Edexcel Biology paper 1 notes


Plant cell

  • Cell membrane - what enters/leaves cell
  • vacuole - keeps plant cell upright
  • cell wall - strengthens cell
  • mitochondria - energy
  • ribosomes  protein synthesis 
  • Cytoplasm - jelly like substance where reactions take place
  • nucleus - dna

Animal cell

  • Cell membrane - what enters/leaves cell
  • mitochodondiria - energy
  • ribosomes - protein synthesis
  • cytoplasm - reactions
  • Nucleus - dna 

Bacterial cell

  • Cell membrane - what enters/leaves cell
  • cytoplasm - reactions
  • chromosome/dna - not in nucleus
  • flagella - movement
  • ribosomes - protein synthesis
  • cell wall


Stem cells = unspecialised cells

uses of stem cells

  • treating parkinsons - growing new brain cells
  • bone and spinal injury - growing new bone cells
  • organ failure - growing new organs/parts of organs

Method for making stem cells

  • nuclei removed from egg cell
  • nuclei from patient cell removed and inserted into empty egg
  • egg starts to develop embryo
  • stem cells turns into new cells

- CONTREVERSY - Human embryos will be created and destroyed

Nervous system

  • Brain, spinal chord (CNS)
  • neurones and nerves

REFLEX goes to the spinal chord, not brain, needs to be a quick reaction

Synapse - slow chemical signal. Neurotransmitter has to diffuse between the neurones


Magnification = image hieght / object hieght

  • Meter (m) = 100cm
  • centimetre (cm) = 1 x 10^-2 metres
  • Millimetre (mm) = 1 x 10^-3 metres
  • Micrometer (mu m ) = 1 x 10^-6 metres
  • Nanometer (nm) = 1 x 10^-9 metres
  • Picometer (pm) = 1 x 10^-12 metres


Enzymes are biological catalysts

Lock and key method - Substratre fits into active site of the enzyme. When the substrate is in the active site this is called the enzyme-substrate complex. The substrate is then split into it's products

  • Temperature affects enzyme activity: optimum temperature = highest rate of reaction. Not a high enough temp = not enough energy. Temp too high = denatured (active site destroyed)
  • pH affects enzyme activity: optimum temp depends on the enzyme, same as temp

Types of enzymes


  • Breaks down fats into fatty acids and glycerol
  • made in pancreas and small intestine
  • works in small intestine


  • Breaks down proteins into amino acids
  • made in stomach, pancreas and small intestine
  • works in stomach and small intestine


  • breaks down starch into sugars
  • made in the salivary gland, pancreas and small intestine
  • works in mouth and small intestine


net movement from high to low concentration (gases or liquid)

eg in lungs (alveoli) co2 diffuses from blood into lungs to be breathed out and oxygen diffuses into blood to be obsorbed


specifically water molecules moving from high to low concentration through semi-permeable membrane

Eg root hair cells absorbing water

Active transport

low to high concentration through a membrane using transport proteins, requires energy


cells divide uncontrollably, leads to tumours.

  • Benign tumours - slow growing and generally harmless
  • Malignant tumours - fast growing, agressive and mobile. can spread to other parts of the body

Risk factors

  • Smoking - can cause lung cancer
  • sun - skin cancer
  • sex - cervical cancer



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