[AP Bio] Cellular Respiration (Ch 7)

Chapter 7, Bioman, Cellular Respiration Chart, POGIL

Fermentation

a catabolic process involving the partial degradation of sugars or other organic fuel that occurs without the use of oxygen

Aerobic Respiration

the most efficient catabolic pathway for organic molecules, in which oxygen is consumed as a reactant along with the organic fuel to produce ATP

Organic Compounds + Oxygen →
Carbon Dioxide + Water + Energy

Cellular Respiration

the catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP

• Degradation of Glucose:
  C₆H₁₂O₆ + 6O₂ →
  6CO₂ + Energy (ATP + Heat)

  • Exergonic, having a free energy change of -686 kcal per mole of glucose decomposed

Redox Reaction

a chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another

• Short for reduction-oxidation reaction

Oxidation

the complete or partial loss of electrons from a substance involved in a redox reaction

Reduction

the complete or partial addition of electrons to a substance involved in a redox reaction

• Adding negatively charged electrons to an atom REDUCES the positive charge of that atom

Reducing Agent

the electron donor in a redox reaction (reduces the other atom by giving it electron)

Oxidizing Agent

the electron acceptor in a redox reaction (takes away electrons from atom)

NAD⁺

oxidized form of nicotinamide adenine dinucleotide, a coenzyme that can accept electrons

NADH

reduced form of nicotinamide adenine dinucleotide, which temporarily stores electrons during cellular respiration

Electron Transport Chain (ETC)

a sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP

4 Stages of Cellular Respiration

1. Glycolysis

2. Link Reaction/Pyruvate Oxidation

3. Krebs Cycle/Citric Acid Cycle

4. Oxidative Phosphorylation (ETC + Chemiosmosis)

Glycolysis

begins the degradation process by breaking glucose into two molecules of a compound called pyruvate, occurring in the cytoplasm of the cell

• Anaerobic Process; done without oxygen

The Link Reaction/Pyruvate Oxidation

where pyruvate is converted into acetyl-CoA, acting as a bridge between glycolysis and the Krebs cycle

• Occurs in mitochondria

Krebs Cycle/Citric Acid Cycle

cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide

• Occurs in mitochondrial matrix

• Main job is to generate NADH & FADH₂

Oxidative Phosphorylation

the production of ATP using energy derived from the redox reactions of an electron transport chain

• Consists of the electron transport chain (ETC) and chemiosmosis, which work together to drive ATP production

Electron Transport Chain (ETC)

a sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP

• Aerobic process; requires oxygen (serves as final electron acceptor at end of ETC)

• Occurs in the inner mitochondrial membrane

• Works together with chemiosmosis to make ATP, making oxidative phosphorylation as a whole

Chemiosmosis

an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work

Substrate-Level Phosphorylation

the enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism

• Transfers a phosphate group from a substrate molecule to ADP, rather than adding an inorganic phosphate to ADP as in oxidative phosphorylation

Acetyl CoA

the highly reactive entry compound for the citric acid cycle in cellular respiration

• Acetyl CoA feeds its acetyl group into the citric acid cycle for further oxidation

Total Yield Per Glucose in Krebs Cycle/Citric Acid Cycle

• 6 NADH

• 2 FADH₂

• 2 ATP

Cytochrome

an iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells

ATP Synthase

a complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP

Chemiosmosis

an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work

• Chloroplasts use chemiosmosis to generate ATP during photosynthesis

• Prokaryotes, as already mentioned, generate Hᐩ gradients across their plasma membranes

Proton-Motive Force

the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (Hᐩ) across a biological membrane during chemiosmosis

Alcohol Fermentation

glycolysis followed by the reduction of pyruvate to ethyl alcohol (ethanol), regenerating NAD⁺ and releasing CO₂

Lactic Acid Fermentation

glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD⁺ with no release of CO₂

Obligate Anaerobes

an organism that only carries out fermentation or anaerobic respiration because they cannot use oxygen and may be poisoned by it

Facultative Anaerobes

an organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present

Deamination

when an amino acid gets its amino group stripped off before feeding into glycolysis or the Krebs cycle

Beta Oxidation

a metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl-CoA

• NADH and FADH₂ are also made during beta oxidation, resulting in further ATP production

What are the reactants of Cellular respiration?

• 6 glucose (C₆H₁₂O₆)

• 6 oxygen (O₂)

What are the products of cellular respiration?

• 6 carbon dioxide (CO₂)

• 6 water (H₂O)

• Energy (ATP)

What phase of cellular respiration occurs in the cytoplasm of the cell?

Glycolysis

Which phases of cellular respiration happen in the mitochondria?

Link Reaction (Pyruvate Oxidation), Krebs Cycle, Oxidative Phosphorylation

Which of the 4 phases of Cellular Respiration require oxygen?

Oxidative Phosphorylation

Which of the 4 phases of cellular respiration produce carbon dioxide?

Link Reaction & Krebs Cycle

Which of the 4 phases of cellular respiration produce water?

Oxidative Phosphorylation

Which of the 4 phases of cellular respiration result in the production of ATP?

• Glycolysis

• Krebs Cycle

How many ATPs (total) are produced for every glucose molecule that undergoes cellular respiration

Amount varies, but up to 38 ATP (under ideal conditions) for most sources

What reactants of ATP must be available in the cell in order to produce ATP?

ADP and P_i (inorganic phosphate)

What are the reduced forms of NAD⁺and FAD?

NADH & FADH₂

Is glucose oxidized or reduced during cellular respiration?

Oxidized, because it loses its electrons and gives them to the electron carriers, NAD⁺ and FAD

What molecules/atoms need to be available to produce NADH?

NAD⁺ + H⁺ 

What molecules are produced as hydrogen ions and electrons were removed from NADH and FADH₂?

NAD⁺ & FAD

Why do organisms release energy gradually?

To slowly release energy (so no explosion happens) and make ATP gradually

How many molecules of ATP are used to start glycolysis?

2 ATP

What is stripped off the remnants of glucose during oxidation?

Electrons & Hydrogens

How is ATP made?

When phosphates get transferred from sugars to ADP to make ATP

Why is the net gain of ATP only 2 ATP in glycolysis despite it making 4 ATP?

2 ATP of the 4 ATP were used to replace the 2 ATP used to break down the glucose molecule

How many pyruvates and NADH are made in glycolysis?

• 2 pyruvates

• 2 NADH

How many carbon atoms are in 1 pyruvate molecule?

3 carbon atoms

What are the final products of glycolysis?

• 2 pyruvates

• 2 NADH

• 2 ATP

Where does the pyruvate from glycolysis move into?

Mitochondria

How much carbon dioxide is released during the Link Reaction?

2 CO₂

What molecule derived from pyruvate is fed into the Krebs Cycle?

Acetyl CoA

What two things does the Link Reaction connect?

Glycolysis to the Krebs Cycle

How many Acetyl CoA, CO₂, and NADH molecules are made at the end of the Link Reaction?

• 2 Acetyl CoA (goes to Krebs Cycle)

• 2 CO₂ (breathed out)

• 2 NADH (goes to ETC)

What molecule is broken down in the Krebs Cycle?

Acetyl CoA

How is Citric Acid made?

When Acetyl CoA (2-carbon molecule) reacts with oxaloacetate (4-carbon molecule) to form citric acid (6-carbon molecule)

What gas is released during the Citric Acid Cycle?

Carbon Dioxide (CO₂)

Where does FADH₂ carry the electrons and hydrogens from the Krebs cycle?

To the Electron Transport Chain (ETC)

What 4-carbon molecule is made at the end of the Krebs cycle?

Oxaloacetate (the same molecule that combines with Acetyl CoA at the beginning of the Krebs Cycle)

What are the products of the Krebs Cycle?

• 2 ATP (used as cell energy)

• 4 CO₂ (breathed out)

• 6 NADH (carries electrons to ETC)

• 2 FADH₂ (carries electrons to ETC)

Where is the electron transport chain (ETC) found?

Inner Membrane of Mitochondria

What ions are pumped from the inner mitochondrial membrane from the matrix?

Hydrogen Ions (H⁺)

What builds up in the mitochondrial intermembrane space as hydrogen ions are pumped across the inner membrane?

High Concentration of Hydrogen Ions (Electrochemical Gradient)

What does oxygen do in the ETC?

Works as electron acceptor (accepts electrons/hydrogens from the matrix) and makes water

As hydrogen ions diffuse through the ATP synthase, what does the protein do?

The ATP Synthase spins and produces ATP as ADP & inorganic phosphate (P_i) combine