AQA GCSE Combined Science: every topic, by paper

Name the parts found in both animal and plant cells.

Nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.

Name three parts found only in plant cells.

Cellulose cell wall, chloroplasts and a permanent vacuole.

What does the nucleus do?

It holds the genetic material that controls the cell.

What is an enzyme?

A protein that acts as a biological catalyst.

Why does each enzyme only work on one substrate?

Its active site has a shape that fits only that substrate.

What happens to an enzyme at high temperature?

It denatures: the active site changes shape so the substrate no longer fits.

Name the four chambers of the heart.

Left and right atria, left and right ventricles.

Why is the left ventricle wall thicker than the right?

It pumps blood around the whole body at high pressure.

What is the job of heart valves?

To stop blood flowing backwards.

What makes up the central nervous system?

The brain and spinal cord.

Describe the path of a reflex arc.

Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.

Why are reflexes important?

They are fast and automatic, protecting the body from harm.

What makes up the central nervous system?

The brain and spinal cord.

Describe the path of a reflex arc.

Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.

Why are reflexes important?

They are fast and automatic, protecting the body from harm.

What is DNA?

The chemical that carries genetic information, in a double helix.

What is a gene?

A section of DNA that codes for a protein.

What is an allele?

A different version of a gene.

What are the charges of protons, neutrons and electrons?

Proton +1, neutron 0, electron −1.

What do atomic number and mass number mean?

Atomic number: number of protons. Mass number: protons + neutrons.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

What is conservation of mass?

Mass is not lost or gained in a reaction; atoms are just rearranged.

Balance: Na + Cl₂ → NaCl.

2Na + Cl₂ → 2NaCl.

Calculate the Mr of H₂SO₄ (H = 1, S = 32, O = 16).

2 + 32 + 64 = 98.

What pH values are acidic, neutral and alkaline?

Below 7 acidic, 7 neutral, above 7 alkaline.

What ion makes solutions acidic?

H⁺ ions.

What is neutralisation?

Acid + base → salt + water (H⁺ + OH⁻ → H₂O).

Name four things that increase the rate of a reaction.

Higher temperature, higher concentration or pressure, larger surface area, and a catalyst.

Explain using collision theory why heating speeds up a reaction.

Particles move faster, so they collide more often and with more energy.

What is a catalyst?

A substance that speeds up a reaction without being used up, by lowering the activation energy.

Give the equation for speed.

Speed = distance ÷ time.

Give the equation for acceleration.

Acceleration = change in velocity ÷ time.

What does the gradient of a distance–time graph show?

Speed.

Give the wave speed equation.

Wave speed = frequency × wavelength.

Compare transverse and longitudinal waves.

Transverse: vibrations at right angles to energy transfer (light). Longitudinal: vibrations parallel (sound).

List the electromagnetic spectrum in order of increasing frequency.

Radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma.

Give the equation for density.

Density = mass ÷ volume.

Why are gases less dense than solids?

Their particles are much further apart.

What is specific heat capacity?

The energy needed to raise 1 kg of a substance by 1 °C.

Give the equation for speed.

Speed = distance ÷ time.

Give the equation for acceleration.

Acceleration = change in velocity ÷ time.

What does the gradient of a distance–time graph show?

Speed.

Give the wave speed equation.

Wave speed = frequency × wavelength.

Compare transverse and longitudinal waves.

Transverse: vibrations at right angles to energy transfer (light). Longitudinal: vibrations parallel (sound).

List the electromagnetic spectrum in order of increasing frequency.

Radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma.