CH 5/6 Practice-Test

1
CH 5/6 Practice-Test

• The questions are in
• no particular order!

2
Atoms and electrons can be recycled indefinitely
energy ________.

1. - since it can be neither created nor destroyed -
   recycles as well
2. can be reorganized when plants reclaim the CO2
   and water produced in respiration
3. must be continuously replaced because every use
   of energy degrades its ability to perform useful
   work
4. can be created when needed through cellular
   mechanisms
5. none of the choices

3
Patients with mitochondrial disorders share many
symptoms, such as muscle weakness, because
mitochondria ________.

1. organize the construction of muscle protein
2. generate the ATP that is necessary for muscle
   contraction
3. store and then release the oxygen used during
   muscle contraction
4. facilitate the transport of glucose across the
   muscle cell membrane

4
Which process below is correctly matched with its
cellular location?

1. glycolysis - mitochondrion
2. Krebs cycle - cytoplasm
3. lactic acid fermentation - cytoplasm
4. electron transfer phosphorylation - Golgi
5. electron transfer phosphorylation cytoplasm

5
Potential energy can be visualized as the energy
________.

1. of motion
2. of position and organization
3. of a falling object
4. of heat or thermal energy
5. that drives muscle contraction

6
In contrast to linear metabolic pathways, in
cyclic pathways, ________.

1. the last step regenerates the same molecule as
   was used in the first step of the sequence
2. the product molecules are arranged in closed-loop
   configurations like the monosaccharides
3. reactants or intermediates are channeled into two
   or more reaction sequences
4. the enzymes are positioned sequentially along a
   membrane
5. only degradative reactions occur

7
Exergonic reactions produce both products and
free energy the free energy may be either
________.

1. heat or light
2. oxidation or reduction
3. kinetic or potential energy
4. heat or muscle contraction
5. mechanical or chemical energy

8
Enzymes lower activation energy by ________.

1. helping substrates get together
2. orienting substrates into positions that favor a
   reaction
3. shutting out water molecules
4. inducing a fit between the enzyme and the
   substrate
5. all of the choices

9
Less than 50 of the energy in glucose is
converted to ATP bond energy the remaining
energy ________.

1. becomes activation energy for the enzymes
2. is stored in fat and metabolized later as needed
3. is carried off by CO2 and water
4. is used to move muscle and drive active processes
5. is converted to heat

10
Regardless of the source of energy, virtually all
living organisms convert their energy source into
________ before using it.

1. glucose
2. carbon dioxide
3. ATP
4. light and heat

11
Where in the mitochondrion are the electron
transfer chains located?

1. in the inner compartment
2. embedded in the inner membrane
3. in the outer compartment
4. embedded in the outer membrane
5. in the mitochondrial matrix

12
How many ATP molecules are formed during the
Krebs cycle for each acetyl-CoA that enters?

• 0
• 1
• 2
• 4
• 6
• We learned this as 2 ATP are formed during the
  Krebs cycle for 2 acetyl-CoA.

13
What statement best characterizes glycolysis?

1. glycogen, a large carbohydrate molecule, is
   broken down to monosaccharides
2. a molecule of glucose is converted into two
   molecules of pyruvate
3. overall, there is a net energy cost to the cell
   during glycolysis
4. the carbon atoms in glucose are oxidized to form
   carbon dioxide and water

14
What cofactor accepts electrons in both
glycolysis and the Krebs cycle?

1. ATP
2. NADP
3. FAD
4. NAD
5. CoA

15
Substrate-level phosphorylation, in contrast to
electron transfer phosphorylation, can occur
________.

1. both in the cytoplasm and the mitochondrion
2. under anaerobic conditions
3. without the aid of the enzyme ATP synthase
4. all of the choices are correct

16
After two turns of the Krebs cycle, the original
glucose is completely disassembled but the cell
has gained only four ATP. What happened to the
bulk of the energy?

1. it has been converted to heat and is no longer
   capable of producing work
2. glucose is a small molecule four ATP was all the
   cell could hope to recover
3. it was used to reduce NAD and FAD but will be
   recovered during electron transfer
   phosphorylation
4. it is still contained within the carbon-oxygen
   bonds of carbon dioxide

17
Prior to entering the Krebs cycle, pyruvate loses
________ and is converted to ________.

1. a water, acetyl-CoA
2. a carbon dioxide, oxaloacetate
3. a carbon dioxide, acetyl-CoA
4. a water, oxaloacetate
5. electrons, lactate

18
What is the role of the molecular oxygen (O2) in
aerobic respiration?

1. it donates H's and electrons
2. oxygen combines with carbon from glucose to form
   CO2
3. it transfers H's from the Krebs cycle by
   temporarily forming water
4. oxygen accepts electrons from the electron
   transfer chain and hydrogen ion to form water
5. oxygen is needed to synthesize ATP

19
The energy released during electron transfer
reactions is initially used to push ________ into
the outer compartment.

1. electrons
2. NADH
3. hydrogen ions
4. oxygen
5. ATP

20
A mitochondrion has a double membrane with the
outer compartment between them. Within the outer
compartment, ________.

1. hydrogen ions accumulate to form the proton
   gradient that drives ATP synthase
2. carbon dioxide accumulates and is stored until it
   can be transported to the lung
3. the matrix containing Krebs cycle enzymes is
   located
4. the soluble electron transport enzymes are found

21
For glycolysis to continue in eukaryotes, NAD
must be regenerated. In anaerobic environments,
this is accomplished by ________, which produces
________ as the end product(s).

1. fermentation, ethanol or lactic acid
2. phosphorylation, ATP
3. an exchange reaction, FADH2 and NAD
4. hydrogenation, NADPH2

22
Substrate-level phosphorylation occurs in only
the ________stage(s) of aerobic respiration.

1. glycolysis and electron transfer
2. Krebs cycle
3. glycolysis
4. glycolysis and Krebs cycle
5. Krebs cycle and electron transfer

23
Careful measurement reveals that the cofactors
coenzyme A, NAD, and FAD are present in cells in
relatively low concentrations. This is not
surprising because ________.

1. each becomes toxic at higher concentrations and
   would damage cell metabolism
2. like enzymes, each can be used over and over
3. they are costly molecules to synthesize and cells
   make them only as needed
4. each is degraded immediately after being used,
   preventing any buildup from occurring
5. their roles in aerobic respiration are extremely
   minor

24
Chemical reactions that end with a net release of
energy are classified as ________.

1. endodermal
2. endothermal
3. endergonic
4. exergonic

25
Activation energy describes the minimum amount of
energy required ________.

1. for the reactants to reach the transition state
   and react
2. before water and carbon dioxide will combine to
   form glucose
3. to raise the temperature of a cell to within its
   homeostatic range
4. before nutrients can cycle between producers and
   consumers

26
How does the release of a phosphate group from
ATP provide energy for other reactions?

1. the associated heat provides the activation
   energy to start the reaction
2. the phosphate collides with one or more of the
   reacting molecules
3. the phosphate is transferred to another molecule,
   energizing it
4. phosphate must be added to the substrate before
   it will enter an active site

27
Which of the following is an example of an
exergonic reaction?

1. 6 CO2 6 H2O - gt C6H12O6 6 O2
2. ATP - gt ADP Pi
3. ADP Pi - gt ATP
4. glycerol 3 fatty acids - gt triglyceride H2O

28
Enzymes are considered catalysts because ________.

1. they make reactions occur much faster than they
   would on their own
2. like a bullet that can be fired once, the enzyme
   is destroyed after each use
3. they are energy carriers, providing the
   activation energy needed to start a reaction
4. all of the choices accurately describe a catalyst

29
Enzymes speed up reactions by lowering the
________ energy.

1. activation
2. kinetic
3. mechanical
4. potential

30
That portion of the enzyme that binds the
substrate is called the ________.

1. allosteric activator site
2. transitional site
3. active site
4. substrate site

31
A molecule becomes reduced when it ________.

1. gains an electron
2. is degraded into smaller products
3. gives up an electron
4. releases hydrogen ion

32
Pickling preserves foods by first soaking them in
strong salt solutions how might this delay
spoilage?

1. bacteria probably don't like the taste of pickled
   foods
2. pickling oxidizes the foods, making them
   unsuitable to bacteria
3. the high salt concentration denatures bacterial
   enzymes
4. salt is an antioxidant

33
In feedback inhibition, ________ usually inhibits
the first enzyme in a metabolic pathway.

1. the first reactant
2. the first intermediate
3. the end-product
4. none of the choices

34
In the absence of oxygen, ________.

1. energy metabolism completely ceases and the
   organism dies
2. a small amount of ATP can be produced using
   glycolysis
3. eukaryotic cells can use alternative electron
   acceptors such as sulfur or iron
4. carbon dioxide molecules can't be constructed and
   the Krebs cycle stops

35
How many ATPs are required for the early stages
of glucose breakdown in glycolysis?

1. 0
2. 1
3. 2
4. 4

36
What is the typical yield of ATP from the
complete aerobic respiration of glucose?

1. 30 (most cells)
2. 32 (liver, heart and kidney cells)
3. 12
4. 6
5. 4

37
What is the final carbon-containing end product
of the complete aerobic respiration of glucose?

1. carbon dioxide
2. pyruvate
3. starch
4. water

38
When muscle cells are deprived of oxygen, they
can continue to form ATP through ________.

1. lactate fermentation
2. alcoholic fermentation
3. anaerobic electron transfer
4. sulfur reduction
5. both alcoholic and lactate fermentation