Biology paper 1

• Veins 


  Carry blood into the heart

  Thin walls- large lumen

  Contains valves - prevents blood backflow

  Blood travels at low pressure
• Artery 


  Carries blood away from the heart

  Thick walls- Small lumen

  No valves

  Blood travels at high pressure
• Capillaries 


  Connect arteries to veins

  Walls are one cell thick

  Walls are permeable - For better diffusion of substances
• Explain why TMV causes restricted growth in plants 


  Less chlorophyll so less photosynthesis

  So less glucose produced

  So less energy released for growth as glucose is needed for respiration

  Less proteins/ cellulose for growth as glucose is needed for making these
• Equation for photosynthesis 


  Carbon dioxide + Water ——> Glucose + oxygen

  6CO2 +6H2O——> C6H12O6 + 6O2
• How is glucose from photosynthesis used

  Starch

  Cellulose

  Amino acids

  Respiration

  Fats
• Anaerobic respiration 


  In animals - Glucose —> Lactic acid

  In animals - Glucose —> Ethanol + Carbon dioxide
• Phloem Cell adaptions 


  Function - transport sugars and nutrients around plant

  Adaptions - sieve plates- allows sugar and amino acids to flow easily

  Made of living cells which are supported by companion cells
• Adaptations of lungs for gas exchange

  Alveoli provide large surface area for gas exchange

  Walls of alveoli are thin - decreasing diffusion path

  Alveoli have a good blood supply ensuring steep concentration gradient
• Xylem adaptations 


  Function- Transport water and mineral ions up the plant from roots to shoots

  Adaptations- No top or bottom walls so it forms continuous hollow tubes which water is drawn upwards

  Outer walls thickened by lignin, strengthening tubes, supporting plant

  Cells are dead, no organelles, allow free passage of water
• Root hair cell adaptations

  Function - absorption of water and mineral ions from soil

  • Adaptations -root hair increases surface area so rate of osmosis is greater
  • Thinner walls - shorter diffusion distance
  • Mitochondria for active transport
  • No chloroplasts
• Nerve cell adaptations 


  Function- conduction of impulses

  Adaptations - Long axon - carries messages over long distances

  Axon covered with fatty sheath - speeds up nerve impulses

  Dendrites - allow neurone to communicate with other nerve cells
• Sperm cell

  Adaptations - Many mitochondria for energy to swim towards eggs

  Acrosome in the head contains contains digestive enzymes which breaks down outer membrane of egg

  Head contains nucleus

  Function - Reproduction - Carry male DNA to egg
• Muscle cell adaptations 


  Contain filaments of protein that slide over each other to cause muscle contraction

  They can contain many well developed mitochondria to provide energy for muscle contraction
• How does the body protect against pathogens

  Non Specific human defence :

  • Skin - Acts as a physical barrier
  • Nose - Has internal hairs which act as a physical barrier to infection
  • Stomach - hydrochloric acid kills pathogens that have been caught in mucus or food/water (chemical barrier)

  Immune system :

  • phagocytes - engulfs pathogens to destroy pathogens
  • Lymphocytes - produce antibodies to destroy pathogens
• Enzyme experiment


  1. Place one drop of iodine solution into each well of a spotting tile

  2. Take 3 test tubes add 2 cm*3 of starch solution, amylase solution and pH 5 buffer solution

  3. Place all 3 tubes into a water bath at 30 degrees c. Leave them for 10 mins to allow solutions to reach correct temp

  4. Now combine the 3 solutions into 1 test tube and mix. Return to the water bath and start a stopwatch

  5. After 30 secs use stirring rod to transfer one drop of solution to a well in spotting tile. Iodine should turn blue black

  6. We now take a sample every 30 secs until iodine remains orange, this means there's no more starch present, reaction is complete

  7. Record the time for this

  8. Repeat experiment with different pH buffers
• Only taking samples every 30 secs - This means we only have an approximate time for the reaction to complete - could shorten the time
• Food tests 


  Iodine for starch :

  • Colour of reagent -orange/brown
  • Positive test - blue/black

  Benedicts for sugar :

  • Colour of reagent - light blue
  • Positive test - green to brick red

  Biuret test for protein :

  • Colour of reagent - blue
  • positive test - lilac

  Sudan III test for lipids :

  • positive test - red layer forms on the surface of the water
• Osmosis practical

  1. Use cork borer to cut5 potato cylinders - trim them to same length
  2. accurately measure and record the length and mass of each cylinder
  3. Measure 10cm3 of the 1.0M sugar solution and transfer to first boiling tube
  4. Repeat step 3 for other concentrations of the solution and distilled water
  5. Add one potato cylinder to each boiling tube
  6. Leave cylinders in boiling tubes overnight in a test tube rack
  7. Remove cylinders from boiling tubes and carefully blot them dry with paper towels
  8. Measure length and mass of each cylinder
  9. calculate percentage change for each cylinder
• Xylem


  Transports water and dissolved mineral ions from roots to leaves
• Phloem


  Transports dissolved sugars produced by photosynthesis from leaves to rest of plant
• Translocation


  Movement of sugars through phloem tissue
• Meristem tissue


  Contains stem cells that can differentiate into different plant tissues, found in growing tips
• Plasma 


  Liquid

  Carries ions, glucose, carbon dioxide
• Red blood cells


  Contains haemoglobin

  carries oxygen

  no nucleus

  biconcave
• White blood cells 


  Phagocytes - engulfs pathogens

  Lymphocyte - produces antibodies and antitoxins
• Platelets 


  Bits of dead cells

  responsible for blood clotting
• Epidermis tissue 


  Layer of tissue that encases the entire plant, protecting against infection and keeping it healthy
• Palisade Mesophyll 


  Where photosynthetic activity takes place

  At the top of the cell

  Contains lots of chloroplasts
• Mesophyll tissue 


  Spongy, large air pockets which facilitate gas exchange
• Meristem 


  Located in shoots and roots

  Plant stem cell

  Enables growth and development
• Guard cells 


  Controls water loss

  opens and closes stomata based on water availability
• Stomata 


  Regulates gas exchange between plant and environment
• Upper epidermis 


  Allows light through

  Transparent
• Waxy cuticle 


  Reduces water loss by preventing evaporation
• Lower epidermis 


  Allows carbon dioxide to enter the leaf

  Allow oxygen and excess water to leave
• Microscopy practical

  1. Peel off epidermal layer on onion using forceps
  2. put on microscope slide, add drop of water
  3. Add 2 drops of iodine solution to stain the cells
  4. Place cover slip on at an angle to make sure there are no air bubbles
  5. Place slide on stage
  6. Turn nosepiece to low power objective
  7. Use coarse adjustment knob to raise the stage until cover slip touches objective
  8. Look into eyepiece and turn fine adjustment knob until image comes into focus
• Microbiology practical

  1. Spray bench with disinfectant then wipe with paper towel
  2. On bottom of agar gel plate mark with permanent marker : 3 segments, a dot in middle of each segment, your initials, date, name and name of bacteria
  3. .Wash your hands with antibacterial handwash
  4. Place different antiseptics onto different filter paper discs
  5. Lift lid of agar gel plate carefully and use forceps to place each filter paper disc onto dots. Note down the antiseptic applied
  6. Tape lid onto agar gel plate securely but loosely enough for oxygen to reach the bacteria.
• Microbiology practical 


  6. Place agar gel plate in incubator at 25 degrees for 48 hours

  7. Measure diameter of the clear zones after 48 hours, calculate a mean

  8. Dont remove lid when measuring

  9. Area of clear zones can be calculated using formula area of a circle
• Explain the effect of a partly blocked coronary artery on the human body (6 marks)

  Less blood containing oxygen and glucose flows to heart muscle

  So heart cells aerobically respire less and respire anaerobically more

  So less energy released and lactic acid is produced

  So muscle contraction is less efficient and less blood is pumped around the body

  So body cells respire aerobically less

  So muscles become fatigued and person gets tired/ breathless