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Biochemistry and molecular science > Module 4 > Flashcards

Module 4 Flashcards

Lipids and membrance

1
Q

What are lipids?

A

Compounds that are low solubility in water. (generally non-polar

Energy storage, structural components in biological membranes, signals and cofactors

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2
Q

What is the glycerol of the fatty acids

A

O at the end of the M shaped carbon

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3
Q

What are the storage lipids

A

Fatty acids, triacylglycerol, waxes

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4
Q

What are the membrane lipids

A

phospholipids, glycolipids, cholesterol

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5
Q

What are the signaling and cofactor lipids

A

Phospholipid derivatives, steroid hormanes, eicosanoids, lipid soluble vitamins(Vit A)

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6
Q

What are the properties of carboxylic acids

fatty acids

A

almost have an even number of carbon bonds, most natural fatty acids are unbranched

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7
Q

What are saturated fatty acids

A

no double bonds between carbons in the chains

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8
Q

What are monounsaturated fatty acids

A

one double bond between carbons in the alkyl chain

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9
Q

What are polyunsaturated fatty acids

A

more than one double bond in the alkyl chain

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10
Q

What properties as carbon skeleton increase

A

Melting point increase, solubility decrease.

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11
Q

Properties of a saturated fatty acid

A

Usually a fully extended conformation, almost a crystalline array stabilized by extensive hydrophobic interactions of the hydrocarbon chain. Longer chain need more energy to disrupt packing

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12
Q

Properties of unsaturated fatty acids

A

Usually cis configuration, usually not conjugated, pack less orderly due to the disorder. Takes lesser energy to disrupt chain

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13
Q

What are trans fatty acids used for

A

Formed by dehydrogenation of unsaturated fatty acid, increase shelf life or stability at high temperature of oil.

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14
Q

What does trans double bond do?

A

allow fatty acid to adopt extended conformation, packed more regularly and show higher melting points than cis forms. rise of cardiovascular disease

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15
Q

What are omega-3 acids

A

essential nutrients
ALA, DHA and EPA
3rd carbon from the end

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16
Q

What are omega-6 fatty acids

A

6th carbon from the end

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17
Q

What are simple triacylglyceral?

A

3 fatty acids are identical

e.g. tristearin, triolein

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18
Q

What are mixed triacylglycerols fatty acids

A

fatty acids differs

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19
Q

Properties of triacylglycerols

A

-hydrophobic
-provide stored energy and insulation
Adventages
-Higher energy yield than oxidation of other fuel sources such as starch or glycogen
-Not hydrated (lighter)

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20
Q

How well does lipids store energy

A

reduce compounds: lots of available energy through oxidation

-hydrophobic nature : good packing

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21
Q

How does lipid insulate from environment

A

Low thermal conductivity
high heat capacity
mechanical protection

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22
Q

Are lipids water repellant

A

yes, hydrophobic nature

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23
Q

What are the compounds that are in the outer biological membrane

A

Glycolipid, oligosaccharide chans of glycoprotein, GPI-anchored protein

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24
Q

What compounds are in the inner biological membrane

A

Sterol, integral protein(through the inner and outer), peripheral protein(both inner and outer)

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25
What are phospholipids
Phosphate group within their polar head group 2 classes of it Glycerophospholipids (glycerol molecule) sphingolipids (based on sphingosine)
26
What is the structure of Glycerophospholipids
glycerol connected to 2 fatty acid and phophate with a alcohol
27
What is the structure of sphingolipids
a L shaped sphingosine connected to a fatty acid and a phosphate with choline group
28
What is the structure of choline
N connected with 4 carbons and connects to one carbon then the O of the phosphate
29
What are the fatty acids connected by in the lipids
ester linkages
30
What are the range of charges for Glycerophospholipids
-4 - 0
31
What are Glycerophospholipids important for
structural and signalling lipids
32
What are the roles of sphingolipids
Distinctive structural and signalling roles | do not always contain phosphate group but can also fall into a glycolipid grouping
33
What are the roles of glycolipids
Contribute to sites of biological recognition (blood type)
34
What are glycolipids
Contains mono or oligosaccharide units in their head group
35
what are oligosaccharide?
polymer containing sugars(carbohydrate)
36
What are sterols
4 fused carbon rings (A, B & C =6 carbon rings, D= 5 carbon ring near fatty acid chain) with a polar head Amphipathic
37
What is the main sterol in animal tissues
Cholesterol
38
What role does sterol play in the membranes
Structural roles, acting as a precursor for steroid hormones
39
What experiment are done to show that the biological membranes are lipid bilayer
electron microscopy of cell membranes
40
What is the fluid mosaic model
Protein embedded in the bilayer sheet by hydrophobic interactions. interaction are noncovalent(allowing fluid, dynamic properties), charges of the lipid head group contribute significantly to surface properties of membranes
41
What determines the packing arrangements
Shape(cross section of head group relative to side chain)
42
How fatty acids form micelles
Wedge shaped lipid unit
43
What form bilayers
phospholipid (creat cylindrical shape)
44
How are vesicle form
folding back on itself
45
What happens to membrane as temperature increases?
Phase transition temperature, becomes fluid when temperature increase. biological membranes are fluid at 37 degrees
46
What are the movement of lipids in membrane
uncatalyzed lateral diffusion(lateral movement and rapid), uncatalyzed transverse diffusion(flipflop slow) The two monolayer can have different composition
47
Properties of lateral diffusion
Stay within the plane of the leaflet and exchange places with neighbours Can be measured by Fluorescence recovery after photobleaching(FRAP)
48
How does TRANSBILAYER MOVEMENT work?
Specialised protein needed(catalysis) Flippases (from outside) Floppase (from inside) Scramblase (either direction, towards equilibrium)
49
How are biological membrane distributed
Asymmetry of distribution, therefore flip-flop(movement between layer) not favoured
50
What can sterols do in the membrane
Prevent phospholipid packing, its concentration modulate membrane fluidity
51
What is membrane raft(lipid raft or microdomains) made of
Sterols and sphingolipids
52
What are the properties of membrane rafts
Slightly thicker, more ordered(less fluid) and harder to dissolve in non-ionic detergent. Possible for lateral diffusion Many lipid modified protein
53
What roles do membrane proteins play?
1. Permit selective entry and exit of molecules from cell eg. via transporters 2. Provide recognition signals e.g. receptors for growth factors 3. Provide structural support to the cell
54
How do proteins interact with the membrane?
1. Integral membrane protein 2. Peripheral protein | Most membrane proteins are free to diffuse laterally in lipid matrix
55
What are Integral membrane proteins
Inbetween membrane
56
what are Peripheral membrane proteins
Associated with outside surfaces
57
How can we distinguish between the types of membrane proteins?
1. the chemical nature of the interaction between protein and membrane 2. the position of the protein relative to the face of the membrane
58
How does peripheral membrane proteins associate with membranes
ionic interactions and H-bonding with: • polar head groups of lipids • integral membrane proteins
59
How does Integral membrane proteins interact with membranes
hydrophobic interactions with: | • acyl chains of membrane lipids
60
Properties of Peripheral Membrane Proteins
1. high salt 2. change pH 3. chelating agent Released from membrane by reagents that disrupt ionic interactions
61
Properties of Intergral membrane proteins
Released from membrane by reagents that disrupt hydrophobic interactions eg detergents (SDS)
62
How does detergent work in membrane protein?
Dissolves membrane and maintain extracted protein in solution by interacting with hydrophobic regions of protein
63
Does all membrane proteins have a unique orientation in the membrane
Yes
64
How can we determine orientation/ arrangement of membrane proteins?
Protease sensitivity of proteins from intact cells trypsin cleaves carbonyl side of lysine and arginine Only has access to outer layer. analyse remaining protein
65
Based on sequence can we predict transmembrane protein domains?
Yes by Genome sequencing projecting
66
How do we know which transmembrane protein domain?
– sequence will consist of hydrophobic amino acids – conformation will be an α-helix – span (segment of protein) equal to width of membrane
67
What is the thickness of membrane and number of residues in alpha helix in membrane
3nm 20 hydrophobic residues
68
How to determine the number of protein and which is in the membrane
using hydropathy index
69
Which substance are permeable to membrane?
Only a few eg O2, CO2, mostly impermeable
70
What are responsible for transferring small water soluble molecules across lipid by layer
Transport proteins
71
What are the classes of membrane transport proteins
Carriers(transporter) and channels
72
How does passive carrier protein transport
undergo conformational change
73
Examples of Passive transporter
GLUT 1( glucose down a concentration gradient, no other substance)
74
What is the mechanism of glucose transport
two conformation, Binding of glucose (from blood plasma) may induce a conformation change from T1 to T2
75
Mechanism of active transporters
Requires energy
76
Example of active transporter
P-type ATPases
77
What is P-type ATPases
membrane proteins that uses ATP hydrolysis to pump ions across membranes
78
What doe p-type ATPases pump
* Na+-K+ ATPase (pumps Na+ out, ↑K+ in cell) * H+-K+ ATPase (pumps H+ out, K+ in; acidifies stomach) * Ca2+ ATPase (pumps Ca2+ out of cytosol)
79
What maintain cell volume and create transmembrane electrical potential
Na and K gradient in animal cells

Biochemistry and molecular science (12 decks)

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