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Chapter 7
Biochemical Pathways used to
Harvest Energy in animals
AKA - Cellular Respiration
When you eat, how does the energy in
your food change into a form your body
can use?
It uses a biochemical pathway to break
down the food molecules into ATP
Biochemical Pathway:
- Chemical reaction (in a living
organism) where the products of 1 reaction
are the reactants in the next.
Pathway 2: Cellular Respiration
Main purpose: convert glucose into ATP
- occurs in all living things (including
plants)
- happens in the mitochondria
Formula for Cellular Respiration:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP
Cellular Respiration: Step One
Glycolysis:
-Break down of glucose (C6H12O6),
a 6-carbon sugar, into 2 smaller, 3-carbon
sugars
- it's universal; all living organisms start
with this step
-produces NADH, used to make ATP
Cellular Respiration: Step Two
- depends on whether oxygen is present
or absent
Glucose
Glycolysis
O2 present
Aerobic
Respiration
O2 absent
Alcoholic
Fermentation
(bacteria &
yeast)
Lactic Acid
Fermentation
(humans &
animals)
Anaerobic respiration:
- forming ATP without oxygen
- less efficient than aerobic respiration
- only makes 2 ATP molecules for every
glucose
2 types:
1. Alcoholic fermentation
2.Lactic Acid Fermentation
Anaerobic
respiration
produces
lactic acid
or alcohol
without
oxygen
Anaerobic Respiration cont...
Alcohol Fermentation:
- glycolysis products are converted into:
*alcohol (ethanol)
* CO2
* 2 ATP
- used by bacteria & fungi
* Brewers of alcohol use yeast (fungus) &
sugar source for fermentation
Anaerobic respiration cont....
Lactic Acid Fermentation:
- happens in animals & humans when oxygen
is used faster than it is taken in
- products of glycolysis are converted into:
* lactic acid
* CO2
* 2 ATP
Lactic Acid Fermentation – No
oxygen needed
Q: I'm a runner and I ran a marathon yesterday,
why am I so sore today?
A: Build up of lactic acid makes you sore & have
muscle cramps.
Q: If lactic acid fermentation can produce ATP
without using oxygen, then why do people die
from lack of oxygen in such a short time?
A: L.A. Fermentation doesn't happen in nerve
cells so brain needs constant supply of O2 to run
things
Aerobic Respiration:
- 3 step process that uses oxygen to
produce ATP
- much more efficient than anaerobic
respiration
- makes ~ 36 ATP molecules from
every glucose molecule
Aerobic Respiration cont...
Step 1: Glycolysis
- breaking glucose into 2 3-carbon sugars,
2 (net) ATP & 2 NADH
Step 2: Kreb's Cycle
- 5 step circular pathway that produces:
* 6 CO2
* 8 NADH and 2 FADH2 (molecules that
“ hold” energy)
* 2 ATP
Kreb's Cycle
Step 3: Electron Transport Chain
- produce ATP when NADH and FADH2
release their electrons to Oxygen
- Each oxygen accepts 2 electrons and 2 H+
ions to form ..... H2O
- waste products: H2O and CO2
- energy trapped: 32 ATP
Produces
32 ATP
So what do a
burning match and
a burning
marshmallow have
in common with
aerobic respiration?