Biology gcse

• Eukaryotic cells


  Plant and animal cells
• Prokaryotic cells


  Bacteria
• 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
• Prokaryotic cell wall


  Composed of peptidoglycan
• Genetic information storage in prokaryotic cells


  Found free within the cytoplasm as: Chromosomal DNA (single large loop of circular DNA), Plasmid DNA
• Plasmids


  Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA, carry genes that provide genetic advantages e.g. antibiotic resistance
• Centimetre (cm)


  1 x 10-2 metres
• Millimetre (mm)


  1 × 10-3 metres
• Micrometre (µm)


  1 × 10-6 metres
• Nanometre (nm)


  1 x 10-9 metres
• Components of both plant and animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Function of the mitochondria

  Site of later stages of aerobic respiration in which ATP is produced
• Composition of the plant cell wall

  Cellulose
• Function of the plant cell wall

  Provides strength, Prevents the cell bursting when water enters by osmosis
• Contents of the permanent vacuole

  Cell sap (a solution of salts, sugars and organic acids)
• Function of the permanent vacuole

  Supports the cell, maintaining its turgidity
• Function of chloroplasts


  Site of photosynthesis
• Cell cycle


  1. Replication of DNA and synthesis of organelles

  2. Mitosis

  3. Division of cell
• Mitosis


  • Produces identical cells which all have the same genetic information
  • Produces additional cells for growth and repair
• First stage of cell cycle

  Cells grow and increase in mass, replicate DNA and synthesise more organelles (eg. mitochondria, ribosomes)
• Second stage of cell cycle

  Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides
• Third stage of cell cycle

  The cytoplasm and cell membrane divide - two identical daughter cells are produced
• Why do scientists use a large set of data when conducting a scientific experiment, e.g. why do something 1000 times and not 10 times

  To calculate a more valid mean  

  OR  

  To reduce the effect of anomalies on the mean  

  OR  

  To calculate a more accurate mean  
• Explain how the production of thyroxine causes an increase in body temperature. 


  .Thyroxine is a hormone that increases your metabolic rate  

  Respiration is a metabolic reaction  

  Respiration releases energy  

  Respiration is exothermic  
• Why do scientists often present their results as percentages?  

  To allow for a comparison to be made 
• Describe how carbon and nitrogen in compounds in the leaves are recycled and used by living trees (6).

  bacteria decay large molecules, respiration releases co2 into the air, co2 is taken in by stomata, co2 used in photosynthesis makes glucose, release of nitrates into soil taken in by roots by active transport, nitrates make proteins
• Label the nerve cell

  Nerve cell:

  A) nucleus

  B) cell body

  C) axon

  D) dendrites

  E) myelin sheath for insulation

  F) synapse

  
• label the sperm cell

  Sperm Cell:

  A) middle section

  B) acrosome

  C) nucleus

  D) tail

  
• label the root hair cell

  Root Hair cell:

  A) nucleus

  B) root hair

  C) large permanent vacuole

  D) mitochondria

  
• Label the plant cell

  Plant Cell:

  A) cell membrane

  B) cellulose cell wall

  C) cytoplasm

  D) permanent vacuole

  E) chloroplasts

  F) nucleus

  
• Label Xylem cell

  Xylem Cell:

  A) hollow tube of xylem

  B) cell walls

  C) lignin spirals

  D) vessels

  
• Label the Phloem Cell

  Phloem Cell:

  A) sieve plates

  B) phloem vessel

  C) mitochondria

  D) companion cells

  E) phloem

  
• Why is it dangerous for the duct leading from the pancreas to the small intestine to be blocked?

  fewer (digestive) enzymes enter small intestine • enzymes break down / digest less food • less absorption of nutrients • less glucose can enter the blood stream •less glucose available for respiration • less absorption of nutrients so fewer amino acids can enter the blood stream, less protein is made for growth
• Why is it dangerous to block the tubes leading to the alveoli in the lungs?

  less oxygen enters blood(stream) / reaches cells / organs / tissues (ignore body / lungs) • (so) less (oxygen) available for (aerobic) respiration • (so) less energy released / available (for growth) do not accept energy produced
• Exam question: Describe how the median age of a group of people can be determined. 


  put ages in (ascending / descending / chronological) order find middle value
• Exam question: Describe how scientists may use stem cells to create healthy lungs that are not rejected by CF patient. 


  take stem cells from patient (bone marrow / skin) remove / change / fix the faulty / CF gene create embryo using these stem cells remove stem cells (from embryo) and stimulate / allow them to divide / differentiate into lung (cells)
• Describe how the human body: • prevents pathogens from entering


  skin • tough / dry / dead outer layer • skin acts as a barrier • sebum / oil on (surface of) skin • sebum / oil repels pathogens • scabs form over cuts or scabs form a barrier • platelets are involved in forming clots / scab stomach • contains (hydrochloric) acid • (HCl) kills bacteria • in food or in swallowed mucus eyes • produce tears • contains enzymes to kill bacteria • tears are antiseptic breathing system • trachea / bronchi / nose produce mucus • mucus is sticky • (mucus) traps bacteria • (mucus) carried away by cilia
• Describe how the human body: • defends itself against pathogens inside the body


  • immune system / white blood cells (WBCs) • WBCs engulf pathogens • antitoxins are produced • (antitoxins) neutralise toxins / poisons (produced by pathogen) • antibodies are produced • (antibodies) help destroy pathogens • memory cells (are formed) • (memory cells give a) more rapid response if pathogen re-enters
• RP3 Osmosis steps: p1

  . 1. Peel a potato or other suitable vegetable (CAN BE CARROT)

  2. Use a cork borer to produce multiple cylinders of potato

  3. place them onto a tile and, using a sharp knife, trim them all to the same length

  4. Measure the mass, using an electronic balance and record mass in g.

  5. Place each cylinder in a test tube and add varying concentrations of salt OR SUGAR solution, label the beaker by their concentrations (e.g 0.0, 0.2 etc)
• RP3 osmosis P2


  .. 6. put covers over beakers and Leave the potatoes overnight

  7. Remove each cylinder and gently roll it onto paper to reduce surface water

  8. Measure the mass of each cylinder and record in g. 9. calculate the percentage change in mass by dividing the changing in mass with the starting mass and then multiplying by 100. 10. plot graph, where the change in mass is 0% that is the concentration inside the potato.