Biology lesson on cellular respiration

What is the main product of aerobic respiration that is a feedback inhibitor of the process?

ATP

If a cell has plenty of ATP and doesn't need to make more, what is done to store the excess energy?

ATP acts as an inhibitor on multiple enzymes within each important step of the pathway for aerobic respiration.

What is ATP? Describe two ways ATP is produced by the cell during cellular respiration.

Adenosine Triphosphate - ENERGY. Substrate-level phosphorylation in which a phosphate is transferred from ADP to form ATP. Oxidative phosphorylation in which an electron transport chain is used to create a proton gradient (chemiosmosis)

At what point in the original glucose molecule completely oxidized?

After the Citric Acid Cycle.

What types of organisms utilize glycolysis?

Almost all organisms, especially ones that use oxygen.

What is an electron carrier? Give two examples of electron carriers used during aerobic respiration.

An electron carrier harnesses the electrons at each step of the breakdown process. NAD+ carries two electrons and proton to form NADH

What are sulfur bacteria? What do they use for their final electron acceptor and what is the product?

Archaea and bacteria found in hot springs. Use SO42- and reduce to H2S

What are methanogens? What do they use for their final electron acceptor an what is the product of this reaction?

Archaea found in the guts of animals and hydrothermal vents. They use CO2 and reduce to CH4(methane)

What is the difference between autotrophs and heterotrophs? Categorize plants, algae, bacteria, animals and fungi in these groups. Which group is larger?

Autotrophs convert solar energy to chemical energy, and heterotrophs must consume organic compounds for energy. Autrotophs include plants, algae, and some protists and bacteria, and heterotrophs is larger because it contains 95% of all organisms - animals, fungi, most protists and prokaryotes.

Why does only 1 glucose molecule lead to 2 pyruvate during glycolysis?

Because a phosphate is added to transform the molecule into two molecules, which leads to 2 pyruvate.

Why is it important to remember the enzyme phosphofructokinase? What regulates the activity of this enzyme?

Because it adds the 2nd phosphate from ATP hydrolysis. It is regulated by negative feedback.

Why is oxygen the final electron acceptor? What is made when oxygen accepts electrons from the electron transport chain?

Because it is so electronegative. It is reduced to water.

Which reaction in glycolysis is the "cleavage" reaction and why?

Because the 6-carbon diphosphate is being cleaved into two 3-carbon molecules.

Why do organisms use anaerobic respiration if it produces less ATP? Why not use aerobic respiration instead?

Because they do not have a mitochondria.

Review the equation for photosynthesis and the oxidation of glucose. How are these equations similar?

C6H12O6 + 6O2 = 6CO2 + 6H2O + ATP Photosynthesis is the reverse of cellular respiration. The plants used carbon dioxide to make the sugars instead of the sugars being broken down into carbon dioxide. It is a cycle.

What macromolecules are found in food that provide energy for the cell? How does the cell derive that energy (what basic type of reaction is used to get energy from these molecules?)

Carbohydrates, proteins, and triglycerides (lipids). Through catabolism by breaking covalent bonds.

What molecules can be made by a cell?

Carbs, proteins, and lipids.

A series of re-dox reactions that breaks down glucose, where oxygen is used as the final electron acceptor and CO2 and ATP are generated is _____________

Cellular Respiration

The enzyme for the first reaction of the Citric Acid Cycle is regulated by ATP. Where there is a lot of ATP this enzyme is ____________________

Citrate Synthase

What is the product of the first reaction of the Citric acid cycle and why is it very important to the regulation of the system?

Citrate is an important product because it is involved in feedback regulation of the entire system.

What other molecules serve as feedback inhibitors during aerobic respiration?

Citrate, and NADH

Organisms that cannot use an inorganic electron acceptor other than oxygen rely on ___________ for ATP production in the absence of oxygen.

Glycolysis

Where are the components of the electron transport chain located in eukaryotes?

It embedded in the inner mitochondria membrane, with more protons being in the inter membrane space.

Why is acetyl CoA important?

It is termed the universal intermediate. All energy processes can eventually point towards acetyl CoA. Since acetyl CoA can go into the Kreb's cycle, then more ATP can be made.

What fermentation reactions are carried out in animal muscle cells when oxygen levels are low? What is the product? Why is it essential to recycle NADH using fermentation even in the absence of oxygen in animal cells?

Lactate dehydrogenase transfers electrons from NADH to pyruvate converting it to lactic acid. Glycolysis is then able to continue even in the event of low oxygen.

Besides glucose, what other molecules can be catabolized for energy by cells? Which of these are more commonly used sources of energy?

Proteins and lipids. Acetyl-CoA.

Write out the reaction including products and reactants from pyruvate oxidation.

Pyruvate + NAD+ + CoA = acetyl CoA + NADH + CO2 + H+

What enzyme converts pyruvate to acetyl CoA? Why is this reaction a very important step during aerobic respiration? What regulates the activity of this enzyme?

Pyruvate dehydrogenase. It is important because NADH+ is reduced to NADH. It represents an important regulatory marker for the entire biochemical pathway.

Indenting the reactions from the Citric Acid Cycle that are redox reactions and substrate level phosphorylation. Be able to understand and recognize what is occurring.

Reactions 3, 4, 6, 8 are redox reactions because they reduced NAD+ to NADH. Reaction 5 is substrate level phosphorylation because ATP is being formed.

Describe fermentation in yeast. What is the byproduct?

Yeast removes the last CO2 group from pyruvate producing acetaldehyde. The byproduct is ethanol.

During cellular respiration glucose is oxidized to CO2 and O2 is the final electron acceptor. Why doesn't the cell immediately hand the electrons to O2? Why is there a need for intermediate steps with electron carriers?

The process must take place in steps because the energy released would be explosive and impossible to harness. Electron carriers help harness the electrons.

Describe the molecular structure of the ATP synthase (including the role of each important subunit)

The protein has a membrane bound portion and a narrow stalk connecting to a knob-like structure that is enzymatic. These subunits are known as F0 (channel for proteins) and F1 (creates ATP)

Explain how the electrons originally gathered from oxidizing glucose powers the ATP synthase that creates ATP.

The protons cause the stalk and F0 subunit to rotate, and this mechanical energy changes the shape of the F1 enzymatic subunit that creates ATP.

What is the fate of the 2 pyruvate molecules in the presence of oxygen? What about the absence of oxygen?

The pyruvate turns into acetyl CoA with oxygen. Without oxygen, it is fermented into ethanol, lactate, or other products.

The first 3 reactions of glycolysis are called the "priming reactions." Explain why. Are these reactions endergonic or exergonic? How do you know?

When 2 ATPs are added and the molecule is "primed" to be split. It is endergonic because it requires energy to add the ATPs.

What is feedback inhibition?

When the metabolic pathway is slowed by its end products.

What is the fate of the electrons held by NADH in the presence of oxygen? What about the absence of oxygen?

With oxygen - aerobic respiration. Without oxygen - fermentation.

Glycolysis takes in one glucose molecule and results in:

2 ATP, 2 NADH, and 2 pyruvate.

If you know that 1 NADH cause 10 H+ to be pumped across the inner mitochondrial membrane and 1 FADH causes 6 H+ to be pumped across, given that it takes 4H+ to generate 1 ATP, how many ATP are generated through oxidative phosphorylation alone during glycolysis?

28

What is a proton pump? What is proton gradient?

A proton pump builds up a proton gradient, which is used to power an ATP synthase.

Which enzymes of aerobic respiration are regulated?

Phosphofructokinase and Pyruvate dehydrogenase

Taking carbon dioxide and making sugars and oxygen takes place during ___________

Photosynthesis

List the 5 components of the electron transport chain and their function.

Complex 1: Where NADH deposits its electrons (proton pump) Complex 2: Where FADH2 deposits its electrons Complex 3: (proton pump) Cytochrome C: (mobile electron carrier) Complex 4: (proton pump)

When ATP is plentiful, what is the fate of Acetyl CoA? What about when ATP levels are low?

Excess ATP inhibits the enzyme for this reaction. When ATP levels are low, Acetyl CoA is used for the synthesis of fat (energy storage)

How are fats broken down? How can this provide energy for the cell?

Fats are broken down into fatty acids and glycerol. Fatty acids are broken off the chain one by one into acetyl-coA to create ATP.

When ATP levels are high what molecules are often made by the cell to store energy?

Fatty acids

How is fermentation different from anaerobic respiration?

Fermentation does not have an electron transport chain

What inorganic molecules can be used as an electron acceptor in the absence of oxygen for certain prokaryotes?

Methanogens and Sulfate reducers.

How is a proton gradient created by the electron transport chain? What is the role of NADH and FADH2?

NADH and FADH2 drop off their electrons in the electron transport chain and those electrons are transferred down the chain. Protons are then pumped across the membrane to create a proton gradient.

Which reactions during glycolysis result in substrate-level phosphorylation?

Oxidation and ATP formation

What happens to the CO2 lost during pyruvate oxidation and the Citric acid cycle? How many carbon atoms are lost with the loss of CO2 from the beginning of glycolysis through 2 turns of the Citric acid cycle? Where did the carbon in that CO2 originate?

The CO2 is preserved in 4 ATP molecules and 12 electron carriers. One carbon is lost through glycolysis and the rest are lost (eight ?) in the Citric acid cycle. The carbon originated from glucose.

Describe in general the catabolism of proteins. How can the breakdown of proteins produce energy in a cell?

The amino group is removed and converted into an intermediate product of either glycolysis or the Citric acid cycles where they enter and produce ATP.

What is the fate of the electrons taken from the glucose molecule during glycolysis? What electron carrier handles them and where does it take them? How will they be ultimately responsible for making ATP?

The electrons get oxidized in NAD+ and NADH is the electron carrier to mitochondria. The two molecules are transformed in pyruvates and creates 4 ATP.

Which of the 2 types of ATP production is used to make ATP through ATP synthase?

The shape of the F1 subunit is changed by F0 through rotation and creates ATP.

How many ATP do you get from 1 molecule of glucose through substrate-level phosphorylation?

Two ATP

Where does pyruvate oxidation occur in eukaryotes? Prokaryotes?

mitochondria, cytoplasm and plasma membrane

What is anaerobic respiration?

respiration without oxygen, typically used by prokaryotes.

What is glycolysis, Citric acid cycle, and the electron transport chain and where do they take place in eukaryotes and prokaryotes?

the breakdown of glucose by enzymes, to 2 pyruvate in the cytoplasm. The citrate acid cycle is a series of reactions that generates electron carriers, in the mitochondria. The electron transport chain is where the electrons travel, which is embedded in the mitochondria's membrane.