biology paper1

• magnification

  magnification=image/actual

  1cm=10mm

  1mm=1000um

  1um=1000nm
• cell specialisation

  sperm cells=long tail to swim faster/enzymes in head to break shell/lots of mitochondria for energy

  nerve cells=long thin axon allows nerves to travel

  muscle cells=full of mitochondria to provide energy

  root hair cells=long thin hair to increase SA to increase water taken
• bacterial reproduction

  bacteria reproduce by binary fission. this is where the bacteria doubles in size then divides into 2

  bacteria can grow in a nutrient broth or agar plate
• aseptic techniques

  • sterilise petri dish
  • sterilise inoculation loop by passing through flame
  • secure the lid of the petri dish with tape and store upside down
  • not kept above 25 degrees
• mitosis process

  1. chromosones pulled too each end of the cell and nucleus divides
  2. the cytoplasm divides
  3. cell membrane divides
  4. forms 2 identical daughter cells
• therapeutic cloning 


  an embryo is produced with same genes as patient. stem cells from the embryo are not rejected by the human body

  • advantages- no rejection/no waiting time
  • disadvantages- transfer of viral infection/ethical objections
  • stem cells from meristems can be used to clone plants
• diffusion

  • movement of particles from high to low
  • gas exchange and waste products from kidneys
  • conc difference increases - increased diffusion
  • temp increase - kinetic energy - move faster - more diffusion
  • surface area increase - more diffusion
• osmosis

  movement of water from high-low conc through partially permeable membrane

  when water moves into cell it swells and becomes turgid

  • animal cells swell until they burst
  • when water moves out they become shrivelled
  • $percentage change=$$change/original x100$
• active transport

  • moves substances from low-high conc
  • plants-root hair cells need mineral ions for growth, high conc of ions inside cell, so ions need to move out of the dilute soil to concentrated cell USES ENERGY
• enzymes

  1. amylase - salivary gland / pancreas - carbs - sugars
  2. protease - stomach / pancreas - protein - amino acids
  3. lipases - pancreas - lipids - fatty acids and glycerol
• bile

  • made by the liver
  • secreted by gall bladder
  • goes into small intestine to help digestion of lipids
  • emulsifies fats so lipids have greater area to work
  • bile is an alkaline- neutralises stomach acid
  • enzyme works best at slightly alkaline pH
• enzymes 


  temperature

  • below optimum-less kinetic energy so enzyme and substrate move slower so less collisions. Rate of reaction decreases
  • above optimum-breaks hydrogen bonds in structure. enzymes active site changes shape so denatures
• gas exchange


  oxygen diffuses from alveoli into blood and CO2 diffuses from blood into alveoli

  adaptations

  • many alveoli- increased SA
• blood vessels

  artery=thick muscle // small lumen // high pressure

  vein=thin walls // wide lumen // has valves

  capillary=1 cell wall thick // low pressure

  $rate of blood flow=$$distance travelled/time$
• red blood cells

  • no nucleus- more room for haemoglobin
  • bioconcave-to increase SA for diffusion
  • packed with haemoglobin to carry oxygen
• white blood cells

  • lymphocytes- attacks specific pathogens and produce antibodies / they attach to pathogens and prevent them from entering cells / can also attach to toxins to act as antitoxins
  • phagocytes - can change shape to engulf pathogen. extend cell membrane around pathogen. pathogen then enters the phagocyte and digested by enzymes= phagocytosis
• coronary heart disease

  Causes: build up of fatty deposits and cholesterol and arteries / makes them narrower and reduces flow of blood

  symptoms: angina // heart failure // heart attack

  treatments:

  stent= small tube to hold artery open

  statins= medication to reduce blood cholesterol

  mechanical valves / transplanted heart / artificial heart
• the leaf

  • plant organ
  • lower epidermal contains guard cells
  • control the opening and closing of stomata
  • where Co2 and H20 enter and exit leaf
• xylem

  • transports water and mineral ions
  • tubes of continuous hollow dead cells
  • do not contain cytoplasm
  • strengthened by lignin
  • transipiration stream- unidirectional
• human defence system

  1. skin-physical barrier / scabs / sweat inhibits pathogens
  2. nose-small hairs and mucus traps particles
  3. tracheal bronchi-mucus traps pathogens and is moved up to the throat by small hairs called cillia
  4. stomach - HCL and protease enzymes in stomach kill pathogens
• drug testing

  1. preclinical testing=test on cells in labs- toxicity
  2. clinical trials=low dosage given to healthy volenteers
  3. clincal trials=different dosage given to healthy volenteers to find optimum dosage
  4. wider clincal=drug given to patients with disease- efficacy
  5. blind trial=some patients given drug, some patients given placebo to test bias
  6. double blind trial=neither scientist or patient know who has drug or placebo-avoid bias
  7. peer review= other scientists working in field review work to check it is valid and reliable
• plant diseases

  • nitrate deficiency- stunted growth-needed to make amino acids which make proteins and are used for growth
  • TMV - brown mosaic patches on leaves / stunted growth
  • Rose black spot - spots on leaves / leaves fall off
  • magnesium deficiency - yellow leaves
  • lack of chlorophyll, so less photosynthesis, so less glucose meaning less respiration so less energy therefore less amino acids and less proteins made SO NO GROWTH
• plant defences 


  physical defence=waxy cuticle will stop microorganisms entering. cell wall contains cellulose which makes it strong so cannot be pierced by microorganisms. bark provides rough layer to prevent entering pathogens

  chemical defence=stinging nettles have poison to stop being eaten. witchhazel chemical kills bacteria

  mechanical defence=thorns and hairs to detect herbivores. venus fly trap. mimicry- yellow spots look like butterfly eggs so they wont lay them
• photosynthesis practical

  1. light intensity= increasing amount of bubbles until levels off. more light energy to react with co2 and water
  2. temperature= increasing temp to 35 increases rate then decreases. provides particles with more kinetic energy so move more
  3. availability of CO2=increases then levels off rate, more to react with water $rate of photosynthesis=$$volume of oxygen/time$
• uses of glucose

  Starch

  Cellulose

  Amino acids

  Respiration

  Fats
• phloem

  • transports sugars from leaves to roots
  • made of living cells with pores in end walls
  • do not have a cytoplasm
  • do not contain lignin
  • called translocation- bidirectional
• respiration

  • aerobic respiration-uses oxygen-in cytoplasm and mitochondria-releases lots of energy
  • $glucose+$$oxygen -> carbon dioxide +$$water$
  • anerobic respiration-without oxygen-only in cytoplasm-when exercising. lactic acid builds up in muscle cells causing fatigue and cramp. this is broken down using oxygen after exercise is finished- oxygen debt
  • $glucose -> lactic acid$
• fermentation


  plant and yeast cells using anerobic respiration

  $glucose -> ethanol +$$carbon dioxide$

  • carbon dioxide causes bread and cakes to rise
  • ethanol makes beer/wine/spirits
• response to exercise

  • during exercise respiration must increase
  • an increase in heart rate so blood flows to cell faster
  • an increase in breathing rate so blood is oxygenated faster
  • increase in breath volume to take in more oxygen