Biology notes

• Cell Differentiation


  The process by which a cell changes to become specialised for its job
• Cell Differentiation


  1. Cells change

  2. Develop different subcellular structures

  3. Perform different functions
• Cell Differentiation


  • Allows cells to carry out specific functions
  • Occurs as an organism develops
  • In most animal cells, the ability to differentiate is lost at an early stage after they become specialised
  • Lots of plant cells don't ever lose this ability
• Cells that differentiate in mature animals

  • Skin cells
  • Blood cells
• Stem cells


  Undifferentiated cells
• Sperm cells


  • Specialised for reproduction
  • Have a long tail and streamlined head to help reach the egg
  • Have lots of mitochondria to provide energy
  • Carry enzymes in the head to digest through the egg cell membrane
• Nerve cells


  • Specialised for rapid signalling
  • Are long to cover more distance
  • Have branched connections at the ends to connect to other nerve cells and form a network
• Muscle cells


  • Specialised for contraction
  • Are long to have space to contract
  • Contain lots of mitochondria to generate the energy needed for contraction
• Root hair cells


  • Specialised for absorbing water and minerals
  • Grow into long "hairs" that stick out into the soil to increase surface area for absorption
• Phloem and xylem cells


  • Specialised for transporting substances
  • Form tubes to transport food and water around plants
  • Phloem cells have very few subcellular structures so substances can flow through easily
  • Xylem cells are hollow in the centre
• The Lungs


  You need to get cage into your blooddream to supply your oels for respinsico. You also need to get rid of garden divide from your blood. This all happens in your lungs when you breathe air in and out.
• The Lungs


  • Are in the Thorax
  • The thones is the top part of your body
  • Is separated from the lower part of the body by the dashesgn
  • The lungs are ke big pink spons and are protected by the rings
  • They're surrounded by the pleural membranes
• Air intake


  1. The air that you breathe in goes through the trache

  2. This splits into two tubes called beanchi (esch one is bronchus), one going to each lung

  3. The bronchi split into progressively smaller tubes called benables

  4. The bronchicles finally and at small bags called sheol where the goo exchange takes place
• Alveoli


  • The lungs contain millions and millions of little ar sace called shell, surrounded by network of blood capilaries
  • This is where gas exchangs happene
• Gas exchange in alveoli


  1. The blood passing next to the alveoli hes just retumed to the lungs from the rest of the body, so it contains lots of carbon dioxide and very little gogen diffuses out of the seclus (high concentration) into the blood (low concentration)

  2. Carbon dioxide diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out

  3. When the blood reaches body calls gen is released from the red blood cells (where there's a high concentration) and diffuses into the body cells (where the concentration is low)

  4. At the same time, carbon dioxide diffuses out of the body cells (where there's a high concentration) into the blood (where there's a low concentration). It's then carried back to the lungs
• Calculating breathing rate


  1. Breathing rate is the number of breaths per minute

  2. To calculate it: number of breaths / number of minutes
• Breathing rate calculations pop up all the time in biology, and you're expected to know how to do them
• Breathing rate calculations are pretty easy