Edexcel IGCSE Biology

• Characteristics of living organisms

  • They respire
  • They move
  • They reproduce
  • They grow and develop
  • They excrete their waste
  • They require nutrition
  • They control their internal conditions (e.g. body temperature, blood pressure, osmoregulation)
  • They respond to their surroundings
• Five kingdoms of living organisms

  • Plants
  • Animals
  • Fungi
  • Protoctists
  • Prokaryotes

  
• Plants


  • Multicellular organisms
  • Cells contain chloroplasts, allowing photosynthesis
  • Cell walls made of cellulose
  • Store carbohydrates as starch or sucrose
• Animals


  • Multicellular organisms
  • Cells do not contain chloroplasts, cannot perform photosynthesis
  • Acquire nutrition by feeding on other plants and animals
  • Cells do not have cell walls
  • Movement involves nervous coordination
  • Store carbohydrates as glycogen
• Fungi


  • Can be multicellular or unicellular
  • Cannot carry out photosynthesis due to lack of chloroplasts
  • Body organised into mycelium of fungal hyphae
  • Hyphae not divided into individual cells
  • Cell walls made of chitin
  • Feed by extracellular secretion of digestive enzymes and absorption
  • May store carbohydrates as glycogen
• Protoctists


  • Mostly microscopic single-celled organisms
  • Some have animal-like features (protozoa), others have plant-like features (algae)
  • Some are pathogenic, like Plasmodium causing malaria
• Prokaryotes


  • Primary form is bacteria
  • Single-celled, no nucleus
  • Smaller than eukaryotic cells
  • Nuclear material in cytoplasm, DNA in single circular chromosome
  • Cell wall made of peptidoglycan
  • Some have slime layer or capsule
  • Some have flagella for swimming
  • Many have plasmids
• Pathogens


  Microorganisms that cause diseases in other organisms
• Viruses


  • Parasites that can only reproduce in a host
  • Smaller than bacteria
  • No cellular structure, only genetic material (DNA or RNA) surrounded by protein coat
  • Not living organisms as they don't carry out all life processes
  • Can infect every type of living organism
  • Wide variety of shapes
• Examples of viruses


  • Tobacco mosaic virus
  • Influenza virus
  • HIV
• Organelle


  Part of a cell with a specific function
• Cell


  The basic structural unit of all living organisms
• Tissue


  A group of cells that work together to perform a specific function
• Organ


  A group of tissues that work together to perform a specific function
• Organ System


  A group of organs that work together to perform a specific function
• Structures present in both plant and animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Structures present only in plant cells, not animal cells


  • Cell wall
  • Permanent cell vacuole
  • Chloroplasts
• Cell Differentiation


  The process by which a cell specializes under the control of genes
• Stem cells


  Cells that can divide many times by mitosis while remaining undifferentiated
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
• Embryonic stem cells


  Found in early development of embryo, can differentiate into any cell type
• Adult stem cells


  Found in specific adult tissues, can specialize into certain cell types but not any type
• Adult stem cell specialization

  • Bone marrow can specialize into different blood cells
• Stem cell therapy


  Using stem cells to treat or repair damaged tissues
• Macromolecules in the body

  • Carbohydrates
  • Proteins
  • Lipids
• Carbohydrates


  Main source for supplying body cells with energy, made up of carbon, hydrogen and oxygen
• Types of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  • Glucose
  • Fructose
• Disaccharides


  • Sucrose
  • Lactose
  • Maltose
• Polysaccharides


  • Starch
  • Glycogen
  • Cellulose
• Test for starch


  Add yellow-brown iodine solution, turns blue-black
• Test for glucose

  Heat Benedict's solution, turns from blue to brick-red
• Proteins


  Made up of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur, needed for growth and repair of tissues
• Amino acids

  Building blocks for proteins, about 20 different ones in living organisms
• Test for proteins


  Add Biuret's solution, turns from blue to purple
• Enzymes


  Biological catalysts that speed up reaction rates without being used up
• Lock and Key Theory

  Substrates collide with and bind to the active site of enzymes if it is complementary
• Factors affecting enzyme activity

  • Enzyme concentration
  • Substrate concentration
  • Temperature
  • pH
• Lipids

  Consist of carbon, hydrogen and oxygen, building blocks are glycerol and fatty acids
• Test for lipids


  Add ethanol, then cold water, a white cloudy layer forms