Biology MCQs
Topic Notes: Biology
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
41
What does the chemical formula O2 represent?
Answer:
free oxygen
The chemical formula O2 represents a diatomic molecule of oxygen, which is the form in which oxygen gas exists in the Earth's atmosphere. It consists of two oxygen atoms bonded together, commonly referred to as molecular or free oxygen, which is essential for aerobic respiration in most living organisms.
42
Which scientific principle states that energy cannot be created or destroyed, but only converted from one form to another?
Answer:
law of thermodynamics
The first law of thermodynamics, also known as the law of conservation of energy, dictates that the total energy of an isolated system remains constant. It asserts that energy is a conserved quantity that can change its form—such as from chemical energy to heat or kinetic energy—but cannot be generated from nothing or permanently eliminated.
43
Which molecule is recognized as the primary energy currency of the cell?
Answer:
ATP
Adenosine Triphosphate (ATP) is the primary energy currency of the cell. It stores and transfers energy through its high-energy phosphate bonds, which are hydrolyzed to fuel various cellular activities. While ADP is a precursor, DNA and RNA serve as genetic information storage and transmission molecules rather than direct energy carriers.
44
What fundamental components combine to form an atom?
Answer:
atoms
The question phrasing is slightly circular, but in the context of basic biological chemistry, subatomic particles such as protons, neutrons, and electrons are the building blocks that constitute an atom. These particles define the identity and chemical properties of the element.
45
Which subatomic particle primarily determines the chemical reactivity and bonding behavior of an atom?
Answer:
electrons
The chemical properties and reactivity of an atom are dictated by its valence electrons. These electrons occupy the outermost shell and are responsible for forming chemical bonds with other atoms through sharing or transfer, thereby determining how elements interact to form compounds.
46
Which biochemical process is defined by the loss of electrons from an atom or molecule?
Answer:
oxidation
Oxidation is defined as the loss of electrons during a chemical reaction. In biological systems, this process is often coupled with reduction, where another molecule gains the electrons, forming a redox reaction essential for energy transfer in cellular respiration and photosynthesis.
47
Which aspect of ATP is primarily responsible for its ability to store and release chemical energy?
Answer:
molecular structure
The ability of ATP to store and release energy is fundamentally determined by its molecular structure, specifically the high-energy phosphoanhydride bonds linking the three phosphate groups. When the terminal phosphate bond is hydrolyzed, a significant amount of free energy is released, which the cell utilizes to perform mechanical, transport, or chemical work.
48
Which chemical process is defined by the gain of electrons?
Answer:
reduction
In chemical reactions, reduction is defined as the gain of one or more electrons by an atom, molecule, or ion. This process is the counterpart to oxidation, which involves the loss of electrons. Together, these processes form redox reactions, which are fundamental to biological energy transfer and metabolic pathways.
49
What fundamental particles are exchanged during oxidation-reduction (redox) reactions?
Answer:
electrons between atoms
Redox reactions are chemical processes characterized by the transfer of electrons between two chemical species. The species that loses electrons is oxidized, while the species that gains electrons is reduced, facilitating energy transfer in biological systems.
50
Which factors influence the potential of electrons to serve as an effective energy source within a biological system?
Answer:
arrangement of atoms and location
The energy potential of electrons in biological molecules is determined by both the specific arrangement of atoms within the molecule, which dictates the electron's orbital energy, and the electron's location relative to other electronegative atoms, which influences its ability to participate in redox reactions.