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Introduction: The biological membrane helps to separate the contents of the cell from the outside environment. Besides protecting the cell and maintaining its shape, the membranes play several vital roles. They help in cell signal and transport of molecules in and out of the cell.
Answer to Problem 1TY
Correct answer: The chemical composition of biological membranes can be best described by the statement, “Biological membranes are bilayers of phospholipids with associated proteins and carbohydrates”. Hence, the correct answer is option c.
Explanation of Solution
Reason for correct answer:
The membrane is made up of a bilayer of phospholipids. It can be confirmed by taking a look at the nature of the membrane which is both fluid and rigid. It consists of polar heads of phospholipids on the outside and is made up of hydrophobic tails from the inside. Thus, the membrane is polar from the exterior of the layer and hydrophobic from the interior.
The presence of proteins can be easily detected by the presence of various peripheral proteins and protruded fragments of integral proteins. Also, the receptors and associated structures confirm the presence of glycolipids and glycoprotein (made up of carbohydrate) in the membrane.
Option c. is given as “Biological membranes are bilayers of phospholipids with associated proteins and carbohydrates”.
Biological membranes are composed of bilayer of phospholipids along with the proteins and carbohydrate molecules. Hence, the correct answer is option c.
Reasons for the incorrect answer:
Option a. is given as, “Biological membranes are bilayers of proteins with associated lipids and carbohydrates”.
Biological membranes are composed of bilayer of phospholipids not proteins. The membrane is associated with proteins and carbohydrate molecules. Hence, option a. is incorrect.
Option b. is given as, “Biological membranes are composed of two layers-one layer of phospholipids and one layer of proteins”.
Biological membranes are not made up of a layer of proteins and a layer of phospholipids. Hence, option b. is incorrect.
Option d. is given as, “Biological membranes are composed of equal numbers of phospholipids, proteins, and carbohydrates”.
The protein and carbohydrate content in the biological membrane is very small compared to the phospholipids. Hence, option d. is incorrect.
Option e. is given as, “Biological membranes are composed of lipids with proteins attached to the outer surface”.
The polar ends of the phospholipids make the polar head on either side of the membrane. This is possible due to the presence of polar side chains of phosphate. The lipids lack polar ends and hence it cannot form a membrane. Hence, option e. is incorrect.
Hence, the options a., b., d., and e. are incorrect.
The biological membranes is made up with phospholipids bilayers along with proteins and carbohydrates.
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Chapter 5 Solutions
Biology
- How does the phospholipid bilayer of a liposome differ from the phospholipid bilayer of the plasma membrane of a cell? (a) The phospholipid bilayer of a liposome contains only phospholipids, without the proteins that are embedded in the plasma membrane of a cell. (b) The phospholipid bilayer of a liposome contains two bilayers of phospholipid molecules, whereas the plasma membrane of a cell contains only one. (c) The phospholipid bilayer of a liposome completely envelops the liposome, whereas the plasma membrane of a cell does not completely envelop the cell. (d) The phospholipid molecules in the phospholipid bilayer of a liposome are oriented with the lipid ends on the outside of the bilayer and the phosphate groups on the inside.arrow_forwardWhich One is NOT TRUE about membranes? a. Membranes rich in fatty acids containing one or more double bonds are more fluid than membranes with no double bonds in fatty acids. b. If cholesterol is present in membranes, the fluidity of membranes will be reduced at moderate and warm temperatures. c. If cholesterol is present in membranes, the fluidity will remain intact at low temperatures. d. If the fatty acids with double bond are present in membranes, the membrane will be viscous.arrow_forwarda) What are the forces that maintain structural integrity of biological membranes?b) Explain how each force mentioned is formed in membrane lipids. c) Comment on lipid to protein ratio in the membrane of molecules that transport insoluble substances in the blood.arrow_forward
- Which of the following are essential components of cell membrane? a. Cholesterol b.Phospholipids c.Long chain polyunsaturated fatty acids d.All of the abovearrow_forwardCell membranes consists mainly of ________ and ________ . a. lipids; carbohydrates c. lipids; phospholipids b. phospholipids; protein d. phospholipids; ECMarrow_forwardThe structure of a lipid bilayer is determined by the particular properties of its lipid molecules. What would happen if A. Phospholipids had only one hydrocarbon tail instead of two?B. The hydrocarbon tails were shorter than normal, say, about 10 carbon atoms long?C. All of the hydrocarbon tails were saturated?D. All of the hydrocarbon tails were unsaturated?E. The bilayer contained a mixture of two kinds of phospholipid molecules, one with two saturated hydrocarbon tails and the other with two unsaturated hydrocarbon tails?F. Each phospholipid molecule were covalently linked through the end carbon atom of one of its hydrocarbon tails to a phospholipid tail in the opposite monolayer?arrow_forward
- What are the properties of lipids responsible for the property of bilayers? Explain. What are the consequences of this property for the structure of the biological membranes?arrow_forwardWhich of the following is incorrect regarding phospholipids?a. The heads are polar.b. The tails are nonpolar.c. They contain a phosphate group in place of one fatty acid.d. They are energy-storage molecules in the cell.arrow_forwardWhich statements are consistent with the fluid-mosaic model of membranes? (a) All membrane proteins are bound to the interior of the membrane. (b) Both proteins and lipids undergo transverse (flip-flop) diffusion from the inside to the outside of the membrane. (c) Some proteins and lipids undergo lateral diffusion along the inner or outer surface of the membrane. (d) Carbohydrates are covalently bonded to the outside of the membrane. (e) The term mosaic refers to the arrangement of the lipids alone.arrow_forward
- 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_forwardA phospholipid is a biomolecule composed of a phosphate group that is bonded to two lipid chains. Which of the following correctly describes the nature of those two components? (a) The phosphate group is hydrophobic, and the lipid chains are hydrophilic. (b) Both the phosphate group and the lipid chains are hydrophilic. (c) Both the phosphate group and the lipid chains are hydrophobic. (d) The phosphate group is hydrophilic, and the lipid chains are hydrophobic.arrow_forwardDraw a sketch of a lipid bilayer, the structure that forms when a lipid such as phosphatidyl serine is dissolved in water.arrow_forward
