Key concepts in biology

• What are the two main types of cells in living organisms?

  Prokaryotic and eukaryotic
• What type of cells are animal and plant cells?

  Eukaryotic
• What are the main organelles found in eukaryotic cells?

  • Cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• What type of cells are bacterial cells?

  Prokaryotic
• What are the main organelles found in prokaryotic cells?

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• What are organelles?


  Structures in a cell that have different functions
• What is the function of the nucleus in eukaryotic cells?

  • Contains DNA coding for proteins needed to build new cells
  • Enclosed in a nuclear membrane
• What is the function of the cytoplasm in eukaryotic cells?

  • Liquid substance where chemical reactions occur
  • Contains enzymes that speed up reactions
  • Organelles are found within it
• What is the function of the cell membrane in eukaryotic cells?


  Controls what enters and leaves the cell
• What is the function of mitochondria in eukaryotic cells?

  Where aerobic respiration reactions occur, providing energy for the cell
• What is the function of ribosomes in eukaryotic cells?

  • Where protein synthesis occurs
  • Found on the rough endoplasmic reticulum
• Why do bacterial cells not share as many similarities in organelles with animal and plant cells?

  Because they are prokaryotic
• What is the function of chloroplasts in plant cells?

  • Where photosynthesis takes place
  • Contains chlorophyll pigment for light absorption
• What is the function of the permanent vacuole in plant cells?

  • Contains cell sap
  • Improves cell's rigidity
• What is the function of the cell wall in plant cells?

  Provides strength to the cell, made from cellulose
• What is the function of the cell wall in bacterial cells?

  Made of peptidoglycan, provides strength to the cell
• What is the function of chromosomal DNA in bacterial cells?

  Floats in the cytoplasm as bacterial cells have no nucleus
• What are plasmids in bacterial cells?

  Small rings of DNA that code for extra genes
• What is the function of flagella in bacterial cells?

  Long, thin tails that allow bacteria to move
• What is differentiation in cells?

  • Process where cells gain new sub-cellular structures
  • Suits them to their specific role
• How do animal and plant cells differ in terms of differentiation?

  • Most animal cells differentiate once
  • Many plant cells retain the ability to differentiate throughout their life
• What is the function of sperm cells?

  • Specialised to carry male DNA to the egg cell
  • Streamlined head and long tail for swimming
  • Many mitochondria for energy
  • Acrosome contains digestive enzymes
  • Haploid nucleus with 23 chromosomes
• What is the function of egg cells?

  • Specialised to accept a single sperm cell
  • Surrounded by a special membrane that becomes impermeable after fertilisation
  • Lots of mitochondria for energy
  • Large size and cytoplasm for division
• What is the function of ciliated epithelial cells?


  • Waft bacteria trapped by mucus to the stomach
  • Long cilia processes aid in this function
• What is the function of root hair cells?

  • Specialised to take up water and minerals
  • Large surface area due to root hairs
  • Large vacuole affects water movement speed
  • Mitochondria provide energy for active transport
• What is the function of xylem cells?

  • Specialised to transport water and minerals
  • Hollow structure formed by dead cells
  • Lignin deposited for strength and pressure resistance
• What is the function of phloem cells?

  • Specialised to carry products of photosynthesis
  • Sieve plates allow movement of substances
  • Energy supplied by mitochondria of companion cells
• Who first observed cells in cork and in what year?

  Robert Hooke in 1665
• What are the characteristics of a light microscope?

  • Two lenses
  • Illuminated from underneath
  • Maximum magnification of approximately 2000x
  • Resolving power of 200nm
• What is the purpose of an electron microscope?

  To view deep inside sub-cellular structures
• What are the two types of electron microscopes?

  • Scanning electron microscope (SEM) for 3D images
  • Transmission electron microscope (TEM) for 2D images
• What is the maximum magnification of a transmission electron microscope?

  Up to 2,000,000x
• What is the resolving power of a scanning electron microscope?

  10nm
• What is the resolving power of a transmission electron microscope?

  0.2nm
• Why are electron microscopes useful for studying viruses?

  • They can view very small structures
  • Useful for identifying viruses that are smaller than bacteria
• What is the formula for magnification of a light microscope?

  Magnification = eyepiece lens magnification x objective lens magnification
• What is the formula for the size of an object?

  Size of object = size of image / magnification
• What is standard form used for?

  To express very large or small numbers conveniently
• What is an example of a number in standard form?


  • \(1.5 \times 10^{-5} = 0.000015\)
  • \(3.4 \times 10^{3} = 3400\)
• What are orders of magnitude?

  • Describes how much bigger or smaller one object is compared to another
  • E.g., 10 times bigger is \(10^{1}\) times bigger