Forces Across Membranes Flashcards

1
Q

What does it mean to say membranes are Dynamic?

A

Constantly formed, maintaines, dismantled or metabolised depending on the cells needs

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2
Q

What makes cell membranes flexible?

A

The fatty acids

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3
Q

What are the 2 classes of membrane protein?

A

Integral

Peripheral

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4
Q

What makes an integral membrane protein?

A
  • Cant be removed without disrupting the membrane

- Amphipathic & oriented the same way as the phospholipids

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5
Q

What are the 4 types of integral membrane protein?

A
  • Channels
  • Carriers
  • Enzymes
  • Receptors
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6
Q

What are peripheral proteins important for?

A

Cell shape & motility

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7
Q

What makes up schwann cell membranes?

A

18% protein

Mainly lipid for insulation against electrical nerve signals

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8
Q

How much protein is in the average cell?

A

Around 50%

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9
Q

What factors aid diffusion?

A

Large surface area
High Permeability
High conc. gradient

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10
Q

What characteristics must a molecule have to diffuse through the lipid bilayer?

A
  • Small
  • Uncharged
  • Hydrophobic (lipophilic)
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11
Q

What is a protein channel?

A

A trans-membranous IMP that act as an aqueous route for ion diffusion

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12
Q

Name the protein channels through which water goes?

A

Aquaporins

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13
Q

What are the two types of ‘gated’ channel?

A

Voltage gated

Ligand Gated

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14
Q

In general what is the electrical gradient across cell membranes?

A

USually the inside is relatively negative to the outside

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15
Q

How do carrier mediated transport systems work?

A

A solute binds to a transmembranous protein
The protein changes coniguration
Solute is now exposed to the other side of the membrane
Solute detaches into the cell

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16
Q

What are the two types of carrier mediated transprot systems?

A

Facilitated transport

Active Transport

17
Q

Difference between facilitated & active transport?

A

Facilitated requires no energy

Active goes against conc. gradient

18
Q

Why are active transport pumps called ATPases?

A

They get their energy from ATP.

19
Q

What is osmolarity?

A

The measure of osmoles of solute per litre of solvent.

20
Q

Osmolarity example:

A

1M glucose has an osmolarity of 1 osmole/L

21
Q

Define osmotic pressure:

A

The pressure required to prevent water movement from high->low conc.

22
Q

Explain hypo-,hyper-,iso- osmotic?

A

Isostomic solutions have same total number of solute particles
Hyperosmostic solution has more solute particles than the ECF
Hypoosmotic have fewer solute molecules than the ECF

23
Q

What is tonicity?

A

Number of non-penetrating particles in solution.

24
Q

Why does only tonicicty determine water movement?

A

Penetrating solutes will move across the membrane to equal concs.
Non-penetrating cant so the water will have to move to compensate.

25
Q

Define endocytosis?

A

Invagination of membrane
Vesicle forms around target
Seperates from membrane on cytoplasmic side
Migrates within cell to destination

26
Q

Exocytosis?

A

Endo but in reverse m8