krit.club logo

Molecular Biology - Cell Respiration

Grade 11IBBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Cell respiration is the controlled release of energy from organic compounds to produce ATPATP. ATPATP from cell respiration is immediately available as a source of energy in the cell.

•

Anaerobic cell respiration gives a small yield of ATPATP from glucose. In humans, the product is lactate (C3H6O3C_3H_6O_3); in yeast and plants, the products are ethanol (C2H5OHC_2H_5OH) and carbon dioxide (CO2CO_2).

•

Aerobic cell respiration requires oxygen (O2O_2) and gives a large yield of ATPATP from glucose. It involves the link reaction, the Krebs cycle, and the electron transport chain.

•

Oxidation and reduction are chemical processes involving the transfer of electrons. In cell respiration, glucose is oxidized (loses hydrogen/electrons) and oxygen is reduced (gains hydrogen/electrons).

•

Glycolysis occurs in the cytoplasm and breaks down one C6H12O6C_6H_{12}O_6 molecule into two molecules of pyruvate (C3H4O3C_3H_4O_3), producing a net gain of 22 ATPATP and 22 NADH+H+NADH + H^+.

•

The link reaction moves pyruvate into the mitochondrial matrix, where it is decarboxylated and oxidized to form an acetyl group, which then attaches to Coenzyme A to form Acetyl−CoAAcetyl-CoA.

•

The Krebs cycle occurs in the mitochondrial matrix. For every turn of the cycle, 22 molecules of CO2CO_2 are released, 33 NADH+H+NADH + H^+ are produced, 11 FADH2FADH_2 is produced, and 11 ATPATP is generated via substrate-level phosphorylation.

•

Chemiosmosis occurs in the inner mitochondrial membrane. The electron transport chain creates a proton (H+H^+) gradient in the intermembrane space, which drives ATPATP synthesis via ATPATP synthase.

📐Formulae

C6H12O6+6O2→6CO2+6H2O+energy (ATP)C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (ATP)}

C6H12O6→2C3H6O3 (Lactate fermentation in animals)C_6H_{12}O_6 \rightarrow 2C_3H_6O_3 \text{ (Lactate fermentation in animals)}

C6H12O6→2C2H5OH+2CO2 (Alcoholic fermentation in yeast)C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2 \text{ (Alcoholic fermentation in yeast)}

ADP+Pi+energy→ATP+H2OADP + P_i + \text{energy} \rightarrow ATP + H_2O

NADH+H+→NAD++2e−+2H+ (Oxidation of NADH)NADH + H^+ \rightarrow NAD^+ + 2e^- + 2H^+ \text{ (Oxidation of NADH)}

💡Examples

Problem 1:

During an intense sprint, a human muscle cell undergoes anaerobic respiration. If 33 molecules of glucose are metabolized, how many molecules of ATPATP and lactate are produced?

Solution:

66 ATPATP molecules and 66 lactate molecules.

Explanation:

In anaerobic respiration (lactate fermentation), each molecule of glucose (C6H12O6C_6H_{12}O_6) yields a net of 22 ATPATP and produces 22 molecules of lactate (C3H6O3C_3H_6O_3). Therefore, 33 glucose molecules ×2=6\times 2 = 6 ATPATP and 3×2=63 \times 2 = 6 lactate molecules.

Problem 2:

Explain the role of the H+H^+ gradient in the mitochondrion.

Solution:

The H+H^+ gradient provides the proton motive force required for ATPATP synthesis.

Explanation:

During the electron transport chain, electrons move through carriers, losing energy which is used to pump H+H^+ ions from the matrix into the intermembrane space. This creates a high concentration of H+H^+. These ions then flow down their electrochemical gradient back into the matrix through the enzyme ATPATP synthase, which uses the kinetic energy to phosphorylate ADPADP into ATPATP.