1. Chapter 4 Cellular Respiration
Anne Van & Cindy Wong

2. Cellular Respiration Overview
equation: C6H12 + 6O2  6CO2 + 6H2O + energy
the means by which cells extract energy stored in food + transfer that energy to molecules of ATP
this energy is instantly available for every cellular activity (ex. muscle contraction, moving cilia)
2 types of cellular respiration: anaerobic (O2 not present) and aerobic (O2 present)
leads to glycolysis, then alcoholic fermentation or lactic acid fermentation (if O2 not present)
leads to glycolysis, then Citric Acid Cycle, ETC, oxidative phosphorylation (if O2 present)

3. ATP (Adenosine Triphosphate)
consists of adenosine (nucleotide of adenine + ribose) and 3 phosphates
unstable molecule as 3 phosphate groups are negatively charged/repel
when 1 phosphate group is removed from ATP by hydrolysis - results in more stable molecule ADP (adenosine diphosphate)
provides energy for all cell activity by transferring phosphates from ATP to another molecule

4. Glycolysis
10 step process – breaks down 1 molecule of glucose into 2-3 molecules of pyruvate/pyruvic acid, releases 4 molecules of ATP
occurs in the cytoplasm + produces ATP without using oxygen
ATP produced by substrate level phosphorylation – direct enzymatic transfer of phosphate to ATP
enzyme that catalyzes 3rd step, phosphofructokinase (PFK) is an allosteric enzyme – inhibits glycolysis when cell contains enough ATP and doesn’t need any more

5. Anaerobic Respiration: Fermentation
an anaerobic catabolic process that consists of glycolysis + alcohol or lactic acid fermentation
originated millions of years ago when there was no free O2 in earth’s atmosphere
sole means by which anaerobic bacteria like botulinum release energy for food
2 types of anaerobes: faculative – can tolerate the presence of O2 and obligate – cannot live in an environment that has O2
can generate ATP during anaerobic respiration as long as there’s adequate supply of NAD+ to accept electrons
glycolysis would shut down if nothing converted NADH back to NAD+

6. Lactic Acid Fermentation
Alcohol Fermentation
Lactic Acid Fermentation
process by which certain cells convert pyruvate from glycolysis into ethyl alcohol and CO2 in the absence of O2
NADH gets oxidized back to NAD+
bread depends
on yeast to
ferment and
produce CO2
– bread rises
beer, wine,
liquor industries
too
pyruvate from glycolysis is reduced to form lactic acid or lactate
NADH gets oxidized back to NAD+
dairy industry uses this process to make cheese, yogurt
human skeletal muscles when blood can’t supply adequate O2 to muscles during strenuous exercise

7. Aerobic Respiration
highly efficient process, produces a lot of ATP when O2 is present
consists of an anaerobic phase (glycolysis) + an aerobic phase (2 parts - citric acid cycle, oxidative phosphorylation)
Citric Acid Cycle
takes place in the matrix of mitochondria, requires pyruvate
completes the oxidation of glucose into O2
turns twice for each glucose molecule that enters glycolysis
generates 1 ATP/turn by substrate level phosphorylation – most of the chemical energy is transferred to NAD+, FAD

8. Structure of Mitochondrion
NAD+ and FAD
enclosed by double membrane, outer membrane is smooth and inner (cristae membrane) is folded – divides into the outer compartment and the matrix
Citric acid cycle happens in matrix
Electron transport chain happens in cristae membrane
are required for normal cell respiration
carry protons/electrons from glycolysis and citric acid cycle to ETC

9. Aerobic Respiration: The Electron Transport Chain
ETC is a proton pump in mitochondria that couples 2 reactions – exergonic and endergonic
uses energy released from exergonic flow of electrons to pump protons against a proton gradient
makes no ATP directly but sets the stage for ATP production during chemiosmosis
carries electrons delivered by NAD, FAD from glycolysis + citric acid cycle to O2 (final electron acceptor)
highly electronegative O2 acts to pull electrons through the ETC

10. Oxidative Phosphorylation and Chemiosmosis
how most energy is produced during cellular respiration
is the phosphorylation of ADP into ATP by oxidation of the carrier molecules, NADH and FADH2
powered by redox reactions of the ETC and protons are pumped from matrix to outer compartment by the ETC
protons cannot diffuse through the cristae membrane – they can only flow down the gradient into matrix through ATP synthase channels
this is chemiosmosis – the key to ATP production – as protons flow through the channels, they generate energy to phosphorylate ADP into ATP

11. Overview of Cellular Respiration

12. Chapter 5 Photosynthesis
Anne Van & Cindy Wong

13. Photosynthesis Overview
process by which light energy is converted to chemical bond energy and carbon is fixed into organic compounds
equation: 6CO2 + 12H2O  C6H12O6 + 6H2O + 6O2
2 main processes – light dependent (uses light energy to directly produce ATP) and light independent reactions (consists of the Calvin Cycle which produces sugar)

14. Photosynthetic Pigments
absorb light energy and use it to provide energy to carry out photosynthesis
2 major pigments in plants: chlorophylls and carotenoids
chlorophyll a, chlorophyll b – green and absorb wavelengths of light in red, blue, violet range
carotenoids – are yellow, orange, and red; absorb light in the blue, green, and violet range
also xanthophyll and phycobilins
antenna pigments – capture wavelengths other than those captured by chlorophyll a (examples: carotenoids, chlorophyll b, phycobilins)

15. The Chloroplast
contains photosynthetic pigments, along with enzymes, that carry out photosynthesis
grana - light dependent reactions
stroma – light independent reactions
grana has layers of membranes – thylakoids (site of photosystems I, II)
enclosed by double membrane

16. Photosystems (PS) 2 photosystems – I, II
light harvesting complexes in thylakoid membranes of chloroplasts – few hundred in each thylakoid
each consists of a reaction center that has chlorophyll a and a region of several hundred antenna pigment molecules
named in order of their discovery not in order they work - PS II operates first, then PS I
PS I absorbs light best in 700 nm range, PS II absorbs light best in 680 nm range

17. Light-Dependent Reactions: Light Reactions
light is absorbed by the photosystems in the thylakoid membranes
electrons flow through electron transport chains
2 possible routes of electron flow: noncyclic flow and cyclic photophosphorylation

18. Noncyclic Photophosphorylation
electrons enter two electron transport chains, ATP and NADPH are formed
process begins in PS II – energy is absorbed, electrons are captured by primary electron acceptor
photolysis - water gets split into two electrons, two protons (H+), and one O2 atom; and O2 molecule gets released
ETC – electrons pass along an ETC that ultimately leads to PS I; flow of electrons is exergonic and provides energy to produce ATP
chemiosmosis – ATP is formed as protons released from water are diffused down the gradient from the thylakoid space
NADP – becomes reduced to form NADPH
PS I – similar to PS II, but this electron transport chain contains ferrodoxin and ends with production of NADPH, not ATP

19. Cyclic Photophosphorylation
sole purpose is to produce ATP, not NADPH, and also no oxygen is released
when chloroplast run low on ATP periodically, cyclic photophosphorylation is carried out to replenish ATP levels
cyclic electron flow takes photoexcited electrons on a short circuit pathway
travel from PS II electron transport chain to PS I, to a primary electron acceptor, then back to cytochrome complex in electron transport chain of PS II

20. The Calvin Cycle
cyclic process that produces 3-carbon sugar, PGAL (phosphoglyceraldehyde)
carbon enters the stomates of a leaf in the form of CO2 and becomes fixed/incorporated into PGAL
carbon fixation is the process that occurs during the cycle
Calvin Cycle is a reduction reaction since carbon gains hydrogen
uses the products of the light reactions – ATP and NADPH
only occurs in the light

21. Overview of Photosynthesis

22. C-4 Photosynthesis CAM Plants
modification for dry environments
C-4 plants show modified anatomy + biological pathways that enable them to minimize excess water loss and sugar production
these plants thrive in hot/sunny places
examples: corn, sugar cane, crabgrass
CAM Plants
CAM plants carry out a form of photosynthesis called crassulacean acid metabolism – another adaptation to dry environments
stomates are closed during the day and open at night
mesophyll cells store CO2 in organic compounds they synthesize at night

23. Example Questions

25. Thanks for Watching!