Cellular Respiration Vocabulary

Cellular Respiration

Overview

  • Cellular respiration: Process by which cells obtain energy from organic molecules.

  • Primary goal: create energy intermediates such as ATP and NADH.

  • Aerobic respiration: Uses oxygen; consumes $$O2andreleases and releases $$ and releases $$CO2$$.

  • Glucose (C6H12O6) is broken down into carbon dioxide and water.
    $$C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O$$

Four Stages of Glucose Breakdown

  1. Glycolysis

    • Glucose (6-carbon molecule) is broken down into two pyruvate molecules (3-carbon).

    • Occurs in the cytosol.

    • Net production of 2 ATP and 2 NADH.

  2. Pyruvate Breakdown

    • Pyruvate is transported into the mitochondria.

    • Oxidized to form two acetyl groups, releasing two CO2CO_2$$CO_2$$ molecules.

    • Produces 2 NADH.

  3. Citric Acid Cycle

    • Acetyl groups are oxidized, releasing four CO2CO_2$$CO_2$$ molecules.

    • Produces 2 ATP, 6 NADH, and 2 FADH2.

  4. Oxidative Phosphorylation

    • NADH and FADH2 are oxidized via the electron transport chain, creating an H+ gradient.

    • The H+ gradient is used to produce approximately 30-34 ATP.

Glycolysis Details

  • Occurs in the cytosol; does not require oxygen.

  • Evolutionarily ancient; nearly identical in all species.

  • Three phases:

    • Energy investment: 2 ATP are hydrolyzed.

    • Cleavage: Glucose is broken into two 3-carbon molecules (glyceraldehyde-3-phosphate).

    • Energy liberation: Produces 2 NADH and 4 ATP (net gain of 2 ATP).

  • Substrate-level phosphorylation: Phosphate group is transferred from an enzyme-bound substrate to ADP.

  • Net products: two pyruvates, two ATP (net), two NADH.

Pyruvate Breakdown (Stage 2)

  • Pyruvate enters the mitochondrial matrix in eukaryotic cells.

  • Pyruvate dehydrogenase complex oxidizes pyruvate, releasing one CO2CO_2$$CO_2$$ molecule per pyruvate.

  • Forms acetyl CoA and one NADH per pyruvate.

Citric Acid Cycle (Stage 3)

  • Occurs in the mitochondrial matrix.

  • Acetyl group from acetyl CoA combines with oxaloacetate (4-carbon) to form citrate (6-carbon).

  • For each acetyl group:

    • Two CO2CO_2$$CO_2$$ molecules are released.

    • One ATP (originally GTP) is produced.

    • Three NADH are produced.

    • One FADH2 is produced.

    • Oxaloacetate is regenerated.

Oxidative Phosphorylation (Stage 4)

  • Two components:

    • Electron Transport Chain (ETC).

    • ATP Synthase.

  • High-energy electrons from NADH and FADH2 are transferred to the ETC.

  • Electrons release energy as they move along the chain, creating an H+ electrochemical gradient.

  • ATP synthase uses the energy in the H+ gradient to synthesize ATP.

Electron Transport Chain (ETC)

  • Located in the inner mitochondrial membrane.

  • NADH and FADH2 are oxidized, and electrons enter the chain.

  • Electrons are passed along protein complexes and organic molecules (e.g., ubiquinone).

  • Energy released is used to pump H+ ions across the inner membrane, forming a gradient.

  • Oxygen accepts electrons at the end of the chain, forming water.

ATP Synthase and Chemiosmosis

  • H+ ions flow through ATP synthase, releasing energy.

  • Energy is used to covalently attach a phosphate group to ADP, forming ATP.

  • Chemiosmosis: ATP synthesis driven by the movement of ions across a membrane.

  • ATP Yield:

    • Glycolysis: 2 ATP

    • Citric Acid Cycle: 2 ATP

    • Oxidative Phosphorylation: 30-34 ATP

ATP Synthase Structure and Function

  • The enzyme has transmembrane and extramembrane parts, including a ring of c subunits

  • H+ ions in the intermembrane space enter a half channel and bind to a c subunit, then rotate around the ring until reaching another half channel that releases H+ into the matrix

  • The gamma subunit rotates, which is attached to the c-subunits, as well

  • The rotation causes conformational changes in the beta subunits, which make up the location where ATP is synthesized, generating three phases: 1) binding of ADP and inorganic phosphate, 2) using induced fit to create ATP, which is now tightly bound, and 3) a release of the ATP

  • The various beta subunits are in different phases at the same time

Metabolic Versatility

  • Besides glucose, other molecules (carbohydrates, proteins, fats) can be used for energy.

  • These molecules enter glycolysis or the citric acid cycle at various points.


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Cellular Respiration Vocabulary

Cellular Respiration

Overview

  • Cellular respiration: Process by which cells obtain energy from organic molecules.
  • Primary goal: create energy intermediates such as ATP and NADH.
  • Aerobic respiration: Uses oxygen; consumes O2O2 and releases CO2CO2.
  • Glucose (C6H12O6) is broken down into carbon dioxide and water.
    C6H12O6+6O26CO2+6H2OC6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O

Four Stages of Glucose Breakdown

  1. Glycolysis
    • Glucose (6-carbon molecule) is broken down into two pyruvate molecules (3-carbon).
    • Occurs in the cytosol.
    • Net production of 2 ATP and 2 NADH.
  2. Pyruvate Breakdown
    • Pyruvate is transported into the mitochondria.
    • Oxidized to form two acetyl groups, releasing two CO2CO_2 molecules.
    • Produces 2 NADH.
  3. Citric Acid Cycle
    • Acetyl groups are oxidized, releasing four CO2CO_2 molecules.
    • Produces 2 ATP, 6 NADH, and 2 FADH2.
  4. Oxidative Phosphorylation
    • NADH and FADH2 are oxidized via the electron transport chain, creating an H+ gradient.
    • The H+ gradient is used to produce approximately 30-34 ATP.

Glycolysis Details

  • Occurs in the cytosol; does not require oxygen.
  • Evolutionarily ancient; nearly identical in all species.
  • Three phases:
    • Energy investment: 2 ATP are hydrolyzed.
    • Cleavage: Glucose is broken into two 3-carbon molecules (glyceraldehyde-3-phosphate).
    • Energy liberation: Produces 2 NADH and 4 ATP (net gain of 2 ATP).
  • Substrate-level phosphorylation: Phosphate group is transferred from an enzyme-bound substrate to ADP.
  • Net products: two pyruvates, two ATP (net), two NADH.

Pyruvate Breakdown (Stage 2)

  • Pyruvate enters the mitochondrial matrix in eukaryotic cells.
  • Pyruvate dehydrogenase complex oxidizes pyruvate, releasing one CO2CO_2 molecule per pyruvate.
  • Forms acetyl CoA and one NADH per pyruvate.

Citric Acid Cycle (Stage 3)

  • Occurs in the mitochondrial matrix.
  • Acetyl group from acetyl CoA combines with oxaloacetate (4-carbon) to form citrate (6-carbon).
  • For each acetyl group:
    • Two CO2CO_2 molecules are released.
    • One ATP (originally GTP) is produced.
    • Three NADH are produced.
    • One FADH2 is produced.
    • Oxaloacetate is regenerated.

Oxidative Phosphorylation (Stage 4)

  • Two components:
    • Electron Transport Chain (ETC).
    • ATP Synthase.
  • High-energy electrons from NADH and FADH2 are transferred to the ETC.
  • Electrons release energy as they move along the chain, creating an H+ electrochemical gradient.
  • ATP synthase uses the energy in the H+ gradient to synthesize ATP.

Electron Transport Chain (ETC)

  • Located in the inner mitochondrial membrane.
  • NADH and FADH2 are oxidized, and electrons enter the chain.
  • Electrons are passed along protein complexes and organic molecules (e.g., ubiquinone).
  • Energy released is used to pump H+ ions across the inner membrane, forming a gradient.
  • Oxygen accepts electrons at the end of the chain, forming water.

ATP Synthase and Chemiosmosis

  • H+ ions flow through ATP synthase, releasing energy.
  • Energy is used to covalently attach a phosphate group to ADP, forming ATP.
  • Chemiosmosis: ATP synthesis driven by the movement of ions across a membrane.
  • ATP Yield:
    • Glycolysis: 2 ATP
    • Citric Acid Cycle: 2 ATP
    • Oxidative Phosphorylation: 30-34 ATP

ATP Synthase Structure and Function

  • The enzyme has transmembrane and extramembrane parts, including a ring of c subunits
  • H+ ions in the intermembrane space enter a half channel and bind to a c subunit, then rotate around the ring until reaching another half channel that releases H+ into the matrix
  • The gamma subunit rotates, which is attached to the c-subunits, as well
  • The rotation causes conformational changes in the beta subunits, which make up the location where ATP is synthesized, generating three phases: 1) binding of ADP and inorganic phosphate, 2) using induced fit to create ATP, which is now tightly bound, and 3) a release of the ATP
  • The various beta subunits are in different phases at the same time

Metabolic Versatility

  • Besides glucose, other molecules (carbohydrates, proteins, fats) can be used for energy.
  • These molecules enter glycolysis or the citric acid cycle at various points.