Biology p1

• Eukaryotic cells

  Cells that contain a true nucleus
• Eukaryotic cells

  • Contain a cell membrane wrapped around cytoplasm
  • Contain a nucleus
  • Contain ribosomes
  • Contain mitochondria
  • Plant cells and algae cells have a cell wall made from cellulose
  • Plant cells contain chloroplasts full of chlorophyll
  • Plant cells contain a permanent vacuole full of cell sap
• Nucleus

  Contains the DNA or genetic material and is responsible for controlling the actions of the cell
• Cytoplasm

  The liquid gel where most of the 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

  The site for aerobic respiration which is used to release energy from glucose
• Cell wall

  Made of cellulose and strengthens and gives support to the cell
• Chloroplasts

  Absorb light and are where photosynthesis takes place
• Permanent vacuole

  A storage of cell sap used to keep the cell rigid to support the plant
• Prokaryotic cells

  Smaller than eukaryotic cells, lack a nucleus, and lack membrane-bound subcellular structures
• Prokaryotic cells have a single circular chromosome and may have small circles of DNA called plasmids
• Prokaryotic cells lack mitochondria and chloroplasts because they are about the same size as bacteria
• Prokaryotic cells have smaller ribosomes than eukaryotic cells
• Bacterial cell walls are not made of cellulose
• Some bacteria have a flagellum to help them move around
• Cell specialization

  • Cells are adapted structurally to suit their function
  • Can involve a change in shape or the presence of more/fewer subcellular structures
• Specialized cells

  • Sperm cell (has a tail and many mitochondria)
  • Nerve cell (very branched shape)
  • Muscle cell (packed with mitochondria and ribosomes)
  • Palisade cells in leaves (have many chloroplasts)
  • Root hair cells (extended shape, no chloroplasts)
• Plants retain unspecialized stem cells throughout their lifetime, allowing them to be cloned from small pieces
• Xylem

  Dead hollow tubes reinforced with lignin that transport water and mineral ions from roots to leaves
• Phloem

  Living cells that transport sugar from leaves to other parts of the plant
• Phloem are not one continuous tube, the ends of each cell are perforated to allow flow between cells
• Conditions for good transpiration

  • Hot, dry, light, with lots of air movement
• These conditions increase the rate of water evaporation from the plant
• Stem cells

  Unspecialized or undifferentiated cells that can become different cell types
• Adult human stem cells are limited in the cell types they can become
• Embryonic stem cells can become almost any cell type
• Therapeutic cloning


  Creating an embryo with the same genes as the patient to harvest stem cells that won't be rejected
• Ethical issues with therapeutic cloning include the embryo not being able to consent
• Plants have meristems containing stem cells that can become any cell type, allowing easy cloning
• Resolution


  The smallest measurement that can be made
• Magnification


  How much bigger the image looks than the actual object
• Light microscopes have a maximum magnification of around 1500x and a resolution of 0.2 micrometers
• Electron microscopes have a magnification up to 500,000x and a resolution down to 1 nanometer
• 10% of GCSE biology marks are for mathematical skills like calculating magnification
• Using a light microscope


  1. Start with stage as high as possible

  2. Use lowest power objective lens

  3. Focus first with coarse wheel, then fine wheel

  4. Switch to higher power objective and focus with fine wheel only

  5. Use a stain to see transparent structures

  6. Troubleshoot if image is out of focus or too small to see
• In a eukaryotic cell, the nucleus contains 23 pairs of chromosomes
• Mitosis


  Cell division used by body cells for growth and repair
• Mitosis involves DNA replication, chromosome separation, and cell division into two identical diploid daughter cells
• Diffusion


  The passive movement of particles from an area of high concentration to an area of low concentration