1. Biochemical analysis of the human plasma membrane would demonstrate the prese
ID: 3519603 • Letter: 1
Question
1. Biochemical analysis of the human plasma membrane would demonstrate the presence of?
2. Which of the following organelles of the cell is not involved with the production and processing of proteins (from DNA to the protein's final location)?
Rough Endoplasmic Reticulum
Ribosomes
Nucleus
Smooth Endoplasmic Reticulum
Golgi Apparatus
3. Which of the following statements is correct describing the plasma membrane structure?
It is a thin structure composed of two protein layers with a lipid layer in middle. Thus it is called the fluid mosaic model because of the fluid lipid layer.
It is composed of three layers consisting of nonpolar lipids, proteins and polar lipids with the proteins firmly sandwiched in place so they cannot move between the non-polar and polar lipids.
It is composed of a bilayer of lipid molecules with hydrophobic nonpolar tails lined up in the center of the membrane and hydrophillic polar heads facing the extracellular fluid and the cytoplasm. Protein molecules float in this fluid lipid bilayer.
It is composed of a bilayer of lipid molecules with hydrophillic nonpolar tails lined up in the center of the membrane and hydrophobic polar heads facing the extracellular fluid and the cytoplasm. Protein molecules float in this fluid lipid bilayer.
a.Rough Endoplasmic Reticulum
b.Ribosomes
c.Nucleus
d.Smooth Endoplasmic Reticulum
e.Golgi Apparatus
Explanation / Answer
1] Human plasma membrane is composed of the following biochemical molecules--
* Phospholipids- which are molecules with a phosphate 'head' [ which is hydrophilic] and a lipid 'tail'[ which is hydrophobic] .
* Glycolipids - this is found in a small quantity in the membrane.
* Sterols -- these are found in between the phospholipids and give flexibility to the cell
* Cholesterol - help to keep the membrane fluid consistent and flexible and controls the movement of molecules in and out of the cell
* Proteins- it makes about 50% of the cell membrane . They lie in between the lipid bilayer but do not make a continuous sheet. They are floating molecules and perform various functions , the most important being the passage for entry and exit of molecules throug the cell membrane.
2] Option [d] smooth endoplasmic reticulum [ it is concerned with lipid synthesis]
Protein synthesis starts from the instruction given by a particular codon on the DNA of the chromosome in the nucleus. Free floating ribosomes or those attached to the rough ER are the exact sites where protein synthesis takes place. Golgi apparatus , which is a complex made up of membrane bound tubules, vesicles and cisternae, store the protein which has been synthesised.
3] Option [c] it is composed of a bilayer of lipid molecules with hydrophobic nonpolar tails lined up in the center and hydrophilic polar heads facing the extracellular fluid and the cytoplasm. Protein molecules float in this bilayer.
This is the 'Fluid Mosaic Model' of the cell membrane and explains all the functions that the cell membrane performs. It also explains why the cell membrane is flexible and selectively permeable to different molecules.
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