelling/maybe bursting

34
Q

What is an isotonic solution

A

equal concentration of solute inside and outside of cell

35
Q

What is the hypothesis of the Fluid Mosaic Model

A

integral proteins are in the actual membrane and peripheral are on the outside

36
Q

What are artificial membrane experiments used for

A

determining how fast different solutes can cross the membrane (if at all) when different types of phospholipids are used

37
Q

What are channel proteins/ion channels

A

selective specialized membrane proteins that form pores or holes in the membrane that allow ions to move from high to low concentrations and from like charge to unlike charge via diffusion
-pore is hydrophilic, exterior is hydrophobic (at least for water ones anyways)

38
Q

What is facilitated diffusion

A

diffusion involving channel proteins and carrier proteins

39
Q

What are gated channels

A

channels that open or close in response to the binding of a particular molecule or to a change in the electrical charge on the outside of the membrane

40
Q

What is passive transport

A

transport that is powered by diffusion along an electrochemical gradient and does NOT require energy

41
Q

What are carrier proteins

A

proteins are involved in facilitated diffusion and that bind to the transported substance and change shape in the process

42
Q

What happens when all carrier protein binding sites are full

A

the carrier channel is SATURATED and the rate of diffusion levels off

43
Q

What is active transport

A

transport that requires energy and works AGAINST an electrochemical gradient

44
Q

How does active transport get its energy

A

from a phosphate group and ATP (phosphate binds to protein, makes ADP, then phosphate unbinds and rejoins ADP to make ATP)

45
Q

How does the Na/K pump work (primary active transport)

A
  1. 3 sodium ions bind
  2. phosphate from ATP binds which makes the pump change shape
  3. sodium ions out, 2 potassium ions bind
  4. phosphate group unbinds which makes pump change shape
  5. potassium in, cycle repeats
    - sets up a concentration gradient that allows other processes to occur
46
Q

What is secondary active transport (cotransport)

A

uses established gradients to move substances, ie. our bodies use the energy from the sodium gradient provided from the Na/K pump to move glucose in against its conc.gradient

47
Q

What is the general function of membrane proteins

A

to allow ions and molecs that normally do not cross lipid bilayers to enter or exit cells

48
Q

What are cotransporters

A

proteins used in secondary active transport

BIO112 (19 decks)

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