Cellular Respiration Overview

Cellular Respiration Overview

• Cellular respiration is a metabolic process that breaks down organic molecules to release energy in the form of ATP (adenosine triphosphate). This energy is used for cellular activities.
• It's a central process for all living organisms.
• Two main types exist: anaerobic (without oxygen) and aerobic (with oxygen).

Anaerobic Respiration

• This type of respiration occurs in the absence of oxygen.
• It's less efficient than aerobic respiration, producing much less ATP.
• It involves a substrate being broken down by enzymes to produce energy in the form of ATP and reduced products.

Aerobic Respiration

• This type of respiration requires oxygen.
• It's highly efficient, producing a large amount of ATP.
• It involves a series of reactions, including glycolysis, the Krebs cycle, and the electron transport chain.

Two Types of Fermentation

• Fermentation is an anaerobic process that follows glycolysis.
• Alcohol fermentation: This involves the conversion of pyruvate to ethanol and carbon dioxide. Common in yeast and some bacteria.
• Lactic acid fermentation: Involves the conversion of pyruvate to lactic acid. Found in animal muscle cells during strenuous exercise when oxygen supply is limited.

Glycolysis

• Glycolysis is the first stage of both aerobic and anaerobic respiration.
• It occurs in the cytoplasm of the cell.
• It involves breaking down glucose (a 6-carbon molecule) into two molecules of pyruvate (a 3-carbon molecule).
• This process yields a small amount of ATP and NADH (electron carriers).

Krebs Cycle (Citric Acid Cycle)

• Occurs in the mitochondrial matrix (in eukaryotes).
• Pyruvate from glycolysis is further oxidized to release carbon dioxide.
• It produces ATP, NADH, FADH₂ (electron carriers), and some byproducts.
• The cycle repeats for each original glucose molecule.

Electron Transport Chain (ETC)

• Takes place in the inner mitochondrial membrane (in eukaryotes).
• NADH and FADH₂ from glycolysis and the Krebs cycle donate electrons to a series of protein complexes.
• The electron transfer releases energy, which is used to pump hydrogen ions (protons) across the membrane creating a gradient.
• The movement of hydrogen ions back across the membrane through ATP synthase generates ATP.
• Oxygen acts as the final electron acceptor, combining with hydrogen ions to form water.

Photosynthesis

• Photosynthesis is the process by which plants and some other organisms convert light energy into chemical energy in the form of glucose.
• Two main types of reactions: Light-dependent and light-independent (Calvin cycle).
• Light-dependent reactions capture light energy and convert it into chemical energy stored in ATP and NADPH.
• Light-independent (Calvin cycle) reactions use ATP and NADPH to convert carbon dioxide into glucose.
• It occurs in chloroplasts.