Biology: Body & Cells
What is the function of the nucleus in a cell?
It controls the cell's activities and contains DNA.
Name the vessels that carry blood away from the heart.
Arteries
What state of matter has a fixed shape and volume?
Solid.
What is the name of the group of unreactive elements found in Group VIII of the Periodic Table?
Noble gases.
What is the equation for speed?
Speed = Distance ÷ Time.
What is conduction?
Transfer of heat through direct contact in solids.
Name two features found only in plant cells.
Cell wall, chloroplast, vacuole.
What molecule in red blood cells transports O2?
Haemoglobin
What is the difference between a molecule and a compound?
A molecule is two or more atoms bonded; a compound is a molecule with different elements.
Calculate the relative formula mass (Mr) of calcium nitrate, Ca(NO₃)₂.
Mr = 40 + 2×(14 + 3×16)
= 40 + 2×62
= 164.
Define acceleration.
Change in velocity (speed or direction) per unit time.
Which surface is best at absorbing infrared radiation?
Dull / matte, black surfaces.
Give three examples of specialised cells.
RBC, WBC, root hair cell, ciliated cell, goblet cell, sperm cell, egg cell, neurone.
What is the role of phagocytes in the immune system?
They engulf and digest pathogens.
Describe metallic bonding.
A lattice of positive metal cations surrounded by a sea of delocalised electrons.
Describe diatomic molecules and give two examples of these molecules.
Molecules that consist of two atoms that share covalent bonds.
F2, Cl2, N2, H2
What happens to an object when the resultant force is zero?
It stays at rest or moves at constant speed.
Define specific heat capacity.
Amount of energy needed to raise the temperature of 1 kg of a substance by 1°C.
Define diffusion and explain one factor that increases its rate.
Net movement of particles from high concentration to low concentration, down the concentration gradient.
Higher temperature increases the rate.
Describe how xylem and phloem differ in function.
Xylem transports water (& dissolved minerals); phloem transports sugars & amino acids.
What is meant by the term “giant ionic lattice”?
A regular 3D arrangement of oppositely charged ions held together by strong electrostatic forces in all directions.
Why do Group I metals become more reactive as you go down the group?
Because the outer electron is further from the nucleus and more easily lost. (there is less attraction between the negative electrons & the positive protons in the nucleus).
A 2.5 kg object is moving in a circle of radius 0.75 m at a constant speed of 4 m/s. Calculate the centripetal force acting on the object.
(Use F = mv² / r)
F = (2.5 × 4²) / 0.75 = (2.5 × 16) / 0.75
= 40 / 0.75
= 53.3 N.
A metal block of mass 2 kg is heated from 20 °C to 60 °C. The specific heat capacity of the metal is 450 J/kg·°C.
Calculate the amount of thermal energy gained by the block.
(Use: Q = mcΔT)
Q = mcΔT
= 2 × 450 × (60−20)
= 2 × 450 × 40
=36,000 J
Explain how temperature affects enzyme activity, and describe what happens when an enzyme is denatured.
As temperature increases, enzyme activity rises until an optimum is reached. Beyond this, the enzyme's shape changes (denatures), so the active site no longer fits the substrate, and the reaction stops.
Explain why someone does not get sick the second time they are infected by the same pathogen.
After the first infection, some lymphocytes become memory cells. Memory cells 'remember' the antigen of the pathogen, and produce more antibodies faster than during a primary infection.
According to collision theory, explain two factors that affect the rate of a chemical reaction, and describe how each one changes the frequency or energy of collisions between particles.
Temperature increases the rate by giving particles more kinetic energy, leading to more frequent and more energetic collisions — increasing the number of successful collisions.
Concentration (or pressure in gases) increases the rate by raising the number of particles in a given volume, which increases the frequency of collisions.
Why are some metals stored under oil, such as lithium and sodium?
Because they react quickly with air or water, and oil prevents contact with moisture and oxygen.
A car of mass 1000 kg is decelerating uniformly from 25 m/s to 5 m/s over a distance of 60 meters. Calculate the magnitude of the decelerating force.
(Use: v2 = u2+2as, then F = ma)
Step 1: Find acceleration
52 = 252 + 2a x 60
25 = 625 + 120a
−600=120a
a=−5 m/s2
Step 2: Use F = ma
F=1000 × (−5) = −5000 N
Explain how conduction and convection work together to heat a pot of water on a metal stove, and describe the role of particle movement in each process.
Conduction first: metal particles in pot gain energy and vibrate more, passing kinetic energy to neighboring particles through direct contact.
Then convection takes over in the water: water at the bottom heats up, expands, becomes less dense, and rises. Cooler, denser water sinks to replace it, forming a convection current.
In both processes, particles gain energy and move more, but only in convection do particles themselves move to transfer heat.