BIO1005 CH 6
Why is glycolysis considered to be the oldest metabolic reaction?
Because it occurs in all cells
How many ATP are made as a result of glycolysis?
Four ATP are made, but the net gain is two
Where does the food come from in the first place?
In most ecosystems, plants and other autotrophs use photosynthesis to make organic molecules such as glucose (C6H12O6) out of carbon dioxide (CO2) and water (H2O). Light supplies the energy. The glucose produced in photosynthesis feeds not only autotrophs but also all of the animals, fungi, and microbes that share the ecosystem
What is the role of ATP synthase?
It uses a hydrogen ion gradient to make ATP
Unlike chemiosmotic phosphorylation,substrate-level phosphorylation does not require
a proton gradient or the ATP synthase enzyme to produce ATP
Which of the following molecules can be used to generate ATP energy?
all- carbs, amino acids and fats
Proteins are digested into monomers called
amino acids
Most cells use carbohydrates as a primary source of energy, but cells can also use
amino acids and lipids to generate ATP.
The Krebs cycle and electron transport chain
are the key ATP-generating processes
The circulatory system
carries the inhaled O2 to cells, where gas exchange occurs.
Krebs cycle is also known as
citric acid cycle
Which of the following best describes anaerobic respiration?
The production of ATP energy from glucose in the absence of oxygen
Glycolysis always occurs in the
cytoplasm
Other yields in respiration cycle
each glucose yields two NADH molecules from glycolysis, two NADHs from acetyl CoA production, and six NADHs and two FADH2s from two turns of the Krebs cycle.
anaerobic respiration
generate ATP from glucose without using O2 -most common in microorganisms.
fermentation
generate ATP from glucose without using O2 -most common in microorganisms.
The pathways of aerobic respiration oxidize
glucose
equation for aerobic respiration
glucose + oxygen → carbon dioxide + water + ATP C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP
What are the starting materials of glycolysis?
glucose and 2 molecules of ATP
Glycolysis
glucose splits into two molecules of pyruvate, producing a net yield of two ATPs and two NADHs -
the 2nd five steps of glycolysis
the pathway then stores some energy in two molecules of the electron carrier, NADH. Other steps extract more of the energy, regaining the two ATP molecules invested earlier plus producing two more. The net gain is therefore two NADHs and two ATPs per molecule of glucose.
glycolysis
(literally, "breaking sugar"), a six-carbon glucose molecule splits into two three-carbon pyruvate molecules. This process harvests energy in two forms. First, some of the electrons from glucose are transferred to an electron carrier molecule called NADH (nicotine adenine dinucleotide). Second, glycolysis generates two molecules of ATP.
Electron transport occurs in
-inner mitochondrial membrane in eukaryotic cells - in the thylakoid membranes of chloroplasts
How can plants release more O2 in photosynthesis than they consume in respiration?
...
How is substrate-level phosphorylation different from chemiosmotic phosphorylation?
...
What is endosymbiosis?
A possible explanation for the origin of mitochondria
How does the Krebs cycle generate CO2, ATP, NADH, and FADH2?
by rearranging and oxidizing citrate though several intermediate molecules. the energy and electrons derived from these chemical reactins are stored in ATP, NADH, and FADH2. A molecule of CO2 is released in two of these chemical reactions.
Besides continuing the breakdown of glucose, the Krebs cycle also has another function not directly related to respiration, what is it
cell uses intermediate compounds formed in the Krebs cycle to manufacture other organic molecules, such as amino acids or fats. the reverse process also occurs; amino acids and fats can enter the Krebs cycle to generate energy from food sources other than carbohydrates
How many ATP, NADH, CO2, FADH2, and H2O molecules are produced at each stage of respiration?
converting glucose to 2 pyruvates 2 ATP and 2 H2O -shuttling 2 pyruvates into the mitochondrian produces 2 NADH -The 2 acetyl CoA enter the Krebs cycle and produce 2 APT, 6 NADH, and 2 FADH2 -From all these products, the electron transport chain can produce up to 36 ATP
ATP synthase
enzyme tacks a phosphate group onto ADP, yielding ATP
None of the steps in glycolysis require
O2, so cells can use glycolysis in both oxygen-rich and anaerobic environments
ATP yields in respiration cycle
Substrate-level phosphorylation yields two ATPs from glycolysis and two ATPs from the Krebs cycle (one ATP each from two turns of the cycle). These are the only steps that produce ATP directly. -the ATP yield from electron transport is three ATPs per NADH and two ATPs per FADH2. Electrons from the 10 NADHs from glycolysis and the Krebs cycle therefore yield up to 30 ATPs; electrons from the two FADH2 molecules yield four more. Add the four ATPs from substrate-level phosphorylation, and the total is 38 ATPs per glucose. However, NADH from glycolysis must be shuttled into the mitochondrion, usually at a cost of one ATP for each NADH. This reduces the net theoretical production of ATPs to 36.
Which respiratory reactions occur in each part of the mitochondrion?
The electron transport chain is located on the inner michondrial membrane. The Krebs cycle occurs in the mitochondrial matrix. (In prokaryotes the electron transport chain is embedded in the cells outer membrane and the Krebs cycle occurs in the cytoplasm.
Mitochondria and chloroplasts share what similarities
Both types of organelles contain DNA and ribosomes. Mitochondrial DNA encodes ATP synthase and most of the proteins of the electron transport chain.
The Krebs cycle completes the oxidation of each acetyl group, releasing
CO2
products generated in glycolysis, acetyl CoA formation, and the Krebs cycle
CO2, ATP, NADH, and FADH2 The cell ejects the CO2 as waste
anaerobic respiration
essentially the same as aerobic respiration, except that an inorganic molecule other than O2 is the electron acceptor at the end of the electron transport chain. Alternative electron acceptors include NO3- (nitrate), SO42- (sulfate), and CO2. The number of ATPs generated per molecule of glucose depends on the electron acceptor, but it is always lower than the ATP yield for aerobic respiration. bacteria and archaea generate ATP by anaerobic respiration
Explain how to arrive at the estimate that each glucose molecule theoretically yields 36 ATPs
glycolysis yields 2 NADH and 2 ATP; the formation of acetyl CoA yields 2 NADH; the Krebs Cycle yields 6NADH, 2 ATP, 2 FADH2. When the NADH and FADH2 from flycolysis and the Krebs cycle contribute their electrons to the ecectron transport chain, they yield a total of 34 ATP that were derived from NADH and FADH2. Once 2 ATP are subtracted (the cost of moving NADH from glycolysis to the intermembrane space), the net yield is 36 ATP per molecule of glucose
Cellular Respiration Includes Three Main Processes
glycolysis, the Krebs cycle, and electron transport
plants absorb much more CO2 in photosynthesis than they release in respiration, and
hey release more O2 than they consume.
glycolysis requires 10 steps, all of which occur in
the cell's cytoplasm
summary of respiration through the Krebs cycle
the combined net output to this point (glycolysis, acetyl CoA formation, and the Krebs cycle) is four ATP molecules, 10 NADH molecules, two FADH2 molecules, and six molecules of CO2. Of course, this process does not capture all of the potential energy in glucose. According to the second law of thermodynamics, some is always lost as heat.
The difference between anaerobic and aerobic respiration is
the electron acceptors.
cell's mitochondria
the sites of respiration
How do NADH and FADH2 power ATP formation?
they deliver energy rich electrons to the electron transport chain to power the concentration of hydrogen ions. those concentrated hydrogen ions are used to power the addition of a phosphate group to ADP
The Krebs cycle turns
twice per glucose molecule
first five steps of glycolysis
use ATP to "activate" glucose, redistributing energy in the molecule and splitting it in half.
what happen in electron transport
uses energy stored in the electron carriers NADH and FADH2 to create a gradient of hydrogen ions across the inner membrane of the mitochondrion. ATP synthase uses this gradient to phosphorylate ADP to form ATP
What do cells do with the ATP they generate in respiration?
ATP is the source of energy to power most of the chemical reactions that take place in the cell
what enzyme facilitates the final stage of ATP synthesis
ATP synthase
No cell can survive without
ATP —adenosine triphosphate
What compound enters the Krebs cycle
Acetyl CoA
plants use O2 to respire
half of the glucose they produce.
a gradient represents a form of
potential energy
Why is it important to regenerate NAD+ during fermentation?
t helps maintain the reactions of glycolysis.
Overview of Aerobic Cellular Respiration
Glucose is broken down to carbon dioxide in three main stages: glycolysis, the Krebs cycle, and the electron transport chain. Along the way, energy is harvested as ATP. Except for glycolysis, these reactions occur inside the mitochondria of eukaryotic cells.
For every glucose molecule that entered glycolysis, how many acetyl CoA molecules are ready to enter the Krebs cycle
2
How many ATP molecules per glucose does fermentation produce?
2
What is the net gain of ATP and NADH for each glucose molecule undergoing glycolysis?
2 ATP and 2 NADH for each molecule of glucose
Electron Transport Chain
3rd step in respiration Energy-rich electrons removed from NADH and FADH2 slowly release their energy as they are transferred along the proteins of the electron transport chain. Membrane-bound enzymes use this energy to pump protons (H+) from the matrix to the intermembrane compartment, establishing a gradient across the inner mitochondrial membrane. As the protons pass through a channel in ATP synthase, the gradient dissipates, and ADP is phosphorylated to form ATP.
Which stage in cellular respiration directly requires the presence of O2?
Electron transport
What happens to the CO2 and H2O waste products of respiration?
Excess CO2 and H2O lave the cell through the plasma membrane; water is used throughout the organism and CO2 is retuned to the external environment
Which of the following molecules has the greatest amount of potential energy?
Glucose
lactic acid fermentation
a cell uses NADH to reduce pyruvate, but in this case, the products are NAD+ and the three-carbon compound lactic acid reduces pyruvate to lactic acid.
aerobic cellular respiration
a cell uses oxygen gas (O2) and glucose to generate ATP. -Plants, animals, and many microbes, especially those in O2-rich environments, use aerobic respiration.
he resulting six-carbon molecule of Krebs cycle is called
a citrate
CO2
a metabolic waste, is exhaled
reduce
add electrons to
How Many ATPs Can One Glucose Molecule Yield?
add the maximum number of ATPs generated in glycolysis, the Krebs cycle, and the electron transport chain -Breaking down glucose to carbon dioxide can yield as many as 36 ATPs, mostly from chemiosmotic phosphorylation at the electron transport chain
three categories of generating ATP
aerobic cellular respiration anaerobic respiration fermentation
What are the three general ways to generate ATP from food, and which organisms use each pathway?
aerobic cellular respiration- plants, animals, bacteria in oxygen rich environments anaerobic respiration- microorganisms fermentation- microorganisms
What are two examples of fermentation pathways?
alcoholic fermentation and lactic acid fermentation
Where in the cell does each of stage of respiration occur?
in a eukaryotic cell, respiration takes place in many different places. glycolysis takes place in the cytoplasm where glucose is converted into pyruvate. Also in the cytoplasm, pyruvate is converted to acetyl CoA which enter the matrix of the mitochondria. within the mitochondrial matrix, the Krebs cycle reactions take place; the results of the Krebs cycle are CO2, NADH and FADH2 molecules. The electron transport chain uses electrons from NADH and FADH2 to pump hydrogen ions across the inner membrane of the mitochondria to the intermembrane compartment. From that compartment hydrogen returns to the mitochondrial matrix through the ATP pump producing ATP from ADP. ATP is then shuttled throughout the cell.
What is the role of O2 in the electron transport chain?
it functions as the final electron acceptor. o2 binds to electrons that have traveled to the end of the transport chain which allows subsequent electrons to move along the pathway.
fermentation is not respiration because
it generates ATP from glycolysis only.
Pyruvate contains three carbon atoms; an acetyl group has only two. What happens to the other carbon atom?
it is released as CO2
ATP is essential because
it powers nearly every activity that requires energy input in the cell: synthesis of DNA, RNA, proteins, carbohydrates, and lipids; active transport across the membranes surrounding cells and organelles; separation of duplicated chromosomes during cell division; movement of cilia and flagella; muscle contraction; and many others
substrate-level phosphorylation
means that a high-energy "donor" molecule physically transfers a phosphate group to ADP, forming ATP.
Krebs cycle occurs in
mitochondrial matrix in eukaryotic cells
What are some examples of alternative electron acceptors used in anaerobic respiration?
nitrate, sulfate and CO2
Where do the O2 and glucose used in respiration come from?
o2 from the environment enters the cell through the plasma membrane, Glucose is provided from digesting other organisms or from photosynthesis
respiration is a--------reaction
oxidation—reduction
fermentation
pathways oxidize NADH to NAD+, which is recycled to glycolysis, but these pathways do not produce additional ATP. Some microorganisms, including many inhabitants of your digestive tract, use fermentation. In these organisms, glycolysis still yields two ATPs, two NADHs, and two molecules of pyruvate per molecule of glucose. But the NADH does not donate its electrons to an electron transport chain, nor is the pyruvate further oxidized. Instead, in fermentation, electrons from NADH reduce pyruvate. This process regenerates NAD+ so that glycolysis can continue, but it generates no additional ATP. Fermentation is therefore far less efficient than respiration. Not surprisingly, fermentation is common among microorganisms that live in sugar-rich environments where food is essentially unlimited In fermentation, ATP comes only from glycolysis. (a) Yeasts produce ethanol and carbon dioxide by alcoholic fermentation.
equation for aerobic respiration is essentially the reverse of
photosynthesis
Why do plants have a reputation for producing O2, if they also consume it?
plants incorporate much of the remaining glucose into cellulose, starch, and other stored organic molecules. Therefore, they absorb much more CO2 in photosynthesis than they release in respiration, and they release more O2 than they consume.
all organisms use the ------stored in food to make ATP
potential energy
Energy-rich ATP is generated from
potential energy in food
electron transport chain therefore uses the energy in NADH and FADH2 to establish a
proton gradient across the inner mitochondrial membrane
chemiosmotic phosphorylation
protons move down their gradient through ATP synthase channels back into the matrix, and ADP is phosphorylated to ATP.
Is pyrucate used directly in the Krebs Cycle
pyruvate moves into the mitochondrial matrix, but it is not directly used in the Krebs cycle because it is ozidized removing CO2 and NAD+ is reduced to NADH. The remaining two-carbon molecule, called an acetyl group, is transferred to a coenzyme to form acetyl coenzyme A (abbreviated acetyl CoA). Acetyl CoA is the compound that enters the Krebs cycle
The pathways of aerobic respiration
reduce (add electrons to) O2
alcoholic fermentation
reduces acetaldehyde to ethanol and loses carbon dioxide
what happens in Krebs cycle
releases CO2 and produces additional ATP and NADH as well as FADH2
is respiration an exothermic or endothermic reaction
releases energy which make it
oxidize
remove electrons from
C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP
reveals that aerobic cellular respiration requires organisms to acquire O2 and get rid of CO2
what happens in glycolysis
splits glucose into two pyruvate molecules and produces ATP and some NADH for later use
Glycolysis produces ATP by
substrate-level phosphorylation
