Evidence For and Against the Davson-Danielli Model of the Membrane Structure
Evidence for and against the Davson – Danielli model of the membrane structure
Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model
1. A lighter area sandwiched in between two darker layers
2. Proteins appear dark in electron micrographs and phospholids appear light. This appearance supports the Davson-Danielli model.
3. Proteins stain darkly, suggesting that the dark pattern of the cytoplasm of the red blood cell is the distribution of proteins
4. M = I/A
M = 1mm/10nm
M = 1mm/0.00001mm
M = 100,000 X
Data based questions
Membranes in freeze-etched electron micrographs
1.
a) membrane proteins
b) the evidence that these proteins were located in the centre of the membrane falsified the Davson-Danielli model of the membrane structure because it stated that the proteins were on the outside of the membrane
2. The inner membrane as the outer membrane is visible to the right
3. Mitochondria have a rounded shape and cristae. They can be seen middle right, left of middle right and lower right
4. There is a golgi apparatus with cisternae and many vesicles
Diffusions of proteins in membrane
1.
Time (min)
Mean
5
0
10
1.5
25
47
40
92
120
100
2.
3. As time progresses there is an increasin number of cells that have markers fully mixed
4. Membrane proteins can move suggesting that the membrane is fluid and therfore supports the Singer-Nicholson model
5. The range bars are a mesure of variability of data. Conclusions can be are less reliable when the data is more varaible
6. The human body temperature is 37 degrees celcius thus it would be the normal temperatre of humany cells
7. The movement of the markers rapidly increases with temperature. This is because the molecules move faster with higher temperatures. It eventually levels off.
8. The membrane proteins hardly move at lower temperatures. This means that the markers are hardly mixed and the phospholipids in the membrane not fully liquid.
9. The movement of membrane
Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model
1. A lighter area sandwiched in between two darker layers
2. Proteins appear dark in electron micrographs and phospholids appear light. This appearance supports the Davson-Danielli model.
3. Proteins stain darkly, suggesting that the dark pattern of the cytoplasm of the red blood cell is the distribution of proteins
4. M = I/A
M = 1mm/10nm
M = 1mm/0.00001mm
M = 100,000 X
Data based questions
Membranes in freeze-etched electron micrographs
1.
a) membrane proteins
b) the evidence that these proteins were located in the centre of the membrane falsified the Davson-Danielli model of the membrane structure because it stated that the proteins were on the outside of the membrane
2. The inner membrane as the outer membrane is visible to the right
3. Mitochondria have a rounded shape and cristae. They can be seen middle right, left of middle right and lower right
4. There is a golgi apparatus with cisternae and many vesicles
Diffusions of proteins in membrane
1.
Time (min)
Mean
5
0
10
1.5
25
47
40
92
120
100
2.
3. As time progresses there is an increasin number of cells that have markers fully mixed
4. Membrane proteins can move suggesting that the membrane is fluid and therfore supports the Singer-Nicholson model
5. The range bars are a mesure of variability of data. Conclusions can be are less reliable when the data is more varaible
6. The human body temperature is 37 degrees celcius thus it would be the normal temperatre of humany cells
7. The movement of the markers rapidly increases with temperature. This is because the molecules move faster with higher temperatures. It eventually levels off.
8. The membrane proteins hardly move at lower temperatures. This means that the markers are hardly mixed and the phospholipids in the membrane not fully liquid.
9. The movement of membrane