Chapter 2c Exam 1 Flashcards
Lactose intolerance is the inability to: A) produce milk proteins.
B) produce lactose.
C) digest cellulose.
D) digest lactose.
D. Lactose is a disaccharide that can’t cross the intestinal membrane. The intestinal walls have transporters for absorbing monosaccharides only. Therefore, lactose must be broken down to its monosaccharide components (glucose and galactose) to be absorbed through the intestinal walls. People who are lactose intolerant stop producing the enzyme to break down lactose to monosaccharides. As a result, the sugar accumulates in the intestine. The bacteria living in the intestine then ferment the lactose and produce a lot of acid and gas (mainly CO2). This leads to diarrhea and a bloating sensation! Lactose-free milk contains added lactose digesting enzymes (lactase) that pre-digest lactose in the milk to avoid this problem.
Organic compounds:
A) always contain nitrogen.
B) are synthesized only by animal cells.
C) always contain carbon and hydrogen.
D) always contain oxygen.
C. Oxides of carbon (e.g., CO2, CO, carbonate ion CO32-, bicarbonate HCO3-, and carbonic acid H2CO3) are NOT organic compounds. Bicarbonate ion is an ionic compound formed between H+ and CO32-, resulting in HCO3-.
Which of the following is an amino group?
A) -OH
B) -NH2
C)-COOH
D) -CO
B. -NH2 is the amino group.
Which of the following contains a carboxyl and an amino group?
A) amino acids
B) fats
C) sugars
D) vinegar
A. Amino acids contain both a carboxyl group (-COOH) and an amino group (-NH2).
Which of the following statements about dehydration synthesis is false? A) One monomer loses a hydrogen atom, and the other loses a hydroxyl group.
B) H2O is formed as the monomers are joined.
C) Covalent bonds are formed between the monomers.
D) Animal digestive systems utilize this process to break down food.
D. Digestion is mainly hydrolyzing molecules, the reverse of dehydration synthesis.
The results of dehydration synthesis can be reversed by:
A) condensation.
B) hydrolysis.
C) polymerization.
D) the addition of an amino group.
B. Hydrolysis breaks down polymers into monomers by adding water.
The molecular formula of most monosaccharides represents a multiple of:
A) CH3O. B) CH2O. C) CHO. D) CHO2.
B. The ratio of C:H:Ois 1:2:1 in carbohydrates.
A molecule with the formula C55H110O55 is probably a(n):
A) oil.
B) steroid.
C) protein.
D) polysaccharide.
D. Remember carbohydrates have the formula: CnH2nOn.
Sucrose is formed:
A) from two glucose molecules.
B) from two monosaccharides through dehydration synthesis.
C) when ionic bonds link two monosaccharides.
D) when glucose and lactose are combined.
B. You also need to know lactose is galactose + glucose and maltose is glucose + glucose; sucrose is glucose + fructose.
A disaccharide forms when:
A) two monosaccharides join by dehydration synthesis.
B) two starches join by dehydration synthesis.
C) two monosaccharides join by hydrolysis.
D) two starches join by hydrolysis.
A. Disaccharides form when two monosaccharides are joined by dehydration synthesis.
High-fructose corn syrup is made from corn. The main carbohydrate in corn is a polysaccharide called:
A) fructose.
B) starch.
C) hydrocarbon.
D) cellulose.
B. Starch is the main storage carbohydrate in plants. Glycogen is the main storage for animals.
Which of the following lists contains only polysaccharides?
A) sucrose, starch, and cellulose
B) starch, amino acids, and glycogen C) cellulose, starch, and glycogen
D) fructose, cellulose, and glucose
C. Cellulose is “fiber” in plants. Starch is stored in both leaves and underground root storage organs (such as potato and carrot). Animal cells generally store glycogen in muscles and in the liver.
Cellulose differs from starch in that: A) glycogen is formed by plants and cellulose by animals.
B) most animals cannot break down cellulose, whereas starch is easily digested.
C) starch is made of glucose monomers, whereas cellulose is made of fructose monomers.
D) cellulose is highly branched, whereas starch is unbranched.
B. Most animals cannot break down cellulose, whereas starch is easily digested.
Foods that are high in fiber are most likely derived from:
A) plants.
B) dairy products.
C) red meats.
D) fish.
E) mushrooms.
A. Fungi do NOT have cellulose; they have chitin in the cell wall! Mushrooms are NOT plants! They are phylogenetically more closely related to animals than to plants.
Cows can derive nutrients from cellulose because:
A) they produce the enzymes that break down cellulose.
B) they chew their food so thoroughly that cellulose fibers are broken down.
C) their intestinal tract contains cellulose-hydrolyzing microorganisms.
D) they convert cellulose into starch, which is easily broken down in the intestinal tract.
C. Cows are ruminants. They have 4 stomachs. They utilize the stomach chambers to ferment cellulose and digest it into glucose. Horses, rodents, rabbits, and other herbivores generally digest cellulose in the cecum and appendix. Humans have a vastly reduced appendix and can no longer digest cellulose. This is most likely because humans are descended from primates that are tree dwellers that feed on fruits and nuts and no longer need to digest cellulose. Therefore, when humans ingest cellulose, not only is the cellulose not digested, but we also actually need to spend energy to expel it from our digestive tract (that’s why celery is a “negative calorie” food because it is mostly cellulose). Cellulose does stimulate intestinal movement (called peristalsis) and can improve digestive health.
The storage form of carbohydrates is ________ in animals and ________ in plants.
A) starch . . . glycogen
B) glycogen . . . starch
C) cellulose . . . glycogen
D) glycogen . . . cellulose
B. Glycogen is the storage form in animals, and starch is the storage form in plants.
Which of the following organisms contain the polysaccharide chitin?
A) animals and plants
B) plants and bacteria
C) fungi and insects
D) insects and plants
C. Both the exoskeleton of insects and the cell wall of fungi (e.g., mushrooms) are made up of chitin. This is another proof that mushrooms are NOT plants and they are phylogenetically closer to animals than to plants.
An oil may be converted into a substance that is solid at room temperature by:
A) adding hydrogens, decreasing the number of double bonds in the molecules.
B) removing water, causing a dehydration synthesis reaction to occur.
C) removing hydrogens, increasing the number of double bonds.
D) cooling it, so that double bonds form and the fats solidify.
A. Adding double bonds (a process known as de-saturation) is actually carried out by some fish, amphibians, and reptiles (poikilotherms) to lower the temperature of “gelling or solidifying” (turning into a gel-like solid, like butter instead of oil). The higher the number of double bonds in the fatty acids, the lower the gelling/solidifying temperature will be.
A diet high in animal products and hydrogenated vegetable margarine may increase the risk for atherosclerosis. This is because:
A) most animal fats are unsaturated and most hydrogenated vegetable margarines contain high levels of steroids.
B) most hydrogenated vegetable margarines are hydrogenated oils and most animal products contain high levels of phospholipids.
C) most animal fats are used for energy storage and most hydrogenated vegetable margarines contain high levels of unsaturated fats.
D) most animal fats are saturated and many hydrogenated vegetable margarines contain high levels of trans fats.
D. Trans fats are unnatural and stay in your arteries 10x longer than saturated fat. This increases the risk of atherosclerosis.
What feature of fats makes them hydrophobic?
A) Fats have carboxyl groups.
B) Fats include one glycerol molecule.
C) Fats have polar fatty acids.
D) Fats have nonpolar hydrocarbon chains.
D. Fats have nonpolar hydrocarbon chains, making them hydrophobic.
Fatty acids are:
A) composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio.
B) composed of carbon, hydrogen, glycerol, and a phosphate group.
C) hydrophobic.
D) composed of four linked rings.
C. Fatty acids are hydrophobic.
Which of the following statements regarding triglyceride molecules is false?
A) Triglycerides consist of three fatty acids attached to a glycerol.
B) Triglycerides play a role in energy storage.
C) Triglycerides are a type of fat.
D) Triglycerides are hydrophilic.
D. Fats (triglycerides) are always hydrophobic.
Fatty acids with double bonds between some of their carbons are said to be:
A) unsaturated.
B) saturated.
C) completely hydrogenated.
D) monoglycerides.
A. “Saturated” means it has the maximum number of hydrogen atoms attached to the carbon chains. “Unsaturated” means not reaching the maximum number of hydrogen attaching to the carbon chains; therefore, some carbon atoms form double bonds with their neighbors.
The development of atherosclerotic disease can result from a diet high in:
A) fiber.
B) protein.
C) saturated fats.
D) sugars.
C. Yes, the higher the amount of saturated fat and trans fat you consume, the higher your bad cholesterol (LDL) level would go and the higher the risk of atherosclerosis. Interestingly, LDL level in blood is more correlated to the amount of saturated fat and trans fat you consume instead of the amount of cholesterol you consume.
