Download in the presence of oxygen

CELLULAR RESPIRATION
OVERVIEW
• C6H12O6 + 6O2  6CO2 + 6H2O + energy (36 ATP)
• Opposite of photosynthesis
• Energy being released from food in the presence of oxygen
• 3 stages of cellular respiration
1. Glycolysis 
No oxygen needed
2. Krebs cycle  Oxygen needed
3. Electron transport chain (ETC)  Oxygen needed
PRESENCE OF OXYGEN
• If reaction takes place using oxygen, it is said to be aerobic
(Krebs and ETC)
• If reaction takes place without oxygen, it is said to be anaerobic
(Glycolysis)
ENERGY IN FOOD
GLYCOLYSIS (SPLITTING OF SUGAR)
• 1st step in cellular respiration
• Glucose (6C) splits into 2 pyruvic acids (3C)
• Occurs in the cytoplasm
• Does NOT require oxygen
• Steps of glycolysis
1. 2 ATP  2 ADP energy released is used to split glucose
2. Transfer of electrons (H + ions) to 2 NAD+ to make 2 NADH
3. 4 ADP  4 ATP
SUMMARY
• 2 ATP  2 ADP, 2 NAD+  2 NADH, 4 ADP  4 ATP,
1 glucose  2 pyruvic acids
• Overall products
• 2 pyruvic acids, 2 NADH, 2 ATP
• Advantages of glycolysis
• Occurs very quickly
• Does not require oxygen
KREBS CYCLE
• 2nd step of cellular respiration
• Takes place in the matrix of the mitochondria
• Requires oxygen
KREBS CYCLE CONT.
• Steps (happen twice)
1. 1 pyruvic acid break down into 1 acetic acid. 1 CO2 are
+
released 1 NAD  1 NADH
2. Acetic acid joins with Coenzyme A  acetyl-CoA
3. Acetyl group is transferred to a 4C molecule to make Citric
acid (6C) starts Krebs cycle (AKA citric acid cycle)
4. 6C molecule gradually breaks down into a 4C molecule
a) 3 CO2 are released in total
b) Electrons are transferred to 4 NADH
c) Electrons are transferred to 1 FADH 2
d) 1 ATP is formed
To ETC
SUMMARY OF KREBS
1. 8 NADH
2. 2 ATP
3. 2 FADH2
4. 6 CO2 released
• Glycolysis & Krebs
a) 10 NADH
b) 4 ATP
c) 2 FADH2
d) 6 CO2 released
ELECTRON TRANSPORT CHAIN
• 3rd and final step of cellular respiration
• Takes place in the inner membrane of mitochondria in
eukaryotes and in the cell membrane of prokaryotes.
• Requires oxygen
ETC CONT.
• High energy electrons from glycolysis & Krebs are transported
to the ETC by NADH & FADH2
• Electrons pass from carriers through the ETC to oxygen to form
water
• As e- pass through ETC they lose energy
• Energy lost from e-, is used to pump H+ across the membrane
• With a high conc. of H+ outside of the membrane and a low
conc. Inside the membrane H+ pass through ATP synthase
• ATP synthase rotates and adds a phosphate group to ADP to
make ATP.
ELECTRON TRANSPORT CHAIN
ATP FORMATION
• For every 2 electrons that pass through the ETC,
enough energy is released to produce 3
molecules of ATP.
• 32 ATP are produced by ETC
• Cellular respiration summary of ATP
• Glycolysis + Krebs + ETC
•
2
+
2
+ 32 = 36 ATP / glucose
• C6H12O6 + 6 O2  36 ATP + 6 CO2 + 6 H2O
FERMENTATION
• Produces ATP from food without the use of oxygen
• Glycolysis produces ATP and NADH, but it can’t continue if
there is no NAD+
• Fermentation returns NADH to NAD +
• Glycolysis and fermentation are called anaerobic respiration
• 2 forms of fermentation
1. Alcoholic fermentation
2. Lactic acid fermentation
ALCOHOLIC FERMENTATION
• Yeast and other microorganisms
• Produce ethyl alcohol and CO 2
• Pyruvic acid + NADH  ethyl alcohol + CO 2 + NAD
+
• Used to make alcoholic beverages and to make bread rise
LACTIC ACID FERMENTATION
• Most organisms
• Pyruvic acid + NADH  Lactic acid + NAD+
• Used to produce food  Gives sour taste
• Cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut
• Humans are lactic acid fermenters
• Muscle cells are best adapted for lactic acid fermentation
TYPES OF FERMENTATION
ENERGY SUPPLY
• Three sources of ATP
1. ATP already in the muscles
2. ATP make through lactic acid fermentation
3. ATP made from cellular respiration
SHORT TERM ENERGY
• Muscles only contain enough ATP for a few seconds of intense
activity
• After that ATP is produced by lactic acid fermentation
• Makes enough ATP for about 90 seconds of activity
• Lactic acid builds up in muscles and takes excess oxygen to
get rid of acid
• In quick bursts of energy, the body uses ATP already in the body
along with ATP made through lactic acid fermentation.
LONG TERM ENERGY
• For activity lasting longer than 90 seconds, cellular respiration is
the only way to continue producing ATP
• Glycogen in the muscles supplies energy for 15 – 20 minutes.
• After that other stored molecules (such as fats) are broken
down.