cell biology - biology paper 1

• Bacteria are prokaryotes, their genetic information is not enclosed in a nucleus
• Binary fission


  The process where one bacterial cell splits into two bacterial cells
• Bacteria can carry out binary fission once every 20 minutes as long as they have enough nutrients and the temperature is suitable
• Calculating the number of bacteria after a given time

  1. Calculate the number of rounds of division

  2. Use the equation: Number of bacteria = 2^n, where n is the number of rounds of division
• The equation Number of bacteria = 2^n, where n is the number of rounds of division, is not given in the exam so it's important to learn it
• Calculating the number of rounds of division


  Time elapsed / Time between divisions = Number of rounds of division
• Mitosis


  The process by which a cell divides into two or more cells
• Body cells


  • Contain 23 pairs of chromosomes
• Gametes


  • Contain unpaired chromosomes
• Chromosomes


  Carry a large number of genes that determine many of our features
• Cell cycle including mitosis


  1. DNA replication

  2. Mitosis

  3. Cytoplasm and cell membrane division
• Eukaryotic cells


  Cells that contain their genetic material enclosed in a nucleus
• Mitosis copies one cell into two
• Eukaryotic cells


  • Contain a nucleus
  • Contain a cell membrane
  • Contain cytoplasm
• Functions of mitosis


  • Essential for growth and development of multicellular organisms
  • Repairs organisms
  • Occurs during asexual reproduction
• Prokaryotic cells


  Cells where the genetic material is not enclosed in a nucleus
• Prokaryotic cells


  • Do not have a nucleus
  • Have a cell membrane
  • Have a cell wall
  • Contain cytoplasm
  • May have plasmids
• Prokaryotic cells


  Are much smaller than eukaryotic cells
• Bacterial cells are an example of prokaryotic cells
• Active transport


  Moves substances from a more dilute solution to a more concentrated solution, against the concentration gradient, requiring energy from respiration
• Diffusion


  Particles move down the concentration gradient, does not require energy from respiration
• Active transport


  Particles are moved against the concentration gradient, requires energy from respiration
• Active transport in animals


  • Cells lining the human small intestine transport sugars like glucose from the lumen (lower concentration) into the cell (higher concentration)
• Cells lining the human small intestine


  • Have many mitochondria to provide the energy needed for active transport
• Active transport in plants


  • Root hair cells transport ions like magnesium from the soil (lower concentration) into the cell (higher concentration)
• Root hair cells


  • Have many mitochondria to provide the energy needed for active transport
• Plants need magnesium to make chlorophyll in the leaves
• The concentration of ions in the soil is lower than the concentration inside the root hair cell