SB2 - Cells and Controls ✓ Flashcards Preview

Edexcel GCSE Biology (9-1) > SB2 - Cells and Controls ✓ > Flashcards

Flashcards in SB2 - Cells and Controls ✓ Deck (46)
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SB2a - How are tumors formed?

  • When cells mutate, they can become cancer cells.
  • This means that they will divide even when they don't require to divide.


SB2a - How many types of chromosones are in a human cell and what is it called when these are alone or paired up?

  • 23 types of chromosomes.
  • When they are paired up to have 46 chromosomes this is a diploid cell and a haploid cell only has 23 chromosomes.
  • Gametes are haploid cells while all other cells in a human are diploid.


SB2a - Describe stages of mitosis


  • Interphase
    • Copies of the chromosomes are formed in the nucleus
  • Prophase
    • The nucleus starts to break up and spindle fibres appear.
  • Metaphase
    • The chromosomes are lined up on the spindle fibre across the middle of the cell
  • Anaphase
    • The chromosome copies are separated and moved to either side of the cell
  • Telophase
    • A membrane forms around each set of chromosomes to from a nuclei
  • Cytokeniesis
    • Cell surface membrane forms separating the two cells (In plants, a cell wall is also formed)


SB2a - What are the products of mitosis called?

Daughter Cells


SB2a - What type of organisms do not require mitosis to occur?

Unicellular organisms


SB2a - Why does asexual reproduction require mitosis?

  • As asexual reproduction only needs one parent, the offspring will have the same DNA as the parent.
  • As the offspring are clones and their chromosomes are identical, their cells are formed by mitosis.


SB2a - Why is mitosis important in organisms?

  • Asexual Reproduction
  • Growth
  • Repairing damage
  • Cell Replacement


SB2b - Define growth.

The increase in size as a result of an increase in size of or numbers (due to cell division) of cells.


SB2b - How are red blood cells specialised for their purpose?

  • Biconcave shape means more surface area for oxygen diffusion.
  • No nucleus means more space for red haemoglobin molecules and carry more oxygen


SB2b - How is the growth of a baby monitored and how does this work?

Using a percentile growth curve:

  • This graph has many lines showing you how a babies conditions compare to the average.
  • The healthiest position would be at 50% as half of the population is above or below you.
  • Being above 98% or below 2% is reason for concern as only 2% of the population is above or below you.


SB2b - What is cell differentiation?

When a less specialised cell is changed to become a specialised one.


SB2c - How are root hair cells specialised for their function?

  • large vacuole - stores absorbed water
  • long projection - increases area for absorption
  • thin cell - allows minerals to pass easily into the cell by reducing the area they have to transport


SB2c - How are xylem cells specialised for their function?

  • They have thick walls containing lignin, giving the xylem a rigid and strong structure
  • The cells rae dead - so all water carried is transported and not used up by the xylem itself
  •  They have no internal structure at all (nucleus, chloroplasts etc.) this makes it easier to transport water and minerals.


SB2c - What are the meristems?

  • A group of cells near the end of each shoot that allow plants to continue growing throughout their lives.
  • They divide rapidly and the cells are elongated and differentiated.


SB2c - What are the zones of differentiation elongation and cell division?

  • D: Where cells are specialised
  • E: Where cells are elongated (vertically extended)
  • CD: Where rapid mitosis occurs (Meristems)


SB2d - How can stem cells be used to treat leukemia?

  • A patient's bone marrow is destroyed using radiation
  • Adult stem cells are inserted into the patient
  • The stem cells will differentiate specialise and divide to form new blood cells and bone marrow


SB2d - What are the problems with using stem cells in medicine? (6)

  • If stem cells continue to divide, it can cause a cancerous tumour to form
  • Stem cells of one person can be rejected by the immune system of another
  • Embryonic stem cells pose an ethical issue
  • Potential long-term side effects are unknown 
  • Stem cells could be contaminated during the operation, so when transferred into the patient it only makes them sicker


SB2d - What is an embryonic stem cell?

A cell in an early stage embryo that is not specialised and can differentiate to form any type of specialised cell.


SB2d - What the ethical risks of using stem cells? (2)

  1. Embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life
  2. May lead to the reproductive cloning of humans


SB2d - Where can adult stem cells be found and how are they different to embryonic stem cells?

Adult stem cells can be found in most tissues including bone marrow but can only differentiate to cells in the tissue around them .


SB2d - Why don't plants have adult stem cells?

Their cells remain able to differentiate freely throughout their lives.


SB2d - What are the benefits of using stem cells in medicine ? (4)

  1. Treating damage or disease
  2. Treating otherwise untreatable diseases
  3. Growing organs for transplants
  4. Used in scientific research


SB2e - How did Phineas Gage's accident prove what the cerebral coretex is used for?

  • Phineas gage had a metal rod stuck inside his brain
  • It was through his cerebral cortex
  • He was still able to walk, but his personality changed
  • This shows that this part of the cerebral cortex controls emotions and personality but not movement or breathing/heart rate


SB2e - The medulla oblongata controls reflexes. What does this mean about its connections?

It connects the brain to the rest of the CNS


SB2e - What are the three major structures of the brain, and what are each of their functions?

  • Cerebral cortex: Main functions and control such as memories language etc.
  • Cerebellum: Controls balance and movement
  • Medulla oblongata: Controls heart and breathing rate


SB2e - What type of cells is the brain mostly made up of?



SB2e - Why may musicians have larger/more developed cerebellums?

So can develop and have more control over their fine movements and timing coordination


SB2f - During brain surgery, what may be done to investigate roles of the brain?

Probing with electricity (electrodes) means that doctors can control the activity of different parts of the brain


SB2f - How does a CT scan work?

  • A CT scan involves an x-ray beam moving in a circle around the head.
  • It produces images that are slices of the brain.
  • Computers can layer and build these up to produce an image


SB2f - How does a PET scan work?

  • Radioactive glucose is injected into the body.
  • More active cells take in more glucose.
  • The PET scan scans for where the most radioactivity is coming from showing the levels of activity in the brain.