Biology Paper 1

• Eukaryotic cell


  Complex cells that contain a nucleus and other membrane-bound organelles
• Prokaryotic cell


  Simple cells that lack a nucleus and the membrane-bound organelles
• Prokaryotic cells are much smaller than eukaryotic cells, have no nucleus, and lack organelles
• All prokaryotic cells are encased by a cell wall
• Salmonella bankanum

  • Width 0.5μm
  • Length 1μm
• Algal cells


  • They are eukaryotic and contain the nucleus, the chloroplast and mitochondria
• Cytoplasm


  Where many chemical reactions occur
• Nucleus


  Contains genetic material, including DNA, which controls the cell's activities
• Cell membrane


  Permeable to some substances, not to others. Controls the movement of substances in and out of the cell
• Mitochondria


  Contains enzymes for Respiration, where most energy is released
• Ribosomes


  Protein synthesis
• Chloroplast


  Where photosynthesis occurs
• Cell wall


  Strengthens cell and supports plant
• Vacuole


  Filled with cell sap
• Specialised cells are cells designed to carry out a particular role in the body
• Specialised cells


  • red blood cells
• Cell differentiation


  • As a cell differentiates, it acquires different sub-cellular structures to enable it to carry out a certain function
• Plant cells can differentiate throughout life, but in mature animals cells, cell division is mainly restricted to repair and replacement
• Magnification


  Ability to make small objects larger
• Resolution


  Ability to distinguish two objects from one another
• Electron microscopes


  • Have up to 1,000,000x magnification, and 250x better resolving power than a light microscope
• Magnification


  Size of image / Size of real object
• Chromosomes carry genetic information in DNA
• Cell division


  1. The cell begins to divide

  2. The cell replicates to form two copies of each chromosome

  3. The nuclear membrane breaks down

  4. The chromosomes line up across the centre of the cell

  5. One set of chromosomes is pulled to each end of the cell and the nucleus divides

  6. The cytoplasm and cell membranes divide to form two daughter cells
• Stem cells


  Cells that have not yet undergone differentiation
• Sources of stem cells


  • Embryo
  • Adult tissues (e.g. brain, eyes, blood, liver, bone marrow, skin, muscle)
  • Meristems of plants
• Stem cells


  • Can be used to produce clones cheaply and quickly
• Benefits of using stem cells


  • Grow organs for transplants
  • Treat patients
  • Treat currently untreatable conditions
• Clinical issues with stem cells


  • Difficulty finding suitable stem cell donors
  • No guarantee of successful therapies
  • Mutations in some stem cells have been observed to behave like cancer cells
  • Stem cells could be contaminated with viruses
• Ethical issues with stem cells


  • Source from IVF embryos
  • Successes not subject to peer review as research is done by commercial clinics
• Diffusion


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


  • Greater surface area
  • Greater difference in concentration
  • Higher temperature
• Substances to diffuse across

  When the surface area to volume ratio is small, there is not much surface area for substances to diffuse across but there are lots of cells inside that need the substances (a high volume)
• Digestive system


  1. Breaks down food into tiny particles

  2. Substances are absorbed into the blood
• Parts of the digestive system


  • Mouth
  • Oesophagus
  • Liver
  • Stomach
  • Pancreas
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Enzymes


  Catalysts in biological reactions that speed up chemical reactions
• Enzyme catalysis


  1. Substrate binding

  2. Catalysis

  3. Products released
• Blood supply


  • Provides an efficient transport network to carry molecules to and from cells
• Osmosis


  The diffusion of water molecules from an area of high to low concentration through a partially permeable membrane
• Investigating effect of concentration on plant mass


  1. Prepare range of sugar solutions

  2. Set up series of boiling tubes with each solution, including a control of distilled water

  3. Take masses of potato before and after experiment

  4. Repeat to improve repeatability