AQA biology paper 1

• 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
• You'll notice 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
• Even though you have to learn the structure of a typical plant cell or a typical animal cell, there isn't really a typical type of cell because there are a wide range of differentiated specialized cells.
• Differentiation


  When various different genes will be turned on and turned off, and that's when it will start to specialize
• Microscopy techniques


  • Very basic starts where you had your lenses and you had to use the focus to see what was going on
  • Slightly more sophisticated lenses
  • 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
  • Twists round into a double helix
  • Further twists round so that it's in a chromosome
  • 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
• Stem cells


  • Have the potential to turn into any other type of cell
  • Used to grow new brain cells for Parkinson's disease
  • Used to grow new bones to fill the gap for brain or spinal injury, bone injuries
  • Used to grow new organs or parts of organs instead of waiting and making someone wait on the incredibly long transfer waiting list
• Making stem cells


  1. Take a nuclei out of an egg cell

  2. Take nuclei from the patient's cell and insert that into the empty egg

  3. Egg can then start to develop into an embryo

  4. Stem cells are then removed from the embryo 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


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

  • Carbon dioxide diffuses from the blood into lungs so they can be breathed out
  • Oxygen diffuses from the lungs into the blood so it can 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
• Osmosis in root hair cells

  • Uptake of water
• Active transport


  Movement across a membrane from a low concentration to a high concentration against the concentration gradient
• Active transport of glucose in the gut

  • Minerals in roots
• 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
• Our hierarchy is cells, tissues, organs, organ systems.
• Digestive system


  • Mouth - mechanically break down food
  • Salivary gland - produce amylase
  • Liver - produces bile
  • Gall bladder - stores bile
  • Small intestine - moves glucose, ions and other things into the blood
  • 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
  • Only one substrate, or a couple of substrates, are going to fit in there
  • Form an enzyme substrate complex
  • Enzyme is either going to break apart things or it is going to join together things
  • Release the products
  • Enzyme is unchanged and can be used again
• Temperature affects enzyme activity

  • Low temperatures - not enough energy
  • Optimal temperature
  • After the peak, the enzymes get denatured
• pH affects enzyme activity

  • Optimal pH
  • Too high or too low, the bonds aren't going to be in place, the active site of the enzyme is going to be breaking down, so again, it is going to be denatured
• Respiratory system


  • Air goes in through the mouth or the nose down into the trachea, into the bronchus, into the bronchiole, 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
• Path of blood flow

  Vena cava, atrium, ventricle, artery, vein, atrium, ventricle, aorta
• Heart features


  • Valves - only allow blood to flow in one direction
  • Right side has a much larger muscle than the left side
• Veins carry deoxygenated blood apart from the pulmonary vein which carries oxygenated blood back into the heart. Arteries carry oxygenated blood apart from the pulmonary artery which carries deoxygenated blood from the heart to the lungs.
• Pacemakers


  Artificial pacemakers can be introduced to help the heart keep time
• Cardiovascular disease


  • Fatty deposits building up in the coronary arteries, the arteries around the heart
  • Can lead to the formation of blood clots
  • Blood clot can block an artery
  • Restricts the oxygen to some cells
  • Cells then die
  • If too many cells die, can lead to a heart attack
• Risk factors for cardiovascular disease

  • Smoking
  • High blood pressure
  • Too much salts or fat in your diet