Topic 5A p2 Flashcards
(17 cards)
Reduction
Reduction is the gain of electrons or hydrogen by a molecule, atom, or ion, or the loss of oxygen. It is one half of a redox (reduction-oxidation) reaction. In biological systems, reduction often occurs during reactions that store energy, such as in respiration or photosynthesis. Reduced molecules tend to have higher energy content.
Oxidation
Oxidation is the loss of electrons or hydrogen by a substance, or the gain of oxygen. It often releases energy and is a key part of many biological processes, such as aerobic respiration. Oxidation reactions are always paired with reduction reactions. In cells, enzymes help control oxidation to prevent damage.
Redox Reaction
A redox (reduction-oxidation) reaction involves both the transfer of electrons and changes in oxidation state. One substance is oxidised (loses electrons), while another is reduced (gains electrons). These reactions are vital in biological processes like respiration and photosynthesis. Energy transfer in cells frequently depends on redox reactions.
Metabolic Pathway
A metabolic pathway is a series of enzyme-controlled reactions where a molecule is gradually converted into a final product. Each step is catalysed by a specific enzyme and often regulated to meet cellular needs. Pathways can be anabolic (building up) or catabolic (breaking down). Examples include glycolysis and the Krebs cycle.
Metabolism
Metabolism refers to the total sum of all chemical reactions that occur within a living organism. It includes both anabolic reactions (which build molecules) and catabolic reactions (which break molecules down). Metabolism provides energy and the building blocks needed for growth, repair, and normal functioning. It is tightly regulated by enzymes and hormones.
Hydrogen Carrier
A hydrogen carrier is a molecule that temporarily holds hydrogen atoms or electrons removed during oxidation reactions. Common biological hydrogen carriers include NAD⁺ and FAD, which become reduced to NADH and FADH₂. These carriers transport hydrogen to other parts of the cell, especially the electron transport chain. They are essential for linking metabolic stages such as glycolysis, the Krebs cycle, and oxidative phosphorylation.
Metabolic Reaction
A metabolic reaction is any chemical reaction that takes place as part of metabolism. These reactions are catalysed by enzymes and may release or require energy. Examples include respiration, photosynthesis, and protein synthesis. Metabolic reactions occur in sequences (pathways) to efficiently manage energy and resources.
Hydrogen Acceptor
A hydrogen acceptor is a molecule that gains hydrogen atoms or electrons during a redox reaction. In respiration, oxygen is the final hydrogen acceptor, forming water when it receives electrons and hydrogen ions. Earlier in the process, molecules like NAD⁺ also act as hydrogen acceptors. Accepting hydrogen is part of energy transfer and is crucial for maintaining metabolic flow.
Intermediate Compound
An intermediate compound is a substance formed temporarily in the middle of a metabolic pathway. It is neither the starting reactant nor the final product but is involved in the transformation of one into the other. For example, pyruvate is an intermediate in respiration. Intermediates often regulate or connect pathways.
Series
In biology, a series refers to a sequence of steps or events that occur in a specific order. It is often used to describe a metabolic pathway or a chain of reactions, like the enzyme-controlled steps of glycolysis. Each part of the series depends on the previous step. Proper sequence is crucial for correct biological functioning.
Electron Transport Chain (ETC)
The electron transport chain is a series of protein complexes in the inner mitochondrial membrane (or thylakoid membrane in chloroplasts) that transfer electrons from hydrogen carriers like NADH and FADH₂ to oxygen. As electrons move through the chain, energy is used to pump protons across the membrane, generating a proton gradient. This gradient powers ATP synthesis. The ETC is the final stage of aerobic respiration.
What Does ‘Overall’ Mean in ‘Overall Reaction’?
In an overall reaction, “overall” refers to the net change after simplifying all intermediate steps. It shows the input and output substances without listing every intermediate or side reaction. For example, the overall equation for aerobic respiration is:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.
Absorption Spectrum
An absorption spectrum is a graph showing the specific wavelengths of light absorbed by a substance, such as chlorophyll in plants. It identifies which wavelengths are taken in and used during processes like photosynthesis. Peaks in the spectrum correspond to wavelengths most effectively absorbed.
Action Spectrum
An action spectrum illustrates the rate of a biological process, like photosynthesis, across different wavelengths of light. It shows which wavelengths are most effective in driving the process, combining absorption and biological activity data. Comparing it with the absorption spectrum helps confirm which pigments are involved.
Chemical Process
A chemical process involves changes in the molecular or atomic structure of substances through chemical reactions. Bonds are broken and formed, resulting in new substances with different properties. Chemical processes underpin many biological activities, such as respiration and digestion.
Biological Process
A biological process is any series of events or reactions carried out by living organisms to sustain life. This includes processes like cell division, photosynthesis, and protein synthesis. These processes often involve complex interactions between molecules and cells.
Model
A model is a simplified representation of a real system or process used to explain, predict, or understand complex phenomena. Models can be physical, mathematical, or conceptual and help scientists test hypotheses. They are useful in education and research when direct observation is difficult.
