Deck 4: Living Chemistry: From Atoms to Cells

Question 1

The enzyme commonly used in PCR,Taq polymerase,synthesizes what macromolecule?

A) DNA
B) RNA
C) proteins
D) polysaccharides

Answer 1

A

Question 2

Polysaccharides are a polymer of what kind of monomer?

A) amino acids
B) deoxyribonucleotides
C) lipids
D) sugars

Answer 2

D

Question 3

What kind of cellular molecule is shown here?

A) an amino acid
B) glycerol
C) a lipid
D) a sugar

Answer 3

D

Question 4

The molecule shown here is a(n)

A) amino acid.
B) monosaccharide.
C) deoxyribonucleotide.
D) ribonucleotide.

Question 5

Which of the following molecular formulas might be of an organic molecule?

A) H₂ O
B) C₂ H₄O
C) CH₄
D) NH₃

Question 6

In this model of a cellular macromolecule,spirals represent alpha helices and arrows represent beta sheets.What does the model represent?

A) an amino acid
B) a protein
C) a ribonucleic acid
D) a polysaccharide

Question 7

Regular,repeating patterns over short regions of a protein are known as the protein's ________ structure.

A) primary
B) secondary
C) tertiary
D) quaternary

Question 8

Which of the following is true of glycerol?

A) It is hydrophobic.
B) It is a component of proteins.
C) It contains three amino groups.
D) It contains three hydroxyl groups.

Question 9

Which arrow is drawn to a hydrogen that can form a hydrogen bond with water?

A) 1
B) 2
C) 3
D) 4

Question 10

A cell's genome consists of 20% thymine.What is the percentage of cytosine?

A) 20%
B) 30%
C) 60%
D) 80%

Question 11

Which of the following is true of glucose?

A) It is a component of DNA and RNA.
B) It can form a ring structure.
C) It contains numerous amino groups.
D) It is a five-carbon sugar.

Question 12

An infectious agent remains infectious after treatment with an enzyme that destroys DNA.What might the infectious agent be?

A) an archaeal cell
B) a bacteria
C) a eukaryote
D) a virus

Question 13

What organic molecule is shown here?

A) a sugar
B) an amino acid
C) a nucleotide
D) a nucleic acid

Question 14

DNA is synthesized by enzymes that use which of the following as substrates?

A) NTPs
B) dNTPs
C) NDPs
D) dNDPs

Question 15

Molecules with which kinds of bonds are hydrophobic?

A) hydrogen
B) ionic
C) nonpolar covalent
D) polar covalent

Question 16

Molecules that are soluble in water are ________ and molecules that are insoluble in water are ________.

A) endergonic;exergonic
B) nonpolar;polar
C) hydrophobic;hydrophilic
D) hydrophilic;hydrophobic

Question 17

Which of the following is true of both lipids and sugars?

A) They both store energy.
B) They are both hydrophobic.
C) They are both hydrophilic.
D) They both contain nitrogen.

Question 18

What type of cellular molecule is shown here?

A) a lipid
B) an amino acid
C) a ribonucleic acid
D) a protein

Question 19

Which bond type is the strongest in the aqueous cytoplasm of a cell?

A) covalent
B) hydrogen
C) hydrophobic
D) ionic

Question 20

Which of the following is a cellular function of lipids?

A) catalysis
B) information storage
C) compartmentalization
D) sugar production

Question 21

The most typical way for a cell to increase the rate of a reaction is by

A) increasing the cell's temperature.
B) increasing the cell's pH.
C) decreasing the cell's pH.
D) using an enzyme.

Question 22

This image shows the effects of cholera toxin on intestinal cells.Which numbered arrow indicates the step of the toxin entering a cell via endocytosis?

A) 1
B) 2
C) 3
D) 4

Question 23

Fill in the blanks with the pair of words below that make the sentence correct.
________ takes up small extracellular particles via membrane invaginations while ________ takes up larger particles.

A) Endocytosis;phagocytosis
B) Phagocytosis;endocytosis
C) A pseudopod;endocytosis
D) A pseudopod;a lysosome

Question 24

Weak acids can

A) never cross cell membranes.
B) cross cell membranes in their uncharged form.
C) cross cell membranes in their charged form.
D) only cross cell membranes with the aid of a transmembrane protein.

Question 25

A reaction with a positive DG and low activation energy will be

A) spontaneous and slow.
B) exergonic and fast.
C) endergonic and fast.
D) endergonic and slow.

Question 26

You place water containing a radioactive isotope of hydrogen on the outside of a cell.Which of the following will increase the rate at which radioactive water appears on the inside of the cell?

A) a decrease in temperature
B) an increase in unsaturated fatty acids
C) an increase in the fatty acid tail length
D) a decrease in membrane surface area

Question 27

The second law of thermodynamics states that

A) energy is neither created nor destroyed.
B) matter is neither created nor destroyed.
C) in energy transformations,disorder tends to increase.
D) in energy transformations,disorder tends to decrease.

Question 28

Bacteria within a phagosome may be destroyed by the fusing of the phagosome with which acidic eukaryotic organelle?

A) endoplasmic reticulum
B) pseudopod
C) lysosome
D) vesicle

Question 29

Which of the following statements accurately describes the relationship between DG and Kₑq?

A) There is no relationship,as they are independent entities.
B) When Keq is greater than 1,DG is negative.
C) When Keq is greater than 1,DG is positive.
D) When Keq is less than 1,DG is negative.

Question 30

An exergonic reaction may still be slow if

A) the activation energy is high.
B) an enzyme is present.
C) product concentrations are low.
D) reactant concentrations are high.

Question 31

Endosomes and phagosomes are both types of

A) catalysts.
B) oxidizing agents.
C) pseudopods.
D) vesicles.

Question 32

In a reaction where substrates A and B combine to form products C and D (A+B yields C+D),which of the following could drive the reaction to the right toward products?

A) decreasing the concentration of A
B) decreasing the concentration of B
C) increasing the concentration of C
D) decreasing the concentration of D

Question 33

A molecule of ATP undergoes hydrolysis yielding AMP and two molecules of phosphate.Which of the following is true of this reaction?

A) The entropy has decreased.
B) The change in free energy,DG,is positive.
C) The change in free energy,DG,is negative.
D) The reaction is endergonic.

Question 34

The bacterial cell wall offers protection against what type of environment?

A) isotonic
B) hypertonic
C) hypotonic
D) endergonic

Question 35

Which statement accurately describes membrane phospholipids?

A) They are entirely hydrophobic.
B) They are entirely hydrophilic.
C) They have hydrophilic phosphate head groups and hydrophobic fatty acid tails.
D) They have hydrophobic phosphate head groups and hydrophilic fatty acid tails.

Question 36

Which of the following molecules would require a transmembrane protein in order to cross a cell membrane?

A) O₂
B) H₂ O
C) CO₂
D) Na+

Question 37

There is no net movement of water into or out of cells when the cells are in which type of environment?

A) isotonic
B) hypertonic
C) hyperosmotic
D) hypotonic

Question 38

In a cell membrane,phosphate head groups

A) only face the extracellular environment.
B) only face the aqueous cytoplasm.
C) bind each other via ionic bonds in the interior of the membrane.
D) face both the extracellular environment and the cytoplasm.

Question 39

You fluorescently label the phospholipid head groups of a small number of phospholipids in the outer leaflet of the cell membrane to observe them over time with a microscope.At time zero,all the fluorescent label is concentrated in one spot.What will you observe at a later time point?

A) The fluorescently tagged phospholipids will still be together,concentrated in a spot.
B) The fluorescently tagged phospholipids will be spread out,but will still all be part of the outer leaflet.
C) The fluorescently tagged phospholipids will be spread out in the outer leaflet and some will have flip-flopped into the inner leaflet as well.
D) It is impossible to predict what will happen to the labeled phospholipids over time.

Question 40

Fill in the blanks with the pair of words below that make the following sentence correct:
NADH is ________ compared to NAD+ because NADH has gained ________.

A) oxidized;electrons
B) oxidized;neutrons
C) reduced;electrons
D) reduced;neutrons

Question 41

What are some structural differences between cellular DNA and RNA?

Question 42

Shown is the outer electron shell of nitrogen.Nitrogen will form ________ bonds with other atoms.

Question 43

Shown are four different representations of methane.Letter ________ shows a space-filling model.

Question 44

What is a condensation reaction?

Question 45

The molecular formula of the amino acid glycine is C₂H₅NO₂.What is the molecular formula of a glycine pentapeptide?

Question 46

What does amphipathic mean?

Question 47

________ is the general name for a six-carbon sugar.

Question 48

Shown are four different representations of methane.Letter ________ shows a structural formula.

Question 49

The sharing of electrons between two atoms forms ________ bonds.

Question 50

Redox reactions involve the movement of ________ from one molecule or atom to another.

Question 51

CASE HISTORY
Water is the most abundant molecule of life-but too much water can be deadly.In the summer of 2010,heavy rains flooded Pakistan,submerging one-fifth of the country.Millions of people were displaced and exposed to water contaminated by microbial pathogens.Diarrheal disease threatened many,especially children.
A ten-year-old boy named Akal developed profuse diarrhea.He showed extreme thirst,but clean drinking water was unavailable.His diarrhea became watery and cloudy with white flecks of intestinal mucus (known as rice-water stool).Akal became listless,his eyes sunken and his skin wrinkled from dehydration.
A nurse observed a sample of Akal's diarrheal fluid under darkfield microscopy.Numerous bacteria swam rapidly,appearing like "twinkling stars." The bacteria,comma-shaped bacilli,stained Gram negative.
Later testing confirmed Vibrio cholerae,the cause of cholera.These bacteria produce cholera toxin,a protein complex that causes intestinal epithelial cells to secrete large amounts of chloride ion (Cl⁻).The high chloride concentration draws out the positively charged sodium ions (Na⁺).The increased extracellular salt (Na⁺ and Cl⁻,or NaCl)causes water to diffuse out of the epithelial cells,leading to dehydration and diarrhea.Without treatment,Akal's chance of death was 50%.
Akal was treated with oral rehydration therapy (ORT),a method invented by Bangladeshi physicians.ORT involves gradual feeding of a solution containing glucose and NaCl to replace ions and water lost through the diarrhea.Within hours,Akal's flesh had rehydrated,and within a week he made a full recovery.
Explain the properties of cell membranes that lead to the loss of water from epithelial cells in response to cholera toxin.

Question 52

Describe the difference between ionic and hydrogen bonds.

Question 53

What is osmosis and why is it important for cells to maintain osmotic balance?

Question 54

CASE HISTORY
In October 2013,Kelsey was a 28-year-old computer programmer who worked for a prominent technology firm in Silicon Valley.In the middle of the night,Kelsey awoke with abdominal cramps and diarrhea.Her temperature spiked as high as 40°C (104°F).She had a bad headache and could not retain sufficient fluids.After three days,her fever subsided,but the diarrhea continued (about 20 times a day)and began showing blood.Kelsey was admitted to the hospital,where she was given intravenous fluids to control her dehydration.The physician asked her about her dietary history preceding the onset of symptoms.Kelsey recalled that the night before onset,she had eaten rotisserie chicken cooked at the supermarket.An antibody test confirmed the diagnosis of Salmonella enterica serovar heidelberg.Because of the severity of her symptoms,Kelsey was treated with antibiotics,although sometimes antibiotics may prolong the persistence of Salmonella.When amoxicillin failed to control the infection because of bacterial resistance,ciprofloxacin was used.Ultimately,Kelsey's illness was one of more than 400 cases in 23 states traced to contaminated chicken from one California farm.Kelsey recovered,but three months later, S.heidelberg could still be detected in her feces.
Kelsey's illness is caused by a facultative intracellular bacterium,meaning when causing infection it may enter human cells.Explain the process by which large particles such as a bacterial cell can enter membrane covered cells like human intestinal epithelia.

Question 55

CASE HISTORY
In October 2013,Kelsey was a 28-year-old computer programmer who worked for a prominent technology firm in Silicon Valley.In the middle of the night,Kelsey awoke with abdominal cramps and diarrhea.Her temperature spiked as high as 40°C (104°F).She had a bad headache and could not retain sufficient fluids.After three days,her fever subsided,but the diarrhea continued (about 20 times a day)and began showing blood.Kelsey was admitted to the hospital,where she was given intravenous fluids to control her dehydration.The physician asked her about her dietary history preceding the onset of symptoms.Kelsey recalled that the night before onset,she had eaten rotisserie chicken cooked at the supermarket.An antibody test confirmed the diagnosis of Salmonella enterica serovar heidelberg.Because of the severity of her symptoms,Kelsey was treated with antibiotics,although sometimes antibiotics may prolong the persistence of Salmonella.When amoxicillin failed to control the infection because of bacterial resistance,ciprofloxacin was used.Ultimately,Kelsey's illness was one of more than 400 cases in 23 states traced to contaminated chicken from one California farm.Kelsey recovered,but three months later,S.heidelberg could still be detected in her feces.
Kelsey's diarrhea could be caused by which of the following:

A) The Salmonella infection created an isotonic environment in the lumen of Kelsey's gut,leading water to leave her epithelial cells.
B) The Salmonella infection created a hypertonic environment in the lumen of Kelsey's gut,leading water to leave her epithelial cells.
C) The Salmonella infection created an acidic environment in the lumen of Kelsey's gut,leading water to leave her epithelial cells.
D) The Salmonella infection created an oxidizing environment in the lumen of Kelsey's gut,leading water to leave her epithelial cells.