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Biochem 2280 > Topic 6 > Flashcards

Topic 6 Flashcards

1
Q

Lipids

A
  • do not dissolve well in water
  • soluable in organic solvents
  • can be enzyme cofactors/ signalling molecules
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2
Q

Calories

A
  • the amount if energy needed to raise the temp of 1kg of water by 1 degree C
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3
Q

1 “Dietary Calorie” = ?

A
  • 1000 scientific calories
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4
Q

Calories in Fat

A
  • 9 cals/ gram
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5
Q

Calories in Carbs

A
  • 4 cals/ gram
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6
Q

Calories in Protein

A
  • 4 cals/ gram
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7
Q

Types of Lipids

A
  1. Fatty Acids
  2. Triglycerols
  3. Glycerphospholipids
  4. Sphingolipids
  5. Steroids
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8
Q
  1. Fatty Acids
A
  • sources of energy
  • structural components of more complicated lipids
  • ends in a carboxylic acid group
  • hydrocarbon chain (linear, not branched, even # of C’s)
  • double bonds almost always have a cis configuration
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9
Q

Saturated Fatty Acids

A
  • no double bonds
  • cannot fit anymore H atoms onto the chain
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10
Q

Monounsaturated

A
  • one double bond
  • usually added between Carbon 9 and 19 (counting from carboxylic end)
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11
Q

Polyunsaturated

A
  • 2 or more double bonds
  • added every 3rd Carbon
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12
Q
  1. Triglycerols
A
  • used to store fatty acids as energy reserves in adipocytes or fat cells
  • ester linkages occur between OH groups + hydrocarbon tails
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13
Q

Glycerol

A
  • 3 carbon chain with 3 hydroxyl groups
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14
Q
  1. Glycerophospholipids
A
  • has a phosphate group attatched
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15
Q

Phosphate Group

A
  • can be modified with different polar/ hydrophillic groups
  • Ex. choline/ serine
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16
Q
  1. Sphingolipids
A
  • amphipathic
  • found in membranes
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17
Q
  1. Steroids
A
  • a system of 4 connected rings
  • 3 with 6 carbons
  • 1 with 5 carbons
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18
Q

Amphipathic Lipids

A
  • more than 1 nature, “2 natures”
  • come together to make biological molecules
  • hydrophilic head group, hydrophobic tail, and R= long hydrocarbon chain
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19
Q

Amphipathic Lipids Associate in a Bilayer

A
  • lipids are not covalently bonded to eachother
  • bilayer is fluid
  • association happens spontaneously in water
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20
Q

Lipids can Diffuse Within the Bilayer

A
    1. lateral diffusion
    1. rotation
    1. flexion
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21
Q
  1. Lateral Diffusion
A
  • moving around relative to eachother
  • rapid
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22
Q
  1. Rotation
A
  • entire lipid is moving
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23
Q
  1. Flexion
A
  • hydrophobic chains
  • carbon - carbon bond can rotate (causing the membrane to be deformed)
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24
Q

Diffusion Rate is Determined By

A
    1. Temperature
    1. Length of Chains
    1. Degree of Unsaturation
    1. Cholesterol
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25
Q
  1. Temperature
A
  • higher temp = more movement = more fluidity
26
Q
  1. Length of Chains
A
  • longer chains = more attraction to molecules (vanderwaals forces)
  • harder for lipids to move relative to eachother = lower fluidity
27
Q
  1. Degree of Unsaturation
A
  • more double bonds = greater fluidity = lipids can’t pack
28
Q

Impact of Cholesterol on Membrane Fluidity

A
  • high temp: hinder lipid movement, decreased fluidity
  • low temp: hinders lipid packing, increased fluidity
29
Q

Bilayers are Asymmetrical

A
  • outer surface of bilayer differs from the inner surface
30
Q

Proteins in the Bilayer

A
  • specifically oriented
  • will not rotate
  • asymmetrically embedded
    ASYMMETRICAL
31
Q

Carbohydrates in the Bilayer

A
  • exist on the outer surface
  • since their functions are primarily on the outer surface
    ASSYMETRICAL
32
Q

Enzymes/ Lipid Head Groupd in the Bilayer

A
  • maintain asymmetry
    ASYMMETRICAL
33
Q

Cholesterol in the Bilayer

A
  • does not remain asymmetrical
    polar groups too small
  • symmetrically distributed on both sides of the membrane (able to switch sides)
    NOT ASYMMETRICAL
34
Q

Transverse Diffusion

A
  • slow
  • unfavoured
  • entropy effect
35
Q

Composition of Membranes by Mass

A
  • proteins: 50% ( more dense)
  • lipids: 50% (less dense)
  • carbohydrates: 1-2%
36
Q

Types of Membrane Proteins

A
  1. Integral Membrane Proteins
  2. Peripheral Membrane Proteins
  3. Lipid- Linked Proteins
37
Q

Types of Integral Membrane Proteins

A
  1. Transmembrane
  2. Not transmembrane
38
Q

Types of Peripheral Membrane Proteins

A
  1. Embedded
  2. On the outside
39
Q

Integral Membrane Protein Definition

A
  • a part of the polypeptide chain is exposed to the hydrophobic part of the membrane
40
Q

Transmembrane Protein Definition

A
  • across a membrane
  • area in the lipid bilayer is hydrophobic ( to match the surrounding lipids)
  • proteins usually span membranes as alpha helices
41
Q

Integral but not Transmembrane Protein Definition

A
  • extens to the hydrophobic interior
  • does not go all the way across
  • favourable for them to stay in the membrane
42
Q

Peripheral Membrane Protein Definition

A
  • on the outside/ sits on the membrane
  • no part enters the membrane
  • easier to purify (easier to lift off the membrane)
  • interacts with lipid heads
43
Q

Embedded Peripheral Membrane Protein Definition

A
  • associated with membrane through a protein embedded in the membrane
  • this protein would be connected to a transmembrane protein (which goes through the membrane)
44
Q

Lipid- Linked Protein

A
  • lipid os covalently attatched
  • lipid is in the membrane
  • no part of the polypeptide interacts with hydrophobic layer
45
Q

Alpha Helix

A
  • backbone has H-bonding (polar)
  • 20 residues (AA) to use an a-helix to cross a membrane (transmembrane)
46
Q

Alpha Helix Side Chains

A
  • hydrophobic which can interact with lipids in a favourable way
47
Q

Multiple Alpha Helices

A
  • centre can be hydrophilic
  • hydrophobic groups exposed to lipids would have to be on the outside
48
Q

Beta Sheets

A
  • can also span membranes
  • hydrophobic exterior, hydrophilic interior
  • ex. succinate dehydrogenase
49
Q

Succinate Dehydrogenase

A
  • 4 different subunits
  • transmembrane protein
  • 2 transmembrane units
  • 2 peripheral units
50
Q

Functions of Membrane Proteins

A
  1. Transporters/ Channels
  2. Receptors
  3. Enzymes
  4. Anchors
51
Q
  1. Transporters/ Channels
A
  • allow things to move across
  • like a door
52
Q
  1. Receptors
A
  • exist on the surface of cells
  • often associate with enzymes
  • scan and wait for a signal to match with their binding site
  • sends signals to both sides of the membrane
53
Q
  1. Enzymes
A
  • associated with membranes
  • can occur without a receptor
  • can either be embedded in the membrane or peripheral
54
Q
  1. Anchors
A
  • structural proteins
  • help give shape to the membrane
55
Q

Facillitated Transport

A
  • can be active or passive
  • an enzyme helps move molecules across a membrane (via transporters and channels)
56
Q

Transporters

A
  • specific binding site
  • need conformational changes during transport
  • clusters of alpha helices to make binding pockets
57
Q

Channels

A
  • open pathway (once channel is open ions can flow across)
  • do not need conformational change
  • discriminates ( only lets certain ions through)
    - ex. sodium channel will ONLY let sodium ions through
58
Q

Passive Transport

A
  • no energy input
  • spontaneous
  • high concentration to low concentration
  • depending on the molecule it does not need to be facillitated by an enzyme
  • EX. a channel
59
Q

Active Transport

A
  • energy input
  • needs to be facillitated
  • low concentration to high concentration
  • EX. transporters
60
Q

Electrochemical Gradient

A
  • because of charge gradient and chemical gradient
  • ions will spontaneously move through this gradient
61
Q

Simporter Definition

A
  • 2 things moving across a transporter in the same direction
62
Q

Mobility of Integral Membrane Proteins

A
  • proteins diffuse in a plane of bilayer, except when restricted
    1. proteins can be bound to something else
    - restricted movement
    2. proteins can move around within a certain boundary

Biochem 2280 (8 decks)

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