Biochem 2280 > Topic 6 > Flashcards

Topic 6 Flashcards

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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
1. Temperature
- higher temp = more movement = more fluidity
26
2. Length of Chains
- longer chains = more attraction to molecules (vanderwaals forces) - harder for lipids to move relative to eachother = lower fluidity
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3. Degree of Unsaturation
- more double bonds = greater fluidity = lipids can't pack
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Impact of Cholesterol on Membrane Fluidity
- high temp: hinder lipid movement, decreased fluidity - low temp: hinders lipid packing, increased fluidity
29
Bilayers are Asymmetrical
- outer surface of bilayer differs from the inner surface
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Proteins in the Bilayer
- specifically oriented - will not rotate - asymmetrically embedded ASYMMETRICAL
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Carbohydrates in the Bilayer
- exist on the outer surface - since their functions are primarily on the outer surface ASSYMETRICAL
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Enzymes/ Lipid Head Groupd in the Bilayer
- maintain asymmetry ASYMMETRICAL
33
Cholesterol in the Bilayer
- does not remain asymmetrical polar groups too small - symmetrically distributed on both sides of the membrane (able to switch sides) NOT ASYMMETRICAL
34
Transverse Diffusion
- slow - unfavoured - entropy effect
35
Composition of Membranes by Mass
- proteins: 50% ( more dense) - lipids: 50% (less dense) - carbohydrates: 1-2%
36
Types of Membrane Proteins
1. Integral Membrane Proteins 2. Peripheral Membrane Proteins 3. Lipid- Linked Proteins
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Types of Integral Membrane Proteins
1. Transmembrane 2. Not transmembrane
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Types of Peripheral Membrane Proteins
1. Embedded 2. On the outside
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Integral Membrane Protein Definition
- a part of the polypeptide chain is exposed to the hydrophobic part of the membrane
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Transmembrane Protein Definition
- across a membrane - area in the lipid bilayer is hydrophobic ( to match the surrounding lipids) - proteins usually span membranes as alpha helices
41
Integral but not Transmembrane Protein Definition
- extens to the hydrophobic interior - does not go all the way across - favourable for them to stay in the membrane
42
Peripheral Membrane Protein Definition
- 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
Embedded Peripheral Membrane Protein Definition
- 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
Lipid- Linked Protein
- lipid os covalently attatched - lipid is in the membrane - no part of the polypeptide interacts with hydrophobic layer
45
Alpha Helix
- backbone has H-bonding (polar) - 20 residues (AA) to use an a-helix to cross a membrane (transmembrane)
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Alpha Helix Side Chains
- hydrophobic which can interact with lipids in a favourable way
47
Multiple Alpha Helices
- centre can be hydrophilic - hydrophobic groups exposed to lipids would have to be on the outside
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Beta Sheets
- can also span membranes - hydrophobic exterior, hydrophilic interior - ex. succinate dehydrogenase
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Succinate Dehydrogenase
- 4 different subunits - transmembrane protein - 2 transmembrane units - 2 peripheral units
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Functions of Membrane Proteins
1. Transporters/ Channels 2. Receptors 3. Enzymes 4. Anchors
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1. Transporters/ Channels
- allow things to move across - like a door
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2. Receptors
- 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
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3. Enzymes
- associated with membranes - can occur without a receptor - can either be embedded in the membrane or peripheral
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4. Anchors
- structural proteins - help give shape to the membrane
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Facillitated Transport
- can be active or passive - an enzyme helps move molecules across a membrane (via transporters and channels)
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Transporters
- specific binding site - need conformational changes during transport - clusters of alpha helices to make binding pockets
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Channels
- 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
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Passive Transport
- 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
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Active Transport
- energy input - needs to be facillitated - low concentration to high concentration - EX. transporters
60
Electrochemical Gradient
- because of charge gradient and chemical gradient - ions will spontaneously move through this gradient
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Simporter Definition
- 2 things moving across a transporter in the same direction
62
Mobility of Integral Membrane Proteins
- 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
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