GCSE GCSE Combined Science 2 — Questions and Answers
Question 1: What is the role of the ribosome in a cell?
- To produce energy
- To synthesise proteins from amino acids following mRNA instructions (Correct answer)
- To replicate DNA
- To control what enters and leaves the cell
Correct answer: To synthesise proteins from amino acids following mRNA instructions
Ribosomes are the sites of protein synthesis in cells. They read the mRNA (messenger RNA) sequence, which carries instructions from DNA, and assemble amino acids in the correct order to build proteins.
Question 2: What is the difference between speed and velocity?
- They are the same
- Speed is a scalar (magnitude only); velocity is a vector (magnitude and direction) (Correct answer)
- Velocity has no direction
- Speed always has direction
Correct answer: Speed is a scalar (magnitude only); velocity is a vector (magnitude and direction)
Speed is a scalar quantity — it only has magnitude (e.g., 50 km/h). Velocity is a vector — it has both magnitude and direction (e.g., 50 km/h north). This distinction is crucial in physics calculations.
Question 3: What is the formula for calculating density?
- Density = volume ÷ mass
- Density = mass × volume
- Density = mass ÷ volume (Correct answer)
- Density = force ÷ area
Correct answer: Density = mass ÷ volume
Density = mass ÷ volume (ρ = m/V). It is measured in kg/m³ or g/cm³. A denser material has more mass packed into the same volume. A substance floats if its density is less than the liquid it is placed in.
Question 4: What happens to the rate of an enzyme-catalysed reaction above the optimum temperature?
- It stays the same
- It increases further
- It decreases rapidly as the enzyme denatures (Correct answer)
- It becomes reversible
Correct answer: It decreases rapidly as the enzyme denatures
Above the optimum temperature, the enzyme's active site changes shape (denatures) and the substrate can no longer fit. The reaction rate falls sharply. Enzymes do not recover from denaturation.
Question 5: What is the atomic number of an element?
- The total number of protons and neutrons
- The number of electrons in the outer shell
- The number of protons in the nucleus (Correct answer)
- The relative atomic mass
Correct answer: The number of protons in the nucleus
The atomic number (proton number) is the number of protons in the nucleus of an atom. It uniquely identifies an element and determines its position in the periodic table. In a neutral atom, it also equals the number of electrons.
Question 6: What is the greenhouse effect?
- The cooling of the Earth by the atmosphere
- The trapping of heat by greenhouse gases in the atmosphere, warming the Earth's surface (Correct answer)
- Plants growing in greenhouses
- The reflection of sunlight off ice caps
Correct answer: The trapping of heat by greenhouse gases in the atmosphere, warming the Earth's surface
The greenhouse effect occurs when greenhouse gases (CO₂, methane, water vapour) absorb outgoing infrared radiation from the Earth's surface and re-emit it back, warming the planet. Enhanced greenhouse effect from human activity causes climate change.
GCSE GCSE Combined Science 2
What is the role of the ribosome in a cell?