cell structure + organisation

• mitochondria

  important for respiration
• eukaryotic cells

  multicellular, eg. plants and humans

  • bigger
  • membrane-bound nucleus containing dna
  • membrane-bound organelles
  • animals - no cell wall, plant - cell wall
  • no plasmids
• prokaryotic

  singlecell eg. bacteria

  • very small
  • no nucleus - loop of dna
  • no membrane
  • cell wall not made of cellulose
  • some genes may be in separate circular structures - plasmids
• specialised cells

  root hair cells + sperm cells

  found in eukaryotic cells

  made to carry out particular jobs
• fats cells

  small amount of cytoplasm

  large amounts of fat

  few mitochondria = little energy

  can expand
• cone cells

  outer pigment contains chemical which changes in colour light

  middle contains lots of mitochondria - see colour, change the outer segment back

  specialised synapses connect to optic nerve, to brain
• root hair cells

  increased surface area - water into cell

  large vacuole - speeds up movement of water
• sperm cells

  long tail for movement

  middle section lots of mitochondria

  top of head (acrosome) stores digestive enzymes

  large nucleus - pass on dna info
• tissue

  group of cells - similar structure and function
• organ 


  group of tissues
• glands

  produce digestive juices containing enzymes that chemically break down food molecules
• stomach

  where digestion of protein in food takes place
• liver

  produce bile, which helps in the digestion of lipids (fats)
• small intestine

  digestion takes place and where the soluble food is absorbed into bloodstream
• large intestine

  water is absorbed from undigested food, producing faeces
• diffusion

  movement of particles from high concentration to low concentration - down a concentration gradient

  it is random - particles collide then some point you have equilibrium

  diffusion is affected by area, temp, concentration

  eg. simple sugars in and out of cells, respiration
• osmosis

  movement of water from a dilute to a more concentrated solution

  must be partially permeable membranes
• dilute

  more water paricles
• concentrated

  less water particles
• hypotonic to cell

  concentration of solutes in the solution outside the cell is lower than the concentration inside the cell
• isotonic to cell

  concentration of solutes in the solution outside the cell is the same as the concentration inside the cell
• hypertonic to cell

  concentration of solutes in the solution outside the cell is higher than the concentration inside the cell
• animal cell

  isotonic - water in and out, normal

  hypertonic - water out, shrivelled

  hypotonic - water in, lysed
• plant cell

  isotonic - water in and out, flaccid

  hypertonic - water out, plasmolysed

  hypotonic - water in, turgid (normal)
• when against a concentration gradient use active transport - low to high

  energy comes from cellular respiration
• animal cell (eukaryotic cells)

  • a nucleus
  • cytoplasm - chemical reactions
  • cell membrane - controls the passage of substances into and out of the cell
  • mitochondria - where most energy is released in respiration
  • ribosomes - protein synthesis occurs
• plant cells (eukaryotic cells)

  • a nucleus
  • cytoplasm - chemical reactions
  • cell membrane - controls the passage of substances into and out of the cell
  • mitochondria - where most energy is released in respiration
  • ribosomes - protein synthesis occurs
  • chloroplasts - absorb light energy to make food
  • permanent vacuole filled with cell sap
  • cell wall - strengthens the cell
• examples of animal tissues

  • muscular tissue - contract to bring about movement
  • glandular tissue - produce substances like enzymes and hormones
  • epithelial tissue - covers some parts of the body
• animal organ


  eg. stomach

  contains:

  • muscular tissues - allow contents to move through the digestive system
  • glandular tissue - produce digestive juices
  • epithelial tissue - cover the outside and inside of the stomach
• plant tissues


  • epidermal tissues - cover plant
  • palisade mesophyll - carries out photosynthesis
  • spongy mesophyll - air spaces to facilitate diffusion of gases
  • xylem and phloem - transport substances around the plant
• plant organs


  • stems
  • roots
  • leaves
• a single celled organism has a relatively large surface area to volume ratio - all necessary exchanges occur across its surface membrane
• the increases size and complexity of an organism increases the difficulty of exchanged materials
• in a multicellular organisms many organ systems are specialised for exchanging materials. effectiveness increases by:

  • having large surface area that is thin - provide a short diffusion path
  • (in animals) having an efficient blood supply
  • (in animals) for gaseous exchange - being ventilated