Biological membranes & the cytoskeleton

Question 1

What are the three major lipids in cell memnbranes?

Answer 1

• phospholipids
• cholosterol
• glycolipids

Question 2

What determines membrane viscosity?

Answer 2

• temperature (rising temperature increases fluidity)
• increase of unsaturated fatty acids and colesterol reduce fluidity

Question 3

The phospholipid bilayer is pemeable and not permeable for…

Answer 3

permeable for:

• water
• small non-polar molecules (e.g. gases)
• lipophilic compounds (e.g. steroids)

in the absence of special channels, the bilayer is not permeable for:

• ions (which are hydrated)
• larger polar molecules
• large lipophilic substances

Question 4

Types of endo/exocytosis:

Answer 4

Exocytosis:

• constitutive secretion
• regulated exocytosis

Endocytosis:

• phagocytosis
• pinocytosis
• receptor-mediated endocytosis

Question 5

Three constituents of the cytoskeleton:

Answer 5

• actin filaments
• mikrotubuli
• intermediate filaments

Question 6

The basic functions of intracellular filaments:

Answer 6

1. Cytoskeleton
   - Mechanic stability of the cell
   - Spatial fixation of organelles and macromolecules
2. Cell movement
   - Amoeboid movement
   - Muscular contraction
   - Flagella and cilia
3. Cell division (mitosis, meiosis)
4. Intracellular transport