Cell biology

• Cells


  The basic building blocks of life that can replicate independently
• Multicellular organisms like animals and plants contain many cells that divide to grow or replace dead cells, not to create new organisms</b>
• Bacteria are single-celled prokaryotic organisms
• Subcellular structures common to animal and plant cells

  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosomes
• Plant cells


  • Have a rigid cell wall made of cellulose
  • Contain a permanent vacuole with cell sap
  • Contain chloroplasts for photosynthesis
• Bacterial cells


  • Lack mitochondria and chloroplasts
  • Have a single circular strand of DNA (nucleoid) instead of a nucleus
  • May have flagella for movement
  • May have plasmids with extra genes
• Photosynthesis occurs in the chloroplasts of plant cells, using chlorophyll to absorb light energy
• Aerobic respiration in mitochondria releases energy for cells
• Ribosomes are the site of protein synthesis in cells
• Animals, Plants, Fungi, Protists, Bacteria, Viruses

  • Animals are multicellular, heterotrophic, and mostly reproduce sexually
  • Plants are multicellular, autotrophic, and get energy from the sun using photosynthesis
  • Fungi can be multicellular or unicellular, are heterotrophic, and use saprotrophic nutrition
  • Protists are mostly unicellular, some are autotrophic, some are heterotrophic
  • Bacteria are single-celled, prokaryotic, and found everywhere
  • Viruses are not living organisms, they are tiny particles that can only reproduce inside living cells
• Groups of living organisms

  • Animals
  • Plants
  • Fungi
  • Protists
  • Bacteria
• Viruses are not considered living organisms and are not part of the five kingdoms of life
• Eukaryotes


  • Animals, Plants, Fungi, Protists are all eukaryotic organisms with DNA in chromosomes and a nucleus
  • Bacteria are prokaryotic organisms without a nucleus
• Eukaryotic cells are 10-100 times larger than prokaryotic bacterial cells
• Viruses are 10-100 times smaller than prokaryotic bacterial cells
• There are an estimated 5-10 million different species of animals on Earth
• There are around 300,000 species of plants
• Fungi


  • Some are multicellular with a mycelium body, others are unicellular
  • They are heterotrophic and use saprotrophic nutrition to digest food outside their body
• Some fungi can be pathogens that cause disease, like athlete's foot
• Protists


  • Mostly unicellular, some are autotrophic, some are heterotrophic
  • A few protist species can cause disease like malaria
• There are likely more species of bacteria than all other kingdoms combined
• Most bacteria are not harmful to humans, many are helpful like those in our gut
• Viruses


  • Tiny particles with a protein coat and genetic material inside
  • They can only reproduce by infecting and using living cells
  • All viruses are considered pathogens that cause harm to their host organisms
• Microscopy


  The use of microscopes
• How light microscopes work

  1. Light from the room hits the mirror

  2. Reflected upwards through the object

  3. Passes through the objective lens

  4. Passes through the eyepiece lens

  5. Into the eye
• Object


  The real object or sample that you're looking at
• Image


  The image that we see when we look down the microscope
• Magnification


  How many times larger the image is than the object
• Magnification = image size / object size
• Resolution


  The shortest distance between two points on an object that can still be distinguished as two separate entities
• Higher resolution


  More details can be seen, less blurry the image
• The images have the same magnification (100x) but different resolutions
• Cell division


  The process through which new cells are generated for growth, development, and repair
• Cell cycle


  • The life cycle of a cell from the time it was made to the time it divides into two new cells
• Cell cycle stages


  1. Growth

  2. DNA replication

  3. Mitosis and division (cytokinesis)
• DNA


  The genetic material that contains the instructions for the development and functioning of living organisms
• DNA in a dividing cell


  • Normally spread out in long strings
  • Condenses into chromosomes during cell division
• Chromosome


  A condensed packet of DNA that contains a large number of genes
• Eukaryotic cells


  • Have two copies of each chromosome, one from each parent
• Humans have 23 pairs of chromosomes, 46 in total