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BIOLOGY
ENERGY FOR ALL NOTES
Metabolism
a. Anabolism = building up of molecules
ex) photosynthesis; making proteins,
lipids, nucleic acids and carbohydrates
b. Catabolism = breaking down of
molecules
ex) digestion, oxidative respiration,
Glycolysis, Kreb’s cycle
The origin of energy on Earth comes from the
_SUN. This energy is also known as
SOLAR ENERGY.
Plants and other organisms, in the process of
PHOTOSYNTHESIS, transform the sun’s energy
into another form of energy, CHEMICAL ENERGY
which is stored in the chemical bonds in the
molecules.
Each time a chemical bond is broken, chemical
energy is RELEASED.
Cellular respiration: process by which food
molecules are broken down to produce ATP.
ATP stands for ADENOSINE TRIPHOSPHATE.
Stages in cellular respiration:
1. Glycolysis is a series of chemical reactions in
the cytoplasm of a cell that breaks down a
molecule of GLUCOSE into two molecules of
PYRUVIC ACID (pyruvate, a C3 compound).
4 ATPs per glucose molecule are produced;
no oxygen is required for this process. This is
known as anaerobic process.
Pyruvic acid moves into the MITOCHONDRIA of
the cell, also known as the powerhouse of the cell.
2. CITRIC ACID CYCLE or KREB’S CYCLE
(TRICARBOXYLIC ACID CYCLE): series of
reactions in which the first reaction is also one of
the end products. This occurs in the
mitochondrion. These reactions require oxygen.
For every turn of the cycle, molecules of ATP and
CO2 are produced.
Carbon dioxide is released as a waste product.
3. ELECTRON TRANSPORT CHAIN: also occurs
in the mitochondria.
In this chain, electrons are transferred from one
protein to another, RELEASING energy in the
process.
OXYGEN is the final electron acceptor in this
process. Oxygen reacts with hydrogen and
electrons to form water (H2O).
Oxygen is important in the body since without it
the proteins cannot pass along the electrons, and
without passing the electrons, proteins cannot
accept new electrons; therefore, ATP production
stops. Organisms need a constant supply of
oxygen to continue life processes (memorize this).
A total of thirty- six (36) ATPS are produced in
cellular respiration.
Fermentation: an ANAEROBIC process that
follows Glycolysis and provides a means to
continue production of ATP until oxygen is
available again.
Types of fermentation:
a. LACTIC ACID FERMENTATION
Examples: lactic acid is produced in the
muscles during strenuous exercise and is
transferred to the blood stream that converts it
back to pyruvic acid.
Lactic acid builds up in the cell results in
muscle fatigue.
Ex) Yogurt production
b. ALCOHOLIC FERMENTATION
Examples: produced by yeast cells and some
bacteria to produce carbon dioxide and ethyl
alcohol.
During baking, yeast cells produce CO2 that
form bubbles in the dough but the yeast are
killed by heat and the bubble pockets are left to
lighten the bread.
Table. Comparison of the types of fermentation to
cellular respiration.
Process
Lactic acid
fermentation
Glucose
Alcohol
Cellular
fermentation respiration
Starting
substance
Process & Glycolysis
interme(pyruvic acid)
diate
product
Lactic acid +
products
2 ATP
Glucose
Glucose
Glycolysis
(pyruvic acid)
Glycolysis
(pyruvic
acid)
Carbon
dioxide +
Alcohol +
2 ATP
Carbon
dioxide +
Water +
36 ATP
Table. Comparison between photosynthesis and
cellular respiration
PHOTOSYNTHESIS
Food synthesized
Energy from the sun
stored in glucose
Carbon dioxide taken in
CELLULAR
RESPIRATION
Food broken down
Energy of glucose
released
Carbon dioxide given off
Oxygen given off
Produces sugars from
PGAL
Requires light
Occurs only in the
presence of chlorophyll
Oxygen taken in
Produces CO2 and H2O
Does not require light
Occurs in all living cells