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The main steps in cellular respiration are shown in the diagram of the cell - HSC - SSCE Chemistry - Question 35 - 2011 - Paper 1
Question 35
The main steps in cellular respiration are shown in the diagram of the cell. Identify the process represented by X, and explain the difference in oxygen requirement... show full transcript
Worked Solution & Example Answer:The main steps in cellular respiration are shown in the diagram of the cell - HSC - SSCE Chemistry - Question 35 - 2011 - Paper 1
Step 1
Identify the process represented by X and explain the difference in oxygen requirements of glycolysis and the chemical processes in mitochondria.
Answer
The process represented by X is the Krebs cycle. Glycolysis occurs in the cytoplasm and does not require oxygen, making it an anaerobic process. In contrast, the processes that occur in the mitochondria, such as the Krebs cycle and oxidative phosphorylation, are aerobic; they require oxygen to proceed. Glycolysis breaks down glucose into pyruvate, producing a small amount of ATP anaerobically, while in mitochondria, the produced pyruvate undergoes further oxidation in the presence of oxygen, resulting in a much higher yield of ATP.
Step 2
Using the general formula for an amino acid, write an equation to show the formation of a dipeptide.
Answer
The general formula for an amino acid can be represented as R-CH(NH₂)-COOH. To form a dipeptide, two amino acids (R1-CH(NH₂)-COOH and R2-CH(NH₂)-COOH) combine, releasing a molecule of water:
This reaction showcases the peptide bond formation through a condensation reaction.
Step 3
Explain the effect of an increase in temperature and a change in pH on the molecular structure of a protein.
Answer
An increase in temperature can lead to denaturation of proteins as the high temperature disrupts the weak interactions that maintain their secondary and tertiary structures. This can result in loss of the protein's functional shape.
Similarly, a change in pH affects the ionization of amino acid side chains, leading to changes in hydrogen bonding and ionic interactions. Extreme pH levels can also denature proteins by disrupting their structure, which affects their biological function. Therefore, both increased temperature and altered pH can significantly compromise protein structure and functionality.
Step 4
The use of muscle cell type changes as the nature of the activity changes.
Answer
Muscle cell types change according to the activity because Type 1 muscle cells (slow-twitch) are more efficient for endurance activities, such as marathon running, where aerobic respiration is vital for sustained energy. In contrast, Type 2 muscle cells (fast-twitch) are utilized more during high-intensity, short-duration activities, like sprinting, as they can quickly produce energy through anaerobic metabolism. Hence, activities that require different energy systems will engage varying muscle fiber types.
Step 5
Use an equation to show how ATP is regenerated during muscle activity.
Answer
ATP is regenerated during muscle activity through the process of cellular respiration. The equation for the regeneration of ATP from ADP is expressed as:
This process occurs primarily in the mitochondria during oxidative phosphorylation, allowing for sustained muscle contractions.