The document discusses energy transformations in living organisms. It explains that glucose is the main source of chemical energy for plants and animals. ATP is the energy currency of cells and is regenerated through cellular respiration. Cellular respiration can occur aerobically, using oxygen to produce more ATP, or anaerobically through fermentation without oxygen. Photosynthesis captures solar energy to convert carbon dioxide and water into glucose and oxygen. Plants have evolved C3, C4, and CAM pathways to photosynthesize that help conserve water in different environments.

1. Ian Anderson (2013)
Saint Ignatius College Geelong
06. Energy transformations.

2. Energy.
 All living organisms require a constant supply of
energy to survive e.g. for cellular processes (incl.
protein synthesis, active transport, digestion
etc.), growth, movement, reproduction, etc.
 Energy = capacity to do work.

3. Energy.
 In plants and animals glucose is the main source of
chemical energy.
 If there is insufficient glucose available, fatty acids and
amino acids can be used instead.
 Chemical energy is present in the chemical bonds.
 When the bonds break, energy is released (i.e. exergonic
reaction).

4. ATP – ADP cycle.
 Adenosine triphosphate (ATP) is the energy currency
of a cell.
 ATP is needed for every activity that requires energy.
 ATP structure – adenosine attached to a sugar group
(ribose), which is bound to a chain of three phosphate
groups.
 = nucleotide (sugar, N containing base and a phosphate
group).
 Immediate energy source lies in the energy rich bond
holding the third phosphate to the rest of the
molecule.

5. ATP – ADP cycle.
Source: Sadava et al. (2011)

6. ATP – ADP cycle.
 Cells make their own ATP in a cyclic process.
 When energy is used ATP is broken down into
Adenosine diphosphate (ADP) and inorganic
phosphate, with energy released.
 ATP is then reformed during cellular respiration.

7. ATP – ADP cycle.
Source: Sadava et al. (2011)

8. Cellular respiration.
 The process that releases energy from glucose
molecules in the form of ATP.
 Cellular respiration is the most important and
common catabolic reaction to all living organisms.
 Occurs in several stages
 [Biochemical/metabolic pathway = each step begins
with a substrate, which is then converted to a
product, which then becomes the substrate for another
chemical reaction (each enzyme controlled)].
Source: Campbell et al. (2011)

9. Cellular respiration.
 First stage = Glycolysis.
 Occurs in cytosol.
 Anaerobic (without oxygen) pathway.
 Glucose is broken down into two pyruvate
molecules, with a net production of two ATP molecules.
 H+ and e- are released as glucose is split and collected by
electron carrier molecule (nictoninamide adenine
dinucleotide).
Glucose  2 pyruvate + 2H2O + 2NADH + 2ATP
(6 carbon sugar) (2 x 3 carbon sugar)

10. Electron carrier molecule.
 H+ and e- are not stable and are quickly picked up by
NAD (nictoninamide adenine dinucleotide) which
acts as an electron carrier.
NAD+  NADH
Source: Russell et al. (2011)

11. Cellular respiration.
Next stage of cellular respiration depends on whether or
not oxygen is available.
 Oxygen available  aerobic pathway.
 Oxygen not available  anaerobic pathway.

12. Cellular respiration
– aerobic pathway.
 Most efficient way of producing ATP.
 Occurs in mitochondria in eukaryotes.
 Pyruvate enters via active transport.
 (Occurs in cytoplasm of prokaryotes).
 Involves two steps
 Krebs cycle (Citric acid cycle).
 Electron-transport chain.

13. Cellular respiration
– aerobic pathway.
Krebs cycle.
 Occurs in fluid matrix of mitochondria.
 Pyruvate molecules converted to two molecules of
acetyl CoA, one molecule of CO2 and 2 H+.
 Acetyl CoA then enters Krebs Cycle where each
molecule is converted into 2 CO2, 4 H+ & 1 ATP.
 H+ are picked up by electron carriers (NAD & FADH).
 A total of 2 ATP molecules produced per initial glucose
molecule.

14. Cellular respiration
– aerobic pathway.
Electron-transport chain.
 Occurs on the cristae (inner membrane) of
mitochondria.
 Energy from the NADH and FADH2 produced in
glycolysis and Krebs cycle used to produce ATP.
 H+ combine with O2 to form H2O.
 A total of 32-34 ATP from each original glucose
molecule.
 34 ATP in prokaryotes & 32 ATP in eukaryotes (2 ATP
used as as NADH produced via glycolysis pass across
mitochondrial membrane).

15. Cellular respiration
– aerobic pathway.
 Total ATP produced via aerobic pathway
 Glycolysis = 2 ATP
 Krebs cycle = 2 ATP
 Electron transport chain = 32-34 ATP
 = total 36-38ATP
Summary reaction of cellular respiration via aerobic
pathway
C6H12O6 + 6O2  6CO2 + 6 H2O + 36-38 ATP

16. Cellular respiration
– aerobic pathway.
Source: Raven et al. (2011)

17. Cellular respiration
– anaerobic pathway.
 Occurs in the cytoplasm of cells.
 No further ATP is produced during the anaerobic
pathway.
 i.e. only 2 ATP produced as a result of glycolysis.
 Anaerobic pathway known as fermentation.

18. Cellular respiration
– anaerobic pathway.
 In animals
 Pyruvate produced by glycolysis is converted to lactic
acid.
 NADH (produced during glycolysis) converted back to
NAD+ (thus allowing it to be reused).
Pyruvate + NADH  lactic acid + NAD+
Source: Campbell et al. (2011)

19. Cellular respiration
– anaerobic pathway.
 In most plants, yeast & bacteria
 Pyruvate is converted to ethanol and carbon dioxide.
 NADH (produced during glycolysis) converted back to
NAD+ (thus allowing it to be reused).
Source: Campbell et al. (2011)
Pyruvate + NADH  ethanol + CO2 + NAD+

20. Energy.
 The sun provides this energy either directly or
indirectly for nearly all life forms.
 Autotrophs – manufacture organic material from
inorganic material [self feeding] e.g. plants, algae &
cyanobacteria.
 Heterotrophs – obtain organic material by feeding on
other organisms (or their products) [feed on others] e.g.
animals, fungi, most bacteria & some protists.

21. Photosynthesis.
 Autotrophs (photoautotrophs) capture solar energy to
help drive the reactions that convert inorganic C to
organic C.
 Overall process = photosynthesis
6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O

22. Photosynthesis.
6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O
 Reaction is anabolic
 Larger molecules made from smaller molecules
 & endergonic
 Needs energy to proceed.
 Equation is a summary of 100’s of reactions that make
up photosynthesis (i.e. it is a biochemical pathway).

23. Photosynthesis.
 Occurs in the chloroplasts
 Membrane bound organelles – inner & outer membrane.
 Stroma – gel-like matrix that fills the interior of a
chloroplast. Rich in enzymes.
 Thylakoid membranes – suspended in the stroma.
Flat, sac-like structures that are stacked like pancakes
known collectively as grana.

24. Chloroplasts.
Source: Russell et al. (2011)

25. Photosynthesis.
 Two main stages
 Light dependent reactions.
 Light independent reactions.
 Each stage confined to specific sites within the
chloroplast.

26. Photosynthesis
- Light dependent reactions.
 Light is essential for these reactions to occur.
 Occurs on the thylakoid membranes of the
chloroplast.
 Chlorophyl absorbs light energy, which is then used to
produce ATP and split water molecules into H+ ions
and O2 gas.
 O2 gas is a waste product.
 ATP, H+ ions and electrons are used in the light
independent reactions.

27. Photosynthesis
- Light independent reactions.
 Also know as the Calvin Cycle.
 Occurs in the stroma of the chloroplast.
 Carbon dioxide is combined with the H+ ions using
energy provided by ATP, to form glucose and water.

28. Photosynthesis.
 Summary reaction of photosynthesis
6CO2 + 12H2O  C6H12O6 + 6H2O + 6O2

29. Photosynthesis.
Factors that affect the rate of photosynthesis.
 Light intensity
 CO2 availability
 Temperature
 Indirect factors
 Lacking nitrogen/magnesium reduces the amount of
chlorophyll produced.
 Dehydration causes stomata to close.

30. Variations in photosynthesis.
Plants adapt to their environment
 C3 plants
 C4 plants
 CAM plants
‘the norm’
Adapted to arid conditions

31. C3 plants.
 Called C3 because the CO2 is first incorporated into a
3-carbon compound.
 Stomata are open during the day.
 Photosynthesis takes place throughout the leaf.
 Adaptive value = more efficient than C4 and CAM
plants under cool and moist conditions and under
normal light because requires less machinery (fewer
enzymes and no specialized anatomy)..
 Most plants are C3.

32. C4 plants.
 Called C4 because the CO2 is first incorporated into a
4-carbon compound.
 Use a different enzyme to capture & convert CO2.
 Adaptive value = reduces the time the stomates are
open and therefore reduces water loss.
 C4 plants include several thousand species in at least
19 plant families. E.g. fourwing saltbush, corn, and
many of our summer annual plants.

33. CAM plants.
 Open their stomates at night.
 Convert the CO2 to an acid that is stored.
 During the day the acid is broken down back into CO2
and used during photosynthesis.
 Adaptive value = stomates are not open during day and
therefore reduces water loss.
 CAM plants include succulents, some orchids and
some bromeliads.