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Biochemistry > Lecture 1: Lipid Bilayers > Flashcards

Lecture 1: Lipid Bilayers Flashcards

1
Q

What is the basis of biological membrane?

A

Lipid bilayer

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2
Q

What does the membrane separate?

A

Two watery aqueous state - cytoplasm and extracellular fluid

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3
Q

What domains do lipid contain?

A

Hydrophobic domain and hydrophilic domain

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4
Q

What is hydrophibicty?

A

Non-polar molecules which repel water 1) non polar substances clump together rather than distributing in water 2) entropic effect - disruption of hydrogen bonds between molecules

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5
Q

What is hydrophilic?

A

Having affinity for water Readily dissolving in water Polar

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6
Q

What does water molecules make with polar/charged molecules?

A

Stable interactions

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7
Q

How do phospholipid react to water?

A

The hydrophilic head faces the water while we hare hydronic tail faces away from water

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8
Q

What is a lipid vesicles?

A

Continuous bilayer with water on the inside and outside

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9
Q

What are the basic properties of lipid bilayers?

A

Self-assembling/self-repairing Flexible Fluid Form permeability barriers Tend to enclose aqueous compartments Able to pinch off and reseal

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10
Q

Self-assembling

A

If lipid is in the right environment you can spontaneously form a bilayer (no energy required) Bilayer only works in the presence of water You can take the structure apart by using organic solvents (lipid bilayer will disintegrate)

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11
Q

Flexible

A

Fluid nature allows them to wobble and wave Allow for growth, division and changing shape

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12
Q

Fluid

A

Weak VDW

Forces will mean lipids can exchange places

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13
Q

Self-repairing

A

Deal up a hole in the bilayer, hole will fill up to prevent the interaction of hydrophobic tails with water

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14
Q

Permeability barriers

A

Continuous bilayer Steroid hormone/ oestrogen/ testestorone - non polar molecules where they act on the nucleus of the cell - bind to the reception - change in gene expression Polar molecules: sugar, ATP

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15
Q

Tend to enclose aqueous compartments

A

Prevent exposed edges, ends will join

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16
Q

Able to pinch off and re-seal

A

Splitting the vesicles into 2 (not always energetically favourable as have to break it first)

17
Q

What does the lipid bilayer or plant cell separate?

A

Interior of the Golgi or ER from cytoplasm - make a barrier between two aqueous compartments

18
Q

Experiment - Gorter and Grendel

A

Classic experiment that convinced the world that membranes were based on lipid bilayers RBC surface area will be calculated to see the total size of the cell Extract lipid from the cells of RBC - dissolve in organic solvents Lipids will separate from other cell organelles Put a drop of lipid in the pipette Lipids are spread out on surface of water with their hydrophilic heads in contact with water and non polar hydrophobic tail sticking out in the air Lipid solution will make a mono layer on surface of liquid
Calculate area covered by the mono layer on RBC. Surface area of mono layer formed was twice as big as the RBC total surface area

19
Q

What was problems associated with GG experiment?

A

Surface tension of the model was greater than surface tension of actual membrane There are different membrane compartments in the cell of animal

20
Q

Davson and Danielli

A

Describe the position of proteins within bilayer Membranes exhibit a characteristic “trilaminar” appearance - 3 layers (2 dark outer layers and a lighter inner region) The cell membrane is made of a phospholipid bilayer sandwiched between 2 layers of globular proteins The polar (hydrophilic) heads of phospholipid are orientated towards the protein layers forming a hydrophilic zone The non polar tails of phospholipid are orientated in between polar bears forming a hydrophobic zone

21
Q

What are problems associated with DD experiment

A

Not all membranes are identical or symmetrical Membranes with different function also differ in chemical composition and structure Membrane are biracial with distinct inside and outside faces A membrane with an outer layer of proteins would be an unstable structure Membrane proteins are not soluble in water and like phospholipid are amphiphatic

22
Q

What was observed in a Freeze fracture (electron microscopy) ?

A

Proteins were embedded and not laying on the outside of the membrane and proteins were globular structures Proved that proteins are hydrophobic, folded, made bigger lumps, proteins are spread everywhere Shower that proteins are able to move about the membrane

23
Q

What is Freeze Fracture ?

A

Specialised preparation technique that splits the plasma membrane along the middle of the phospholipid

24
Q

What is the fluid mosaic model?

A

Membranes are composed of phospholipid bilayer with various protein molecules floating around within it

25
Q

Mosaic

A

The phospholipid bilayer is embedded with proteins, resulting in a mosaic of components

26
Q

What are he properties of fluid mosaic model

A

Partially hydrophobic System is fluid

27
Q

Singer and Nicholson

A

Current model of plasma membrane

28
Q

Phospholipid

A

Main fabric of the membrane

29
Q

Cholesterol

A

Attached between phospholipids

30
Q

Integral proteins

A

Embedded within the phospholipid layers

31
Q

Peripheral proteins

A

On the inner or outer surface of the phospholipid bilayer; not embedded within the phospholipids

32
Q

Carbohydrates (glycoproteins and glycolipids)

A

Generally attached to proteins on the outer membrane layer

33
Q

How are mitochondria a bacteria ?

A

They have their own membrane which can be sequenced

34
Q

Mitochondria and chloroplast in plant cell started out as bacteria, what happened next?

A

Symbiosis in the cytoplasm

35
Q

What is symbiosis?

A

When two different species benefit from living and working together

36
Q

In what conditions can few mitochondria live?

A

Anaerobic conditions

Biochemistry (15 decks)

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