Bio paper 1

• Figure 1

  shows animal cells.Some of the cells are dividing by mitosis for growth and repair.1/4

  
• Describe the process of cell division by mitosis.


  after DNA replication one set of chromosomes is pulled toeach end of the cell

  nucleus divides

  cytoplasmorcell membrane divides to form two cells
• Describe how mitosis produces two genetically identical cells.


  genetic material / DNA / is doubled / replicated

  
  

  each set of chromosomes are pulled to the poles of the cell

  the nucleus divides

  
  

  cytoplasm divides

  
  

  cell membrane divides to form two cells

  
  

  the set of chromosomes in each new cell are identical (to one another)
• Purpose of mitosis


  Growth and Repair
• Name the type of cell division used by bacteria


  Binary fission
• Suggest why the number of cells levels out at


  Q.shortage of nutrients / oxygen

  
  

  so cells die

  
• A cell divides to form two new cells every 24 hours.

  How many days will it take for the original cell to divide into 8 cells?

  3See an expert-written answer!We have an expert-written solution to this problem!
• One of these cell with 10 chromosomes divides by mitosis to produce two new cells.

  How many chromosomes will each new cell contain after mitosis?

  10
• Give why u might not take stem cells from embryo


  .• unethical

  • (against) religious / cultural / personal beliefs

  • the method is not (fully) tested

  • risk of infection

  • (heart cells) may be rejectedSee an expert-written answer!We have an expert-written solution to this problem!
• What is the name of the type of cell division that produces sperm cells?


  Meiosis
• Describe the cell cycle


  (stage 1)DNA / chromosomes replicate / duplicate

  mitochondria / ribosomes / sub-cellular structures increase in number

  (stage 2)one set of chromosomes is pulled / moved to each end of the cell

  (stage 3)the cytoplasmandcell membrane divides (to form two cells)
• Describe

  threedifferences between the processes of mitosis and meiosis.answers must be comparative

  • mitosis produces two (daughter) cells but meiosis produces four (daughter) cells

  
  

  • one cell division in mitosis but two cell divisions in meiosis

  
  

  • mitosis produces cells with two of each chromosome, but meiosis produces cells with one of each chromosome

  
  

  • mitosis produces genetically identical cells, but meiosis produced genetically different cells
• Complete the table

  
• Describe

  onesimilarity between the processes of mitosis and meiosis.• DNA doubles / copies / replicates (once)

  
  

  • increase in the number of mitochondria / ribosomes / sub-cellular structures
• Which cell is

  notdividing by mitosisC

  
• Cell

  EinFigure 2contains 8 chromosomes.CellEdivides by mitosis.How many chromosomes will each new cell contain?8

  
• What is a stem cell?


  an undifferentiated / unspecialised cell

  
  

  that can differentiate / become / change into (many) other cell types
• Name stem cells in plants


  Meristem
• Where is meristem tissue found?


  Growing regions of a plant (roots and shoots)
• Stem cells are cells which have

  notyet been specialised to carry out a particular job.Bone marrow cells are one example of stem cells.

  Explain how a transplant of bone marrow cells can help to treat medical conditions.(bone marrow) cells differentiate into many other types of cell

  (so) will cure diseases where new cells are neededorwill cure diseases where cells are damagedSee an expert-written answer!We have an expert-written solution to this problem!
• Name the process by which stem cells form specialised cells.


  Differentiation
• Name

  onemedical condition that could be treated using heart cells created from an embryo.cardiovascular disease / CVD

  
  

  (coronary) heart disease / CHDSee an expert-written answer!We have an expert-written solution to this problem!
• Give

  oneway a malignant tumour differs from a benign tumour.(malignant tumours) invade / spread to other tissues via the blood (benign don’t)or(malignant tumours) form secondary tumours in other organs
• What causes the formation of a tumour?


  Uncontrolled cell division
• How are cancer cells different?


  Abnormal shape

  
  

  Divide uncontrollably
• Evaluate the use of stem cells from a patient's own bone marrow instead of stem cells from an embryo.

  Give a conclusion to your answer.

  embryos advantages• can create many embryos in a lab• painless technique• can treat many diseases / stem cells are pluripotent / can become any type of cell (whereas bone marrow can treat a limited number)embryos disadvantages• harm / death to embryo• embryo rights / embryo cannot consent• unreliable technique / may not workbone marrow advantages• no ethical issues / patient can give permission• can treatsomediseases• procedure is (relatively) safe / doesn’t kill donor• tried and tested / reliable technique• patients recover quickly from procedurebone marrow disadvantages• risk of infection from procedure• can only treat a few diseases• procedure can be painfulboth procedures advantagecan treat the disease / problemboth procedures disadvantages• risk of transfer of viral infection• some stem cells can grow out of control / become cancerous
• Suggest why it is ethically more acceptable to take stem cells from an umbilical cord instead of using stem cells from a 4-day-old embryo produced by In Vitro Fertilisation (IVF).

  4-day embryo is a (potential) human life

  
  

  destroying/damaging (potential) human life
• Why would it

  notbe possible to treat a genetic disorder in a child using his own umbilical cord stem cells?stem cells have same faulty gene
• What is meant by the term diffusion?


  movement / spreading out of molecules / particles

  from (an area of) high(er) concentration to (an area of) low(er) concentration
• Calculate value

  Xin the table above.3

  
• Name substances that can diffuse into cells


  • oxygen

  • carbon dioxide

  • glucose / sugar

  • water

  • ions / minerals / salts
• Earthworms have a large surface area to volume ratio.

  Suggest why a large surface area to volume ratio is an advantage to an earthworm.

  (earthworm) can absorb more oxygen (in a given time)orincreases / more gas exchange
• What is osmosis?


  • water moves through a partially permeable membrane

  • from dilute to (more) concentrated solution through a semi permeable membrane

  • (it's a) passive (process)
• Suggest

  twofactors that affect the rate of diffusion• concentration gradient

  • surface area

  • thickness of exchange surface

  • presence of a blood / circulatory system

  • temperature (of surroundings)
• When placed into a beaker of water:


  • a red blood cell bursts• a plant cell doesnotburst.Explain why the red blood cell bursts but the plant cell doesnotburst.water enters (the cells) by osmosis / diffusion

  plant cell has a cell wall (which prevents it from bursting)See an expert-written answer!We have an expert-written solution to this problem!
• Describe a method to investigate osmosis in potatoes.


  1. Cut three pieces of potato of the same size.

  2. Record the mass of each potato piece.

  3. Add 150 cm3 of 0.4 mol/dm3 salt solution to a beaker.

  4. Place each potato piece into the beaker.

  5. After 30 minutes, remove each potato piece and dry the surface with a paper towel.

  6. Record the mass of each potato piece.

  7. Repeat steps 1 to 6 using different concentrations of salt solution.
• Explain why the potato pieces in the high salt concentration increased in mass.


  mass increased because water entered by osmosis

  
  

  from a dilute solution in the beaker to a more concentrated solution in the plant cells

  
  

  through a partially permeable membrane
• Explain why the potato pieces in the low salt concentration decreased in mass.


  watermoves out of cells / potato

  by osmosis

  because the solution in the cells / potato is less concentrated than outside
• What is the independent variable in the investigation?


  Concentrations of salt solution.
• Why did the student dry the surface of each potato piece with a paper towel in step


  5?To make sureonlythe potato mass was measuredallow (to) removeexcesswater / solution / liquid