5.2: Cellular Respiration
(Aerobic Respiration)
Energy Review
Plants—make food (sugar) through photosynthesis
 Animals and other organisms—get food by eating plants
and animals

Cellular Respiration

Cellular respiration— glucose and food are broken
down to make energy (ATP) in ALL organisms
 Occurs in the mitochondria of eukaryotes
 Occurs in the cytoplasm of prokaryotes
Cellular Respiration Equation
C6H12O6 + O2
CO2 + H2O + energy
Cellular Respiration

Aerobic Respiration: breaking down of glucose
molecules into smaller pieces in the presence of
oxygen to produce ATP
Cellular Respiration

THREE STEPS OF AEROBIC RESPIRATION
1. Glycolysis
2. Kreb’s/Citric Acid Cycle
3. Electron Transport Chain (ETC)
Cellular Respiration
1. Glycolysis: occurs in cytoplasm; glucose is split in
half, forming a pyruvate molecule
 2 ATP released
 Electrons released and carried to mitochondria
by NADH
Cellular Respiration
Glycolysis quiz

Where does glycolysis take place?

What molecule is used in glycolysis?

What are the products of glycolysis?

What ultimately happens to each of these
products?

Write an equation that represents glycolysis
Cellular Respiration
2. Kreb’s/Citric Acid Cycle: occurs in the
mitochondria; pyruvate is split into smaller pieces
 CO2 gas released (we breathe it out)
 2 ATP released
 Electrons released and move to mitochondrial
membrane by NADH and FADH2
Cellular Respiration
NAD+
FAD+
NADH
FADH
NAD+
FAD+
Krebs/Citric Acid Cycle Quiz

Where does the CAC occur?

What molecule is used in the CAC?

What are the products of the CAC?

What happens to each of these products?

Write an equation that represents the CAC
Cellular Respiration
3.
Electron Transport Chain (ETC): made of
proteins; occurs in the mitochondria
NADH & FADH2 drop off electrons at proteins
 Electrons lose energy as get passed from protein to
protein
 Energy used to make ATP (ATP Synthase)
 32 ATP made
 Electrons finally passed to OXYGEN to make
WATER

Cellular Respiration
TOTAL ENERGY: 36 ATP from 1 glucose
ETC quiz

What is the ETC?

What molecules bring the electrons to the ETC?

What happens as the electrons get passed from protein
to protein down the ETC?

What happens to the extra energy?

What happens to the electrons at the end of the ETC?
CR Animation
Glucose
ATP
Pyruvate
NADH
FADH2
NADH
Glycolysis
O2
Krebs Cycle (CAC)
CO2
ATP
ETC
H2O
ATP
Cellular Respiration
(Anaerobic Respiration)
Cellular Respiration

Anaerobic Respiration: breaking down glucose
molecules into smaller pieces the ABSENCE of oxygen
to produce ATP
Cellular Respiration

TWO STEPS OF ANAEROBIC RESPIRATION
1. Glycolysis: occurs in cytoplasm; glucose is split in
half, forming a pyruvate molecule
 2 ATP released
 Electrons released and carried to mitochondria
Cellular Respiration

TWO STEPS OF ANAEROBIC RESPIRATION
 2. Fermentation: breaking down pyruvate without
oxygen
Cellular Respiration

Lactic acid fermentation: pyruvate is broken down
into lactic acid + ATP
 2 ATP released

Lactic acid builds up as in muscle cells & causes burning
sensation (muscle cramping) during strenuous exercises
C-C-C
pyruvate
+
NADH
e’ carrier

H-C-C-C + ATP + NAD+
 lactic acid energy
carrier
Cellular Respiration

Alcoholic fermentation: pyruvate is broken
down into alcohol, carbon dioxide, and ATP in
yeast and bacterial cells
 2 ATP released

Used in making bread and alcohol beer
C-C-C + NADH  C-C-OH +
Pyruvate + e’ carrier
CO2 + ATP
alcohol + carbon + energy
dioxide
Eat
Cellular Respiration
Digestion
Glycolysis
Oxygen is
present
Aerobic
respiration
No oxygen is
present
Fermentation
(anaerobic respiration)
Citric acid
cycle
Electron
transport chain
In yeast
In animals
Alcoholic
fermentation
Lactic acid
fermentation
Cellular Respiration
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Photosynthesis
food synthesized
requires energy
Chloroplast
Only autotrophs
vs. Respiration
food broken down
produces energy
mitochondria/cytoplasm
Autotrophs and heterotrophs
(all living cells)