Grade 12 Biology unit 3: Energy Transformation

Photosynthesis uses light energy from the sun. The chloroplast is where photosynthesis happens, and ATP and glucose are products or energy carriers, not the original source of energy.

In the photosynthesis equation, the plant uses water and releases oxygen gas (O₂) as a by-product. Carbon dioxide is taken in, not released.

The textbook says glycolysis occurs in the cytosol of the cell and does not require oxygen. The Krebs cycle and electron transport happen in the mitochondria.

The chapter describes chlorophyll a as the most important chlorophyll. It is the green pigment found in all plants, algae, and cyanobacteria. Carotene and fucoxanthin are accessory pigments.

Glycolysis breaks one glucose molecule into two molecules of the three-carbon compound pyruvate. The net reaction shows 2 Pyruvate, 2 ATP and 2 NADH.

The chapter says that in plants like maize, sorghum and sugarcane, the first product of carbon dioxide fixation is not the three-carbon molecule phosphoglycerate. It is the four-carbon compound oxaloacetic acid.

In alcohol fermentation, pyruvate is decarboxylated (releasing CO₂) to form acetaldehyde, which is then converted to ethanol. Lactic acid is the product of lactic acid fermentation in muscle cells and some bacteria, not yeast.

The textbook says that in photorespiration, RuBisco, instead of combining with CO₂, combines with O₂. This is why photorespiration is a wasteful process in plants.

CAM plants open their stomata at cool night and close them during the hot, dry day. Closing the stomata during the day minimizes water loss. The CO₂ is taken in at night and stored as malic acid.

As electrons move down the electron transport chain, protons are pumped out of the matrix. This creates a proton gradient, and the flow of protons back through ATP synthase drives the making of ATP. This is called chemiosmosis.