Membrane Structure Flashcards

1
Q

What is the width of the cell membrane?

A

5nm

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2
Q

What are the main functions of the cell membrane?

A
  • Control what enters and exits the cell.
  • Maintains the difference in ion concentration across the membrane
  • Participates in joining and interaction with neighbouring cells.
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3
Q

What lipids are found in the membrane?

A

Phosphoglycerides, sphingolipids and sterols.

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4
Q

What do sterols have connected to their polar heads?

A

A rigid steroid ring.

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5
Q

How does cholesterol affect the membrane?

A

Stiffens it.

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6
Q

What kind of lipids form micelles?

A

Single tailed lipids.

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7
Q

What kind of lipids form bilayers?

A

Double tailed lipids.

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8
Q

Why did the membrane take the structure of a sphere?

A

As a planar bilayer would leave the edge lipid exposed which is unfavourable.

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9
Q

How do unsaturated hydrocarbon chains on lipids affect the cell membrane?

A

The phospholipids pack less tightly and so the membrane is more fluid.

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10
Q

What are rafts?

A

Areas of the membrane with an increased concentration of proteins.

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11
Q

What are examples of ligand binding receptors?

A

Hormone receptors and growth factor receptors.

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12
Q

Where do adhesion molecules form contact?

A

On neighbouring cells.

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13
Q

What is the function of adhesion molecules?

A

To regulate cell shape, growth and differentiation.

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14
Q

What is the function of pores and channels?

A

To allow water/ions to pass through the lipid bilayer.

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15
Q

What is the function of carrier proteins?

A

To couple with molecules in facilitated diffusion.

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16
Q

What is the function of pumps?

A

They use energy from ATP hydrolysis to drive transport of substances against their concentration gradient.

17
Q

What do the short carbohydrate chains on the membrane allow the cell to do?

A

Identify other cells.

18
Q

What allows bending of the bilayer?

A

Proteins

19
Q

What does cell adhesion result from?

A

Interactions between proteins or carbohydrates.

20
Q

What is homotypic cell adhesion?

A

The same type of molecule binds on each membrane.

21
Q

What is heterotypic cell adhesion?

A

Different molecules bind on each cell.

22
Q

What are the three types of cell junctions?

A

Tight junctions, desmosomes and gap junctions.

23
Q

What is the function of tight junctions?

A

To prevent substances moving between cells and cell migration.

24
Q

What is the function of desmosomes?

A

To hold cells tightly together but still allows substances to move in the extracellular matrix.

25
Q

What is the function of gap junctions?

A

They run between pores and allow substances to pass between cells.

26
Q

What is the function of integrin?

A

To allow epithelial cells to attach to the extracellular matrix.