Topic 10 - Cellular Respiration Flashcards
Cellular respiration
The process by which organisms transform food energy into ATP in the presence of oxygen
What is the chemical equation for cellular respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (38 ATP and heat)
What are the four main steps of cellular respiration? Describe them briefly.
- Glycolysis
- Process of breaking glucose into 3-carbon molecules (pyruvate) with the production of ATP and NADH - Pyruvate oxidation
- The decarboxylation and oxidation of pyruvate to produce acetyl-CoA (in preparation for the Krebs cycle under aerobic conditions) - Krebs cycle
- Series of enzyme-catalyzed reactions of central importance in all living cells for extraction of energy from carbohydrates
- Acetyl group from acetyl-CoA is attached to oxaloacetate to form citrate
- Citrate is oxidized, producing NADH, FADH2, CO2, and ATP
- Oxaloacetate reenters the cycle - Oxidative phosphorylation
- ETC: series of electron carriers embedded in the inner mitochondrial membrane (cristae) that shuttles electrons from NADH and FADH2 to molecular oxygen; in the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water
- Chemiosmosis: process in which ATP is produced in cellular metabolism by the involvement of a proton gradient across a membrane (electrochemical gradient); the potential energy of the H+ gradient is used to generate ATP by ATP synthase
Name where each step of cellular respiration takes place in the cell.
- Glycolysis - cytoplasm
- Pyruvate oxidation - mitochondria
- Krebs cycle - mitochondrial matrix
- Oxidative phosphorylation - cristae/inner membrane of mitochondria
What are the net products of glycolysis (per glucose)?
2 ATP
2 NADH
2 pyruvate
What are the net products of pyruvate oxidation (per glucose)?
2 CO2
2 NADH
2 acetyl-CoA
What are the net products of the Krebs cycle (per glucose)?
2 ATP
4 CO2
6 NADH
2 FADH2
Oxalacetate to start cycle over
What are the net products of oxidative phosphorylation (ETC and chemiosmosis)? Why?
34 ATP
- NADH and FADH2 bring their electrons to ETC
- 1 NADH = 3 ATP
- 1 FADH2 = 2 ATP
- As a result for ETC, 10 NADH x 3 = 30 ATP, plus 2 FADH2 x 2 = 4, therefore 34 ATP are produced.
What is the TOTAL amount of ATP produced by cellular respiration?
38
Substrate-level phosphorylation
Production of ATP from ADP using energy from a chemical reaction and a phosphate group from a reactant
Oxidative phosporylation
Production of ATP using the process of chemiosmosis in the presence of oxygen
ATP synthase
Membrane-embedded protein complex that adds a phosphate to ADP with energy from protons diffusing through it
How is energy transferred in the ETC/chemiosmosis?
Electron transport is a series of redox reactions; as the electrons are transferred, the electron energy is used to pump H+ across the membrane from the matrix to the inter-membrane space. From there, H+ moves back to the matrix through chemiosmosis.
What is the role of NAD+ and NADH in cellular respiration?
- Electron accepters/carriers used to transfer energy (electrons) during cellular respiration
- NAD+ accepts electrons from other molecules and becomes reduced; this reaction forms NADH, which can then be used as a reducing agent to donate electrons
- NADH is the source of electrons in the ETC
What is the source of electrons in the ETC (in cellular respiration)?
NADH
What is the final acceptor of electrons in the ETC (in cellular respiration)?
O2
How is water formed from the ETC?
O2 binds with H+ in the matrix, forming water.
How is a concentration gradient used to generate ATP?
Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin and catalyze conversion of ADP to ATP
What happens if no oxygen is present?
Anaerobic respiration - if oxygen is not present, other molecules become the final electron acceptor depending on the organism
- In animals and bacteria, it is pyruvate (when pyruvate is reduced it becomes lactic acid)
- In yeast, acetyl aldehyde is reduced and becomes ethanol
What are the reactants of cellular respiration?
Glucose (C6H12O2) and oxygen (O2)
What are the products of cellular respiration?
Water (H2O), carbon dioxide (CO2), and energy (ATP and heat)
Why is cellular respiration important?
It converts food (organic molecules) into usable energy for cells.
