1. Cellular respiration is the process that releases energy from food in the presence of oxygen. It involves the breakdown of glucose and other food molecules, capturing some energy to produce ATP and other compounds while releasing carbon dioxide and water. 2. ATP is the "energy currency" of cells. It is used to store and transport chemical energy within cells to power energy-requiring cellular processes. ATP is regenerated through catabolic reactions when its phosphate bonds are broken. 3. NADH and FADH2 act as electron carriers that shuttle energy extracted from nutrients to sites of ATP production through oxidative phosphorylation. NADPH similarly transports energy but for biosynthesis rather than ATP production.

1. Introduction : Metabolism
นวชค 204 ชีวเคมีเบื้องต้น
https://phys.org/news/2016-09-tracking-bugs-reveal-secret-cancer.html

2. Energy
• Energy: the capacity to do work
• Energy can exist in two states:
– Kinetic energy – energy of motion.
– Potential energy – stored energy.
• Chemical energy – potential energy
stored in bonds, released when bonds
are broken.
• Energy can be transformed form one
state to another.
• Energy can take many forms: chemical,
mechanical, electric current, heat, light

3. Fig. 6.1

4. Miller, Kenneth R., and Joseph S. Levine.,( 2010), Chapter 9 : Cellular respiration and fermentation, Miller & Levine Biology, 9th Edition, Boston, 1034 pages.
When you are hungry, how do you feel?
Food serves as a source of energy
How does food get converted into a
usable form of energy?
A calorie is the amount of energy needed to raise the temperature of 1 gram
of water 1 degree Celsius.
For example, 1 gram of the sugar glucose releases 3811 calories of heat
energy when it is burned.
https://www.shutterstock.com/video/clip-21796042-stock-footage-macro-of-burning-sugar-with-flames.html

5. 5
Flow of Energy
• Most forms of energy can be converted to heat energy.
• Heat energy is measured in kilocalories.
• One calorie = the amount of heat required to raise the
temp of water by 1oC
1 kilocalorie (kcal) = 1000 calories (Cal.)

6. Cell break down food molecules gradually, capturing a little bit of chemical
energy at key steps.
This enables cells to use the energy stored in the chemical bonds of foods like
glucose to produce compounds such as ATP that directly power the activities of
the cell.
6O2 + C6H12O6  6CO2 + 6H2O + Energy
Cellular respiration is the process that releases energy from
food in the presence of oxygen.
What kind of EN

7. • The precursor is converted into a
product through a series of
metabolic intermediates called
metabolites.
Part 2 : BIOENERGETICS AND METABOLISM
• Metabolism is the sum of all the
chemical transformations taking place in
a cell or organism.
• Metabolism occurs through a series of
enzyme-catalyzed reactions that
constitute metabolic pathways)
Metabolism

8. 8
 Two categories of cellular chemical reactions:
1.Anabolic Reactions
 Build larger molecules for growth, repair, reproduction
 Dehydration Synthesis Reactions
 require energy and nutrients
2.Catabolic Reactions
 Breakdown larger molecules
 Hydrolysis Reactions
 mobilize nutrients for energy making it available to the cell
8
Metabolism

9. Catabolism is the degradative phase of metabolism in which organic
nutrient molecules (carbohydrates, fats, and proteins) are converted
into smaller, simpler end products (such as lactic acid, CO2, NH3) and
also release energy, some of which is conserved in the formation of
ATP and reduced electron carriers (NADH, NADPH, and FADH2); the
rest is lost as heat.
In anabolism, also called biosynthesis, small, simple precursors are
built up into larger and more complex molecules, including lipids,
polysaccharides, proteins, and nucleic acids. Anabolic reactions
require an input of energy, generally in the form of the phosphoryl
group transfer potential of ATP and the reducing power of NADH,
NADPH, and FADH2.
Metabolism

11. 11
Metabolism
 Metabolism is the sum total of all anabolic and
catabolic reactions that occur in the cell
 The metabolism of cells is carried out and controlled
by the enzymes
– There are catabolic enzymes – those that cleave larger
molecules into smaller ones
 Ex. Hydrolysis Reactions
– There are also anabolic enzymes – those that assemble
smaller molecules into larger ones
 Ex. Dehydration Reactions
11

12. Figure 5_03b

13. 13
Regulation of Biochemical Pathways
 Metabolism is tightly regulated
 There is a delicate balance between all of the
reactions that take place in the cell
 Metabolism is commonly regulated 3 ways:
1. Enzymatic competition for substrate
2. Gene regulation
3. Enzyme inhibition
13

14. ATP
• ATP is a molecule that is used as an Energy
Currency in cells.
• ATP is the molecule that cells use for store, transfer,
and provide energy.
– ATP’s can be broken down to provide energy for
endergonic reactions.
• The energy from ATP is used to fuel anabolic
reactions.
– recall: for growth, repair, and reproduction
https://www.youtube.com/watch?v=00jbG_cfGuQ
ATP & Respiration: Crash Course Biology #7

15. 15
ATP - Energy Currency of Cells
• ATP = Adenosine TriphosPhate
= + Adenosine (ribose and adenine— as same as RNA)
+ Three inorganic phosphates (functional group PO4)

16. 16
• ATP stores energy in the covalent bonds
between phosphates:
– Phosphates are highly negative, therefore:
• the phosphates repel each other
• much energy is required to keep the phosphates bound
to each other
• Energy is released when the bond between
two phosphates is broken
ATP - Energy Currency of Cells

17. Figure 5_12

18. 18
Energy Currency of Cells — ATP - ADP Cycle
these reactions are reversible...

19. 19
Other Functions of ATP
 ATP regulates enzyme activity
 Phosphorylation and dephosphorylation -
process of adding or removing phosphate groups
- can activate or deactivate enzymes
 ATP serves as a source of phosphate groups

20. NADH and FADH2: The body’s energy shuttles
• When breaking down nutrients, metabolic reaction release
high-energy electrons.
• Further reactions transfer energy from these electrons to ATP.
• One major electron acceptor is NAD+, a derivative of the B
vitamin niacin.
• The other major electron acceptor is FAD, a derivative of the B
vitamin riboflavin. When FAD accepts 2 high-energy electrons,
it picks up 2 protons and forms FADH2.

21. • The metabolic pathways have several energy-
transfer points where an NAD+ accepts 2 high-
energy electrons and 2 hydrogen ions (2
protons- H+) to form NADH+H+.
NADH : The body’s energy shuttles

22. NADPH : An energy shuttle for biosynthesis
• Energy powers: the assembly of building into
complex molecules of carbohydrate, fat, and protein.
• NADPH, an energy-carrying molecule similar to
NADH, delivers much of the energy these
biosynthetic reactions require.
• Although both molecules are energy carriers, their
metabolic roles are vastly different. Whereas the
energy carries by NADH primarily produces ATP,
nearly all the energy carried by NADPH drives
biosynthesis.
• When a reaction transforms NADPH into NADP+,
NADPH release its cargo of two energetic electrons.

23. • Key concept ATP is the energy currency of the body. Your body
extracts energy from food to produce ATP.
• NADH and FADH2 Are hydrogen and electron carriers that shuttle
energy to ATP production sites. NAPH is also and electron carrier,
but it shuttles energy for anabolic processes.