Cell biology

• What re the differences between eukaryotic and prokaryotic cells?

  Prokaryotic cells are much smaller than eukaryotic cells. Eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, while prokaryotes do not
• What is the prokaryotic cell wall composed of?

  Peptidoglycan.
• What are plasmids?

  small circular- contain dna
• What is order of magnitude?

  A power to the base 10 used to quantify and compare size.
• What is a centimetre?

  1 x 10-2 metres
• What is a millimetre (mm)?

  1 × 10-3 metres
• What is a micrometre (um)

  1 × 10-6 metres
• What is a nanometre (nm)?

  1 × 10-9 metres
• What is the difference in order of magnitude between a human hair (100 µm) and the HIV virus (length = 100 nm)?

  100 µm = 10-4 m

  100 nm = 10-7 m

  -4-(-7) = -4 + 7 = 3
• List the components of both plant and animal cells?

  ● Nucleus

  ● Cytoplasm

  ● Cell membrane

  ● Mitochondria

  ● Ribosomes
• List the additional cell components found in plant cells (3)?

  • Chloroplasts
  • Permanent vacuole
  • cell wall
• Other than storing genetic information what is the function of the nucleus?

  Controls cellular activities
• Describe the structure of cytoplasm?

  ● Fluid component of the cell.

  ● Contains organelles, enzymes and dissolved ions and nutrients.
• What is the function of cytoplasm?

  Site of cellular reactions e.g. first stage of respiration. Transport medium.
• What is the function of the cell membrane?

  Controls the entry and exit of materials into and out of the cells
• What is the function of the mitochondria?

  Site of later stages of aerobic respiration in which ATP is produced.
• What is the function of the ribosomes?


  Joins amino acids in a specific order during translation for the synthesis of proteins.
• What is the plant cell wall made of?

  Cellulose
• What is the function of the plant cell wall

  ● Provides strength.

  ● Prevents the cell bursting when water enters by osmosis.
• What does the permanent vacuole contain?

  Cell sap
• What is the function of the permanent vacuole?

  Supports the cell, maintaining its turgidity
• What is the function of chloroplasts?

  Site of photosynthesis
• Describe how sperm cells in animals are adapted to their function

  ● Haploid nucleus contains genetic information.

  ● Tail enables movement.

  ● Mitochondria provide energy for tail movement.

  ● Acrosome contains enzymes that digest the egg cell membrane.
• Describe how nerve cells in animals are adapted to their function

  ● Long axon allows electrical impulses to be transmitted all over the body from the central nervous system.

  ● Dendrites from the cell body connect to and receive impulses from other nerve cells, muscles and glands.

  ● Myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell.
• Describe how muscle cells in animals are adapted to their function

  ● Arrangement of protein filaments allows them to slide over each other to produce muscle contraction.

  ● Mitochondria to provide energy for muscle contraction.

  ● Merged cells in skeletal muscle allow muscle fibre contraction in unison.
• Describe how root hair cells are adapted to their function

  ● Large surface area to absorb nutrients and water from surrounding soil.

  ● Thin walls that do not restrict water absorption.
• Decribe how xylem cells in plants are adapted to their function

  ● No upper or lower margins between cells to provide a continuous route for water to flow.

  ● Thick, woody side walls strengthen their structure and prevent collapse.
• Describe how phloem cells in plants are adapted to their functions

  ● Sieve plates let dissolved amino acids and sugars be transported up and down the stem.

  ● Companion cells provide energy needed for active transport of substances along the phloem.
• What is cell differentiation?

  The process by which cells become specialised
• Why is cell differentiation important?

  Allows production of different tissues and organs that perform various vital functions in the human body
• at what point in their life cycle do most animal cells differentiate?

  Early in their life cycle
• For how long do plant cells retain the ability to differentiate?

  Throughout their entire life cycle
• What is the purpose of cell division in mature animals?

  Repair and replacement of cells
• What changes does a cell go through as it differentiates?

  Becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell
• Define magnification?


  The number of times bigger an image appears compared to the size of the real object
• Define resolution 


  The smallest distance between two objects that can be distinguished
• How does a light microscope work?

  Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.
• What are the advantages of a light microscope?

  ● Inexpensive

  ● Easy to use

  ● Portable

  ● Observe both dead and living specimens
• What is the disadvantage of light microscopes?

  Limited resolution.
• How does an electron microscope work?

  It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.