F212 Flash Cards - last min revision

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  • Created by: Emma
  • Created on: 20-05-13 20:53
Describe and explain how transpiration contributes to the mechanism of water transport up the stem. (4)
Water loss replaced. Down Ψ grad. Water from xylem. Moves down pressure grad which is created when H2O leaves. Tension. Mass Flow. Continuous column of water.
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Describe the features of the xylem that allow water to flow in one end and out of the other. (2)
Xylem vessel walls are lignified/ Bordered pits allow movement of water between vessels -Continuous tube -no cytoplasm in xylem vessel elements
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State two adaptations of sieve tube elements that allow mass flow to occur. (2)
-Little cytoplasm -Elongated elements joined end to end to form a column -Sieve plates
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State and explain the importance of lignin in the xylem vessel. (3)
-Strengthens xylem wall so it doesn’t collapse -Waterproofs xylem wall so less water is lost through xylem walls -Pattern allows flexibility in xylem so stem doesn’t break
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Why does ringing the bark of a tree lead to swelling above the ring? (2)
-Sugars cannot pass the cut -This decreases the Ψ of the cells above the ring so water moves into those cells - Increased cell division to make more cells to store sugar - Cut causes infection
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Xylem
Cells joined end to end in continuous column/ lignified/ no cell walls/ no organelles/ bordered pits/ transpiration stream
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Phloem
Sieve tube element - no nucleus, few organalles, little cytoplasm/ companion cells/ many plasmodesmata/ many mitochondria/ translocation of assimilates
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Movement of water up the xylem
Water leaves leaf creating transpiration stream/ stream. Water molecules are cohesive (stick together). Column of water moves upwards -cohesion-tension theory. Adhesion - water molecules attracted to lignified walls
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Pathways through the plant
Symplast pathway (through living parts of the cell, through plasmodesmata), Apoplast pathway (non-living parts of cells i.e. cell wall until it gets to waxy endodermis/ casparian ***** - joins symplast) Vacular pathway (through vacuoles by osmosis)
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Active loading into phloem
Loading of sucrose into phloem. Ψ decreases. hydrostatic pressure increases - so that is higher at source than sink and forced down pressure grad to sink. Sucrose unloaded and taken up by facilitated diffusion. Some water returns to xylem.
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Companion and mesophyll cells
H+ Ions pumped out of companion cell to mesophyll using ATP. Creating grad between cells of H+ Ions. H+ re-enter companion cells with sucrose attached using co-transporter proteins. Sucrose moves down conc grad into phloem by facilitated diffusion.
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Evidence for the mass flow model
Using radioactive traces and x-ray the results (in an enclosed environment) Ringing experiment - take out phloem and xylem swells. Aphids. Is an active process, test with metabolic inhibitor to stop enzyme used in ATP - plant dies. rate of transport.
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Evidence against mass flow model
Not all solutes in the phloem sap move at the same rate. Sucrose is moved to all parts of the plant at the same rate rather than to those more quickly with lower concs.The role of the sieve plates is unclear.
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Adaptions of Xerophytes
Hairy leaves + sunked stomata trap water vapour. Create high Ψ outside stomata. Reduce Ψ grad. Rolled/ small leaves reduce SA. Fewer stomata which close during the day, mostly on underside of leaf reduce diffusion. Thick waxy cuticle is impermeable
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Adaptions of gaseous exchange system
Cartilidge (hold airway open) Thin squamous epithelium (short diffusion distance) Surfactant (reduce surface tension so alveoli don't collapse) Maintained conc grad. Elastic fibres (expel air) Macrophages/neutrophils to engulf pathogens.
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Explain why transpiration is unavoidable during the day
Stomata are open for gaseaous exchange for photosynthesis. Water vapour leaves down Ψ grad. High temp during day causes greater evaporation
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Cytoskeleton
Provides pathways for substances to move along the microtubules using ATP. Used in protein synthesis, exo-cytosis, and for chromosomes in cell division
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Exocytosis
Vesicle fuses with plasma membrane, secreting....(named substance)
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Homologous pair of chromosomes
One chromosome from mum and dad. Carry same genes but different alleles. Usually similar length. Centromere in same position. Same bonding pattern in meiosis.
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Golgi apparatus
Packing and modifying of proteins and lipids. Also produces lysosomes.
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Hydrostatic Pressure decreasing away from heart
Distance from heart increases. Pressure drops further away from heart. Capillaries spread into lots of little ones, great no. of them. Reduced resistance. Cross-sectional area of capillaries greater
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Veins
Wider lumen. Lower pressure. Less smooth muscle, elastic fibres and collagen - don't need to actively constrict. Deoxygenated blood. No valves.
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Arteries
Narrower lumen (maintain high pressure) Thick wall with lots of collagen to withstand pressure. Endothelium is folded (so artery can expand), More smooth muscle and elastic fibre (actively constrict, maintain pressure when heart relaxes)
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Bohr Shift
Curve to right of haemoglobin. Actively respiring tissue needs more O2 to release more energy. It also produces more CO2 which takes up room on haemoglobin, so less room for O2, and more of it is released.
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State two other processes, apart from the copying of genetic material, that take place during interphase. (2)
-Checking for mutations in replicated DNA by enzymes -Growth of cell -Protein synthesis
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State two ways in which cell division in plants differs from cell division in animals. (2)
- In plant cells a cell plate is formed whereas in animal cells a cleavage furrow is formed. -In plants only meristem cells can divide whereas in animals most cells are capable of dividing.
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Name two parts of the plant that contain meristem cells. (2)
-Root tip -Cambium in stem -Bud
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Outline the process of budding in yeast. (2)
-The nucleus divides by mitosis -The cell buldges on one side - Nucleus, cytoplasm and organelles move into buldge. -The bud pinches off the cell
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State three reasons why mitosis is important to organism. (3)
-Growth of tissue -Repair tissue -Asexual reproduction
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Capillaries, tissue fluid etc.
At arterial end. Plasma moves out of blood into tissue fluid. Proteins remain in capillary. Fluid moves down hydrostatic pressure gradient. etc
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Why does the potometer only give an estimation of the rate of transpiration (2)
The potometer measures water uptake, not all the water is lost however though. Some is used within the plant.
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Steps when setting up a potometer?
Leaves are dry / Capillary tube attached under water / vaseline or tight seal where the rubber meets the plant stem/ healthy shoot/ cut off last 2-3cm / check no air bubbles.
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Glycoproteins
Act as antigens, recognise themselves as self / cell signalling / receptor / binding site for hormone to trigger a response / cell adhesion in a tissue / attach to H2O molecules to stabilise membrane
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Meiosis
Not genetically identical. Produce haploid cells/ gametes. 4 cells are produced instead of two.
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Things to remember
Where is substance going? Upwards, to other vessel etc. What increases? Waste substances removed. Mainting concentration gradients.Surface area. BE SPECIFIC. STATE THE OBVIOUS
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Mitosis - Interphase, Prophase, Metaphase
1) DNA replicates 2) Chromosome supercoil, visible, nuclear envel breaks down, centriole divide by 2, more opp ends, form spindle 3) Chromosomes line up in middle 4) Attach to spindle threat at centromere
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Mitosis - Anaphase, Telephase, Cytokineses
4) Replicated sister chromatids seperate, centromere splits, spindle fibres shorten, chromatids apart 5) Chromatids reach poles, nuclear envelope forms around each, spindle breaks down, chromos uncoil no longer visible 5) Cytokinesis - cell division
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Conversions and resolutions
AIM. micometer 10^-6m. Nanometre 10^-9m. Light = 200nm, x1500 / TEM = 0.1nm, x500,000 / SEM = 0.1nm, x100,000
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Hydrocarbonate Ions Formation
CO2 + H2O --(carbonic anhydrase)--> HCO3- (Chlorine shift maintains charge) + H+ Ions --> HHb (haemoglobinic acid)....HbO8 --> Hb and 4O2
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Prokaryotes vs eukaryotes
Pro = unicellular, cell wall, no nuclear envelope, naked DNA, no membrane bound organelles, smaller ribosomes, plasmids, no cytoskeleton Eu = usually no cell wall, DNA as chromosomes in nucleus, large ribosomes, cytoskeleton/ both sometimes flagella
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Other cards in this set

Card 2

Front

Describe the features of the xylem that allow water to flow in one end and out of the other. (2)

Back

Xylem vessel walls are lignified/ Bordered pits allow movement of water between vessels -Continuous tube -no cytoplasm in xylem vessel elements

Card 3

Front

State two adaptations of sieve tube elements that allow mass flow to occur. (2)

Back

Preview of the front of card 3

Card 4

Front

State and explain the importance of lignin in the xylem vessel. (3)

Back

Preview of the front of card 4

Card 5

Front

Why does ringing the bark of a tree lead to swelling above the ring? (2)

Back

Preview of the front of card 5
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