B1

• This video is going to cover the biology paper 1 AQA exam
• Topics involved in paper 1


  • Cell biology
  • Organization
  • Infection and response
  • Bioenergetics
• Animal and plant cells

  Have a nucleus
• Bacterium


  Has a loop of DNA, no nucleus
• Cell structures and their functions

  1. Cell membrane controls what substances move in and out

  2. Mitochondria is where energy is released

  3. Ribosomes is where protein synthesis occurs
• Cell wall


  Function is to provide structure and support
• Chlorophyll


  Makes the cell green, located in the chloroplast
• Calculating magnification


  Magnification = size of image / size of real object
• Cell cycle stages


  1. Growth and chromosome replication

  2. Chromosome separation

  3. Cytoplasm and cell membrane division
• Mitosis


  Process that makes two identical new body cells for growth and repair
• Genetic material is made from DNA
• Gene


  Section of genetic material on a chromosome
• Stem cells


  Can differentiate into specialized cells
• Bone marrow stem cell transplant


  Can help treat medical conditions by differentiating into red blood cells to cure anemia
• Differences between mitosis and meiosis

  • Mitosis produces 2 daughter cells, meiosis produces 4
  • Mitosis produces diploid cells, meiosis produces haploid cells
  • Mitosis produces genetically identical cells, meiosis produces genetically different cells
• Similarity between mitosis and meiosis is that DNA replicates
• Diffusion


  Net movement of particles from high to low concentration
• Increasing CO2 concentration or number of open stomata

  Increases rate of CO2 diffusion into mesophyll cells
• Lungs adapted for efficient gas exchange by diffusion

  • Many alveoli to increase surface area
  • Thin capillaries for short diffusion pathway
  • Breathing maintains concentration gradient
  • Rich blood supply brings CO2, removes O2
• Osmosis


  Process by which water molecules enter root hair cell
• Active transport


  Process used to transport nitrate ions into root hair cell against concentration gradient, requires energy
• Small intestine adapted for efficient absorption

  • Projections called villi provide large surface area
  • Villi walls are very thin for short diffusion distance
  • Intestine is long to increase absorption time
  • Rich blood supply maintains concentration gradient
  • Cells contain many mitochondria to provide energy for active transport