Biology paper 1

• Cells

  The basic building blocks of life that can replicate independently
• Multicellular organisms like animals and plants contain many cells that divide to grow or replace dead cells, not to create new organisms</b>
• Bacteria are single-celled prokaryotic organisms
• Animal and plant cells (eukaryotic cells)

  • Have a cell membrane, nucleus, cytoplasm, mitochondria, ribosomes
  • Plant cells also have a cell wall, permanent vacuole, chloroplasts
• Bacterial cells (prokaryotic cells)

  • Have a cell membrane, cell wall, ribosomes, cytoplasm, circular DNA (no nucleus)
  • Some have flagella for movement
  • Some have plasmids rings with extra genes
• Photosynthesis

  Chloroplasts in plant cells use chlorophyll to absorb light energy and convert it into glucose
• Cellular respiration

  Mitochondria in cells break down glucose to release energy
• Cells are the smallest unit of life that can replicate independently
• Equation for photosynthesis?


  Carbon dioxide water=glucose +oxygen(6CO2 + 6H2O → C6H12O6 + 6O2)
• Cell membrane


  Its partially permeable, which means it allows some substances to diffuse through but not others
• Cytoplasm


  It contains nutrients and salts and its where many of the chemical reactions take place in a cell
• Nucleus


  the nucleus contains DNA: which contains the genetic code to make up new proteins
• red blood cells(transport oxygen around the body)

  • no nucleus for more oxygen to bind the haemoglobin
  • red pigment called haemoglobin
  • bi-nonconcave disc shape to increase surface area to volume ratio
• root hair cell(absorb mineral ions and water from soil)

  • lots of mitochondria for energy for active transport of mineral ions from the soil
  • long projection speeds up the absorption of water and mineral ions by increasing the surface area of the cell
• Sperm cell(Fertilise the egg)

  • tail to swim to the egg and to fertilise it
  • Enzymes in the head-allow the sperm to penetrate the egg more easily
  • lots of mitochondria to provide energy
  • Streamlined head to aid swimming
• Nerve cell (carry electrical impulses around the body)

  • Branched endings(dendrites)which allow connections to be made with other neurons /effectors
  • fatty myelin sheath surround the axon and increase the transmission speed of the electrical impulses
  • lots of mitochondria in the synapse to provide energy for making neurotransmitter
  • long axons to move impulse along the body
• Palisade cell (to enable photosynthesis the leaf)

  • lots of green chloroplast containing chlorophyll to absorb light energy
  • located at the surface of the leaf where it can absorb the most light energy
• Magnification=Image size/actual size
• Light vs Electron microscope

  • Light=low resolution, electron=high resolution
  • light=low magnification, electron=high magnification
  • light=cheap , electron=expensive
  • light=uses light , electron=uses electrons
• Optical microscope


  • Has a stage to place the microscope slide
  • Has a light source (lamp or mirror) to illuminate the slide
  • Has objective lenses with different magnifications (4x, 10x, 40x)
  • Has an eyepiece lens with 10x magnification
  • Has coarse and fine focusing dials
• Using an optical microscope to view a prepared slide

  1. Place slide on stage and secure with clips

  2. Select lowest power (4x) objective lens

  3. Slowly turn coarse focus dial to lower lens until it almost touches slide

  4. Look through eyepiece and turn coarse focus dial to bring cells into focus

  5. Use fine focus dial to sharpen focus

  6. Calculate total magnification by multiplying eyepiece (10x) and objective (4x, 10x, 40x) lens magnifications
• Optical microscopes have limited detail - cannot see organelles like ribosomes
• Mitosis

  Cell division which produces two identical diploid cells for growth and repair
• Differentiation

  Cells become specialised
• Stem cells

  Can develop into different cell types
• Daughter cells


  Cells formed from the division of a cell
• In mitosis, two cells called daughter cells are produced, each identical to the parent cell
• Estimating length of cell cycle phases

  Number of cells at that state / Total number of cells x Total length of time in cell cycle
• Cell division

  1. Interphase(95%)-cells grow bigger, DNA replicated(chromosomes are doubled)+increase number of subcellular structures
  2. Mitosis(5%)-complete set of chromosomes is pulled to each end of the cell, +nucleus divides to form 2 nuclei
  3. cytokinesis(5%)-cytoplasm and cell membrane are dividing to form two identical daughter cells
• adult stem cell(bone marrow)+can only differentiate into types of blood ADVANTAGES

  • few ethical issues
  • established technique for treating diseases
  • relatively safe to use as treatment donors recover quickly
  • DISADVANTAGES
  • requires a donor-long wait
  • can only differentiate into certain types of specialised cells-can be used to only treat fewer diseases
• Embryonic stem cells can differentiate into any type of specialised cell in the body .e.g. .nerve/muscle cell


  ADVANTAGES

  • can treat wide range of diseases
  • may be possible to grow a whole replacement organs
  • no donor needed-obtained from spare embryos from fertility clinics

  DISADVANTAGES

  • ethical issues as the embryo is destroyed(each embryo is a potential human life)
  • risk of tranferring viral infections to the patient
  • newer treatment so under researched-not yet clear if they can cure as many diseases as through
• plant meristem(roots and shoots of plant)-can differentiate into all cell types


  ADVANTAGES

  • rare species of plants can be cloned to prevent extinction
  • plants with desirable traits-such as disease resistance can be cloned to produce large numbers of identical plans
  • fast and low-cost production of large numbers of plant DISADVANTAGES
  • cloned plants are genetically identical-whole crop is at risk of being destroyed by a single disease
• Therapeutic cloning

  • cells from patients own body are used to create a cloned early embryo of themselves
  • Stem cells from this embryo can be used for medical treatments and growing new organs
  • the stem cells have the same genes as the patient-less likely to be rejected when transplanted
• Nanometers


  Smallest unit of length you need to know
• Units of length

  • Nanometers
  • Micrometers
  • Millimeters
  • Meters
  • Kilometers
• Each unit is 1,000 times bigger or smaller than the one next to it
• Converting between units of length

  1. Divide by 1,000 to convert to a larger unit

  2. Multiply by 1,000 to convert to a smaller unit
• Converting 6 millimeters

  • 6 millimeters = 0.006 meters = 0.000006 kilometers
  • 6 millimeters = 6,000 micrometers = 6,000,000 nanometers
• To convert between non-adjacent units, convert in steps
• • Naked eye can see down to 100 micrometers
  • Light microscope can see down to 500 nanometers
  • Electron microscope can see down to 0.1 nanometers