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2012-12-14 13:57:21

2012 Jan And Old Papers
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  1. Explain What Is Meant By Facilitated Diffusion
    Movement Of Substances Down A Concentration Gradient

    Through Either A Channel Or Carrier Protein
  2. Explain What Is Meant By Osmosis
    Movement of water molecules from higher to lower water potentialdown a water potential gradient

    Across partially permeable membrane
  3. Explain Ways In Which The Structure Of The Leaf of a dicotyledonous plant is adapted for gaseous exchange.
    • Thin So There Is A short diffusion pathways
    • Many stomata providing a Large surface area for gas and so gases do not have to pass through cells to reach mesophyll
    • Air spaces in mesophyll to allow faster diffusion 
  4. Give The Function Of Each Organelle Below

    Mitochondrion   -  Aerobic Respiration To Produce ATP

    Rough Endoplasmic Reticulum   -   Protein Synthesis

    Smooth Endoplasmic Reticulum   -    Transport Of Proteins/Lipids + Production Of Lipids

    Golgi Body    -     Modifying And Packaging Proteins
  5. Explain one way in which a palisade cell is adapted for photosynthesis
    • Many chloroplasts  to trap or absorb light energy
    • Elongated cells for maximum light absorption and light penetration
    • Chloroplasts move  to trap or absorb more light energy
    • Rangeof pigments can absorb a range of wavelengths and colours for max light absorption
    • Large Surface Area. for rapid CO2  absorption
  6. Give one function of the cell wall.
    • protection
    • maintain shape 
    • preven tlysis
    • strength
    • support
  7. Name two structures present in eukaryotic cells that are not present in the cells of prokaryotes.
    Nucleus With Nuclear Envelope

    Mitochondria / chloroplasts / SER / RER/  Golgi apparatus / linear DNA / chromosomes / lysosomes / vacuole / vesicles / cellulose cell wall
  8. Give one similarity in the way in which active transport and facilitated diffusion transport substances across the membrane.
    involves carrier proteins
  9. Give one way in which active transport differs from facilitated diffusion
    Requires energy/requires use of ATP

    Moves substances  against a concentration gradient
  10. Explain how three features of a plasma membrane are adapted it for its functions
    Phospholipid bilayer forms a barrier to water soluble / charged substances and allows non-polar substances to pass whichalso maintains a different environment on each side  -compartmentalisation

    Bilayer is fluid; can bend to take up different shapes for phagocytosis

    Channel proteins to let water soluble/charged substances through in facilitated diffusion;

    Carrier proteins allow facilitated diffusion / active transport;

    Glycoproteins / glycolipids for cell recognition / act as antigens / receptors; 
  11. Explain how the inner membrane is adapted to its function in Mitochondria
    Increased Surface Area For Respiration Enzymes
  12. Give one feature of a prokaryotic cell that is not found in an eukaryotic cell.
    • Plasmid
    • Capsule
    • smaller ribosomes
    • complex cell wall
    • mesosome
  13. Describe and explain how water in the mesophyll cells passes out of the leaf In The Appoplast Pathway
    • Pathway from cells along cell walls / through spaces and out through stomata by diffusion
    • Down a Water Potential / diffusion / concentration gradient
  14. Explain how two adaptations of their leaves reduce water loss from xerophytes
    Sunken stomata, reduce air movement/diffusion gradient;

    Rolled leaves reduce surface area for evaporation / encloses still air around stomata;

    Waxy cuticle, reduce cuticular evaporation /impermeable to water

    Few stomata, to reduce SA for diffusion

    Small leaves reduce SA for diffusion
  15. Describe and explain how water is exchanged between the blood and tissue fluid as blood flows along the capillary.
    • HydrostaticPressure forces water out;
    • Hydrostatic Pressure  is higher than Water Potential
    • Proteins remain in blood Which increases Water Potential So Water Potential is now higher than Hydrostatic Pressure
    • Water returns by osmosis along Water Potential gradient            
    • Water moves out at arteriole end and back in at venule end
  16. Explain how xylem tissue is adapted for its function.
    • long cells - tubes with no end walls 
    • Continuous water columns
    • No cytoplasm / no organelles to impede or obstruct flow which allows easier water flow;
    • Thickening - lignin support  to withstand tension and
    • is waterproof
    • Pits in walls allow lateral movement and water to get round blocked vessels
  17. The diameter of the trunk decreased during the same period,reaching its minimum when the flow rate was highest.
    Use your knowledge of the cohesion-tension theory to suggest an explanation for this decrease.
    Adhesion/attraction of water molecules to walls of xylem results in tension as water is pulled up the stem

    Which Pulls In The Walls 
  18. Explain how the cuticle of a xerophytic plant  reduces water loss.
    Its waxy so impermeable to water / is waterproof which stops water from passing through
  19. Use your knowledge of the cohesion-tension theory to explain how water in the xylem in the roots moves up the stem.
    Water evaporates/transpires which reduces water potential and creates water potential gradient increasing the osmotic gradient so water moves via the apoplast pathway

    Water drawn out of xylem creates tension/pulling effect

    Cohesive forces or H bonding between water molecules causes water moves as a column 
  20. Explain how the structure of the arteries reduces fluctuations in pressure.
    Elastic tissue/fibres expand and recoils to smooth the pressure surges 
  21. Explain how the structure of capillaries is related to their
    Endothelium is one cell thick and is made of flattened cells giving a short diffusion pathway

    Narrow lumen reduces rate of flow allowing more time for diffusion

    Gaps / pores between cells increase rate of diffusion and fluid movement out of vessel
  22. In one cardiac cycle, the volume of blood flowing out of the heartalong the pulmonary artery is the same as the volume of blood returning alongthe pulmonary vein. 
    Explain why the volumes are the same although the speed of flow in the artery is greater thanin the vein.
    Larger wider lumen so greater volume carried
  23. Suggest a function of the coronary artery
    Supply Oxygen And Glucose To The Heart Muscle
  24. Explain the importance of the ventricles beginning to contract at the Apex
    So more blood can be forced towards the aorta/pulmonary 

    • Artery so ventricles can empty completely; 
    • So semi lunar valves are forced open and Atrioventriculer valves forced closed 
  25. In The Formation Of Tissue Fluid What Causes The Fluid To Leave The Capillary
    Hydrostatic Pressure 
  26. In The Formation Of Tissue Fluid What Causes The Fluid To Return To The Capillary
    Osmosis Due To The Lower Water Potential In The Capillary 
  27. Describe how water is taken up by root hairs and reaches the xylem in the root.
    • Root hair cells have lower water potential than soil due to active uptake of ions so water enters root hair cells by osmosis
    • Then passes along apoplast pathway through cell wallsb passes along symplast pathway through plasmodesmata /cytoplasm
    • Casparian strip forces water from apoplast into symplast
    • Water moves from cell to cell and enters xylem by osmosis
    • Salts are pumped into xylem to lower water potential
  28. The structure of a vein allows blood to flow in one direction.  Explain how.
    Contain semilunar valves and valves work in one direction only
  29. In some diseases, lymph vessels in the legs may become
    blocked.  Explain how this leads to swelling of the tissues in the feet and ankles.
    Swelling caused by fluid build up

    Because fluid cannot be drained into lymph vessels
  30. Use your knowledge of the mass flow hypothesis to explain how sucrose is moved in a plant.
    Sucrose made in leaves by photosynthesis from breakdown of storage compounds; 

    Sucrose actively transported into phloem by companion/transfer cells

    Water potential decreases so water enters by osmosis; 

    Hydrostatic pressure increases in growing areas/sinks /storage areas so sucrose is removed
  31. Explain how oxygen is loaded, transported and unloaded in the blood.
    Partial pressure of oxygen is high in lungs

    O2 binds to Haemoglobin  and forms oxyhaemoglobin  in red blood cells

    Haemoglobin has a high affinity for oxygen so dissociation occurs when partial pressure of O2 is low

    Dissociation is increased by high CO2

    Partial pressure of O2 is low in respiring tissues
  32. Name the phase during which DNA replication occurs.
  33. Describe what happens to the chromosomes during each of the following stages of mitosis
    Prophase    –    Chromosomes Supercoil

    Metaphase   –   Chromosomes Line Up At The Equator And Spindles Attach To Centromeres

    Anaphase – Centromere Splits And Chromosomes Move Apart To Opposite Poles Of The Cell
  34. Name The Air Sacs In The Lungs And State Why There Are Many Of Them

    To Provide A Large Surface Area
  35. Describe The Role Of Elastic Fibres In The Wall Of The Alveoli During Ventilation 
    To Recoil And Prevent Bursting

    To Return The Air Sac To Its Original Shape

    To Help Expel Air
  36. Explain How Refreshing The Air In The Alveoli Helps Maintain A Steep Concentration Gradient
    • Increases Partial Pressure And Concentration Of Oxygen In The Alveoli
    • So Concentration Of Oxygen Is Higher In The Alveoli Then In The Blood

    • Decreases Partial Pressure And Concentration Of Carbon Dioxide In The Alveoli
    • So Concentration Of CO2 Remains Lower In The Alveoli Than In The Blood 
  37. Describe How Cells Are Organised Into Tissues Using
    Xylem And Phloem
    • XylemConsists Of Vessels In Which The Walls Are Lignified And Made Waterproof.
    • They Are Also Hollow With No Organelles. This Allows A Continuous Transpiration Stream To Transport Water And Minerals

    • Phloem Contains Sieve Tube Elements And Companion Cells.
    • Sieve Tubes Have No Nucleus And Few Organelles And Very Little Cytoplasm.Allowing Translocation To Take Place In Order To Transport Sucrose Around ThePlant 
  38. Suggest Two Advantages Of Keeping Blood Inside Vessels
    To Maintain Higher Blood Pressure

    Increase Rate Of Flow And Delivery

    Blood Flow Can Be Diverted And Directed
  39. Explain How The Wall Of The Artery Is Adapted To Withstand And Maintain High Pressure
    • Thick Wall Contains Thick Layer Of Fibrous Protein Collagen Which Provides Strength    
    • EndotheliumWall Is Folded So It Is Not Damaged When Wall Stretches
    • Thick Layer Of Elastic Fibres To Cause Recoil And Return Artery To Original Shape

    Thick Layer Of Smooth Muscle Constricts The Lumen Of The Artery Which Makes It Narrow 
  40. Explain The Difference Between Magnification And Resolution 
    Magnification is the number of times the image is compared to the actual object

    • Resolution is the ability to distinguish between two
    • separate points 
  41. Explain Why Transpiration Is Unavoidable During The Day 
    • Stomata are open to allow, gaseous exchange for the entry of carbon dioxide and exit of oxygen which is essential for photosynthesis
    • Water vapour leaves the leafdown a water vapour potential gradient

    Higher temperatures during the daycauses greater evaporation

    So some water vapour loss through leaf surface happens all the time
  42. Outline How Vesicles Are Moved From One Cell To Another
    Microtubules and Microfilaments in Cytoskeleton provide, pathways for movement

    Vesicles moves along these

    Microtubules can extend and break down to guide the vesicle

    The process uses metabolic energy known as ATP
  43. Describe How Extracellular Enzymes Are Secreted From

    When The Vesicle Fuses With The Plasma Membrane Of The Cell

    Then Discharging And Releasing Its Contents; The Enzymes