biology

• Hey, guys, here is your whole topic summary for the first paper in AQA Biology. Now remember, this is just a summary of everything.
• If you want a full checklist of absolutely everything you need to know with thousands of questions, keywords; long, long lists of things you need to know for chemistry and physics, you can get them.
• The free version (mumbles) which is over my website, or if you wanna ease, have Amazon print it out for you, you can get it over there.
• Plant cell


  • Cell membrane - responsible for determining which bits going in and out of the cell
  • Cell wall - important for structure
  • Vacuole - important for structure
  • Cytoplasm - where most of the reactions take place
  • Ribosomes - responsible for protein synthesis
  • Chloroplasts - green bits
  • Mitochondria - pink ones, where energy is produced
  • Nucleus
• Animal cell


  • Cell membrane - controlling what goes in and out
  • Mitochondria - where energy is produced
  • Ribosomes - responsible for protein synthesis
  • Cytoplasm - where most of the reactions take place
  • Nucleus - where the DNA's hold, the control center of the cell
• There are several features of a plant cell that an animal cell doesn't share, for example, the cell wall, the vacuole, the chloroplasts.
• If you look up at these pages yourself, you can download them, the free-version guide from my website.
• Bacterial cell


  • Cell membrane - controlling what goes in and out
  • Cytoplasm - where most of the reactions take place
  • Chromosome - DNA not in a nucleus
  • Flagella - used for locomotion
  • Ribosomes - for protein synthesis
  • Cell wall
• There isn't really a typical type of cell because there are a wide range of differentiated specialized cells.
• Cross-section of leaf


  • Contains lots of different types of cells
• Neuron


  • Looks very different to a muscle cell, which is going to look very different to a skin cell or very different to a set of cells in the gut
• All cells start off looking the same and then various different genes will be turned on and turned off, and that's when it will start to specialize, that's when differentiation will take place.
• Microscopy techniques have varied wildly over the time, from the very, very basic starts where you had your lenses and you had to use the focus to see what was going on, to ones that you're probably more familiar with in school which have slightly more sophisticated lenses, to the massive ones that I used to work on, electron microscopes, where they're all controlled by computer.
• Magnification


  Equals image height over object height
• DNA


  A long strand of deoxyribonucleic acid, made of lots of letters: As, Ts, Cs and Gs, which twist round into a double helix
• The double helix is still ridiculously long, so it further twists round so that it's in a chromosome, and this chromosome is located in the nucleus of a cell.
• Mitosis


  1. DNA in the nucleus needs to condense into chromosomes

  2. Chromosomes line up down the middle

  3. Checks take place to make sure the chromosomes aren't gonna go astray

  4. Chromosomes are pulled apart to either end of the cell

  5. New nuclei will form

  6. Two identical daughter cells separate
• Stem cells


  Have the potential to turn into any other type of cell
• Stem cells can be used to grow new brain cells, new bones, and new organs or parts of organs.
• To make stem cells, we take a nuclei out of an egg cell, we take nuclei from the patient's cell and insert that into the empty egg, the egg can then start to develop into an embryo, and from this embryo, the stem cells are then removed and turned into new cells.
• This does come with quite a lot of controversy because human embryos are going to be created and then destroyed, and there were lots of religious objections to this, people just saying that life starts when embryos are created, and people who object to the destruction of embryos.
• Diffusion


  The movement of gases or any particles that dissolved in solution moving down a concentration gradient from a high concentration to an area of low concentration
• Diffusion in the lungs

  • Carbon dioxide diffuses from the blood into the lungs to be breathed out, and oxygen diffuses from the lungs into the blood to be taken around the body
• Diffusion in the gut

  • Digested food moves from the gut cavity into the blood so that it could be taken around the rest of the body
• Osmosis


  The movement of water through a partially-permeable membrane from the area of high water concentration to an area of low water concentration
• Active transport


  The movement of substances across a membrane from a low concentration to a high concentration against the concentration gradient
• Tissue


  One type of cell carrying out one function
• Organ


  Made up from lots of different types of cells carrying out a joint function
• Organ system


  A group of organs that work together to carry out a function
• The hierarchy is cells, tissues, organs, organ systems.
• Digestive system


  • Mouth - mechanically breaks down food
  • Salivary gland - produces amylase
  • Liver - produces bile
  • Gall bladder - stores bile
  • Small intestine - moves glucose, ions and other things into the blood and has a very large surface area
  • Stomach - churns out food, produces hydrochloric acid
  • Pancreas - produces enzymes
  • Large intestine - removes excess water
  • Rectum and anus - gets rid of waste food
• Lipase


  Breaks down fats into fatty acids and glycerol, made in the pancreas and small intestine, works in the small intestine
• Protease


  Breaks down proteins into amino acids, made in the stomach, pancreas and small intestine, works in the stomach and small intestine
• Amylase


  Breaks down starch into sugars, made in the salivary glands, pancreas and small intestine, works in the mouth and small intestine
• Enzyme mechanism


  Enzyme has a specifically-shaped active site that only certain substrates can fit into, forms an enzyme-substrate complex, then breaks apart or joins things together, releases the products, and the enzyme is unchanged and can be used again
• Temperature affects enzyme activity

  Low temperatures - not enough energy, optimal temperature, high temperatures - enzymes get denatured
• pH affects enzyme activity

  Optimal pH, too high or too low - bonds break down and the active site of the enzyme is denatured
• Respiratory system


  • Air goes in through the mouth or nose down into the trachea, then into the bronchus, then into the bronchiole, and into the alveoli where gas exchange happens
  • Diaphragm moves up and down to bring air in and out
  • Heart pumps blood around the body
  • Intercostal muscles allow the ribcage to expand
  • Ribs protect the lungs
• Cardiovascular system


  • Double system - blood gets pumped from the heart to the lungs, goes back to the heart and then gets pumped around the rest of the body
  • Right side - pumps blood to the lungs, left side - pumps blood to the rest of the body
  • Valves only allow blood to flow one way
  • Veins carry deoxygenated blood, arteries carry oxygenated blood
• Pacemakers can be introduced to help the heart keep time, and tubes can be used to unblock arteries in cardiovascular disease.