BIOCHEMISTRY W/1 TERM ACHEIVE ACCESS
9th Edition
ISBN: 9781319425746
Author: BERG
Publisher: MAC HIGHER
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Chapter 12, Problem 20P
Interpretation Introduction
Interpretation:
The mechanism that help in the establishment and maintenance of asymmetric membranes should be determined.
Concept introduction:
The cell membrane is a thin and flexible layer present around the cells of all living things. It is also known as cytoplasmicor plasma membrane. Its usual function is to separate the inner side of cells from the outside.
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Check out a sample textbook solutionStudents have asked these similar questions
Which of the following statements is/are incorrect?
1. The cell membrane is purely hydrophobic.
2. Glycerophospholipids have a phosphate derivative group that is known as the polar head group.
3. The individual glycerophospholipid molecules that aggregate become covalently linked to each other to form a lipid bilayer.
4. The interfacial region of a lipid bilayer is polar due to the polar head groups of the lipid molecules that make up the bilayer.
O 1 and 3
O 1 only
O 2 and 4
O 3 only
O 4 only
Two theories of membrane structure are
discussed below.
Unit Membrane Model
Phospholipid molecules are the most abundant
type of lipids in cell membranes. Each consists of a
nonpolar, hydrophobic tail, and a polar, hydrophilic
head. The phospholipid chains orient themselves to
form a bilayer with the tails pointed inward and the
hydrophilic heads lined up on both sides of the
bilayer. An extended monomolecular layer of protein
coats both the outside of the membrane and the
inside of the bilayer, but the protein does not
penetrate the bilayer.
When thin slices of membranes were examined
with an electron microscope, three layers were seen:
two electron-dense layers, with one wider layer
between them.
It was believed that the electron-dense layers
represented proteins, and the lighter area
represented lipids.
Fluid Mosaic Model
The structure of the fluid mosaic membrane is a
bilayer of phospholipid molecules with proteins
inserted into the bilayer. Hydrophilic regions of both
the lipids…
The composition of a cell membrane is not uniform for all types of cells.Some cell membranes are more rigid than others. Rigidity is determinedby a variety of factors, one of which is the structure of the carbon chains in the phospholipids that comprise the membrane. One example of aphospholipid was drawn, and another, having C–C double bonds in its carbon chains, is drawn here. Which phospholipid would be present in the more rigid cell membrane and why?
Chapter 12 Solutions
BIOCHEMISTRY W/1 TERM ACHEIVE ACCESS
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- Explain the following statement: The structure of all biomembranes depends on the chemical properties of phospholipids, whereas the function of each specific biomembrane depends on the specific proteins associated with that membrane.arrow_forwardb) Cellular membranes are generally found in environments that contain lots of water. Draw a diagram of what the phospholipid bilayer of a plasma membrane would look like if it were placed in a hydrophobic environment. (**Note that you only have to draw the phospholipid bilayer, you don't have to draw the other major components again as you did in part a) poned In salt wer (ho byorout obods f.Cplan why sctive tnsport is requind in tive tre nolaib beisio c) What part or parts of a cellular membrane play(s) a role in determining the fluidity of the membrane? pslomlo belowarrow_forwardLipid bilayers are said to behave like two-dimensional fluids. What does this mean? What drives the movement of lipid molecules and proteins within the bilayer? How can such movement be measured? What factors affect the degree of membrane fluidityarrow_forward
- Discuss the permeability of the phospholipid bilayer to the molecules and ions listed below. Is the bilayer freely permeable, somewhat permeable, or impermeable to each of these? 1. OH- 2. H* 3. 0₂ 4. C6H12O6 5. H₂O 6. CO₂ Which is not a major function of the protein in cell membranes? They are important for membrane transport They are important for cell-to-cell joining They function as enzymes They regulate membrane fluidity Which is not true about cell membranes? They frequently flip-flop from one side of the membrane to the other - They can move freely within one side of the bilayer Fatty acid tails of phospholipids form the membrane interior The interior of the bilayer is hydrophoicarrow_forwardMs. Sassa, a biology professor, wanted to demonstrate to her students the applicability of a dialyzing membrane (DM) as a model for the cell membrane by enclosing an aqueous solution in a DM bag and immersing in a beaker containing a different solution. Substances available which are permeable to the DM include 0.02 M NaCl, 0.03 M glucose, and 0.01 M glucose. The only substance available which is completely impermeable to the DM is the 0.01 M lactose. Using the substances given and materials such as a beaker, stirring rod, and string, draw ONLY ONE set-up that can be demonstrated by Ms. Sassa that will satisfy ALL of the following conditions: a. No solute will exhibit a net diffusion out of the cell. b. Glucose will exhibit a net diffusion into the cell. c. NaCl will exhibit a zero net movement. d. No net movement of lactose from the inside to outside of the cell. Make sure to label properly the substance inside the beaker and inside the DM bag.arrow_forwardWhich of the following is true about integral membrane proteins 1. They are always alpha helical 2. They only contain beta sheets 3. They are usually unfolded 4. They usually have long stretches of hydrophobic residuesarrow_forward
- Name: b) Cellular membranes are generally found in environments that contain lots of water. Draw a diagram of what the phospholipid bilayer of a plasma membrane would look like if it were placed in a hydrophobic environment. (**Note that you only have to draw the phospholipid bilayer, you don't have to draw the other major components again as you did in part a) c) What part or parts of a cellular membrane play(s) a role in determining the fluidity of the membrane? 8) Indicate which of the five major types of membrane protein (adhesion, enzymatic, recogniti receptor, and transport) is most likely to be involved in each of the situations described below: a) An oncologist wants to study the cells from a certain tumour that has been surgically remov from a patient. However, she must first treat the tumour with a solution affects a membrane protein on the tumour cells. Because of the effect of the solution on the membrane protein, the tumour tissue falls apart into individual cells. Type of…arrow_forwardLiposomes have long been investigated as drug delivery mechanisms in humans and animals, but only recently have they started to be used clinically in targeted cancer therapies and now, vaccines. Liposomes are simply vesicles with a phospholipid bilayer that contain an inner aqueous compartment. Hydrophilic compounds could be carried in the buffer inside the liposome or hydrophobic drugs within the membrane itself. For instance, the Moderna and Pfizer mRNA vaccines actually use liposome technology to deliver the SARS-CoV-2 spike mRNA to human cells. The liposomes fuse with the plasma membrane allowing the contents of the liposome to enter the cytosol of cells. Of course, once the mRNA is in the cytosol is can be translated to protein on a ribosome. Explain why nucleic acid won’t get through the plasma membrane on its own. Discuss the energetic restrictions to movement through the membranearrow_forwardWhich of the following is/are true about the Cellular Membrane Structure: A. All membranes from plants, animals and microorganisms have similar biomolecular ultrastructure but varies in the types of lipids found. B. All membranes examined that have 2 dark-staining layers in the electron microscope indicated the presence of a layer exposed to the outer cell surface and another facing the cytiplasmic layer. C. The plasma membrane of cells are seen as thin, rigid, gel-like structure that is around 5-10nm thick. D. Some membranes have more protein components and some have similar percentage composition as the lipids. A, B, C only B, C, D only A, C, D only A, B, D onlyarrow_forward
- The fluid mosaic model of membrane structure has been very useful in explaining membrane behavior. However, the description of membrane as proteins floating in a phospholipid sea is oversimplified. Describe some components of membrane that are restricted in their lateral motion.arrow_forwardFor the lipids within the bilayer that comprise the plasma membrane: O The hydrophilic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells, with hydrophobic ends buried in the center of the lipid bilayer. The hydrophobic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells, with hydrophilic ends buried in the center of the lipid bilayer. The hydrophilic ends face the outside (extracellular/exoplasmic face) of the cells and the hydrophobic ends face inside (cytoplasmic face) of the cells. O Hydrophobic and hydrophilic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells randomly. The hydrophobic ends face the outside (extracellular/exoplasmic face) of the cells, the hydrophilic ends face inside (cytoplasmic face) of the cells.arrow_forwardAccording to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? They frequently flip-flop from one side of the membrane to the other. They have hydrophilic tails in the interior of the membrane. They can move laterally along the plane of the membrane. They are free to depart from the membrane and dissolve in the surrounding solution.arrow_forward
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