A) Phospholipids are important in membrane structure B) Serine is a molecule tha

Question

A) Phospholipids are important in membrane structure B) Serine is a molecule that may be part of a phosphoglyceride C) Phosphatidic acid contains two fatty acids and a phosphate group. D) Sphingolipids are the predominant phospholipid in membranes. E) Phospholipids are amphipathic. 19) Which of the following is true of fatty acids? A) Fatty acids are synthesized by the stepwise addition of three carbon units. B) Unsaturated fatty acids are usually branched. C) Fatty acids with 24 carbons are most common. D) Saturated fatty acids have no double bonds between carbons. E) Laurate is an unsaturated fatty acid 20) Which of the following is true of glycolipids? A) Glycolipids are usually found on the exterior surface of the plasma membrane B) Laurate is a glycolipid. C) Fructose and sucrose are often part of glycolipids. D) Glycolipids contain phosphatidic acid. E) Usually more than 10 sugar units are attached to the glycolipid 21) Which of the following is not a steroid? A) testosterone B) estradiol C) cortisol D) aldosterone E) epinephrine 22) Which of the following is not a polymer of numerous monomer units? A) lipids B) proteins C) nucleic acids D) carbohydrates E) starch Chapter 7: 23) Each of the following is a function of membranes except A) defining cell and organelle boundaries. B) sites for specific biochemical functions C) information storage. D) regulation of transport. Copyright O 2012 Pearson Education, Inc.

Explanation / Answer

Ans 19: Fatty acids are long chain carboxylic acids.

They can be of two types: saturated fatty acids, which do not have double bonds in the carbon chain and unsaturated fatty acids, which have one or more double bond.
Fatty acids are synthesized by the stepwise addition of acetyl coA, a two carbon compound.
saturated fatty acids are usually branched.
Fatty acids with 14 or 16 carbons are the most common.
Laurate is a 12 carbon saturated fatty acid.

So the answer is option (D).

Ans 20: Glycolipids are membrane lipids which have a carbohydrate unit covalently bound to the lipid.
Laurate is a 12 carbon long saturated fatty acid.
Glactose and glucose are often found in glycolipids.
Glycolipids contain fatty acid, glycerol or sphingosine.
A single monosaccharide or an oligosaccharide can be present in the glycolipids.

So the answer is option (A).

Ans 21: epinephrine is a hormone, secreted by the adrenal gland. epinephrine is a type of amine called catecholamines. It is synthesized from the amino acid tyrosine, in the adrenal medula.

So the answer is option(C).

Ans 22: Lipids is a generallised term for the molecules which are soluble in non polar solvents. Common lipids are long chain fatty acids, cholesterol, triglycerides and phospholipids. Lipids do not have polymeric molecules.

Proteins are the polymeric molecules made up of amino acid subunits.
nucleic acids are polymeric molecules made up of nucleotides.
Carbohydrates are a group of molecules which have monomeric (monosaccharides) as well as polymeric (polysaccharides) molecules.
Starch is a polymer of glucose units joined in alpha1-4 and alpha 1-6 glycosidic linkages.

So the answer is option (A).

Ans 23: Membranes define the boundry of cell or a cellular compartments.
Membranes are also the sites of biochemical reactions like the iner mitochondrial membrane is the site of oxidative phosphorylation.
They also regulate the transport of molecules as in endocytosis and exocytosis.
Membranes do not store information. this function is particularly related to the nucleic acids DNA and RNA.

So the answer is option (C).

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