biology 121 exam 3
Terms in this set (118)
Substrate-level phosphorylation occurs in which stages of cellular respiration?
Glycolysis and the citric acid cycle
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction _____ electrons and loses ________.
loses electrons and loses potential energy.
When electrons move closer to a more electronegative atom, what happens?
More energy is released
Describe the results of the following reaction with respect to oxidation and reduction.
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes _____.
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____.
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle. T or F
The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport chain.
Carbohydrates and fats are considered high-energy foods why ?
They have a lot of electrons associated with hydrogen
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
Starting with one molecule of glucose, the energy-containing products of glycolysis are _____.
2 NADH, 2 pyruvate, and 4 ATP
In glycolysis, for each molecule of glucose oxidized to pyruvate _____molecules of ATP are used and _____ molecules of ATP are produced.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
Most of the CO2 from the catabolism of glucose is released during _____.
Citric acid cycle
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of _____.
Which electron carrier(s) function in the citric acid cycle?
NADH and FADH2
Carbon dioxide (CO2) is released during which of the stages of cellular respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
The three listed steps result in the formation of _____.
acetyl CoA, NADH, and CO2
Which component is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
Which of the following events takes place in the electron transport chain?
the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle
The electron transport chain is a series of ______.
The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because it explains _____.
How ATP is found
During aerobic respiration, electrons travel downhill in which sequence?
food → NADH → electron transport chain → oxygen
Where are the proteins of the electron transport chain located?
Inner membrane of the mitochondria
During aerobic respiration, which of the electron carrier directly donates electrons to the electron transport chain at the lowest energy level?
glucose → NADH → electron transport chain → oxygen
The primary role of oxygen in cellular respiration is to _____.
Act as an electron acceptor
During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?
In chemiosmosis, what is the most direct source of energy that is used to convert ADP + i to ATP?
Energy derived from proton gradient
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the _____.
lowering of pH in the mitochondrial matrix
Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?
an endergonic reaction coupled to an exergonic reaction. T or F
In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
It increases the surface for oxidative phosphorylation.
Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in _____.
all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors
Which stage of cellular respiration would normally occurs regardless of whether or not oxygen (O2) is present?
Which stage of cellular respiration occurs in the cytosol of a eukaryotic cell?
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of _____.
Ethanol and CO2
One function of both alcohol fermentation and lactic acid fermentation is to _____.
Oxidize NADH to NAD+
An organism is discovered that thrives in both the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism _____.
Is facultative anaerobic
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
it is found in the cytosol, does not involve oxygen, and is present in most organisms.
Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?
High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of _____.
Glycolysis is active when cellular energy levels are _____; the regulatory enzyme, phosphofructokinase, is _____ by ATP.
The process of photosynthesis probably originated in _____
In autotrophic bacteria, where is chlorophyll located?
Plants photosynthesize only in the ______ but respire in_____ and ______.
Light; light; dark
Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide.
it comes from water.
Every ecosystem must have ______
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic. T/F
The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?
Other pigments absorb light in addition to chlorophyll a.
What wavelength of light in the figure is most effective in driving photosynthesis?
Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment?
Blue and violet
Halobacterium has a photosynthetic membrane that appears purple. Its photosynthetic action spectrum is the inverse of the action spectrum for green plants. (That is, the Halobacterium action spectrum has a peak where the green plant action spectrum has a trough.) What wavelengths of light do the Halobacterium photosynthetic pigments absorb?
Green and yellow
Why are there several structurally different pigments in the reaction centers of photosystems?
This arrangement enables the plant to absorb light energy of a variety of wavelengths.
If pigments from a particular species of plant are extracted and subjected to paper chromatography, what will happen?
Paper chromatography would separate the pigments from a particular plant into several bands of different colors
In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and _____.
carotenoids and other pigments are still present in the leaves
What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?
An electron is excited.
As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?
It is used to establish and maintain proton gradient
The final electron acceptor associated with photosystem I is _____.
The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?
In the thylakoid membranes, the pigment molecules in a light-harvesting complex _____.
Absorb and transfer light energy to the reaction center chlorophyll
Which of the following are directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be to _____.
to test for liberation of O2 in the light.
What are the products of linear electron flow?
ATP and NADPH
As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. Where did the extra ATP molecules come from?
Cycle electron flow
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will most directly affect the _____.
Synthesis of ATP
In a plant cell, where are the ATP synthase complexes located?
Thylakoid membrane and inner mitochondrial
In mitochondria, chemiosmosis moves protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis moves protons from the _____.
Stroma to the thylakoid space
Which of the following statements best describes the relationship between photosynthesis and respiration?
Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during _____.
Photosynthesis and respiration
What is the relationship between the wavelength of light and the quantity of energy per photon?
They are inversely related
Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What function do they have in plants?
Dissipate excessive light energy
In a plant, the reactions that produce molecular oxygen (O2) take place in _____.
thylakoid membrane and inner mitochondrial membrane
The accumulation of free oxygen in Earth's atmosphere began with the origin of _____.
Cyanobacteria using photosystem II
Photophosphorylation is most similar to _____.
Oxidative phosphorylation in cellular respiration
What are the products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
ATP and NADPH
Where does the Calvin cycle take place?
What is the primary function of the Calvin cycle?
In the process of carbon fixation, RuBP attaches a CO2 to produce a six-carbon molecule, which is then split to produce two molecules of 3-phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs to happen to complete the Calvin cycle?
Regeneration of RuBP
Describe correct sequence of flow of electrons during photosynthesis?
H2O to NADPH to Calvin Cycle
Which of the following does NOT occur during the Calvin cycle?
release of oxygen
What compound provides the reducing power for Calvin cycle reactions?
What would be the expected effect on plants if the atmospheric CO2 concentration was doubled?
C3 plants would have faster growth, C4 plants would be minimally affected
Why are C4 plants able to photosynthesize with no apparent photorespiration?
They use PEP carboxylase to initially fix CO2
CAM plants keep stomata closed in the daytime, thus reducing loss of water. Explain.
They can do this because they fix CO2 into organic acids during the night
The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?
Each one minimizes photorespiration and optimizes the calvin cycle
Compared to C3 plants, C4 plants can continue to fix CO2 even at lower ____?
CO2 Concentrations and high oxygen concentrations
Photorespiration generates _______and consumes ___ and _____.
Carbon; ATP; oxygen
In yeast signal transduction, a yeast cell releases a mating factor which binds to _______ on the membranes of other types of yeast cells.
Quorum sensing is cell-cell communication in eukaryotes T or F
In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?
Aggregation of bacteria that can cause cavities
Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?
Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must have ?
Have receptors that recognize and bind with the hormone molecule
In which of the following ways do plant hormones differ from hormones in animals?
Plant hormones most often travel in air as a gas.
When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?
Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?
Glycogen breakdown was observed only when epinephrine was administered to intact cells.
A G-protein receptor with GTP bound to it is in its _____ state.
Testosterone functions inside a cell by binding with a _____ ________ that enters the nucleus and activates specific genes.
One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?
Receptor tyrosine kinases
A drug designed to inhibit the response of cells to testosterone would most likely result in _____ transcriptional activity of certain genes.
Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells . Why .
Intracelluar receptors are present only in target cells
If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?
It would not be able to activate the G protein on the cytoplasmic side of the plasma membrane
Which of the following is true of steroid receptors?
The receptor may be inside the nucleus of a target cell.
Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?
receptor tyrosine kinase activity
Which of the following is characteristic of a steroid hormone action?
internal receptor binding
The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids . Why.
Steroid hormones are lipid soluble so they can diffuse through the lipid bilayers of the cell membrane
What does it mean to say that a signal is transduced?
The physical form of the signal changes from one form to another
In general, a signal transmitted via phosphorylation of a series of proteins results ?
In a conformational change to each protein
The toxin of Vibrio cholerae causes profuse diarrhea. How.
It modifies a G protein involved in regulating salt and water secretion
Which of the following would most likely be an immediate result of a growth factor binding to its receptor?
protein kinase activity
Adenylyl cyclase has the opposite effect of which of the following?
An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?
Protein kinase is an enzyme that _____ or ________ other proteins by adding a phosphate group to them
Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?
serine and threonine
Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. The second messenger in this pathway is _____.
Transcription factors control _______.
Gene expression. It regulates the synthesis of DNA in response to the signal
What are Scaffolding proteins ?
INTERACT/ Bind with/ multiple signal pathways. It is a large molecule in which several proteins are attached