cellular and molecular biology exam 4
CO2 is released in which steps of the citric acid cycle as shown below?
Steps 3 and 4
Diseases that disrupt the function of mitochondria are particularly harmful to muscle and nerve cells for what reason?
These cells need large amounts of ATP to function normally.
How do enzymes maximize the energy harvested from the oxidation of food molecules?
They allow the stepwise oxidation of food molecules, which releases energy in small amounts.
How do specialized brown fat cells take advantage of oxidative phosphorylation to generate heat?
They contain a carrier protein that dissipates the proton gradient across the inner mitochondrial membrane.
What is true of the organelles that produce ATP in eukaryotic animal cells?
They evolved from bacteria engulfed by ancestral cells billions of years ago.
What is true of mobile electron carriers?
They ferry electrons between one respiratory complex and the next.
Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in a eukaryotic cell?
mitochondrion
What type of enzyme catalyzes the shifting of a chemical group from one position in a molecule to another?
mutase
Stage 1 of photosynthesis is in large part equivalent to what process?
oxidative phosphorylation
The ethanol in wine and beer is produced from metabolic reactions carried out by the yeast Saccharomyces cerevisiae. Since it is of great commercial value researchers have studied factors that influence ethanol production. To maximize ethanol yield which environmental factor should be limiting?
oxygen
In mitochondria what is the final electron acceptor in the electron-transport chain?
oxygen (O2)
What serves as the final electron acceptor in the photosynthetic electron-transport chain that carries electrons from photosystem II?
photosystem I
Which of these is able to boost electrons to the very high energy level needed to make NADPH from NADP+?
photosystem I
When nutrients are plentiful
plants can store glucose as what?, starch
When protons move down their electrochemical gradient into the mitochondrial matrix what do they do?
produce ATP
In the electron-transport chain as electrons move along a series of carriers they release energy that is used to do what?
pump protons across a membrane
The movement of electrons through the electron-transport chain in mitochondria does which of the following?
pumps protons out of the mitochondrial matrix
What are the end products of glycolysis?
pyruvate, NADH, ATP
Which of the following are consumed as fuel within mitochondria? (SELECT ALL THAT APPLY)
pyruvate, amino acids, fatty acids, acetyl CoA
The synthesis of ATP in glycolysis occurs by which process?
substrate-level phosphorylation
The NADH generated during glycolysis and the citric acid cycle feeds its high-energy electrons to which of the following?
the electron transport chain
In this illustration of the structure of ATP synthase which of the components rotate?
1 &5
For every three molecules of CO2 that enter the carbon-fixation cycle what is produced and what is consumed?
1 molecule of glyceraldehyde 3-phosphate is produced and 9 molecules of ATP + 6 molecules of NADPH are consumed.
Which of these glycolytic reactions is catalyzed by a kinase? (select all that apply)
1,3-bisphosphoglycerate → 3-phosphoglycerate, glucose → glucose 6-phosphate, fructose 6-phosphate → fructose 1,6-bisphosphate
When fatty acids are oxidized to produce acetyl CoA each cycle of the reaction removes how many carbon atoms from the fatty acid molecule?
2
From one glucose molecule how much net energy (in the form of ATP and NADH) is produced during glycolysis?
2 ATP, 2 NADH
About how many molecules of ATP are produced by the complete oxidation of glucose to H2O and CO2?
30
Approximately how many molecules of ATP can be produced in mitochondria from the complete oxidation of a single glucose molecule?
30
What occurs in the first step of the citric acid cycle?
A two-carbon molecule is combined with a four-carbon molecule to form citrate.
Which activated carrier contains a high-energy bond whose hydrolysis releases a large amount of free energy?
ATP
What provides the fuel to convert CO2 into sugars in chloroplasts?
ATP and NADPH generated in the photosynthetic light reactions
Most of the energy released by oxidizing glucose is saved in the high-energy bonds of what molecules?
ATP and other activated carriers
The drug 2 4-dinitrophenol (DNP) makes the mitochondrial inner membrane permeable to H+. The resulting disruption of the proton gradient inhibits the mitochondrial production of ATP. What additional effect would DNP have on the transport of ATP out of the mitochondrial matrix?
ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane.
Not all fat cells are equivalent. Humans and other animals contain both white fat cells and brown fat cells named after their color. Because increases in brown fat cells may aid weight loss researchers are interested in factors that control the ratio of white fat cells and brown fat cells as detailed in a 2017 article in Obesity Reviews. What is the mechanism for how brown fat cells aid weight loss?
Brown fat cell mitochondria contain an uncoupling protein
The citric acid cycle converts the carbon atoms in acetyl CoA to which of the following?
CO2
In this simplified diagram of the reactions of the carbon-fixation cycle which step is catalyzed by the enzyme Rubisco?
E
Which is true about electrons as they move through the electron-transport chain?
Electrons start out at very high energy and lose energy at each transfer step along the electron-transport chain.
During oxidative phosphorylation why does a single molecule of NADH result in the production of more ATP molecules than a single molecule of FADH2?
FADH2 and NADH feed their electrons to different carriers in the electron-transport chain.
Which activated carriers are produced by the citric acid cycle?
FADH2, NADH, GTP
During electron transport which serves as a ready source for protons that can be pumped across the membrane?
H2O
In the electron transport chain the oxygen atoms in O2 become part of which of the following molecules?
H2O
When an electron is removed from the reaction center of photosystem II the missing electron is replaced by an electron from which of the following?
H2O
Which part of the mitochondrion contains the same mix of small molecules and inorganic ions as the cytosol?
Inner Membrane
Which of the following statements are true of mitochondria? (SELECT ALL THAT APPLY)
Inside a cell, they are mobile, constantly changing shape and position. They contain an outer membrane, an inner membrane, and two internal compartments.They are similar in size and shape to bacteria.They contain their own DNA and RNA.
Which part of the mitochondrion contains the proteins that carry out oxidative phosphorylation?
Intermembrane space
Which is true of ATP synthase?
It can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient.
What does the pyruvate dehydrogenase complex do?
It converts pyruvate into acetyl CoA in the mitochondrial matrix.
During photosynthesis what happens in the water-splitting step?
It generates essentially all of the O2 in the Earth's atmosphere.
Which of the following is true of NADH?
It has a weak affinity for electrons and a negative redox potential.
What happens to the ATP produced during stage 1 of photosynthesis?
It is consumed within the chloroplast to produce glyceraldehyde 3-phosphate.
What is true of the process of combining CO2 and H2O to make a carbohydrate?
It is energetically unfavorable.
When the difference in redox potential between two molecules is highly positive what is true of the transfer of electrons between them?
It is highly favorable.
Which statement is true of glycogen phosphorylase?
It is inhibited by glucose 6-phosphate and by ATP.
In terms of energy production what is true of cell respiration?
It is more efficient than a gasoline-powered engine.
During the citric acid cycle what happens to the acetyl group in acetyl CoA?
It is oxidized to produce CO2.
What happens to the energy captured during glycolysis and the citric acid cycle by the activated carriers NADH and FADH2?
It is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane.
What is true of nitrogen fixation?
It reduces N2 to ammonia (NH3).
Which part of the mitochondrion contains the enzymes needed to complete the oxidation of food-derived molecules?
Matrix
Although the citric acid cycle itself does not use O2 it requires a functioning electron transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle?
NAD+
The electron-transport chain in mitochondria accepts high-energy electrons directly from which molecule?
NADH
Most of the energy for the synthesis of ATP comes from which molecule?
NADH produced by the citric acid cycle
In the electron-transport chain in chloroplasts which molecule serves as the final electron acceptor?
NADP+
Investigators introduce two proteins into the membrane of artificial lipid vesicles: (1) an ATP synthase isolated from the mitochondria of cow heart muscle and (2) a light-activated proton pump purified from the prokaryote Halobacterium halobium. The proteins are oriented as shown in the diagram. When ADP and Pi are added to the external medium and the vesicle is exposed to light would this system produce ATP?
No, because ATP synthase is not oriented correctly.
In a culture of green alga that is carrying out photosynthesis in the presence of CO2 in the laboratory what would happen to the levels of ribulose 1 5-bisphosphate and 3-phosphoglycerate in the minutes after the lights were turned off and the cultures were plunged into darkness?
Nothing would happen because the Calvin cycle is not light-dependent.
In eukaryotic cells what is the final electron acceptor in the electron transport chain?
O2
Which part of the mitochondrion contains porins?
Outer Membrane
Why does cytochrome c oxidase bind to oxygen very tightly?
Release of partially reduced oxygen radicals can damage the cell.
Below is a table listing the reactions that constitute the 10 steps of glycolysis along with the change in free energy (ΔG°) for each step. Based on the data which steps in glycolysis are effectively irreversible?
Steps 1, 3, and 10
What could be true of a baby born following mitochondrial replacement therapy a treatment designed to prevent the transmission of mitochondrial defects?
The baby would have genetic material from three "parents" in each cell.
How does the photosynthetic machinery produce enough energy to transfer electrons from H2O to NADPH?
Two photosystems operating in series couple their electron-energizing steps.
Which of the following drives the production of ATP from ADP and Pi by ATP synthase?
a proton (H+) gradient
In photosynthesis what drives the generation of ATP by ATP synthase?
a proton gradient across the thylakoid membrane
What type of enzyme catalyzes the rearrangement of chemical bonds within a single molecule?
isomerase
Which two-carbon molecule enters the citric acid cycle?
acetyl CoA
The proton gradient that drives ATP synthesis during photosynthesis is generated by which of the following?
an electron carrier that pumps protons out of the stroma into the thylakoid space
Which of the following organisms have mitochondria in their cells? (select all that apply)
animals, yeasts, plants
Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones?
catabolism
The buildup of lactic and formic acids generated by anaerobic fermentation likely favored the evolution of which of the following?
cells that could pump protons
In a test tube NADH has a strong tendency to do what?
donate electrons to O2
In humans and other mammals gluconeogenesis is most likely to occur in which type of cells?
liver cells
In plant cells where does the citric acid cycle take place?
mitochondria
Which of the following processes generates the largest number of ATP molecules?
electron transport chain
In which of the following locations are polymeric food molecules digested into their monomeric subunits? (select all that apply)
extracellular space & lysosomes
Determine whether the following statement is true or false: The oxygen consumed during the oxidation of glucose in animal cells is returned to the atmosphere as CO2.
false
You are packing for a hiking trip during which you'll be burning a lot of calories with physical activity. You want to pack as efficiently as possible since you need to carry a tent and all your food. You can get the most calories out of 5kg of food if it is in the form of
fat
Under anaerobic conditions which metabolic pathway regenerates the supply of NAD+ needed for glycolysis?
fermentation
It is energetically favorable for protons to flow in which direction?
from the intermembrane space to the mitochondrial matrix
The electron-transport chain pumps protons in which direction?
from the matrix to the intermembrane space
When food is plentiful animals can store glucose as what?
glycogen
For many anaerobic microorganisms which metabolic pathway is the principal source of ATP?
glycolysis
Useful energy is obtained by cells when sugars derived from food are broken down by which processes?
glycolysis, the citric acid cycle, and oxidative phosphorylation
Which reaction releases the most energy?
hydrolysis of 1,3-bisphosphoglycerate to 3-phosphoglycerate
The electrochemical proton gradient across the mitochondrial membrane can be used to drive which processes?
import of pyruvate into the mitochondrial matrix, export of ATP from the mitochondrial matrix, import of ADP into the mitochondrial matrix
In an animal cell where are the proteins of the electron-transport chain located?
inner mitochondrial membrane
In step 6 of glycolysis glyceraldehyde 3-phosphate which has one phosphate group is converted into 1 3-bisphosphoglycerate which has two. Where does the extra phosphate group come from?
inorganic phosphate
What does the term "gluconeogenesis" refer to?
the synthesis of glucose from small organic molecules such as pyruvate
For each acetyl group that enters the citric acid cycle what activated carriers are produced?
three NADH, one FADH2, one GTP
In what form do plant and animal cells store fat?
triacylglycerol
How many ATP molecules must be invested during the first part of glycolysis for each molecule of glucose broken down?
two
The oxygen atoms required for the citric acid cycle to produce CO2 ultimately are derived from which of the following?
water
