Biology Paper 1

• How are the alveoli specialised to maximise diffusion of O2 and CO2


  enormous surface area

  good blood supply

  very thin walls

  a moist lining
• How are the villi specialised to absorb digested food into the blood more quickly

  increase surface area

  a single layer of surface cells

  a very good blood supply
• what is absorbed in the small intestine

  excess water from the food
• what is produced in the small intestine

  digestive enzymes
• what does the stomach produce 


  protease enzyme pepsin and hydrochloric acid
• what does the pancreas produce

  protease

  amylase

  lipase
• What is active transport 


  movement of particles against a concentration gradient from an area of lower concentration to an area of higher concentration using energy used from respiration
• Examples of active transport 


  root hairs taking in minerals

  taking in glucose from the gut and kidney tubules
• what is transpiration stream


  the movement of water from a plants roots through the xylem and out of the leaves
• what is translocation 


  the movement of dissolved sugars around a plant
• what is transpiration 


  The loss of water from a plant
• What is the structure of the phloem 


  columns of elongated living cells

  transport goes both ways
• What is the structure of the xylem 


  made of dead cells, with no end walls

  strengthened with lignin

  only goes in one direction
• What is the epidermal tissue 


  Covers whole plant, covered with a waxy cuticle
• What is palisade mesophyll tissue 


  where most photosynthesis happens, have lots of chloroplasts
• What is the spongy mesophyll tissue 


  Contains big air spaces for gas diffusion
• What are nitrates needed for

  To make proteins and therefore growth
• What are magnesium ions needed for

  making chlorophyll which is needed for photosynthesis
• Signs of lack of nitrates 


  Stunted growth
• Signs of lack of magnesium ions 


  Yellow leaves and chlorosis
• Signs of plant disease 


  Stunted growth

  spots on leaves

  patches of decay

  discolouration

  malformed stem or leaves

  abnormal growths
• Process of binary fission 


  dna and plasmids replicate

  cell gets bigger and circular dna strands move to opposite ends of cell

  cytoplasm begins to divide and new cell walls are formed

  cytoplasm divides and 2 daughter cells are produced
• What happens in preclinical testing

  Drugs are tested on human cells and tissue, then on live animals to test for efficacy, toxicity and dosage
• What happens in clinical trials pt 1

  Drug is tested on healthy volunteers using a very low dose to test for side effects

  Then tested on patients suffering from the illness to find optimum dose
• What happens in clinical trials pt 2

  Double blind trials- doctor and patients dont know who has received the placebo or drug

  Results arent published until they’ve been peer reviewed
• What is phagocytosis 


  White blood cells engulf and digest pathogens