Topic 1

• Characteristics of living organisms


  • Movement
  • Reproduction
  • Sensitivity
  • Control
  • Growth
  • Respiration
  • Excretion
  • Nutrition
• MRS C GREN


  Acronym to remember the characteristics of living organisms
• Eukaryotes


  • Organisms that have a nucleus and organelles that are found within a plasma membrane
• Subcellular structures found in plant and animal cells


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Nucleus


  Contains the genetic material, which codes for a particular protein. Enclosed in a nuclear membrane.
• Cytoplasm


  Liquid substance in which chemical reactions occur. Contains enzymes (biological catalysts, i.e. proteins that speed up the rate of reaction). Organelles are found in it.
• Cell membrane


  Contains receptor molecules to identify and selectively control what enters and leaves the cell
• Mitochondria


  Where aerobic respiration reactions occur, providing energy for the cell
• Ribosomes


  Where protein synthesis occurs. Found on a structure called the rough endoplasmic reticulum.
• Plants


  • Multicellular organisms
  • Cells contain chloroplasts which is the site of photosynthesis: chlorophyll pigments within the chloroplast structure absorb light from the Sun
  • Cellulose cell walls which provide strength to the cell
  • Contain a permanent vacuole, which stores cell sap and improves the cell's rigidity
  • Store carbohydrates as starch or sucrose
• Animals


  • Multicellular
  • Cannot photosynthesise
  • Do not have cell walls
  • Have nervous systems in order to coordinate movement
  • Store carbohydrates as glycogen
• Fungi


  • Body is usually organised into a mycelium of thread-like structures called hyphae which have many nuclei but some are single-celled
  • Cell walls are made of chitin
  • Feed by extracellular secretion of digestive enzymes which break it down into smaller pieces, which can then be absorbed (saprotrophic nutrition)
  • May store carbohydrates as glycogen
• Protoctists


  • Single-celled organisms
  • Some have features like animals cells, such as Amoeba, that live in pond water
  • Others are more like plants and have chloroplasts, such as Chlorella
• Prokaryotes


  • Do not have a nucleus or membrane-bound organelles
• Bacteria


  • Single-celled and very small
  • Have a cell wall, cell membrane, cytoplasm and plasmids
  • Lack a nucleus but have circular chromosomes of DNA
  • Some can carry out photosynthesis but they mainly eat off of other organisms, either dead or alive
• Pathogens


  • Fungi
  • Bacteria
  • Protoctists
  • Viruses
• Viruses


  • Small particles (much smaller than bacteria) - not living organisms
  • Parasitic: can only reproduce within living cells, can infect every type of living organisms, hijacks the cell mechanisms to create millions of copies of itself and then spreads within the host by cell bursting
  • Come in a wide variety of shapes and sizes
  • Do not have a cellular structure but have one type of nucleic acid (either DNA or RNA) and a protein coat
• Bacteria

  • Can reproduce many times through binary fission
  • Produce toxins that can damage cells
• Protists


  • Parasitic - use animals as their hosts to live in
• Fungi


  • Produce spores that can spread in the wind or between people
  • Can treat with fungicides