Cellular
Respiration!
Cellular Respiration
• Purpose: process that releases energy by
breaking down glucose and other foods in
the presence of oxygen
– (In most cases – we can also make energy
WITHOUT oxygen)
Cellular Respiration
• Cellular respiration is also known
as aerobic respiration - this
means it uses oxygen
–Anaerobic respiration – does
NOT use oxygen
Aerobic: process which requires oxygen
Aerobic: process which
requires oxygen
Respiration Equation
6 O2 + 1 C6H12O6  6 CO2 + 6 H2O + 36 ATP
sugar (glucose)
6 oxygen
_____+ 1 ____
carbon + 6 ____+
water 36 ATP
 6 ____
dioxide
(energy)
_____
Chemical Energy and ATP
• A T P (adenosine triphosphate) is the
main chemical compound in cells that
stores and releases energy
How does it work?
• ADP is ATP with one less phosphate
• Energy is stored in the bond between the
three phosphates
• ATP must lose a phosphate to become
ADP
How does it work?
• When the phosphate bond is broken,
energy is released
– Like breaking a glow stick or a hot/cold pack
How does it work?
*[ATP] breaks down to [ADP + Phosphate]
and releases energy to carry out life
processes
Why do we need ATP?
• ATP is “energy currency” in the cell
• When ATP breaks down into ADP, it
provides energy for cellular processes:
– Making proteins
– Energy for photosynthesis
– Active transport
Why do we need ATP?
• Our cells store a limited amount of ATP
– only enough for a short period of activity
• cells regenerate ATP from ADP as needed
• ***like recharging and using a cell phone
Cellular Respiration
• Purpose: process that releases energy by
breaking down glucose and other foods in
the presence of oxygen
– (In most cases – we can also make energy
WITHOUT oxygen)
Respiration Equation
6 O2 + 1 C6H12O6  6 CO2 + 6 H2O + 36 ATP
sugar (glucose)
6 oxygen
_____+ 1 ____
carbon + 6 ____+
water 36 ATP
 6 ____
dioxide
(energy)
_____
Where do the reactants come from?
1. Glucose (sugar) comes
from the foods we eat
(or in the case of plants…
they make their own food)
Where do the reactants come from?
2. Oxygen comes from
the air/atmosphere
Where does cellular respiration occur?
• Aerobic respiration occurs in the
mitochondria
of both plant
and animal cells
Cellular Respiration
• Starts with Glycolysis (process producing
ATP molecules)
• It then goes in one of two directions
depending on whether oxygen is available.
• If O2 is available -> Krebs cycle …
Electron transport chain (all
aerobic)
• If O2 is NOT available -> Fermentation
(anaerobic)
Stages of Cellular Respiration
1. Glycolysis
• Occurs in the cytoplasm
• A very fast, anaerobic process of
“splitting glucose”
• Produces 2 ATP molecules overall
Stages of Cellular Respiration
IF OXYGEN IS PRESENT…
2. Kreb’s Cycle
• Occurs in the mitochondria
• Aerobic process
3. Electron Transport Chain
• Occurs in the mitochondria
Stages of Cellular Respiration
IF OXYGEN IS NOT PRESENT
2. Fermentation
• Anaerobic respiration occurs
Anaerobic respiration (fermentation)
• Releasing energy from food by producing
ATP without oxygen
2 types of fermentation
1) alcoholic fermentation (plants, bacteria)
-produces alcohol and CO2
2) lactic acid fermentation (animals)
-produced in muscles during rapid
exercise…
Anaerobic Respiration
• Anaerobic respiration, or
fermentation, takes
place in the cytoplasm
Anaerobic Respiration
• It is a different way to make ATP
compared to aerobic respiration
because it DOES NOT use oxygen.
• Glycolysis only makes:
•2 ATP
•Lactic acid
- Toxic (harmful
to cells)
Plants are different…
Plants don’t make lactic acid…
For plants, fermentation makes…
Alcohol
(which is why it’s called alcoholic fermentation…)
2 Types of Fermentation
1. alcoholic fermentation
– Produces alcohol and carbon dioxide
2 Types of Fermentation
1. alcoholic fermentation
Example: used by yeast cells. When they
run out of oxygen, they give off CO2 – this
causes bread dough to rise.
• Remember…
•Glycolysis only makes:
•2 ATP
•Lactic acid
- Toxic (harmful
to cells)
2 Types of Fermentation
2) lactic acid fermentation
– During rapid exercise,
oxygen isn’t supplied fast
enough to the muscles
–Muscles must produce
their own ATP by lactic acid
fermentation
Ex. of Lactic acid fermentation
2 Types of Fermentation
lactic acid fermentation
– Lactic acid is toxic (it
makes your muscles sore)
Comparing Aerobic vs. Anaerobic
Aerobic
Anaerobic
Respiration
Respiration
• Takes place in the • Takes place in the
mitochondria
cytoplasm
Comparing Aerobic vs. Anaerobic
Aerobic
Respiration
• Produces LOTS
of ATP
Anaerobic
Respiration
• Very little ATP
produced
Comparing Aerobic vs. Anaerobic
Aerobic
Respiration
• Endurance
Anaerobic
Respiration
• Used for short
bursts of
energy
Comparing Aerobic vs. Anaerobic
Aerobic
Respiration
• No harmful
effects or toxins
produced
Anaerobic
Respiration
• Produces lactic
acid (toxic)
Comparing Aerobic vs. Anaerobic
Aerobic
Respiration
• Much more
efficient
Anaerobic
Respiration
• Less efficient
Anaerobic Respiration
• ***You get WAY more ATP from aerobic
respiration than you do from anaerobic
respiration (fermentation).
• Fermentation is mostly used to provide
organisms with short-term bursts of
energy when oxygen is not available.