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Flashcards in Membranes and Membrane Proteins Deck (16)
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What are the general functions of the Plasma Membrane?

- Highly selective permeability layer
- Control on an enclosed chemical environment
- Recognising Signalling molecules


What is the composition of a Lipid Bilayer?

In reference to Protein, Carbs, Water, Fat

- 20% of total weight is water

Of dry weight:

40% Lipid
60% Protein
1-10% Carbs


What are the 4 methods of Phospholipid movement?

- Lateral Diffusion
- Rotation
- Flip Flop
- Flexion


Compare Cerebrosides and Ganglioside Glycolipids

Cerebro: Sugar monomer on head group

Ganglio: Sugar multimer on head group


Describe the structure of Cholesterol

- Polar head group
- Rigid planar steroid ring structure
- Non polar hydro carbon tail


Explain how Cholesterol has paradoxical effects on fluidity?

- Reduced phospholipid chain motion, REDUCED fluidity

- Reduced phospholipid packing, INCREASED fluidity


Outline the Functional and Biochemical evidence of Membrane Proteins?

Funcional :
- Facilitated Diffusion
- Specific Cell responses
- Ion gradients

- Freeze Fracture
- Gel Electrophoresis of Proteins


What are the 3 ways protein move?

- Lateral Diffusion
- Rotation
- Conformational change


What are 3 restrictions on Protein mobility?

- Association of Membrane proteins
- Association of extra membranous proteins
- Proteins tend towards fluid phase/ low cholesterol regions


Compare the 2 different membrane protein types?

- Span entire Membrane
- Act as channels
- Hydrophobic interactions

- On surface
- Structural strength
- Hydrophilic interactions


Describe the RBC skeleton composition
Identify the Adapter and Integral proteins

Spectrin and Actin are held in place by Band 4.1 and Ankyrin (Adapter proteins), binded to Glycophorin A and Band 3 (Integral proteins)


Compare the 2 types of Haemolytic Anaemias
- Cellular basis
- Physiological Result

Which abnormal cell is removed by which organ?

Hereditary Spherocytosis:
- Spectrin deleted by 40%-50%
- RBCs round up, less resistant to lysis
- Cleared by spleen

Hereditary Elliptocytosis:
-Defect In Spectrin
- Elliptical RBCs


Describe the biosynthesis of Secreted proteins in 5 steps

1. Two ribosome subunits come together to read mRNA, make a Signal Sequence

2. Signal Sequence is recognised and binded to by a Signal Receptor Particle (SRP), which prevents further peptide Synthesis

3. SRP binds to a Docking Protein bringing the ribosome complex to the ER membrane.

4. Signal Sequence is released and picked up by a Signal Sequence Receptor, and moved through a Protein Translator Complex

5. Signal peptidase cleaves the Signal Sequence, as it is no longer needed to move Protein towards ER


Describe Membrane Protein Biosynthesis after the Signal Sequence is picked up by Signal Sequence Receptor

1. Protein is fed through the ER membrane until a hydrophobic Stop-Transfer is reached. Ribosome is pushed away

2. Ribosome makes rest of protein in cytoplasm


How is the Orientation of a secretory protein controlled?

1. N terminal goes through ER membrane towards lumen

2. (+)ve charges on N terminal stick to Signal Sequence Receptor, forming a loop of protein

3. Signal Peptidase cleaves N terminal, so that it can continue growing into lumen


How is the orientation of a Membrane Protein controlled?

1. While passing through membrane, Hydrophobic Stop-Transfer sequence holds N terminal in membrane

2. Signal peptidase cleaves N terminal

3. Peptide growth continues with C terminal being inside cytoplasm