Photo AI
Write an essay on one of the topics below - AQA - A-Level Biology - Question 7 - 2021 - Paper 3
Question 7
Write an essay on one of the topics below. Either The importance of complementary shapes of molecules in organisms Or The importance of ions in metabolic processes
Worked Solution & Example Answer:Write an essay on one of the topics below - AQA - A-Level Biology - Question 7 - 2021 - Paper 3
Step 1
The importance of complementary shapes of molecules in organisms
Answer
Complementary shapes of molecules are crucial in biological systems, particularly in the interactions between enzymes and substrates. The specificity of enzymes can be explained by the 'lock and key' model, where the enzyme (the lock) has a specific shape that only fits a certain substrate (the key).
-
Enzyme-Substrate Interaction: The shape of the active site of an enzyme is complementary to the shape of its specific substrate. This allows for effective binding, which is essential for catalytic activity.
-
DNA and RNA Structure: The complementary base pairing in DNA (Adenine with Thymine, and Cytosine with Guanine) is vital for the accurate replication and transcription of genetic information, influencing protein synthesis.
-
Hormonal Interaction: Hormones are also shaped to fit specific receptors on target cells. For example, insulin’s shape allows it to bind to insulin receptors, facilitating glucose uptake into cells.
-
Antibody Function: The specific shape of antibodies allows them to bind to antigens (pathogens), which is crucial for the immune response, demonstrating how shape influences function.
-
Transport Proteins: Membrane proteins, such as channels and carriers, also display complementary shapes that allow for selective transport of molecules across membranes, critical for cellular homeostasis.
In summary, the complementary shapes of molecules not only drive biochemical reactions but also ensure the integrity of biological processes essential for life.
Step 2
The importance of ions in metabolic processes
Answer
Ions play a critical role in numerous metabolic processes, influencing physiological activities and maintaining homeostasis within organisms.
-
Enzymatic Activity: Many enzymes require metal ions as cofactors for their catalytic activity. For example, magnesium ions are essential for ATP functioning and enzyme catalysis.
-
Nerve Impulse Transmission: Ions such as sodium (Na+) and potassium (K+) are fundamental in creating action potentials in neurons. The movement of these ions across the membrane generates electrical signals crucial for communication in the nervous system.
-
Muscle Contraction: Calcium ions (Ca2+) are pivotal in muscle contraction. When a muscle cell is stimulated, calcium is released from the sarcoplasmic reticulum, enabling the interaction between actin and myosin filaments, leading to contraction.
-
pH and Acid-Base Balance: Hydrogen ions (H+) contribute to the acidity or alkalinity of the body, which is vital for various biochemical reactions and metabolic processes. Maintaining pH involves buffers, respiration, and renal function, heavily regulated by ions.
-
Osmoregulation: Ions help regulate osmotic pressure, which is crucial for maintaining cell structure and function. For instance, sodium ions are integral in regulating fluid balance and blood pressure.
In conclusion, ions are indispensable for a myriad of metabolic pathways, showcasing their significance in the biological functions that sustain life.