𝐈𝐈 - 𝐜𝐞𝐥𝐥𝐬 & 𝐜𝐨𝐧𝐭𝐫𝐨𝐥

• what do chromosomes contain?

  genetic information.
• why do multicellular organisms use mitosis?


  growth or to replace cells that have been damaged.
• what happens in interphase?


  duplication of DNA.
• what happens in prophase?


  ~ chromosomes condense.

  ~ membrane around the nucleus breaks down.

  ~ chromosomes lie free in the cytoplasm.
• what happens in metaphase?


  chromosomes line up at the centre of the cell.
• what happens in anaphase?


  ~ spindle fibres pull chromosomes apart.

  ~ chromatids are pulled to opposite ends of the cell.
• what happens in telophase?


  membranes form.
• what happens in cytokinesis?

  cytoplasm and cell membrane divide to produce two daughter cells.
• what is cell differentiation?


  the process by which a cell changes to become specialised for its function.
• what is cell division?

  mitosis.
• what is cell elongation?

  a plant cell expands, making the cell bigger.
• how does growth in animals occur?

  cell division.
• how does growth of height occur in plants?

  cell elongation.
• where does cell division occur in plants?

  meristems, such as roots and shoots.
• what is cancer?

  uncontrolled cell division which results in a mass of abnormal cells, also known as a tumour. if a tumour invades and destroys surrounding tissue, it is also known as cancer.
• what are percentile charts used for?

  monitoring growth.
• what would the 75th percentile on a weight chart mean?

  75% are lighter and 25% are heavier.
• what are undifferentiated cells known as?

  stem cells.
• where are stem cells found in plants?


  meristems.
• where are stem cells found in humans?

  embryos.
• what are the risks of using stem cells?

  ~ tumour development.

  ~ disease transmission.

  ~ rejection by the body.
• what is the ethical issue around using embryonic stem cells?

  each one could be a potential human life.
• what does the central nervous system consist of?

  brain and spinal cord.
• what is a stimulus?

  a change in your environment.
• what are stimuli detected by?

  receptors, such as the eyes or skin.
• what happens when a stimulus is detected?


  the information is converted to a nervous impulse and sent along sensory neurones.
• how do impulses travel through the central nervous system?

  along relay neurones.
• what is the response route?


  stimulus > receptor > sensory neurone > central nervous system > motor neurone > effector > response.
• what are the features of a sensory neurone?

  ~ receptor cells.

  ~ one long dendron.

  ~ one short axon.
• what are the features of a motor neurone?

  ~ many short dendrites.

  ~ myelin sheath.

  ~ one long axon.

  ~ effector cells.
• what are the features of a relay neurone?

  ~ many short dendrites.

  ~ cell body.

  ~ axon.
• what is a myelin sheath?

  an electrical insulator which speeds up an electrical impulse.
• what is a synapse?


  the connection between two neurones.
• what is a reflex?

  an involuntary response to a stimulus.
• why are reflexes faster than normal responses?

  they go through the unconscious part of the brain or the spinal cord.
• what is the reflex arc route?


  stimulus > sensory neurone > relay neurone > spinal cord > motor neurone > muscle contracts.
• how do reflexes protect the eye?

  light receptors make the iris contract leading to the pupil becoming smaller.