Biology 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.
• Types of 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. They 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.
• Cell


  The basic building block of all living organisms
• Chloroplast


  An organelle which is the site of photosynthesis
• DNA


  A double-stranded polymer wound to form a double helix. It carries the genetic code
• Eukaryotic cell


  A type of cell found in plants and animals that contains a nucleus
• HIV

  An infectious virus that weakens the immune system and can lead to AIDS (acquired immunodeficiency syndrome)
• Hyphae


  Long filaments of a fungus that contain many nuclei
• Influenza virus


  An infection virus that causes influenza (the flu)
• Lactobacillus bulgaricus


  A rod-shaped species of bacterium used to produce yoghurt from milk
• Mucor


  A multicellular fungus that has a hyphal structure
• Mycelium


  A collection of thread-like hyphae in a fungus
• Pathogens


  Microorganisms that cause infectious disease
• Photosynthesis


  An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• Plasmids


  Loops of DNA found in the cytoplasm of prokaryotic cells
• Plasmodium


  Pathogenic protoctists that cause malaria
• Pneumococcus


  A spherical, pathogenic bacterium that causes pneumonia
• Prokaryotic cell


  A type of cell found in bacteria that does not contain a nucleus
• Protoctists


  Microscopic single-celled organisms
• Saprotrophic nutrition


  The mode of extracellular nutrition in which digestive enzymes are secreted onto the food outside the cell and the products of digestion are absorbed
• Tobacco Mosaic Virus (TMV)


  A widespread plant pathogen affecting many species of plants which produces a mosaic pattern on the leaves. It infects chloroplasts and limits plant growth
• Virus


  A non-living organism that can only reproduce inside host cells. Viruses have no cells, but possess a protein coat containing nucleic acids (DNA or RNA)