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Cell Biology > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

Who was the first to determine that membranes are made of lipids and how?

A

Charles Overton.

He saw that lipid-soluble substances could penetrate plant root tips, while water soluble molecules could not. So, membranes are made of lipids

-also speculated that mixtures of cholesterol and lecithin were involved.

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2
Q

What scientist dissolved phospholipids in benzene, layered the sample on a water surface to let the benzene evaporate, and consequentially observed that only a monolayer of phospholipids remained?

A

Irving Langmuir

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3
Q

Who were the second to dissolve phospholipids in benzene and what did they do differently?

A

Evert Gorter and F. Grendel

They calculated the number of erythrocytes used in the experiment, and found that the erythrocytes had a phospholipid BILAYER. The law of thermodynamics was used to make the model of the bilayer depicting the hydrocarbon tails pointed inward and the phosphate heads pointed outward.

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4
Q

What are the issues with the Gorter and Grendel model? (2)

A
  • The surface tension of a lipid bilayer is higher than cellular membranes
  • Solutes (sugar and protein) can’t get across this membrane model
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5
Q

Who were the first to suggest that proteins coat the outer sides of the bilayer?

A

Hugh Davson and James Danielli

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6
Q

What are the issues with the Davson-Danielli model?

A
  • Membrane proteins are hydrophobic and cannot easily be removed from the membrane - requires aggressive extraction
  • Protein-lipid compositions of other membranes varied greatly.
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7
Q

Who did the Freeze-Fracture and fluorescent recovery after photobleaching (FRAP) experiments?

A

Singer Nicolson - Mosaic Model.

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8
Q

How did Singer Nicolson perform the Freeze-Fracture experiment?

A
  • Quick-froze membrane with liquid N
  • Split membrane with cold microtome
  • peeled back the P face (protoplasmic/towards the cell)
  • sprayed with electron dense material to observe with SEM

Discovered bumps and valleys, theorized proteins go through the membrane.

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9
Q

How did Singer Nicolson perform the FRAP experiment?

A
  • Fluorescent label GFP placed on membrane protein
  • Laser bleached small spot of membrane
  • Observed the recovery of fluorescence into the spot

Indicated the membrane was fluid

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10
Q

How are lipids added?

A

To the cytosolic side

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11
Q

What are the 4 main lipid components?

A
  1. Phospholipids
  2. Sphingomyelin
  3. Glycolipids
  4. Cholesterol
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12
Q

Which lipid component is involved in Niemann Pick disease and why?

A

Sphingomyelin

Sphingomyelinase enzyme meant to break down sphingomyelin is defective

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13
Q

What are the two types of glycolipids and their associated diseases?

A
  1. Cerebrosides - Gaucher

2. Gangliosides - Tay Sachs

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14
Q

What are the symptoms of Niemann Pick A&B? (6)

A

Mutation of Sphingomyelinase

  • enlarged liver/spleen
  • deterioration of NS
  • deterioration of movement/coordination
  • cherry red spot in eye
  • shortness in height
  • some lung disease
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15
Q

What gene is defective in Niemann Pick disease type C?

A

Gene NPC1. Meant for transport of cholesterol and lipids, also required for fusion with membrane.

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16
Q

What are the symptoms of Niemann Pick disease type C? (4)

A
  • Build up of fat within cells
  • Severe liver disease
  • Lung infections
  • Cells defective in NPC1 are resistant to filovirus (ebola)
17
Q

Where is the defect present for Tay Sachs disease?

A

Defect in lysosomal enzyme: Hexosaminidase A

18
Q

What are the symptoms of Tay Sachs disease? (6)

A
  • GM2 ganglioside in nerves can’t be broken down
  • Begins 3-6 months
  • developmental delay
  • paralysis
  • loss of vision and hearing
  • death in 3-5 years
19
Q

Where is the defect present for Gaucher disease?

A

Defect in lysosomal enzyme: B-glucocerebrosidase

20
Q

What are the symptoms of Gaucher disease? (4)

A
  • Excess glucocerebroside
  • enlarged spleen
  • yellow spots in eye
  • anemia
21
Q

Invitro translation requires…? (10)

A
  1. ribosomes
  2. mRNA
  3. tRNA
  4. initiation factors
  5. elongation factors
  6. termination factors
  7. cofactors
  8. amino acetyl tRNA synthase
  9. amino acids
  10. rabbit reticulocyte or wheat germ lysate
22
Q

What part of the protein is translated first?

A

N-terminus

then the carboxy-terminus

Cell Biology (2 decks)

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