Infection and response

• The immune system is made up of cells, tissues, organs, and proteins that work together to defend the body against infection.
• Primary immunodeficiencies result from genetic mutations affecting various aspects of the immune system, while secondary immunodeficiencies can be caused by factors such as HIV/AIDS, chemotherapy, malnutrition, aging, and stress.
• Immunodeficiency disorders occur when there are defects in the components of the immune system, resulting in increased susceptibility to infections.
• Phagocytic cells engulf and destroy foreign particles through endocytosis.
• Phagocytosis is the process whereby macrophages engulf and destroy foreign particles using receptor molecules on their surface.
• Physical barriers include the skin, which acts as a barrier to prevent entry into the body, and mucus secreted by glands in the respiratory tract, digestive tract, and reproductive organs, which traps bacteria and other particles.
• when looking through microscope we use: stain (iodine or methlamene) to add contrast and stain specific cell structures

  coverslip: to protect the microscope and stop specimen from drying out
• MICROSCOPY- mandatory practical, onion and liver observation
• 1. add drop of water to center of slide
  2. cut up onion, use tweezers to peel of epidermal tissue. or... scrape of some liver, use needle to remove any lumps
  3. use tweexers to place sample in center of slide (water)
  4. add iodine- to stain (for liver add and mix in glycerol)
  5. place coverslip on top: wipe of excess die, try not to have any air bubbles, they obscure view
• 1. clip (prepared) slide onto stage
  2. select lowest- powered objective lense (ie: the lowest magnification)
  3. use course adjustment knob to move stage up ---> just bellow objective lense
  4. look down eyepiece, use course adjustment knob ---> move stage downwards until in (rough) focus
  5. adjust the focus with fine adjustment knob ---> clear image
  6. repeat with higher- powered objective lense (higher magnification)
• cells range is sizes:

  animal cells: 0.01mm-0.05mm

  plant cells: 0.01mm-0.1mm

  microscopes magnify image of a biological specimens. compund microscopes have an eyepiece (what you look through) and objective lenses (ones with magnification options)

  magnification of microscope= mag. of eyepiece x mag. of objective

  calculation magnification of an image:

  magnification = size of image/ real size of object
• 1mm = 1000um = 100nm = 1um

  1mm= 1000um

  1mm= 1,000,000nm

  1um= 1000nm
• Cytoplasm


  Jelly-like substance which contains dissolved nutrients and salts where chemical reactions take place
• Nucleus


  Contains genetic material (ie:DNA) that genetic material controls cells activities
• Cell membrane


  Permeable to some and not other substances, controls movement of substances in/out of cell
• Mitochondria


  Contains enzymes needed for respiration, also where most energy is released from respiration
• Ribosomes


  Where protein synthesis occurs
• Chloroplasts


  Contain (green pigment) chlorophyll ---> absorbs light for photosynthesis and contains enzymes for photosynthesis
• Cell wall


  Made from cellulose, strengthens cell and supports cell
• Vacuole


  Filled with cell sap ---> keep cell turgid
• eukaryotic vs prokaryotic: eukaryotic cells have a nucleus and membrane bound organelles
• eukaryotic vs prokaryotic

  size: eukaryotic are 5um-100um. prokaryotic are 0.2um-2um

  outer layer: both have a cell membrane

  eukaryotic have additional call walls in they're plants

  prokaryotic are all surrounded by cell wall
• eukaryotic vs prokaryotic

  genetic material: eukaryotic have DNA stored in nucleus. prokaryotic calls have DNA as a single molecule, found free in the cytoplasm. additional DNA is found in rings called plasmids

  
  

  types of cell division: eukaryotic divide by mitosis and prokaryotic divide by binary fission
• sperm cell adaptations

  • head of sperm contains genetic material
  • the acrosome (outer head layer) contains enzymes to penetrate the egg
  • middle piece is packed with mitochondria which release energy for swimming
  • streamline shape and tail enables fast swimming
• nerve cell - axon - long projection that carries electrical impulses away from the cell body
• nerve cell adaptations

  cell is specialised for rapid signalling ---> electrical signals

  • cell has extensions and branches to communicate with other nerve cells
  • cell is extended (long) so nerves can run to and from body to the central nervous system
  • covered in fatty sheath: insulates nerve, speeds up the nerve impulse
• muscle cell adaptations

  function is to contract rapidly ---> movement

  • contains filaments of protien so the cells can slide over each other which causes muscle contraction
  • contain many (well developed) mitochondrai to provide energy for contraction
  • in skeletal muscles the cells merge so the muscle fibers contract in unison
  • cells are long which means more space to contract
• red blood cell adaptions

  job is to transport oxygen around the body

  • contain the red pigment haemoglobin which carried oxygen
  • they have a biconcave shape which gives a large surface area for absorbing oxygen
  • do not have a nucleus: to get through small places (ie: capillaries) and give a high surface area to volume ratio
• phloem cell adaptations

  are adapted to transport products of photosynthesis (sugar, glucose and amino acids) from leafs to where needed in plant

  • companion cells (adjacent to the sieve tubes) provides energy required to transport substances in the phloem
• xylem cell adaptations

  function is to transport water and dissolved minerals from roots up the plant

  • no top or bottom walls between the xylem vessels, meaning there's a continuous column of water running through
  • walls are thick and woody to support the plant
• root hair cell adaptations

  • large surface area to provide contact with soil water
  • thin walls allow for easy movement of water
• chromosomes carry genetic informations in a molecule called DNA
• mitosis: a type of cell division, it ensures that when a cell divides, each new cell produced has the same genetic information as the original cell
• DNA exists in a cell's nucleus within structures called DNA

  gene: the section of a chromosome which contains the code for the production of a particula protien
• each chromosome = single molecule of DNA

  each human cell contains 46 chromosomes ---> 23 pairs

  each chromosome in a pair carries same types of genes

  23rd pair is the sex gene. male: XY female: XX
• a cell divides when an organism grows or needs to replace damaged cells. cell cycle:

  DNA synthesis: single strand of DNA (which makes up chromosomes) produces an exact copy of itself

  • cell growth
  • DNA synthesis (chromosomes are now double stranded)
  • further growth, the DNA is checked for errors
  • mitosis
  • the cytoplasm seperates ---> 2 new cells formed
  • temporary resting period, or the cell stops dividing
• mitosis

  1. cell begins to divide
  2. DNA replicates, forming 2 copies of each chromosme
  3. nucleur membrane breaks down, the chromosomes line up in the center of the cell
  4. one set of chromosomes is pulled to each end and nucleus begins to divide
  5. cytoplasm and cell membrane divide to form 2 daughter cells
• stem cells

  stem cells are cells that have not undergone differentiation (unspecialised ---> specialised)

  embryonic stem cells: the cells in embryos are (all) stem cells and can differentiate into any type of cell
• stem cells

  adult stem cells- are only found in certain parts of the body and can only differentiate into related cell types

  ie: cells in bone marrow can only differentiate into blood cells and immune system cells

  adult stem cells are found in the:

  brain, eyes, blood, heart, liver, bone marrow, skin and muscle
• stem cells in plants

  meristems: where cells are dividing (and so undergoing mitosis) in the plant shoots root

  cells in meristems can differentiate into any type of plant cell at any point (in the plants life)