GCSE BIO PAPER 1

• Eukaryotic cells


  Cells that contain a true nucleus
• Components of eukaryotic cells

  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Ribosomes
  • Mitochondria
  • Cell wall (plant cells)
  • Chloroplasts (plant cells)
  • Permanent vacuole (plant cells)
• Nucleus


  Contains the DNA or genetic material and controls the actions of the cell
• Cytoplasm


  Liquid jelly where most chemical reactions in the cell take place
• Cell membrane


  Responsible for controlling what can go into and out of the cell
• Ribosomes


  Used to synthesize protein
• Mitochondria


  Site for aerobic respiration to release energy
• Cell wall (plant cells)

  Made of cellulose, strengthens and gives the cell support
• Chloroplasts (plant cells)


  Absorb light and are where photosynthesis takes place
• Permanent vacuole (plant cells)


  Storage of cell sap, used to keep the cell rigid to support the plant
• Prokaryotes (e.g. bacteria)


  Lack a true nucleus and membrane-bound subcellular structures
• Prokaryotes have a single circular chromosome and may also have small circles of DNA called plasmids
• Prokaryotes have smaller ribosomes than eukaryotes
• Binary fission


  Rapid reproduction of bacteria by division
• Bacteria can be cultured in petri dishes or broth to investigate disinfectants and antibiotics
• Streak plate method


  1. Sterilize equipment

  2. Inoculate plate with sample

  3. Spread in zigzag pattern

  4. Incubate upside down
• Incubate bacteria at 25°C to avoid growing human pathogens
• Can calculate area of bacterial colonies using πr^2
• Zone of inhibition test

  1. Cover agar plate in bacterial culture

  2. Add paper discs soaked in antiseptics

  3. Measure clear zones around discs
• Bigger zones of inhibition indicate more effective antiseptics
• Cell specialization


  Cells are adapted structurally to suit their function
• Xylem


  Transport water and mineral ions from roots to leaves
• Phloem


  Transport sucrose from leaves to other parts of the plant
• Good conditions for transpiration


  Hot, dry, light, windy
• Stem cells


  Unspecialized cells that can differentiate into specialized cells
• Embryonic stem cells can become any cell type, adult stem cells are more limited
• Therapeutic cloning uses embryonic stem cells genetically matched to the patient
• Meristems


  Plant stem cells that can become any cell type
• Resolution


  Smallest measurement that can be made
• Magnification


  How much bigger the image looks than the actual object
• Types of microscopes


  • Light microscopes
  • Electron microscopes (scanning and transmission)
• Light microscopes have a maximum magnification of around 1500x
• Electron microscopes have a much greater magnification and resolution than light microscopes
• Using a light microscope

  1. Start with low power objective

  2. Focus with coarse then fine adjustment

  3. Switch to higher power objective

  4. Use stain to see transparent components
• Mitosis is cell division for growth and repair, meiosis is for gamete production
• Be very careful with spelling of similar biological terms
• Nucleus


  Part of a eukaryotic cell
• Chromosomes


  23 pairs in a human body cell, each containing about a thousand different genes made of DNA
• DNA (deoxyribonucleic acid) is important for mitosis and genetics
• Mitosis


  One of the two types of cell division, used by body cells for growth and repair