Biology 1202B Lecture Notes - Lecture 2: Protein Structure, Fluid Mosaic Model, Conformational Change

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20 Apr 2016

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Membranes are composed of a selective permeable phospholipid: barrier to water- soluble molecules, allows for uptake of key nutrients and elimination of waste products. Proteins embedded or attached to the membrane perform membrane functions: transport, signaling, etc. Saturation refers to c bonds to h: fully saturated- bound to maximum number of hydrogen, unsaturated- c=c (double bonds) Spontaneous formation in aqueous environment: hydrophobic effect of non-polar tails and polar heads, tails interact with each other, heads interact with water. Structure is favoured because it is the lowest energy state. Membrane fluidity influenced by type of fatty acid and temperature o. Saturated molecules are more densely packed (linear: unsaturated molecules are less densely packed (kinks, as temperature drops the random motion of lipids slows down. More unsaturated molecules will have a lower. Fluidity lost at a certain point (gelling) gelling point of the membrane. Keeping membrane fluid is essential to cell function.

Related Questions

Cholesterol is transported in the bloodstream in lipoproteinparticles. There are several classes of lipoprotein particles, butone of the most important classes is called Low-densitylipoproteins (LDL). LDL particles are composed of a single moleculeof a large protein called apolipoprotein, as well as thousands ofcholesterols molecules and phospholipids. Part of theapolipoprotein forms the surface of the particles and faces theaqueous phase, while other parts face the hydrophobic interior ofthe particle where they interact with cholesterol and thehydrophobic tails of the phospholipids. When cells need additionalcholesterol, they produce a receptor protein on the surface oftheir plasma membrane that binds to the apolipoprotein andinitiates the uptake of LDL particles into the cell via a processcalled endocytosis.

1. What is the likely reason that LDL particles are used totransport cholesterol in the blood stream?

a. Cholesterol in LDL particles easily inserts into lipidbilayers

b. Cholesterol id largely insoluble in aqueous solutions

c. Cholesterol is synthesized within LDL particles

d. LDL particles can form lipid rafts in the lipid bilayer

2. What is the most likely location of phospholipids in LDLparticles?

a. Bound to the hydrophilic domain of apolipoprotein

b. In the lipid bilayer that surrounds LDL particles

c. On the surface interacting with the aqueous environment aswell as interacting with the hydrophobic core of the particle

d. Within the hydrophobic core of the particle

3. What best describes the class of protein that apolipoproteinbelongs to?

a. Amphipathic proteins

b. Cell surface proteins

c. Membrane associated protein

d. Multipass membrane proteins

4. What kind of molecule on the surface of the cell would bemost likely to serve as a receptor for LDL particles?

a. a cholesterol binding protein

b. a glycolipid

c. a phospholipid

d. trans membrane protein

5. What conditions would be most likely to trigger increaseduptake of LDL particles by cells?

a. increased glycolipid synthesis

b. increased plasma membrane growth

c. increased protein secretion

d. increase protein synthesis

Biology 1202B Lecture Notes - Lecture 2: Protein Structure, Fluid Mosaic Model, Conformational Change

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