1-Cell biology

• eukaryotic organisms always have a nucleus and are multicellular
• prokaryotic organisms don't have a nucleus and are unicellular
• mitochondria supply the cell with energy through aerobic respiration
• in a plant cell there is:

  • permanent vacuole
  • chloroplasts
  • cell wall
  • ribosomes
  • mitochondria
  • cell membrane
  • cytoplasm
  • nucleus
• in a bacteria cell there is:

  • circular strand of DNA
  • plasmids
  • ribosomes
  • flagella
  • cytoplasm
  • cell membrane
  • cell wall
• ribosomes are where protein synthesises/ is made
• diffusion is affected by temperature, concentration gradient, surface area
• how these factors affect diffusion:

  • temperature- more energy to the particles so they move faster and diffuse more quickly
  • concentration gradient- the larger the concentration gradient(difference in concentration), the higher the rate of diffusion
  • surface area- the larger the surface area, the higher the rate of diffusion
• • osmosis and diffusion happen down a concentration gradient
  • active transport happens against a concentration gradient
• • concentration gradient is the difference in concentration
  • surface area to volume ratio decreases as organisms get larger which means a larger distance for molecules to diffuse across
• pros of light and electron microscopes:

  • light- easy to use, cheaper
  • electron- higher resolution, able to see subcellular structures
• cons of light and electron microscopes:

  • light- lower resolution, not able to see subcellular structures
  • electron- expensive, hard to use
• magnification is how many times larger the image is than the object
• resolution is the shortest distance between two points on an object that can still be distinguished as two separate entities
• the pathway of light is:

  1. light source
  2. stage
  3. microscope slide
  4. object
  5. objective lens
  6. body tube
  7. eyepiece lens
  8. eye
• units for magnification

  • magnification- no units
  • image- centimetres
  • object- micrometres
• human cells have 23 chromosome pairs so 46 chromosomes
• stem cells can:

  • divide by mitosis
  • can differentiate into specialised cells
• examples of animal stem cells:

  • embryonic stem cells- found in embryos
  • adult stem cells- found in bone marrow
• plant stem cells are found in the meristems in:

  • roots
  • shoots
• differentiation in plant and animal stem cells:

  • plant- can differentiate into any specialised cell for their entire life
  • embryonic- can differentiate into any specialised cell
  • adult- can differentiate only into blood cells: red, white or platelets
• • differentiation is the process by which cells become specialised
  • specialised cells are cells adapted to perform a particular function
• pros of using stem cells in medicine:

  • embryonic- can differentiate into any specialised cell
  • adult- won't cause rejection if taken from patient, not in limited supply
• cons of using stem cells in medicine:

  • embryonic- limited supply, can cause rejection, ethical issues(potential for human life)
  • adult- can only differentiate into different blood cells, can transmit viruses, can cause tumour
• surface area to volume ratio, larger organisms need:

  • exchange systems- for substances to go in and out of the body
  • transport systems- to transport substances to the parts of the body that need them
• examples of exchange surfaces in humans:

  • alveoli- oxygen and carbon dioxide to diffuse in and out of body/ blood stream
  • villi- nutrients absorbed from small intestine to blood stream
• Specialised exchange surfaces are a part of an organism over which substances are exchanged with the environment
• purpose of general features of exchange surfaces:

  • large surface area- lots of molecules can diffuse at the same time
  • thin membrane- shorter distance for diffusion
  • permeable membrane- to pass through surface
  • diffusion gradient- strong concentration gradient means substance(air or food) is constantly replaced
• 1000 μm=1 mm, 10 mm=1 cm, 100 cm=1 m
• general features of exchange surfaces:

  • large surface area
  • thin membrane
  • permeable membrane
  • concentration gradient
• cell cycle/ mitosis

  1. cell grows and increases its subcellular structures such as mitochondria and ribosomes
  2. cell duplicates it's DNA, forming x shaped chromosomes
  3. chromosomes line up at the centre of the cell
  4. chromosomes are pulled to each side of the cell
  5. the cell divides into two, creating two identical daughter cells
• osmosis in plant cells

  • in pure water the cell becomes turgid (enlarged with water) but does not burst due to the strong cell wall
  • in a more concentrated solution it becomes flaccid
  • in a very concentrated solution it undergoes full plasmolysis
• osmosis in animal cells

  • in a concentrated solution it becomes flaccid
  • in a normal concentration it will keep it's normal shape
  • in a dilute solution it will become turgid until bursting