BIOLOGY WHOLE AQA

• there's a lot of you here which is amazing so just give me a thumbs up because obviously yesterday there was a lot of issues with the sound quality I hope you can hear me okay I assume you guys can hear me thank you
• so let's get started so how the this live stream is going to work is you may have seen already um we're going to go through a lot of exam questions and we're going to start in this live stream we're going to go through the first half of the topics which you can see on screen now on the left hand side and then on the live on the night before the exam we're going to go over the second half of the topics and how we're going to go over the topics is we're going to go over exam questions to help revise each part of the topic
• if anyone has any questions you can just put your questions in the chat and I'll stop hopefully and try and answer your questions but I want to get through as many questions as possible
• so let's get started I recommend you trying to answer the questions alongside me doing it as well
• Proaryotic cell


  Cells without a true nucleus
• Recall and describe the function of a typical structure in a proaryotic cell

  1. Cytoplasm

  2. Cell membrane

  3. Cell wall

  4. Bacterial DNA

  5. Plasmid DNA
• Differences between proaryotic and eukaryotic cells

  • Proaryotic cells are smaller
  • Proaryotic cells have genetic material freely suspended in cytoplasm
  • Proaryotic cells have plasmids
• Similarities between proaryotic and eukaryotic cells

  • Both have cytoplasm
  • Both have cell membranes
  • Both contain genetic material
• Mitochondria


  Site of aerobic respiration where energy is released
• Ribosomes


  Site of protein synthesis from amino acids
• Nucleus


  • Controls cell activities
  • Contains genetic material
• Differentiation


  How a cell changes over time to become specialized
• Advantages and disadvantages of plant stem cells

  • Advantages: Rare species can be cloned, Crops with useful adaptations can be cloned
  • Disadvantages: Cloned plants may compete with other plants, Cloned plants more susceptible to diseases
• Microscope practical


  1. Equipment: Light microscope, glass slide, cover slip, scalpel, iodine

  2. Prepare slide: Cut thin section of onion, peel epidermis, place on slide, stain with iodine, add cover slip

  3. View under microscope: Move slide up with coarse focus, adjust fine focus
• Reasons for unclear view through microscope

  • Dirty objective lens
  • Improper focusing
• Advantages of electron microscope

  • Higher magnification
  • Higher resolution
• Mitosis


  Cell division process that produces two genetically identical cells
• Importance of mitosis


  Repairs cells

  Replaces cells like skin and blood
• Stages of mitosis


  Replication of subcellular structures and DNA

  Separation of chromosomes to opposite ends

  Division of cytoplasm and cell membrane
• How mitosis produces genetically identical cells

  Chromosomes replicate and separate equally to form two identical daughter cells
• Diffusion


  Net movement of particles from high to low concentration down the concentration gradient
• Importance of steep concentration gradient

  Greater the difference, faster the rate of diffusion

  No diffusion occurs with same concentration
• Adaptations for transport in plant and animal cells

  • Small intestine: Villi increase surface area, good blood supply

  Lungs: Alveoli increase surface area, thin walls

  Plant roots: Root hairs increase surface area

  Gills: Thin, folded structure increases surface area
• The greater the difference in concentration, the faster the rate of diffusion
• With the same concentration, no diffusion will take place
• Concentration gradient


  The difference in concentrations between two areas
• Adaptations for transport in cells

  • Villi in small intestine
  • Alveoli in lungs
  • Gills in fish
  • Xylem and phloem in plants
• Villi


  • Small finger-like projections that increase surface area
  • Good blood supply with capillary network
  • Thin membrane
• Alveoli


  • Increase surface area
  • Good capillary network
  • Thin for rapid transport
  • Elastic walls to expand and contract
• Gills


  • Very thin, like skin
  • Absorb oxygen from water via osmosis and diffusion
• Lamellae


  • Small projections on gills that increase surface area
• Required practical for osmosis

  1. Cut potato cylinders to same diameter and length

  2. Measure and record length and mass

  3. Add potato cylinders to 3 test tubes with different salt solutions

  4. Leave overnight

  5. Remove potatoes, pat dry, and remeasure length and mass

  6. Calculate percentage change
• Plotting results on a graph


  Shows the point where there is 0% change, which represents the normal concentration
• Active transport


  Requires energy to move substances from an area of lower concentration to an area of higher concentration
• Principles of organization


  Levels of organization from cells to genes to DNA to chromosomes
• Enzymes


  Biological catalysts that break down large insoluble molecules into small soluble molecules
• Release of bile into small intestine

  Neutralizes acid and emulsifies fats, increasing surface area for lipase enzymes
• Protease works more effectively in the stomach

  The acidic conditions provide the optimum pH for protease to work
• Food tests


  1. Grind food into smaller particles

  2. Add to water and shake

  3. Filter to get liquid

  4. Test for starch, protein, fat, sugar
• Effect of pH on enzyme activity practical

  1. Set up 3 test tubes with starch, amylase, and pH 5 buffer

  2. Heat to 30°C in water bath

  3. Transfer 1 drop to spotting tile every 30 seconds until iodine no longer changes color