Biology Paper 1

• Eukaryotic cells


  • Have nucleus, cell membrane, cytoplasm, mitochondria, ribosomes
  • Plants also have chloroplasts, cell wall and vacuole (sugar, water, nutrients)
• Prokaryotic cells


  • Have loose genetic information (plasmids), cell membrane, cytoplasm, cell wall
• Stem cells


  Cells that can differentiate to become specialised
• Light microscope


  • Has less zoom and for regular use
• Electron microscope


  • Has more zoom and higher resolution, but cannot view living cells entirely
• Microscope operation


  1. Eyepiece

  2. Base

  3. Objective (can change)

  4. Coarse adjustment (makes large changes)

  5. Fine adjustment (makes small changes)
• Gene

  Is genetic information
• DNA


  Genetic information
• Chromosomes

  Contain genetic information
• Nucleus


  Contains genetic information in plant and animal cells
• Diploid


  46 chromosomes
• Haploid


  23 chromosomes in humans, as only half of the genetic information, to divide between parents
• Mitosis


  All contents of cell copied, and moved to the sides, then cell splits, creating two identical cells
• Meiosis


  Same as mitosis, but cells split again at the end, all containing half of the original cell
• Stem cells


  Used for healing injuries, with bone marrow or therapeutic cloning
• Cloning plants


  Take cuttings, with meri(stem) cells, and use rooting powder to stimulate growth, which is cheap and easy
• Therapeutic cloning


  A diploid is taken from the target, and an egg from a donor, the nuclei are removed, and one is implanted into the other cell, to create a zygote, which is electrically shocked, stimulating mitosis, creating stem cells genetically identical to one of the people
• Pros of Bone Marrow


  • Ethical
  • Reliable
• Cons of Bone Marrow


  • Limited treatment options
  • Painful
  • Risk of rejection
  • Require donor
• Pros of Therapeutic Cloning


  • Bountiful
  • Versatile
  • Safe
  • Painless
• Cons of Therapeutic Cloning


  • Unreliable
  • May not work
• Bacterial reproduction


  Binary fission, like mitosis
• Log2(population)


  (n) * division time = time
• Diffusion


  Movement of particles from a high concentration to a low concentration
• Factors affecting diffusion rate


  • Large surface area
  • Thin cell walls/short diffusion pathway
  • Close proximity to blood vessels
  • Hotter temperature of particles
• Surface Area to Volume ratio

  High (Small cube) heats/cools quickly, and low heats/cools slowly
• Semi-permeable membrane


  Only water can pass through
• Osmosis


  Diffusion of water from a dilute to a concentrated region through a semi-permeable membrane
• Active transport


  Movement of substances from an area of low concentration to high concentration against a concentration gradient, requires energy from respiration
• Carbohydrates, fats/lipids, and proteins

  Need to be broken down by enzymes
• Vitamins, minerals, fibres and water


  Do not need to be broken down by enzymes as they are soluble
• Starch test


  Iodine, turning orange to blue/black
• Glucose test


  Benedicts and boiling water, turning blue to orange
• Protein test


  Biuret solution, turning blue to lilac
• Enzymes


  • Specific to food types
  • Work best at 37°C
  • Become denatured at higher temperatures (40>), losing their complimentary shape
  • Work best in acidic conditions, killing the bacteria on food
• Bile


  Produced in the liver, neutralises acid on food from the stomach, making it slightly alkaline, emulsifies fats to increase enzyme action
• Carbohydrase


  Breaks carbs into glucose in the salivary glands, pancreas and small intestine
• Protease


  Breaks protein into amino acids in the stomach, small intestine and pancreas
• Lipase


  Breaks fats into fatty acids and glycerol in the pancreas and small intestine
• Blood


  Plasma, which contains red and white blood cells and platelets