b1- cells

• eukaryotic cells


  plant + animal cells

  contain a nucleus that contains DNA
• cytoplasm - jelly-like substance inside the cell where chemical reactions take place
• cell membrane - controls what enters/leaves the cell
• mitochondria - site of aerobic respiration, produces ATP
• ribosomes - sites of protein synthesis
• chloroplasts - found only in plant cells, contain chlorophyll which is used to make food from sunlight
• nucleus- contains genetic information (DNA)
• cell wall- maintains rigid structure of cell (plant cell only)
• permanent vacuole- contains cell sap (plant cell only)
• prokaryotic cells


  smaller + simpler than eukaryotic cells

  could be bacteria cells
• light microscopes


  use light and lenses to form an image of a specimen and magnify it, allow us to see individual cells and large subcellular structures
• electron microscope


  more expensive than light microscopes, have a higher magnification and higher resoloution
• magnification= image size/ actual size
• differentiation- the process where cells become specialised to perform a specific function
• sperm cells


  specialised for reproduction.

  long tail + stream lined head to help it swim to the egg, there are also lots of mitochondria in the cell to provide the energy needed.
• nerve cells


  specialised for rapid signalling

  • cells are long (to cover more distance) and have branched connections at their ends to connect to other nerve cells and form connections throughout the body
• muscle cells


  specialised for contraction

  the function of a muscle cell is to contract quickly

  • these cells are long and contain lots of mitochondria to generate the energy needed for contraction
• root hair cells


  specialised for absorbing water and minerals

  • cells on the surface of plant roots which grow into long hairs that stick out into the soil
  • gives the plant a big surface area for absorbing water and mineral ions
• phloem cells


  transport food around plants

  • few subcellular structures so that stuff can flow through them
• xylem cells


  transport water up them

  • hollow in the centre
• mitosis


  used to grow or replace cells that have been damaged
• stages of mitosis

  1. the cell has to grow and increase number of subcellular structures
  2. it then duplicates its DNA
  3. chromosomes line up at the centre and cell fibres pull them apart
  4. membranes form around each of the new sets of chromosomes and these become the nuclei of the two new cells
  5. lastly the cytoplasm and cell membrane divide to form two new daughter cells
• embryonic stem cells- can differentiate into any type of cell, can be used to treat diseases
• diffusion- the movement of particles from an area of high concentration to an area of low concentration
• osmosis- the movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of lower water concentration
• active transport- movement of molecules from a low concentration to a high concentration through a membrane AGAINST A CONCENTRATION GRADIENT
• root hair cells take in minerals using active transport
• cells use diffusion to take in substances they need and get rid of waste products

  • for example: oxygen and carbon dioxide are transferred between cells and the environment during gas exchange
• exchange surfaces are adapted to maximise effectiveness

  • they have a thin membranes to allow for a short diffusion distance
  • they have a large surface area so lots of substances can diffuse at once
  • in animals they have a good blood supply + are ventilated
• gas exchange happens in the lungs and the alveoli, where oxygen and carbon dioxide diffuse in and out of the blood
• alveoli are specialised to maximise diffusion of oxygen and carbon dioxide

  • they have an large surface area
  • a moist lining
  • very thin walls
  • a good blood supply
• villi- increase surface area for absorption of nutrients and waste

  • they have a single layer of surface cells and a very good blood supply
• the structure of leaves lets gases diffuse in and out of cells, and water vapour diffuse in and out of the leaf

  • the underneath of a leaf is an exchange surface, its covered in little holes called stomata which co2 diffuses in through
  • oxygen and water vapour also diffuse out of the stomata
  • the size of stomata are controlled by guard cells
  • flattened shape of leaf increases surface area