cell structure

• cell wall

  • It is composed of a non-living material called cellulose, which is a type of carbohydrate.
  • This structure strengthens the cell, provides it with structure/support and prevents the cell from bursting when water enters it.
  • All substances can pass across it, so it is described as fully permeable.
• chloroplasts


  These contain the green pigment chlorophyll, which is used to absorb light energy and make glucose during the process of photosynthesis
• nucleus

  • The largest size organelle, it controls cells' actions.
  • It contains structures called chromosomes which carry the genetic material/DNA
  • These contain all the information needed for making new cells or new organisms.
• cytoplasm

  A jelly like solid in which MOST of the chemical reactions needed for life take place.
• cell membrane

  This forms a thin boundary between the cell cytoplasm and outside. It is permeable (entry & exit) to some substances but not all, so is described as semi permeable.
• mitochondria

  These are found in the cytoplasm.

  AEROBIC respiration occurs in these organelles, during which oxygen and sugar react to release energy, making the

  2 waste products water and carbon dioxide.
• vacuole

  This contains a liquid called cell sap which acts as a

  reservoir of nutrients, dissolved sugars, mineral ions etc. It

  also helps to keep the cell rigid for support by expanding.
• ribosomes

  protein synthesis
• Why don’t all plant cells have chloroplants?

  Chloroplasts are needed for photosynthesis. Some plant cells are in the roots so don’t get sunlight and therefore don’t perform photosynthesis, so they don’t need chloroplasts.
• Which organisms contain chloroplasts?

  plants
• Inside which cell structure does aerobic

  respiration take place?

  mitochondria
• Name the structure that contains the genetic material in plant and animal cells.

  Nucleus
• Why is cellulose important for plant cells?

  Very strong, forms cell walls and provides support
• How is a sperm cell adapted for fertilising an egg?

  • tail for swimming
  • mitochondria for energy
  • digestive enzymes to break outer layer of egg
• In what form is DNA found inside prokaryotic cells?

  ring of DNA/plasmid
• Which cells have the smallest ribosomes?

  prokaryotes
• which cell types do not have plasmids

  Eukaryotes
• why can an electron microscope have a higher resolution than a light microscope.

  uses electrons which have a shorter wavelength
• how are nerve cells adapted for sending rapid nerve impulses?

  long dendrites with many connections to other cells
• How are muscle cells adapted for contraction?

  Many mitochondria to supply energy
• what are the structures in plants which are responsible for the translocation of sugars?

  phloem
• Where in a muscle cell would energy be transferred from for contraction?

  Mitochondria
• Where in a pancreatic cell would the hormone insulin be made?

  ribosome/endoplasmic reticulum
• what is known as the ability to distinguish two points that are very close together?

  resolution
• by which process are phosphate ions taken up by root hair cells?

  active transport
• explain why light microscope specimens must be very thin.

  so light rays can pass through them and reach the eye
• Why must DNA be stained?

  DNA is invisible/colourless and stain is required to see it
• how is phloem is adapted for its function?

  • long thin tubes connected by strands of cytoplasm. sugars pass from one cell to the next through cytoplasm
  • sieve tubes connect one cell to the next for translocation
  • companion cells provide energy for sugar transport
• Why do light microscopes have a maximum useful magnification?

  resolution limited by wavelength of light rays
• why would we use iodine to stain onion cells?

  onion cell structures are invisible; iodine stains the nucleus and other cell structures so they are visible
• Nerve cell/neurone function

  carry electrical impulses around the body
• How does the nerve cell structure relate to its function?

  • Branched endings, called dendrites, to make connections with other neurones or effectors
  • Myelin sheath insulates the axon to increase the transmission speed of electrical impulses
  • Long to cover more distance
  • Large nucleus containing genetic information to be passed on
• Sperm cell function

  Fertilise an ovum

  (egg cell)

  (Carry the male DNA

  to the female DNA)
• how does the sperm cell structure relate to its function?

  • Streamlined head and tail to swim to the ovum and fertilise it
  • Lots of mitochondria to release energy from respiration, enabling the sperm to swim to the ovum
  • Enzymes in acrosome to digest through egg cell membrane
• what is this cell?

  Striated muscle cell

  
• muscle cell function

  Contract and relax

  to allow movement
• How does the structure of the muscle cell relate to its function?

  • Contains protein fibres which can slide over each other and contract to make the cells shorter
  • Lots of mitochondria to release energy from respiration allowing the muscles to contract
  • Cells are long to allow space to contract
  • Store glycogen - can be converted to glucose for respiration
• what is this cell?

  Phloem cell

  
• What is this cell?

  Palisade cell

  
• What is this cell?

  Xylem cell