P1

• one lifestyle factor that can increase the risk of cardiovascular disease

  smoking and drinking alcohol
• where in a cell would the cystic fibrosis gene be found

  nucleus
• 3 features of the alveoli that help maximise gas exchange

  • cili- increased s.a.
  • once cell thick- smaller diffusion distance
  • maintain conc gradient - good blood supply
• which leaf tissue contains the most chloroplasts

  palisade mesophyll
• the leaf tissue that contains many air spaces is the spongy mesophyll
• the plant tissue that can differentiate throughout the life of the plant is the meristem
• substances that strengthen xylem tissue

  cellulose and lignin
• explain the result for the potato pieces in the 0.6 mol/dm$^3$ salt solution


  the salt solution was more concentrated with salt than the potato so the water from the potato moved out of the potato to the more concentrated (hypertonic) solution by osmosis
• explain why the result for the potato pieces at 1.0 mol/dm$^3$ was different from the result at 0.6 mol/dm$^3$


  the salt conc at 1.0 mol/dm$^3$ was more concentrated so more mass was lost as there is a steeper conc gradient
• suggest why doctors are concerned about antibiotic resistance

  • disease become more common
  • new antibiotics take time and money to develop
  • current/ available antibiotics don't kill certain bacteria
• why does antibiotic B more resistant (has larger white circle around it) than antibiotic Cto the bacterium

  antibiotic B has a larger inhibition zone than C so is more effective
• why is the bacterium not resistant to antibiotic C (has white circle around it in the petri dish)

  antibiotic C has an inhibition zone which means the bacterium cannot spread/ grow further
• suggest why viruses cannot grow on agar

  viruses need to replicate
• why is it difficult for scientists to develop drugs to destroy viruses

  the keep mutating and changing shape
• which disease is caused by a virus that damages wbc

  aids
• why is starch present when tested in the green parts of a leaf and not the white sections

  the green parts of the leaf are filled with chlorophyll and the white parts are not which allows light to photosynthesise and glucose to be turned into starch
• which ion is deficient in a plant with yellow leaves

  magnesium
• give the scientific term that describes the yellow colour of leaves

  chlorosis
• the rate of photosynthesis is affected by different factors

  how could the oxygen produced during photosynthesis be used to measure the rate of photosynthesis?

  rate= amount/ time
• describe a change that occurs in a cell before the cell begins to divide

  • DNA replicates to form 2 copies of each chromosome
  • subcellular structure doubles
• what is involved in preclinical testing of drugs

  testing the drugs on live tissues in a laboratory
• explain why muscle cells have a lot of mitochondria [3]

  • muscle cells need lots of energy for muscle contraction
  • mitochondria is where (aerobic) respiration takes place
  • having many mitochondria increases rate of energy release, muscle cells have high demands during exercise
• explain the effect of temperature on the rate of photosynthesis [3]

  • as rate of temp increases, rate of photosynthesis increases
  • because enzymes involved work faster at higher temps
  • higher temp increases kinetic energy for enzyme- substrate complex to form
• explain how variations in humidity change transpiration rates [4]

  • higher humidity reduces transpiration rate as less water vapour diffuses out
  • lower humidity increases transpiration as steeper conc gradient
  • water vapour conc gradient affects rate of diffusion through stomata
  • plants may close stomata in very low humidity to prevent excessive water loss
  • humidity affects the opening and closing of stomata through guard cell regulation
• explain how water moves through a plant from the roots to the atmosphere. include structures and processes involved [6]

  • water moves through the plant through transpiration
  • root hair cells have large s.a. to absorb water
  • water enters roots through osmosis
  • water is transported up to the stem through the xylem
  • water moves up due to transpiration pull
  • water diffuses into leaves from xylem
  • water evaporates from leaf into air spaces
  • water vapour diffuses out through stomata
  • guard cells control opening and closing of stomata
• explain how a leaky heart valve causes difficulty during exercise. (4/4)

  • valve prevents backflow of blood in the heart
  • leaky valve can cause backflow of blood in heart- cannot correctly pump blood to the lungs or the body
  • so less oxygen to muscles
  • so less aerobic respiration
  • so less energy released
  • so less muscle contraction
  • so anaerobic respiration takes place causing build up of lactic acid and oxygen debt
  • lactic acid causes muscle fatigue- difficulty in exercise
• long-term consequences of persistent valve dysfunction (4/4)

  • heart works harder to pump blood
  • less blood pumped efficiently around the body
  • less oxygen reaches body- breathing issues as oxygen not transported to lungs
  • less aerobic respiration
  • experiences fatigue and tiredness during normal activities
  • reduced exercise ability- less muscle contraction
  • more anaerobic respiration so build up of lactic acid
  • may increase risk of cardiovascular diseases
• which component of the blood carries glucose

  plasma
• explain how the small intestine is adapted to help with nutrient absorption [3]

  • villi provide a large s.a.
  • capillaries are one cell thick fo a shorter diffusion distance
  • small intestine is very long, increasing time for absorption
  • good blood supply to maintain conc gradient
• define double circulatory system

  blood is pumped to lungs by right side and to the body by the left
• explain why having only one ventricle makes the circulatory system less efficient than having 2 ventricles [2]

  oxygenated and deoxygenated blood mixes so less oxygen reaches body/ cells
• tiger salamander has double circulatory system. explain why it may die in water with a low conc of oxygen [3]

  • less steep conc gradient
  • less oxygen diffuses into cells
  • less aerobic respiration so less energy released
• what causes an infection

  • a virus
  • a bacterium
• covid-19 if a virus. explain why antibiotics would not be advised fo treatment [4]

  • caused by a virus not bacteria
  • antibiotics only work on bacterial infections
  • they target bacterial cell structures (e.g cell wall) that viruses don't have
  • viruses replicate inside host cell
  • antibiotic cannot distinguish difference b/w host cells and viruses inside them
• describe 2 ways stem cells could be used in agriculture[2]

  • used to increase crop yield in farming
  • protecting rare species from extinction
• explain the ethical considerations related to stem cell research [4]

  • embryonic stem cells cannot be asked while adults can so are better to use
  • research involves harming/ destroying stem cells
  • ethical concerns as it harms an unborn life
  • some religious groups believe embryos have human rights
• 2 aseptic techniques to use when testing efficacy of antibiotics in a petri dish [2]

  • sterilize equipment before use
  • secure lid of petri dish with tape
• importance of aseptic techniques [3]

  • more accurate results
  • prevent contamination from other microorganisms
  • ensure safety by preventing spread of potentially harmful microorganisms
• explain why a student would be unable to observe cells under a microscope

  • use iodine to stain the sell
  • place slide slowly at an angle ontop the onion cell to avoid bubbles
• explain the advantaaaages of using an electron microscope to view cells [3]

  • it has a higher magnification- able to zoom into cells more
  • higher resolution- clearer image
  • able to see subcellular structures