The Function of ATP

1. Energy Storage and
Utilization

2. ATP (Adenosine Triphosphate) – the major source of energy in cell metabolism.
- chemical energy converted from “electron energy”
The Function of ATP
 transport work moving substances across cell membranes.
 used for mechanical work, supplying the energy needed for muscle
contraction.
 supplies energy not only to heart muscle (for blood circulation) and skeletal
muscle (such as for gross body movement), but also to the chromosomes and
flagella to enable them to carry out their many functions.
 A major role of ATP is in chemical work, supplying the needed energy to
synthesize the multi-thousands of types of macromolecules that the cell needs
to exist.
 used as an on-off switch both to control chemical reactions and to send
messages.

3. Plants use the energy in ATP molecules to move water, repair themselves, and
grow.
Plants vital energy conversions:
1. Light energy Electron energy
2. Electron energy Chemical energy (ATP
3. Chemical energy (ATP) sugars
Respiration - the process in which nutrients are converted into useful energy in a
cell

4. Photosynthesis
- The entire process of trapping light energy into the bonds of a sugar
molecule.
Two processes involves:
1. Light-dependent Phase – solar energy is trapped and used to
excite electrons to higher energy levels. These electrons are then
passed down an electron transport chain, and the energy released is
used to make ATP. After the electrons have completed their passage
down the electron transport chain, they are passed to a second
photosystem (known as photosystem I) and more light energy is
harvested. Once the electrons have been given this energy, they are
passed to molecule known as NADP (that then becomes NADPH) and
held there ready to be used in the next phase of photosynthesis.

5. NAD - Nicotinamide adenine dinucleotide - is an important coenzyme found
in cells. It plays key roles as a carrier of electrons and a participant in metabolic
redox reactions, as well as in cell signaling.
Nicotinamide adenine dinucleotide phosphate (NADP) - is the reduced form
of NAD. The main role of NADP in metabolism is the transfer of electrons from one
redox reaction to another, which is very important in the release of energy from
nutrients.

6. Nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) - is the
reduced form of NADP.
The NADPH oxidase complex is a cluster of proteins that donate an electron
from NADPH to molecular oxygen (O2) to produce superoxide (O2-). This initiates
the respiratory burst, a key step in immune defense against bacterial and fungal
pathogens. The importance of this process to human health is manifested in
chronic granulomatous disease (CGD), which refers to any of several hereditary
diseases in which certain oxidase proteins are defective.
An important role for NADPH oxidase in phagocytes is bacterial killing, which
occurs in phagosomes.

7. Chloroplasts – an organelle that converts sunlight, carbon dioxide, and water
into sugars in the process of photosynthesis.
Photosystem II – embedded in the thylakoid membranes of chloroplasts,
special solar collectors composed of pigment molecules, the major ones of which
are chlorophyll a and chlorophyll b.
Photolysis (“splitting by light”) – a process when the solar collector
loses two of its electrons, they are replaced by electrons from an enzyme. The
enzyme recovers its electrons by splitting a water molecule.
Hydrogen ions are formed and oxygen gas is given off as a waste product.
2H2O 4H+ + 4e + O2 or
Photosystem I – second solar collector

8. 2. The Light-independent Phase – short-term chemical and electron
energy in the ATP and NADPH molecules are converted into long-term chemical
energy in the covalent bonds of sugar molecules. The electrons are moved away
from oxygen atoms and toward the carbon and hydrogen atoms. This is a
nonspontaneous reaction requiring an input of energy that is then stored for later
use by the cell.
- Light-independent reactions of photosynthesis or dark reaction of
photosynthesis
Photosynthesis:
CO2 + 2H2O CH2O + H2O + O2
-

9. Cellular Respiration
- the most efficient way for cells to harvest energy stored in food.
Respiration :
C6H12O6 + O2 CO2 +H2O + Energy
glucose oxygen carbon water
dioxide

10. Aerobic Respiration
- A vast majority of organisms break down sugar molecules all the way to
carbon dioxide and water.
Three major stages:
1. Glycolysis – glucose molecules (from starch or sucrose) are broken down into
smaller 3-carbon units called pyruvate and some of the energy released is
trapped as ATP and NADH.
- Does not require oxygen
2. Krebs Cycle – the pieces of the glucose molecule left after glycolysis are
broken all the way down to carbon dioxide. GTP (a nucleotide similar to ATP),
NADH, and other high-energy molecules are formed.
GTP - Guanosine triphosphate

11. 3. ATP Synthesis – NADH molecules formed in glycolysis and Krebs cycle are
converted back to NAD molecules so that they be reused.

12. Anaerobic Respiration
- Some organisms that do not require oxygen to regenerate.
- Organisms depend on glycolysis to generate ATP and on fermentation to
regenerate NAD. A byproduct of this reaction is ethanol.
Fermentation is a metabolic process that converts sugar to acids, gases and/or
alcohol.
Pyruvate + NADH Ethanol + CO2 + NAD

13. Respiration and Photosynthesis
Compared
Photosynthesis
1. Occurs only in the chlorophyll-
bearing cells of plants
2. Needs the presence of light
3. Water and carbon dioxide are used
4. oxygen is given off as a waste
product
5. Food is built or synthesized
6. The weight of the plant is increased.
7. Energy is stored
Respiration
1. Occurs in every living plant and
animal cell
2. Occurs at all times
3. Water and carbon dioxide are given
off as waste products
4. Oxygen is used in the process
5. Food is destroyed to release its
energy.
6. The weight of the plant is decreased
7. Energy is released.