1 - Cell Structure

• Eukaryotic - cells where genetic materials is stored in the nucleus
• Eukaryotic Cells are bigger than prokaryotics
• Eukaryotic cells are found in plants, animals and fungi.
• Prokaryotic - cells where genetic materials is stored in a single DNA loop in the cytoplasm
• Prokaryotic do not contain mitochondria, nucleus or chlorplasts
• Some prokaryotic cell contain small rings of DNA called plasmids, these can replicate and move between cell so the genetic material can be shared.
• Plant and Animal Cell:

  A) Cell Wall

  B) Cell Membrane

  C) Ribosomes

  D) Nucleus

  E) Vacuole

  F) Cytoplasm

  G) Mitochondria

  H) Chlorplasts

  
• Nucleus - controls all activity of the cell and contains chromosomes that make proteins to produce new cells
• Cytoplasm - jelly-like fluid that fills the cell, where chemical reactions occur
• Cell Membrane - controls what substances enters and leaves the cells
• Mitochondria - where aerobic respiration occurs
• Ribosomes - responsible for protein synthesis
• Chloroplasts - contains chlorphyll that absorbs light to do photosynthesis
• Cell Wall - surrounds the cell and increases the structural strength of the cell
• Vacuole - filled with sap that keeps cell rigid to support the cell
• Cell differentiation is the process by which a cell changes into a specialised cell by developing new sub-cellular structures so it can perform a specific function
• Adaptions of sperm cell:

  • Streamlined head - to be able to reach the egg cell as fast as it can.
  • Acrosomes - found at the tip of the head. It contains the digestive enzymes needed to penetrate the egg cell.
  • The Head - contains the nucleus. This is carrying one half of an organism's genetic material
  • Middle Section - filled with mitochondria to provide energy for the cell to travel to the egg cell.
  • Flagellum - allows the sperm cell to travel to the egg cell
• Adaptions of nerve cell:

  • Axon - electrical signals travel along. Long axons, which increases the distance that electrical signal can travel.
  • Myelin Sheath - this surrounds the axon and stops nerve signals from leaking out. This increases the speed of transmission of signals.
  • Dendrites - branches of a nerve cell. Dendrites spread outwards from the cell body to transfer signals to other neurons.
• Adaptions of muscle cell:

  • loads of mitochondria - provides lots of energy
  • protein fibres - muscle can contract and move
• Plant cells can differentiate to produce all types of plant cells at any time during the life of the plant.
• Adaptions of root hair:

  • no chlorplasts as no light underground so can't do photosynthesis
  • longe projections - increase surface area for water and mineral absorption
  • large vacuole - speeds up movement of water by osmosis
  • lots of mitochondria for active transport
• The xylem is specialised to transport water up the stem and into the leaves.
• Adaptions of xylem:

  • lignin - strengthens cell wall to withstand pressure of water and support stem
  • end walls of dead cells - movement of water is easier
• The phloem is specialised to transport food products to parts of the plant where they are needed.
• Phloem is bi-directional while xylem is uni-directional
• Adaptions of phloem:

  • Sieve plates - allows water carrying dissolved food to move freely up and down the tube.
  • Companion cells - supports the internal structure that help to keep the plant alive.
  • Mitochondria - transfers energy needed to move dissolved food up and down the plant.
• Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration.
• Factors affecting diffusion:

  • temperature
  • surface area
  • difference in concentration
• Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution to a concentrated solution
• A partially permeable membrane allows small molecules through, but won't let larger molecules pass through.
• Active Transport is the movement of particles against the concentration gradient so require energy
• Adaptions of exchange surfaces:

  • Thin membrane - reduces the diffusion distance.
  • Large Surface Area
  • Ventilation - to maintain a high concentration difference
  • Bigger Surface area to Volume ratio