Metabolism and Photosynthesis Quiz

Metabolism

• Metabolism refers to all chemical transformations occurring within living organisms.
• These transformations are essential for the survival and functioning of living organisms.
• Metabolites are the end products or intermediates of these metabolic processes.

Primary Metabolites

• Primary metabolites are directly involved in normal growth, development, and reproduction.
• They are essential for proper growth.
• Examples include ethanol, lactic acid, certain amino acids, L-glutamate, L-lysine, and citric acid.

Secondary Metabolites

• Secondary metabolites are derived from primary metabolites.
• They don't play a direct role in growth, development, or reproduction.
• They are often produced during the stationary phase of growth.
• Examples include atropine, erythromycin, and bacitracin.

Photosynthesis

• Photosynthesis is the process of capturing light energy and converting it to chemical energy stored in sugar molecules.
• Occurs in chloroplasts of green organisms.
• The overall process can be summarized as: 6CO2 + 12H2O + light energy -> C6H12O6 + 6O2 + 6H2O

Photosynthesis Steps

• Carbon dioxide enters through stomata, water is absorbed by roots, and both are transported to leaves.
• Chlorophyll absorbs light energy to split water molecules into hydrogen and oxygen.
• Hydrogen and carbon dioxide are used to produce glucose.
• Oxygen is released as a waste product.
• Glucose provides energy for plant growth and development.

Pigments in Photosynthesis

• Pigments absorb light energy at specific wavelengths.
• Important pigments include Chlorophyll a, Chlorophyll b, and carotenoids.
• They are located within the thylakoids of chloroplasts.

Light Reaction of Photosynthesis

• Occurs only in the presence of sunlight.
• Takes place in the thylakoid membranes of chloroplasts.
• Grana, membrane-bound sacs within the thylakoid, gather light and are called photosystems.
• Two types of photosystems: Photosystem I and Photosystem II.
• Light energy is converted to ATP and NADPH, which are used in the dark reaction.
• Water is used and oxygen is produced.
• Chemical equation: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP

Dark Reaction of Photosynthesis (Calvin Cycle)

• Also called carbon-fixing reaction.
• Occurs in the stroma of the chloroplast.
• Utilizes NADPH and ATP from the light reaction.
• Plants capture carbon dioxide through stomata and proceed to the Calvin cycle.
• ATP and NADPH convert six molecules of carbon dioxide into one glucose molecule.
• Chemical equation: 3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi

Calvin Cycle Stages

• Carbon fixation: CO2 combines with RuBP, producing a six-carbon compound that splits into two 3-PGA molecules.
• Reduction: ATP and NADPH convert 3-PGA molecules into G3P.
• Regeneration: Some G3P molecules form glucose, while the rest are recycled to regenerate RuBP.

Glycolysis

• Converts glucose into pyruvate.
• Occurs in the cytosol and is independent of oxygen.
• Generates a net gain of two ATP molecules.

Citric Acid Cycle (Krebs Cycle)

• Occurs in the mitochondrial matrix under aerobic conditions.
• Oxidizes acetyl-CoA to form carbon dioxide.
• Reduces coenzymes, generating ATP in the electron transport chain.
• Eight-step process.

Biosynthesis of Secondary Metabolites

• Multi-step, enzyme-catalyzed process.
• Simple compounds are modified, converted, or joined to form macromolecules.
• Building blocks are derived from primary metabolites, primarily from photosynthesis, glycolysis, and the Krebs cycle.
• Important building blocks include acetyl CoA, shikimic acid, mevalonic acid, and malonic acid.

Building Blocks by Carbon Units

• C1 derived from S-methyl of L-methionine
• C2 derived from acetyl-CoA
• C5 derived from isoprene units
• C6-C3 units (phenyl propyl units) derived from phenylalanine or tyrosine through the shikimic acid pathway.

Shikimic Acid Pathway

• Biosynthesis of phenolic compounds, alkaloids, and other aromatic compounds.
• Occurs in chloroplast plant cells.
• Activated by environmental stresses like pathogens, herbivores, inappropriate pH, temperature, UV radiation, saline stress, and heavy metals.
• Pathway starts with phosphoenol pyruvate and erythrose-4-phosphate, ending with chorismate.

Shikimic Acid Pathway Steps

• Phosphoenol pyruvate and erythrose-4-phosphate react to form 3-deoxy-D-arabino-heptulosonate 7-phosphate.
• Shikimate kinase catalyzes the phosphorylation of shikimate to form shikimate 3-phosphate.
• Shikimate 3-phosphate couples with phosphoenol pyruvate to give 5-enolpyruvylshikimate-3-phosphate.
• 5-enolpyruvylshikimate-3-phosphate is transformed into chorismate by chorismate synthase.

Test your knowledge on metabolism and its crucial processes in living organisms. This quiz covers primary and secondary metabolites, as well as the fundamentals of photosynthesis. Challenge yourself to understand how these biochemical transformations support life.