Cellular Respiration Reading Guide Flashcards
What is a redox reaction? What is oxidation? What is reduction? What happens to electrons in these cases?
Redox reaction: reactions where reduction and oxidation reactions occur together
Reduction: gaining electrons
Oxidation: losing electrons
What are electron carriers? Explain how NADH, FADH2, and NADPH carry electrons and thus energy via redox reactions.
Class of compounds that bind and carry high-energy electrons between compounds in pathways. NAD can be oxidized to make NAD+ or reduced to make NADH after the molecule accepted two electrons and a proton. NAD+ can accept electrons from organic molecules. NAD+ is an oxidizing agent, meaning that it removes electrons. FAD+ is reduced to form FADH2, and it is used in energy extraction from sugars.
Compare and contrast substrate level phosphorylation and oxidative phosphorylation
Substrate level phosphorylation: phosphate group is removed from an intermediate, free energy is used to add third phosphate to available ADP molecule to make ATP
Oxidation phosphorylation: generation of ATP through chemiosomosis during glucose catabolism and harnesses energy of sunlight in light reactions
Comparisons: both make ATP
Describe how glucose is converted to pyruvate during glycolysis. What are the net products of glycolysis per one molecule of glucose?
Glycolisis starts with s six carbon ring shaped structure of one glucose molecule and ends with two molecules of three carbon sugar called pyruvate. Glycolisis has two phases: the first part traps glucose molecule in cell and uses energy to modify it so six carbon sugar is split into two three carbon molecules, the second part extracts energy from molecules and stores it as ATP and NADH.
Net products: 2 pyruvate molecules + 2 NADH + 2 ATP
Where do the NADH molecules generated from glycolysis go?
It is continuously oxidized back into NAD+. NAD+ has to be in the system to start the second step of glycolysis. If oxygen is in the system, NADH is oxidized and high-energy electrons from the hydrogen are released and produce ATP.
Why is glycolysis considered to be an anerobic reaction?
It does not use oxygen directly
How does pyruvate enter mitochondria?
Through the inner mitochondrial membrane by a transport protein called the mitochondrial pyruvate carrier
Describe the overall three steps of pyruvate oxidation, making sure to describe what happens to pyruvate, acetyl CoA, carbon dioxide (CO2), NAD+ and NADH.
1) A carboxyl group is removed from pyruvate, releasing a molecule of carbon dioxide. This reaction makes a 2 carbon hydroxyethyl group bount to pyruvate. This steps happens twice because there are 2 pyruvate molecules made at the end of glycolysis.
2) hydroxyethyl group is oxidized to an acetyl group, electrons are picked up by NAD+ to form NADH which later generates ATP
3) acetyl group is transferred to CoA to make a molecule of acetyl CoA
What product from pyruvate oxidation enters the citric acid cycle?
Acetyl CoA
For each molecule of acetyl CoA and each “turn” of the cycle, how many molecules of CO2 are released? How many molecules of ATP are formed by substrate level phosphorylation? How many NADH and FADH2 (which is the reduced form of FAD) molecules are produced?
2 carbon dioxide molecules are released per acetyl group fed into the cycle. one ATP molecule is produced by substrate-level phosphorylation. Three NADH, one FADH2 are produced.
Where do the NADH and FADH2 molecules generated from the citric acid cycle go?
They connect with the last portion of aerobic respiratin, electron transport chain, and make ATP molecules
Give a brief description of the electron transport chain: what is it made of and what happens to electrons as they move down the chain?
Series of electron transporters embedded in the inner mitochondrial membrane that moves electrons from NADH and FADH2 to molecular oxygen. Protons are pumped from the matrix to the intermembrane space, and oxygen is reduced to make water.
What is the main outcome of the electron transport chain?
water
Describe how ATP synthase makes ATP from ADP and inorganic phosphate. What type of molecule is ATP synthase?
It uses a proton gradient to form ATP from ADP and an inorganic phosphate. The protein is a generator that is turned by the force of hydrogen ions diffusing through it down their gradient. The turning facilitates the additional phosphate group to ADP to form ATP used potential energy of the hydrogen ion gradient. ATP synthase is an enzyme.
Why is it accurate to describe ATP synthase as an ion channel operating in reverse?
It allows protons to flow along its concentration gradient from the lumen and exit into the stroma. It flows from the inside of the mitochondria to the outside of the mitochondria.
Explain what chemiosmosis is and how it relates to ATP synthase function.
Free energy from redox reactions is used to pump hydrogen ions across the mitochondrial membrane. It generates energy used by ATP synthase to make ATP. As protons flow through ATP synthase, a conformational change happens and it allows ADP and an inorganic phosphate group to combine and form ATP.
Why is maintaining a H+ gradient via the electron transport chain so important to generating ATP?
The energy in the electron transport chain powers proton pumps that create a charge gradient that lets protons flow along their concentration gradient that powers ATP synthase and converts ADP into ATP.
How is glycogen used as a fuel for cellular respiration?
Glycogen is a polymer of glucose that is an energy storage molecule in animals. Excess glucose is stroed as glycogen when there is an adequate amount of ATP present. Glycogen allows ATP to be produced for a longer period of time during exercise.
How is sucrose used as a fuel for cellular respiration?
Sucrose is a disaccharide with a molecule of glucose and fructose bonded together through a glycosidic bond. Fructose, galactose, and glucose are absorbed into the bloodstream during digestion. Fructose and galactose make the same amount of ATP molecules as glucose.
How are amino acids used as fuel for cellular respiration?
Amino acids can be synthesized from intermediates and reactants.
How are lipids used as fuel for cellular respiration?
Lipids connect the glucose pathway and contribute to membrane flexibility. Triglycerides (fatty acids) are used for energy storage in animals. Fatty acids are catabolized through beta-oxidation that takes place in the matrix and converts fatty acid chains into two carbon units of acetyl groups.
How can proteins and fats be used in cellular respiration? What steps of cellular respiration do they enter?
Amino acids derived from proteins feed into the citric acid cycle. Acetyl groups picked up by CoA to from acetyl CoA from fatty acids feeds into the citric acid cycle.
Why do we need to eat food and breathe oxygen?
We need to eat food because if we are starving, some amino acids are shunted into glucose catobolism pathway,s which depletes the body of protein reserves. We breathe oxygen because it is a final electron acceptor in the electron transport chain and allows the process to make ATP.
Where in the cell does glycolysis occur?
cytoplasm
