PRE 2016

• (IMAGE) WHICH ONE OF THE PROCESSES P, Q OR R INVOLVES NITRIFICATION?

  R

  
• (IMAGE) THE DIAGRAM INCLUDES ONE PROCESS IN WHICH MICROORGANISMS ADD AMMONIUM IONS TO SOIL.

  DESCRIBE ANOTHER PROCESS CARRIED OUT BY

  MICROORGANISMS WHICH ADDS AMMONIUM IONS TO SOIL.

  1. protein / amino acids broken down into ammonium ions
  2. by Saprobionts

  
• DENITRIFICATION REQUIRES ANAEROBIC CONDITIONS. PLOUGHING AERATES THE SOIL. EXPLAIN HOW PLOUGHING WOULD AFFECT THE FERTILITY OF THE SOIL.

  1. fertility increased as more nitrate formed
  2. less denitrification as fewer denitrifying bacteria
• ONE FARMING PRACTICE USED TO MAINTAIN HIGH CROP YIELDS IS CROP ROTATION. THIS INVOLVES GROWING A DIFFERENT CROP EACH YEAR IN THE SAME YIELD.

  SUGGEST TWO WAYS IN WHICH CROP ROTATION MAY LEAD TO HIGH CROP YIELDS.

  1. grow crops with nitrogen-fixing bacteria
  2. different crops use different ions from soil
  3. different crops have different pests
• GIVE A BIOLOGICAL MOLECULE THAT CONTAINS:

  1. NITROGEN: amino acid, protein, enzyme, urea, chlorophyll, DNA
  2. PHOSPHORUS: DNA, RNA, ATP, phospholipids, nucleic acid

  
• DESCRIBE THE ROLE OF MICROORGANISMS IN PRODUCING NITRATES FROM THE REMAINS OF DEAD ORGANISMS.

  1. saprobionts break down remains into ammonia
  2. ammonium ions into nitrite and then into nitrate
  3. by nitrifying bacteria - Nitrification
• UPWELLING OFTEN RESULTS IN HIGH PRIMARY PRODUCTIVITY IN COASTAL WATERS. EXPLAIN WHY SOME OF THE MOST PRODUCTIVE FISHING AREAS ARE FOUND IN COASTAL WATERS.

  1. nitrate - phosphate nutrients for growth of plants / producers
  2. more producers / consumers so more fish move to the area with the plants

  
• NITRATE FROM FERTILISER APPLIED TO CROPS MAY ENTER PONDS AND LAKES. EXPLAIN HOW NITRATE MAY CAUSE THE DEATH OF FISH IN FRESHWATER.

  1. growth of algae on surface blocks light from reaching plants
  2. no photosynthesis so plants die
  3. saprobiontic microorganisms
  4. respire anaerobically
  5. so less oxygen for fish to respire
• (IMAGE - NITROGEN CYCLE) NAME PROCESS P and Q

  P = Nitrification

  Q = denitrification

  
• LEGUMINOUS CROP PLANTS HAVE NITROGEN FIXING BACTERIA IN NODULES ON THEIR ROOTS. ON SOILS WITH A LOW CONCENTRATION OF NITRATE IONS, LEGUMINOUS CROPS OFTEN GROW BETTER THAN OTHER TYPES OF CROP. EXPLAIN WHY.

  1. nitrogen to ammonia
  2. produce protein / amino acids / DNA / RNA

  
• APPLYING VERY HIGH CONCENTRATIONS OF FERTILISER TO THE SOIL CAN REDUCE PLANT GROWTH. USE YOUR KNOWLEDGE OF WATER POTENTIAL TO EXPLAIN WHY.

  1. Soil has lower water potential than roots
  2. osmosis from plant to soil

  
• (IMAGE) SUGGEST THE PURPOSE OF EACH OF THE THREE LEAF TREATMENTS

  1. NO GREASE: so that the stomata are open for normal carbon dioxide uptake
  2. GREASE ON LOWER SURFACE: stops carbon dioxide uptake through upper surface / cuticle
  3. GREASE ON BOTH SURFACES: seals stomata which stops all carbon dioxide uptake

  
• (IMAGE) DESCRIBE THE RESULTS SHOWN FOR TREATMENT 1

  1. the mean rate of carbon dioxide uptake was constant but fell after the light was turned off
  2. uptake started to fall at 60 minutes from 4.5 to 0, reaching its lowest at 80 minutes

  
• (IMAGE) THE STOMATA CLOSE WHEN THE LIGHT IS TURNED OFF. EXPLAIN THE ADVANTAGE OF THIS TO THE PLANT.

  1. because water is lost through stomata
  2. so closure prevents water loss
  3. maintaining water content in the cells

  
• (IMAGE) TREATMENT 2 SHOWS THAT EVEN WHEN THE LOWER SURFACE OF THE LEAF IS SEALED THERE IS STILL SOME UPTAKE OF CARBON DIOXIDE.

  SUGGEST HOW THIS UPTAKE OF CARBON DIOXIDE CONTINUES.

  carbon dioxide uptake still continues through the upper surface of the leaf / cuticle

  
• (IMAGE) IN BOTH TREATMENT 1 AND TREATMENT 2, THE UPTAKE OF CARBON DIOXIDE FALLS TO ZERO WHEN THE LIGHT IS TURNED OFF. EXPLAIN WHY.

  1. carbon dioxide isn’t needed for photosynthesis in the dark, instead it’s produced by respiration
  2. so there is no diffusion gradient for carbon dioxide into the leaf and instead out of the leaf because of respiration

  
• (IMAGE) WHAT MEASUREMENTS SHOULD THE STUDENT HAVE TAKEN TO DETERMINE THE RATE OF PHOTOSYNTHESIS?

  Oxygen production and time

  
• (IMAGE) OTHER THAN TEMPERATURE AND PH, GUVE TWO FACTORS WHICH SHOULD BE KEPT CONSTANT DURING THIS INVESTIGATION

  1. intensity of light
  2. species of algae
  3. carbon dioxide concentration
  4. time

  
• (IMAGE) THE STUDENT DID NOT USE A BUFFER TO MAINTAIN THE PH OF THE SOLUTION. EXPLAIN WHAT WOULD HAPPEN TO THE PH OF THE SOLUTION DURING THIS INVESTIGATION.

  1. pH increases
  2. as more carbon dioxide is removed as it’s needed for photosynthesis

  
• (IMAGE) SUGGEST AND EXPLAIN WHY THE RATE OF PHOTOSYNTHESIS WAS LOW BETWEEN 525NM AND 575NM WAVELENGTHS OF LIGHT

  1. these wavelengths of light are more reflected than absorbed
  2. light is needed for the light dependent reaction - photolysis
  3. represents green light / colour of chlorophyll

  
• (IMAGE)

  1. There Is an increase in carbon dioxide due to respiration occurring at night
  2. as there’s no Photosynthesis at night as it occurs in light
  3. rate of photosynthesis is greater than respiration because there’s a greater uptake of carbon dioxide in the light
  4. there’s a decrease in carbon dioxide concentration higher Up and more lower
  5. this is because on the ground there’s less photosynthesis and more respiration as well as microorganisms that produce carbon dioxide

  
• (IMAGE) GIVE TWO FACTORS WHICH COULD BE LIMITING THE RATE OF PHOTOSYNTHESIS IN THE SUN PLANT BETWEEN POINTS A AND B

  1. temperature
  2. Carbon dioxide

  
• (IMAGE) EXPLAIN WHY CARBON DIOXIDE UPTAKE IS A MEASURE OF NET PRODUCTIVITY

  net productivity = (gross) photosynthesis - respiration = shows gross photosynthesis

  
• (IMAGE) USE THE INFORMATION IN THE FIGURE TO EXPLAIN HOW THE SHADE PLANT IS BETTER ADAPTED THAN THE SUN PLANT TO GROWING AT LOW LIGHT INTENSITIES.

  1. The shade plant has a lower rate of respiration as less carbon dioxide is released in the dark at 0 light intensity
  2. there’s a greater net productivity as more sugars

  
• DESCRIBE HOW ACETYLCOENZYME A IS FORMED IN THE LINK REACTION

  1. oxidation of pyruvate means a hydrogen is removed from it and carbon dioxide is released
  2. addition of coenzyme A
• (IMAGE) EXPLAIN HOW OXALOACETATE ENABLES THE ACETYLCOENZYME A TO THEN BIND TO THE ENZYME

  1. the shape of the active site changes, moulding around the substrate
  2. therefore the substrate and active site now become complementary

  
• ANOTHER SUBSTANCE IN THE KREBS CYCLE IS CALLED SUCCINYL COENZYME A. THIS SUBSTANCE HAS A VERY SIMILAR SHAPE TO ACETYLCOENZYME A. SUGGEST HOW PRODUCTION OF SUCCINYL COENZYME A COULD CONTROL THE RATE OF THE REACTION CATALYSED BY CITRATE SYNTHASE

  1. is a competitive inhibitor so attaches to the active site
  2. which prevents enzyme-substrate complexes from forming
• IN MUSCLES, PYRUVATE IS CONVERTED TO LACTATE DURING ANAEROBIC RESPIRATION. EXPLAIN WHY CONVERTING PYRUVATE TO LACTATE ALLOWS THE CONTINUED PRODUCTION OF ATP DURING ANAEROBIC RESPIRATION

  1. oxidises reduced NAD
  2. NAD is used in glycolysis, so it can continue
• IN MUSCLES, SOME OF THE LACTATE IS CONVERTED BACK TO PYRUVATE WHEN THEY ARE WELL SUPPLIED WITH OXYGEN. SUGGEST ONE ADVANTAGE OF THIS

  Pyruvate is used in respiration - lactic acid toxic and can cause muscle fatigue
• (IMAGE) EXPLAIN THE LINE BETWEEN P AND Q

  1. No aerobic respiration / electron transfer / oxidative phosphorylation
  2. Because there’s no respiratory substrate so there’s nothing to respire

  
• (IMAGE) EXPLAIN THE LINE BETWEEN Q AND R

  • oxygen concentration falls because:

  1. Aerobic respiration uses oxygen
  2. oxygen is the terminal electron acceptor
  3. oxygen Combines with protons and electrons to form water

  
• (IMAGE) THE RESPIRATORY SUBSTRATE AND ADP ADDED AFTER 5 MINUTES (Q) WERE PART OF A BUFFERED ISOTONIC SOLUTION. WHAT OTHER SUBSTANCE WOULD THE BUFFER OR SOLUTION HAVE TO CONTAIN?

  phosphate ions / inorganic phosphate

  
• (IMAGE) DESCRIBE AND EXPLAIN THE DIFFERENCE BETWEEN LINE R AND S (ANIMAL MITOCHONDRIA) AND LINE R TO T (PLANT MITOCHONDRIA)

  1. Oxygen Concentration continues to fall in plants But stays constant in animals
  2. oxygen concentration falls more slowly in plants than before cyanide added
  3. because aerobic respiration continues in plant mitochondria
  4. because electron transfer / oxidative phosphorylation continues in plant mitochondria

  
• (IMAGE) FOR THE FIRST 10 MINUTES, THE TAP ATTACHED TO TUBE A WAS LEFT OPEN AND THE SYRINGE FROM TUBE B WAS REMOVED. SUGGEST THREE REASONS WHY THE APPARATUS WAS LEFT FOR 10 MINUTES

  1. equilibrium reached
  2. allow for expansion / pressure change in apparatus
  3. allow respiration rate of seeds to stabilise

  
• (IMAGE) SUGGEST AND EXPLAIN WHY THE CHOSEN TEMPERATURE WAS 20°C FOR THIS EXPERIMENT

  1. Optimum temperature for normal growth of seeds
  2. optimum temperature for enzymes involved in respiration

  
• (IMAGE) DURING THE EXPERIMENT, THE COLOURED LIQUID IN TEH TUBING MOVED TOWARDS TUBE B. EXPLAIN WHAT CAUSED THIS.

  1. oxygen is taken up by the seeds
  2. carbon dioxide that’s being released is absorbed by potassium hydroxide
  3. volume / pressure in B decreases

  
• (IMAGE) EXPLAIN WHY A LAYER OF OIL IS REQUIRED IN THIS INVESTIGATION

  prevents oxygen being absorbed

  
• (IMAGE) SUGGEST WHY THE RATE OF GAS PRODUCTION DECREASED BETWEEN 50 AND 60 MINUTES

  glucose becomes a limiting factor / decreases, increase in ethanol / yeast / cells die / toxins build up

  
• YEAST CAN ALSO RESPIRE ANAEROBICALLY. THE STUDENT REPEATED THE INVESTIGATION WITH A FRESH SAMPLE OF YEAST IN GLUCOSE SOLUTION, BUT WITHOUT THE OIL. ALL OTHER CONDITIONS REMAINED THE SAME. EXPLAIN WHAT WOULD HAPPEN TO THE VOLUME OF GAS IN THE SYRINGE IF THE YEAST WERE ONLY RESPIRING AEROBICALLY

  1. stays relatively the same
  2. same volume of oxygen uptake and carbon dioxide release

  
• RESPIRATION PRODUCES MORE ATP PER MOLECULE OF GLUCOSE IN THE PRESENCE OF OXYGEN THAN IT DOES WHEN OXYGEN IS ABSENT. EXPLAIN WHY

  1. oxygen is the final electron acceptor where it combines with electrons and protons
  2. oxidative phosphorylation / electron transport chain provides most ATP / only glycolysis occurs without oxygen / no Krebs and no link reaction