Lecture 6 Condensed Studying - BIO 1210

photosynthesis

used by autotrophs to make organic food molecules

photosynthesis equation

6CO₂ + 6H₂O + light energy →→→ C₆H₁₂O₆ + 6O₂

cellular respiration

used by autotrophs and heterotrophs to get chemical energy of organic food molecules

cellular respiration equation

C₆H₁₂O₆ + 6O₂ →→→ 6CO₂ + 6H₂O + ATP

cellular respiration is…

aerobic and exergonic (releases energy), which is used to synthesize ATP

redox reactions

• hydrogens are moved from glucose to oxygen during cellular respiration

• removal of hydrogens from glucose yields carbon dioxide

• addition of hydrogen to oxygen yields water

oxidation (OIL)

loss of electrons (oxidation is loss)

reduction (RIG)

reduction (reduction is gain of electrons, more negative)

glucose is oxidized into carbon dioxide

loses hydrogens

oxygen is reduced into water

gains electrons

redox reactions = reduction-oxidation

happens together

redox reactions involving oxygen

gets energy

glycolysis

• step 1 of cellular respiration

• doesn’t need oxygen

• happens in cytosol (fluid) of the cell

step 1 of glucolysis

6-carbon glucose splits into two 3-carbon molecules called G3P (need 2 ATP for this)

step 2 of glycolysis

G3P are oxidized and NAD+ is reduced to NADH

step 3 of glycolysis

converts oxidized G3P into two 3-carbon pyruvate molecules (gives back 2 ATP per pyruvate, so 4 total)

step 4 of glycolysis

ATP is made through substrate-level phosphorylation (enzyme gives a phosphate from substance to ADP, making ATP)

overall, glycolysis

produces 2 net ATP, 2 NADH, and 2 pyruvate

pyruvate oxidation

step 2 of cellular respiration

step 1 of pyruvate oxidation

carbon from each pyruvate is removed at CO2, making acetic acid

step 2 of pyruvate oxidation

acetic acid is oxidized and NAD+ is reduced to NADH

step 3 of pyruvate oxidation

NADH carries electrons to electron transport chain

step 4 of pyruvate oxidation

conenzyme A binds to oxidized acetic acid, making acetyl CoA (enters citric acid cycle)

overall, pyruvate oxidation

produces 2 CO2, 2 NADH, and 2 acetyl CoA

citric acid cycle

step 3 of cellular respiration

step 1 of citric acid cycle

coenzyme A is released from acetyl CoA and recycled

step 2 of citric acid cycle

the 2-carbon acetic molecule binds to a 4-carvon oxaloacetate molecule, making a 6-carbon citric acid molecule (2 per glucose?)

overall, the citric acid cycle

produces 2 CO2 (4 total), 1 ATP (2 total), 3 NADH (6 total), 1 FADH2 (2 total)

step 3 of the citric acid cycle

NADH and FADH2 carry electrons to the electron transport chain

step 4 of the citric acid cycle

4-carbon oxaloacetate is regenerated to start the cycle again

by the end of the citric acid cycle,

glucose is completely broken down to CO2

electron transport chain

• step 4 of cellular respiration

• aerobic process (need oxygen)

• energy is released during a redox reaction involving oxygen because oxygen is very electronegative, produces water

step 1 of electron transport chain

• NADH and FADH2 (from glycolysis and citric acid cycle) is at the top of the chain

• oxygen is at the bottom, pulling the electrons down the chain

step 2 of electron transport chain

NADH and FADH2 lose their electrons and are oxidized to NAD+ and FAD, then recycled back to glycolysis and citric acid cycle

step 3 of electron transport chain

electrons move down the chain through proteins embedded in the mitochondrial cristae, and relese bits of energy to pump H+ across the inner membrane

step 4 of electron transport chain

cchemiosmosis occurs: outside is lots of H+ (lots of potential energy), H+ wants to go back down so it passes through ATP synthase (an enzyme), which changes potential energy to kinetic energy, which spins the ATP synthae

step 5 of electron transport chain

oxidative phosphorylation: when ATP synthase spins, P + ADP = ATP

step 6 of electron transport chain

water is produced as electrons (and hydrogens) reduce oxygen

overall, electron transport chain

produces 32 ATP

overall, cellular respiration

produces 2 ATP (from glycolysis), 2 ATP (from citric acid cycle), 32 ATP from electron transport chain — making 36 total ATP

fermentation

(anaerobic process) conversion of food to ATP

fermentation is modified glycolysis

• glucose splits into 2 pyruvate molecules and 2 net ATP is made

• no oxygen means no electron transport chain, so need NAD+

• pyruvate is reduced when NAHD oxidizes to NAD+, making lactic acid (2 lactic acid per glucose molecule)

lactic acid fermentation

• in human muscle cells, as exercise continues, oxygen supply doesn’t meet demands, so muscles switch to anaerobic lactic acidfermentation, which makes your muscles “burn”

• in bacteria, makes cheese, yogurt, pickles, etc.

alcohol fermentation

• produces ethanol (ethyl alcohol) and carbon dioxide (instead of lactic acid)

• from yeasts (unicellular fungi)