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Biology > Chapter 1.3 Membrane Structure > Flashcards

Chapter 1.3 Membrane Structure Flashcards

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1
Q

What does the word amphipathic mean?

A

A substance that has both, hydrophobic and hydrophilic properties, is called amphipathic

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2
Q

What structure does the membrane of a cell have?

A

It is a phospholipid bilayer

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3
Q

Which different properties called that the two different parts of the phospholipid bilayer have?

A
  • the phosphate head is hydrophilic

- the hydrocarbon tails are hydrophobic

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4
Q

What does hydrophilic mean?

A

attracted to water

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5
Q

What does hydrophobic mean?

A

not attracted to water

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6
Q

How are the two different parts of the Phospholipid bilayer called?

A
  • phospate head

- hydrocarbon tails (lipids)

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7
Q

Is phosphate attracted to water?

A

Yes, Phosphate is hydrophilic

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8
Q

Are lipids attracted to water?

A

No, lipids are hydrophobic

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9
Q

How does the arrangement of Phospholipid Bilayers happen?

A

When phospholipids are mixed with water the phosphate heads are attracted to the water, but the hydrocarbon tails are attracted to each other=phospholipids on the outside&hydrocarbon tails facing inwards, towards each other

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10
Q

Who did find out about the membranes phospholipid bilayer-structure?

A

Gorter and Grendel

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11
Q

When did Gorter and Grendel find out about the phospholipid bilayer-structure of the cell’s membrane?

A

First experiments were made in 1924

The lipid bilayer model was published in 1927

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12
Q

How did Gorter and Grendel find out about the double membrane of cells?

A

-count the red blood cells in a blood sample
-calculated the membrane surface of all blood cells
-getting the blood cells to burst (adding distilled water)
-putting the bursted blood cells in a centrifuge
-putting the isolated membrane lipids on water (they will form a monolayer)
-calculating the area that the lipids need
(Look up: www.u-helmich.de/bio/cytologie/04/Membranen05.html)

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13
Q

What did Gorter and Grendel find out when they made their experiments?

A

They found out that the area of the phospholipids is twice as large as the area of a cells membrane
Therefore they concluded that the membrane must consist of a phospolipid bilayer

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14
Q

What was wrong about Gorter’s and Grendel’s lipid bilayer model?

A

-did not explain where protein are located in a cell membrane

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15
Q

Who tried to optimize Gorter and Grendel’s model?

A

Davson and Danielli

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16
Q

What did Davson and Danielli propose?

A

They proposed that the phospholipid bilayer was sandwiched by proteins.

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17
Q

Why did Davson and Danielli propose the sandwich model?

A
  • It would explain how membranes, despite being very thin, are a effective in moving some substances
  • The high magnification electron micrographs of membranes showed two dark lines with a lighter band in between=trilaminar structure (proteins appear dark, phospholipids light)
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18
Q

What were problems with the Davson-Danielli model?

A
  • freeze etched electron micrographs
  • structure of membrane proteins
  • fluorescent antibody tagging
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19
Q

What are freeze etched electron micrographs and how did they not fit with the Davson-Danielli model?

A

Freeze fracturing was used to split open the membrane and revealed irregular rough surfaces within the membrane

These rough surfaces were interpreted as being transmembrane proteins, demonstrating that proteins were not solely localised to the outside of the membrane structure

20
Q

Why did the structure of membrane proteins not fit the Davson-Danielli model?

A

Improvements in technology allowed proteins to be extracted from membranes. They were found to be very varied in size and globular in shape

21
Q

What is fluorescent antibody tagging and why did it not fit the Davson-Danielli model ?

A
  • Membrane proteins from two different cells were tagged with red and green fluorescent markers respectively
  • When the two cells were fused, the markers became mixed throughout the membrane of the fused cell
  • This demonstrated that the membrane proteins could move and did not form a static layer

Fluorescent antibody tagging of membrane proteins showed they were mobile and not fixed in place

22
Q

Which model replaced the Davson-Danielli model?

A

The fluid mosaic model/ Sanger-Nicolson model

23
Q

What does the fluid mosaic model look like?

A
  • proteins occupy a variety of positions in the membrane
  • proteins are likened to the tiles in a mosaic
  • proteins are able to move
24
Q

When did Sanger and Nicolson propose the fluid mosaic model?

A

1966

25
Q

What is the primary function of the cell membrane?

A

Forming a barrier through which ions and hydrophilic molecules cannot easily pass

26
Q

What part of the cell membrane has the function to form a barrier through which ions and hydrophilic molecules cannot easily pass?

A

The phospholipid bilayer

27
Q

What are the three components of the cells membrane?

A
  • the phospholipid bilayer
  • membrane proteins
  • cholesterol
28
Q

What functions do the membrane proteins have?

A
  • cell adhesion
  • active transport
  • passive transport
  • communication between cells
  • hormone interaction
29
Q

How is it called when a protein has a carbohydrate chain attached to it?

A

the combined structure is called glycoprotein

30
Q

Membrane proteins can be divided into which three groups?

A
  • Integral proteins
  • Peripheral proteins
  • globular proteins
31
Q

What are integral proteins?

A

Integral proteins are embedded in the hydrocarbon chain in the center of the membrane

32
Q

Are integral proteins hydrophilic or hydrophobic?

A

rather Hydrophobic

33
Q

What are Peripheral proteins?

A

Peripheral proteins are not embedded in the membrane. Most of them are attached to the surface of integral proteins

34
Q

Are peripheral proteins hydrophilic or hydrophobic?

A

peripheral proteins are hydrophilic

35
Q

How are membrane proteins called that are embedded in the phospholipid bilayer?

A

They are called integral proteins

36
Q

How are membrane proteins called that are anchored to the surface of the phospholipid bilayer?

A

They are called peripheral proteins

37
Q

What does the activity rate of a cell membrane depend on?

A

The protein content

The more proteins in the membrane, the more active

38
Q

What is cholesterol?

A

Cholesterol is a type of lipid, a steroid

39
Q

Is cholesterol hydrophilic or hydrophobic?

A

Cholesterol is mostly hydrophobic, just the hydroxyl group (-OH) on its end is hydrophilic

40
Q

What is cholesterol attached to in the cells membrane?

A

To the hydrophobic hydrocarbon tails in the centre of the membrane, just the hydroxyl group (-OH) is hydrophilic, therefore it is attached to the phosphate heads

41
Q

What state of matter is the cell membrane in?

A

The cell membrane does not exactly correspond to one of the three states of matter. The hydrocarbon tails usually behave as a liquid, but the hydrophilic phosphate heads act more like a solid. Overall the membrane is seen as fluid as components of the membrane are free to move.

42
Q

What problems could occur if a cell membrane would be too fluid?

A

the membrane would be less able to control which substances can pass through

43
Q

What problems could occur if the cell membrane was not fluid enough?

A

the movement of the cell and substances within would be restricted

44
Q

What is the cholesterol in the cell membrane good for?

A
  • allows these membranes to work effectively over a wide range of temperatures
  • maintains the fluidity of the membrane (not too fluid, but still flexible
45
Q

What cells do not have a cell membrane containing cholesterol

A

Plant cells, they have a cell wall

46
Q

What are globular proteins?

A

Globular proteins go through the whole plasma membrane, they usually are channels for active transport

Biology (5 decks)

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