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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 (or citric acid cycle). Glycolysis is an anaerobic process that occurs in the cytoplasm and does not require oxygen, while the chemical processes in the mitochondria, including the Krebs cycle and oxidative phosphorylation, are aerobic processes that require oxygen to complete cellular respiration efficiently.
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, where R represents the variable side chain of the amino acid. The formation of a dipeptide from two amino acids can be shown as:
ightarrow ext{Dipeptide} + H_2O$$ This reaction involves the removal of a water molecule (condensation reaction) to form a peptide bond.Step 3
Explain the effect of an increase in temperature and a change in pH on the molecular structure of a protein.
Answer
An increase in temperature can lead to denaturation of proteins, disrupting the hydrogen bonds and ionic interactions that maintain the secondary and tertiary structures. As the temperature rises, the kinetic energy of the molecules increases, which can cause these bonds to break, leading to a loss of functional shape.
Similarly, a change in pH alters the ionization state of amino acids, affecting their ability to interact with one another. Extreme pH conditions can alter the charge of the amino acid side chains, thereby disrupting interactions critical for maintaining the protein's structure. Both temperature and pH shifts can significantly impact a protein's functionality.
Step 4
The use of muscle cell type changes as the nature of the activity changes. Give reasons for this.
Answer
Muscle cell types are adapted for different types of activities. Type 1 muscle cells, or slow-twitch fibers, are more efficient in utilizing oxygen and are suited for endurance activities, such as marathon running. These fibers are fatigue-resistant but produce less force and power. In contrast, Type 2 muscle cells, or fast-twitch fibers, excel in generating short bursts of strength and speed, making them ideal for activities such as sprinting. As the nature of physical activity changes, the demand for energy and the type of muscle fiber utilized also shifts to meet the specific energy requirements.
Step 5
Use an equation to show how ATP is regenerated during muscle activity.
Answer
ATP is regenerated during muscle activity through cellular respiration, particularly during oxidative phosphorylation. The equation can be represented as:
ightarrow ext{ATP}$$ In the electron transport chain, energy derived from the breakdown of glucose ultimately leads to the phosphorylation of ADP to ATP, allowing muscle cells to sustain contraction.