Respiration IN Plants flash cards

1. 1.What is cellular respiration?

   The mechanism of breakdown of food materials (respiratory substrates) within the cell to release energy, trapped to synthesise ATP.

   Hint: Breakdown of food to release energy

2. 2.Why are green plants and cyanobacteria not fully dependent on other organisms for food?

   They can prepare their own food (glucose) by photosynthesis and derive energy from it; they are autotrophs.

   Hint: They photosynthesise

3. 3.What is the ultimate source of energy for all living organisms (except chemosynthetic)?

   The Sun; energy is trapped by green plants during photosynthesis and stored in the bonds of carbohydrates.

   Hint: Trapped during photosynthesis

4. 4.Which molecule is the compound that acts as the energy currency of the cell?

   ATP (Adenosine triphosphate).

   Hint: Energy currency

5. 5.Why can plants not have specialised respiratory organs like animals?

   Each plant part takes care of its own gas exchange; there is little transport of gases, low O2 demand, and large surface-to-volume with living cells at surfaces.

   Hint: No transport of gases needed

6. 6.Through which structures do gases diffuse in and out of plant parts?

   Stomata (in leaves and stems) and lenticels (in woody stems and roots); loose packing of cells provides intercellular spaces.

   Hint: Stomata and lenticels

7. 7.What are the most common respiratory substrates?

   Carbohydrates (glucose); fats and proteins can also be broken down; organic acids may also be used.

   Hint: Usually carbohydrates

8. 8.Define respiratory substrate.

   The compounds that are oxidised during respiration to release energy, e.g. glucose, fats, proteins, organic acids.

   Hint: Compound that is oxidised

9. 9.Why is glucose the favoured substrate and how is it made available?

   Glucose is the form usually oxidised; all other substrates (starch, fats, proteins) are converted into it (or enter the pathway) before respiration.

   Hint: Others converted to it

10. 10.What is the overall equation for aerobic respiration of glucose?

    $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + energy$.

    Hint: Glucose + oxygen

11. 11.How does biological oxidation of glucose differ from combustion (burning)?

    In cells, glucose is broken down in many small enzyme-controlled steps so energy is released gradually and trapped as ATP, not lost all at once as heat/light.

    Hint: Step-wise, controlled release

12. 12.Define glycolysis.

    The partial oxidation of one glucose molecule into two molecules of pyruvic acid; from Greek glycos (sugar) and lysis (splitting).

    Hint: Splitting of sugar

13. 13.Who gave the scheme of glycolysis and what is it also called?

    Gustav Embden, Otto Meyerhof and J. Parnas; hence the EMP pathway.

    Hint: EMP pathway

14. 14.Where in the cell does glycolysis occur?

    In the cytoplasm (cytosol).

    Hint: Cytoplasm

15. 15.Is glycolysis aerobic or anaerobic?

    It is common to both aerobic and anaerobic respiration and does not require oxygen; it occurs in all living organisms.

    Hint: Common to both; no O2 needed

16. 16.In plants, from where is the glucose for glycolysis derived?

    From sucrose (the end product of photosynthesis and the main transported sugar), broken down by invertase into glucose and fructose; or from stored starch.

    Hint: From sucrose or starch

17. 17.What is the first step of glycolysis?

    Glucose is phosphorylated to glucose-6-phosphate using ATP (enzyme hexokinase).

    Hint: Glucose → glucose-6-phosphate

18. 18.How many ATP molecules are used (invested) in glycolysis?

    2 ATP are consumed (in phosphorylation steps).

    Hint: Two ATP invested

19. 19.How many ATP molecules are produced by substrate-level phosphorylation in glycolysis?

    4 ATP are produced, giving a net gain of 2 ATP per glucose.

    Hint: 4 gross, net 2

20. 20.What is the net ATP gain in glycolysis per glucose?

    Net 2 ATP (4 produced minus 2 consumed).

    Hint: Net two

21. 21.How many NADH + H+ molecules are formed in glycolysis?

    2 molecules of NADH + H+ are formed (during oxidation of glyceraldehyde-3-phosphate).

    Hint: Two NADH

22. 22.What is the end product of glycolysis?

    Two molecules of pyruvic acid (pyruvate) per glucose.

    Hint: Pyruvic acid

23. 23.Name the six-carbon intermediate formed from glucose-6-phosphate that is split.

    Fructose-1,6-bisphosphate, which splits into two 3-carbon molecules (glyceraldehyde-3-phosphate / DHAP).

    Hint: Fructose-1,6-bisphosphate

24. 24.Into which two triose phosphates does fructose-1,6-bisphosphate split?

    3-phosphoglyceraldehyde (PGAL / glyceraldehyde-3-phosphate) and dihydroxyacetone phosphate (DHAP).

    Hint: PGAL and DHAP

25. 25.What is substrate-level phosphorylation?

    Direct synthesis of ATP by transfer of a phosphate group from a phosphorylated substrate to ADP, as happens in glycolysis and the Krebs cycle.

    Hint: ATP directly from substrate

26. 26.What are the three metabolic fates of pyruvic acid?

    (1) Lactic acid fermentation, (2) alcoholic fermentation, and (3) aerobic respiration (complete oxidation via Krebs cycle).

    Hint: Lactate, alcohol, or aerobic

27. 27.What determines which fate pyruvic acid follows?

    The cellular need and the availability of oxygen; the type of organism/tissue.

    Hint: Depends on O2 and cell type

28. 28.Define fermentation.

    The incomplete oxidation of glucose under anaerobic conditions by certain organisms, in which pyruvate is converted to lactic acid or ethanol + CO2.

    Hint: Incomplete anaerobic oxidation

29. 29.What are the products of alcoholic fermentation?

    Ethanol (ethyl alcohol) and CO2; catalysed by pyruvic acid decarboxylase and alcohol dehydrogenase.

    Hint: Ethanol + CO2

30. 30.Which organisms carry out alcoholic fermentation?

    Yeast and some other microbes (and plant cells under anaerobic conditions).

    Hint: Yeast

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