B8

Question 1

What are living things and non living things composed of?

Answer 1

The same types of chemical elements.

Question 2

What is a mechanistic view?

Answer 2

Life is chemically based and obeys universal, physical, and chemical laws.

Question 3

What elements make up 98% of the mass of every living organism?

Answer 3

C, H, N, O, P, S

Question 4

What are Na and K essential for?

Answer 4

Nerves and function.

Question 5

What is Ca function?

Answer 5

Biological signalling

Question 6

What is iron important for?

Answer 6

Important component of Haemoglobin

Question 7

What do plants need molybdenum for?

Answer 7

Incorporate nitrogen into biologically useful substances.

Question 8

What are macro and micronutrients?

Answer 8

Macronutrients - required in large amounts
Micronutrients - required in trace amounts.

Question 9

Molecular weight is determined from atomic mass

Answer 9

All contain the same number of entities (atoms/ions/molecules) - avogadros number

Question 10

What are the macronutrients obtained from water or CO2?

Answer 10

Hydrogen, carbon, oxygen

Question 11

What are the macronutrients obtained from soil?

Answer 11

N, P, K, Ca, Mg, S, Si

Question 12

What are the micronutrients obtained from soil?

Answer 12

Cl, Fe, B, Mn, Na, Zn, Cu, Ni, Mo

Question 13

What is the prevalence of nitrogen?

Answer 13

Proteins, nucleic acids, chlorophyll, deficiency = chlorosis

Question 14

What is the prevalence of potassium?

Answer 14

Enzyme activator, concentrates in meristems, stomatal regulation, deficient = chlorosis and brown tips.

Question 15

What is the prevalence of calcium?

Answer 15

Middle lamella, movement of substances through cell membranes, deficiency = terminal bud dead, young leaves hooked and withered, roots die.

Question 16

What is the prevalence of phosphorus?

Answer 16

Respiration, cell division, high energy compounds, deficiency = stunted growth, leaves darker green, lower leaves purple.

Question 17

What is the prevalence of magnesium?

Answer 17

Chlorophyll, enzyme activator, deficiency = yellowing of leaves between veins

Question 18

What is the prevalence of sulfur?

Answer 18

Part of some amino acids e.g. cysteine, Fe-S proteins important in electron transfer, deficiency = chlorosis, dead spots, veins lighter in colour.

Question 19

What is the prevalence of iron?

Answer 19

Respiration, chlorophyll formation, deficiency = large veins remain green but chlorosis in remainder

Question 20

What is the prevalence of manganese?

Answer 20

Enzyme activation, photolysis, deficiency = dead spots, veins remain green, chlorosis effects on young leaves

Question 21

What effects the amount of essential elements plants get?

Answer 21

Often one limiting nutrient, uptake influenced by environmental conditions. Soil pH, saturation. Can also be harmful in high amounts.

Question 22

How does uptake of inorganic nutrients occur?

Answer 22

Uptake takes place through epidermis of root and is usually an active process requiring the expenditure of metabolic energy. Uptake often aided by mycorrhiza, particularly through phosphorus uptake. Transport across root appears to be mainly along symplast pathway (protoplast to protoplast via plasmodesmata). Evidence suggest that ions are loaded into xylem vessels.

Question 23

Uptake of inorganic nutrients - cation exchange capacity?

Answer 23

Cations attracted to negative charged soil particles. K+ higher in roots therefore harder to uptake - active transport against conc gradient.

Question 24

How is ion uptake an active process?

Answer 24

Mineral composition of roots is different to the soil e.g. higher K+ conc in root. Thus ion uptake is selective e.g. ratio of k+:na+ higher in roots. Some ions are taken up against a chemical potential gradient which requires an input of energy I.e. active. Nitrate and phosphate must be transported against an electrochemical gradient - they are both anions.

Question 25

How are inorganic nutrients transported to the shoot?

Answer 25

Mineral nutrients are transported upwards in xylem (transpiration stream). Some nutrients move laterally from xylem into surrounding tissue of roots and shoots. Others transported to leaves. Active transport systems supply specific cells with nutrients. Mg, Fe, and N needed to build chlorophyll in leaves. Nutrients imported into leaves via the xylem may be exchanged with the phloem and translocated with sucrose.

Question 26

What is mycorrhiza?

Answer 26

Intimate, mutualistic, symbiotic association between root and fungus. Helps roots obtain mineral nutrients, fungus gets sugars in return. 2 types - ectomycorrhiza, important to forest trees, endomycorrhiza, present on the roots of most plants.

Question 27

Endomycorrhiza

Answer 27

The fungus penetrates the outer cortex and makes intimate contact with the cell membrane but does not enter protoplasm. Phosphorus is supplied to the plant cells via arbuscules. Vesicular-arbuscular mycorrhiza are very common in herbaceous plants.

Question 28

Ectomycorrhiza?

Answer 28

Fungus forms a sheath around the root and grows between cells to form hartig net. Form mushroom fruiting bodies.

Question 29

What are orchid mycorrhiza?

Answer 29

Orchidaceae family has more than 20,000 species. All mycoheterotrophic at one stage - usually as seeds, seeds very small with no nutrient reserves. Fungal symbiont provides carbon during germination.

Question 30

What relationship do wintergreen, willow, and girdled knight have?

Answer 30

Pyrola minor has ectomycorrhizal association with tricholoma cingulatum and salix caprea. The fungus is like a pipe allow nutrients to pass between the willow tree and wintergreen.

Question 31

What sites have unique soil properties?

Answer 31

Brownfield sites

Question 32

What forms of nitrogen are available to plants?

Answer 32

Nitrate (NO3-) - important in many ecosystems, and for crops
Ammonium (NH4+) - in acidic soils
Nitrogen (N2) - only plants that have symbiotic relationship with N-fixing prokaryotes.
Organic nitrogen - parasites, carnivorous plants.

Question 33

What happens in nitrate (NO3-) assimilation?

Question 34

What happens in nitrate (NO3-) assimilation?

Answer 34

NO3- -uptake> NO3- -2e- nitrate reductase> NO2- -6e-> NH4+ -2e-> amino acids -> proteins, nucleoid acids, other organic N. Requires energy and reducing power. Reduced ferredoxin required.

Question 35

What happens in Nitrogen fixation (N2 fixation)?

Answer 35

Root symbiosis - legumes : rhizobium. Lead symbiosis - gunnera

Question 36

What is nitrogen fixation catalyse by?

Answer 36

Nitrogenase

Question 37

Nitrogen fixation - what is nitrogenase?

Answer 37

A large protein complex associated with the prokaryote partner. It contains Mo and Fe and catalyses the following reaction.
N2 + 8H+ + 8e- + 16ATP -> 2NH3 + H2 + 16ADP + 16 Pi
Requires lots of energy supplied by plant
Requires reduced ferredoxin
Requires anaerobic conditions

Question 38

What happens with nitrogen fixation in legumes?

Answer 38

Nitrogenase activity is inhibited by oxygen. Nodule cells make leghaemoglobin, which binds to oxygen. Rhizobium forms an infection thread through root hair, root cells undergo mitosis to form nodule.

Question 39

What are the impacts of nitrogen pollution?

Answer 39

Historically limits plant growth. Human activity increased N emission and deposition. Short term acts as fertiliser. long term disruptive effects. Disrupt natural cycle C:N ratios. Bryophytes most sensitive. Eutrophication and acid rain. Favours growth of invasive species. Phase shifts of plant communities, global problem.