Lipid Structure and Function- Biochem

A novel disease causes cell membranes to become too fluid, decreasing regulation of molecules between the intracellular and extracellular environments. Which of the following is a possible cause of the disease? A. Absence of cholesterol in the cell membrane B. Increase in saturated fatty acids in the cell membrane C. Increase in LDL production D. Absence of K+ ion channels embedded in the cell membrane.

A. Cholesterol influences cell membrane rigidity by adding structure and integrity, which serves to make the membrane less fluid. Decreasing the amount of cholesterol in the membrane would make the phospholipids pack less efficiently at high temperature therefore making the membrane leaky. An increase in saturated fats could decrease fluidity. LDL are not in cell membranes. K+ are embedded in the membrane and would not effect the membrane fluidity.

The structure below is an example of which of the following types of signaling molecules? (See picture #83) A. Prostaglandins B. Steroids C. Peptide hormone D. Cytokines

A. Prostaglandins- 20 carbon lipid that contains one ring Steroids- four cycloalkane rings fused together: 3 cyclohexane and one cyclepentane Peptide hormone- amino acid chain Cytokines- small protein that is composed of amino acids

Which of the following correctly characterizes the structural difference between sphingomyelins and glycosphingolipids? A. Both have fatty acid backbones, but only glycosphingolipids have sugars B. Sphingophospholipids have a charges head group, while glycosphingolipids have a polar but uncharges head group C. Sphingomyelins are amphipathic, while glycosphingolipids are nonpolar D. Sphingophospholipids have a glycerol head groups, while glycosphingolipids have glucose head groups

A. Sphingomyelins are a major class of sphingolipids that are also phospholipids (sphingophospholipids). These molecules contain a phosphodiester bond. Their head groups have no net charge. They are a major components in the plasma membrane of cells producing myelin, the insulating sheath for axons. Sphingolipids with head groups composed of sugars bonded to glycosidic linkages are considered glycosphingolipids. These molecules contain no phosphodiester linkage; are referred to as neutral glycolipids because they have no net charge at physiological pH.

What functional groups are present on palmitate? A. Carboxylate B. Amine C. Aldehyde D. Phosphate

A. Palmitate is the deprotonated form of palmitic acid, a fatty acid. Fatty acids contain two main functional groups: an aliphatic chain and a carboxylic acid. When the carboxylic acid is deprotonated it is called a carboxylate.

Which of the following best describes how a testosterone receptor might provost prostate cancer growth? A. testosterone is a steroid hormone that passes through the cell membrane, binds to an intracellular androgen receptor, leading to alter Jean expression. A conditionally activated androgen receptor will create a response even in the absence of testosterone. B. testosterone is a steroid hormone that passes through the cell membrane, binds to an intracellular androgen receptor, leading to alter gene expression. A constitutively activated androgen receptor will create a response when in the absence of testosterone. C. testosterone is a steroid hormone that binds to a membrane GPCR, initiating a secondary cascade that will modify gene expression in the target cell. A mutated gene that codes for testosterone might overexpress testosterone, supporting tumor growth. D. testosterone it's a steroid hormone that binds to a membrane receptor tyrosine kinase, initiating a secondary Cascade that will modify gene expression in the target sell. A mutated gene that codes for testosterone my overexpressed testosterone, supporting tumor growth.

B. Testosterone is a steroid hormone, which is derived from cholesterol which is nonpolar. As a result of these hormones can easily across the cell membrane. Steroid hormone receptors are usually intracellular or intra-nuclear. Upon binding to the receptor, steroid hormone receptor complex is undergo confirmational changes. The receptor can then bind directly to DNA resulting in either increase or decreased transcription of a particular gene. C anf D are out because their state that it is a membrane bound receptor. Constitutively active receptors, not conditionally activated ones, can be active even if testosterone is not present. This is why constitutively active receptors might lead to unregulated cell growth.

Which of the following correctly identifies the chemical composition of phosphatidylcholine? A. one fatty acid, one glycerol, two phosphate, and one ethanol amine molecules B. two fatty acids, one glycerol, one phosphate, and one choline molecule C. Three fatty acids, one glycerol, one phosphate, and one choline molecule D. Two fatty acids, one glycerol, and one phosphate molecule

B. phosphatidylcholine will be a glycerophospholipid backbone ( two fatty acids chains, a glycerol backbone, and a phosphate group)with a choline attached to the head.

Chemicals used to clean drains clogged by grease often have NaOH as a component of the solution. What is the purpose of the NaOH? A. NaOH condenses the fatty acids and glycerol, clearing the drain B. NaOH hydrolyzes triacylglycerols that clog the drain, increasing miscibility with water C. NaOH breaks the micelles that clog; eventually smaller micelles will form that can be washed away D. NaOH fully reduces all unsaturated fatty acids, making them easier to wash down the drain

B. NaOH can be used in the process of saponification of triacylglycerols, the main component in grease. NaOH forms glycerol and soap, a sodium salt of the fatty acid, Soaps act as surfactants, forming micelle; a micelle can dissolve a lipid-soluble molecules in its fatty acid core, and then washed away with water because of its shell of carboxylate head groups.

(see picture #84) Which of the following conclusions could be inferred from the table? A. Linolenic acid is more saturated than oleic acid B. Stearic acid is likely to be a solid at room temperature C. Linolenic acid has more double bonds then oleic acid D. Palmitic acid improves the stacking of the other acids

C. Fatty acids that are fully saturated will only have single bonds meaning that they have no pi bonds. Such fatty acids have a greater van der Waal's forces leading to more stable overall structure. Since they are more stable they are likely to be solid at room temperature. This is supposed to unsaturated fatty acids which include one or more double bonds in their chains. This leads to kinks in the chain which prevent efficient stacking and decrease the van der Waal's forces; these are usually more unstable and tend to melt at lower temperatures. When looking at the table we can determine that melting point increases with palmitic acid and oleic acid composition, and decreases with linoleic acid. This must mean that palmitic acid and oleic acid are relatively more saturated compared to linoleic acid. This means that linoleic acid must have more double bonds.

Considering the properties of glycogen and triglycerides, which of the following is the most likely reason the body stores the bulk of its calories in the form of triglycerides and not glycogen? A. Glycogen is difficult just store in large quantities because of its hydrophobic nature B. triglyceride store fewer calories per gram than glycogen leading to less efficient storage C. Glycogen storage requires a significant amount of water well triglyceride storage does not D. triglyceride storage requires a significant amount of water while glycogen storage does not

C. Triglycerides do not require water storage and therefore a pact more efficiently; it is also known the triglyceride store energy more efficiently since their carbon chains are used to make Acetyl CoA which can be used to make energy. Glycogen on the other hand pulls water along during it storage and contains many oxygen molecules that don't contribute to energy generation

Which of the following reactions will form wax? A. glycerol + phosphoric acid + 2 arachidonic acid B. Triacylglycerol + NaOH C. CH3(CH2)28CH2OH + CH3(CH2)24COOH D. CH3(CH2)15(CH)2(CH2)11COOH + H2

C. Waxes are esters of long chain fatty acids with long chain alcohols (OH)

If data in a study on cholesterol levels show that the mean is 150 mg/dL and that the data approximately follow a normal distribution, it can be inferred that: A. the mode and the median will be significantly less than the mean B. the mode and the median will be significantly greater than the mean C. the mode and median will be approximately equal to the mean D. nothing can be inferred about the relationship of the mode and median to the mean

C. We know that in normal distribution the three measure of central tendency are all approximately equal.

Which of the following is NOT an example of function of binding proteins? A. Transport of substances that are insoluble in water B. Sequestration of solutes C. Regulation of gene transcription D. Concurrent enzymatic function of the binding protein

D. Binding proteins functions: transport of insoluble molecules (ex albumin transporting hormones in the blood), sequester substrates( certain solutes are needed at concentrations not found naturally and binding proteins can help sequester these substrates to make them available for biological use), play a role in transcription of genes by binding to DNA and helping to form the DNA-transcription-enzyme complex

(See picture #84) Which of the following is likely the most abundant amino acid in subdomains IIA and IIIA? A. Serine B. Glutamate C. Agrinine D. Leucine

D. Paragraph 1 states that albumin is a carrier for hydrophobic molecules, so it would follow that subdomains IIA and IIIA, the principle binding regions, are rich in hydrophobic amino acid side chains. The amino acids in this region should not have anything on their side chains that carry a charge or would interact well with water.

Cystic fibrosis leads to abnormal Cl- and Na+ transport across certain epithelial membranes, leading to thick, viscous mucus. Mucus buildup limits the exocrine function of the pancreas, impairing digestion. Absorption of certain vitamins depends on proper pancreatic function. Which vitamin would most likely be deficient in a patient with cystic fibrosis? A. B6 B. B12 C. C D. K

D. We know that the pancreas aids in digestion throughout endocrine function of releasing digestive enzymes. One enzyme is Lopez which is released into the duodenum to help digestion of fats. We know that the fat soluble vitamins are A, D, E, and K. Therefore if the pancreas isn't functioning properly a patient without trouble absorbing the fat soluble vitamins.

Which of the following is a hormone derived from cholesterol? 1. Testosterone 2. Estradiol 3. Cortisol 4. Aldosterone A. 3 B. 1 and 2 C. 2 and 3 D. 1, 2, 3, and 4

D. Cholesterol is used as a backbone for all steroid hormones. It is a lipid based molecule that allows these hormones to transverse the relatively lipophilic plasma membrane of cells and enter the nucleus through diffusion. All of the hormones are steroid hormones derived from cholesterol.