Biology  5/e   Raven/Johnson
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Glucose: Glucose is a six-carbon sugar – a monosaccharide. Its molecular formula is C₆H₁₂0₆. It is the primary energy-Electron energy levels: Electrons orbit around the nucleus of their atom in specific paths called orbitals and at specific energy levels. The further out from the nucleus that an electron is, the greater the energy it contains. Moving the electron closer to the nucleus lowers its energy as energy is released. Similarly, if energy is added to the electron, it is raised to a higher energy level and orbits further from the nucleus. When electrons absorb light energy, they are raised to higher energy levels. When electrons are transferred from one molecule to another, they take their energy with them.

Chloroplasts: Chloroplasts are the organelles that carry out photosynthesis in the cells of eukaryotic plants and algae. They apparently are endosymbionts, derived from photosynthetic bacteria such as cyanobacteria. They have a complex internal membrane structure consisting of disk-shaped sacs called thylakoids that are stacked into grana.

Chemiosmosis: Chemiosmosis is one of the two ways of synthesizing ATP. A proton pump first uses energy to force protons out across a membrane against their concentration gradient. The protons then diffuse back in across the membrane through special channels. This diffusion back in is coupled with the conversion of ADP + P_i to ATP.

Oxidation-reduction: Oxidation is the loss of an electron and therefore the loss of energy; reduction is the gain of an electron and energy. Hydrogen ions often accompany the electrons in their movements. When one substance is oxidized, another substance in the reaction is reduced since the electron must be transferred to something. Oxidation-reduction reactions are a key way that energy is transferred within living systems.

Glycolysis: Whether under anaerobic or aerobic conditions, glycolysis is the first stage in the process of cellular respiration. During glycolysis, glucose is converted to pyruvate, more ATP is produced than is used up, and NAD⁺ is reduced to NADH. What happens next depends on whether the cell is in an anaerobic environment (fermentation occurs) or in an aerobic environment (aerobic respiration occurs). This chapter shows that the glucose that is the foundation for cellular respiration comes from photosynthesis.

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