ENERGY RELEASE IN THE CELL: Chapter 9
I.
II.
Background
A.
Energy requirements in living things:
 All living things need energy.
 Varies how they obtain this energy.
 Living things may be:
Autotrophs – produce their own nutrients
Heterotrophs – can’t produce their own food therefore they need to
take in nutrients.
B.
Fate of products of digestion:
 Starches – broken into simple sugars
 Fats – broken into fatty acids and glycerol
 Proteins – broken into amino acids
 Nucleic Acids – broken into nucleotides
~Why the hydrolysis of these products isn’t energy efficient: doesn’t
release enough energy only about 4 kcal’s but if glucose is broken
down 277 kcal’s of useful energy.
C.
Terms
1.
Glycolysis:
 Splitting of glucose
 Series of enzyme releasing steps
 Can occur aerobically or anaerobically
 Aerobically – in the presence of oxygen
 Anaerobically – in the absence of oxygen
a.
were the first organisms
 Requirements
a. ATP
b. NAD or NADP
2.
ATP- look at attached diagram - FUNCTION
3.
NAD & NADP– look at attached diagram - FUNCTION
4.
Oxidation reactions – involve the removal of H’s
 Glucose is oxidized during glycolysis
 Glucose loses H’s
5.
Reduction reactions – involves accepting H’s
 NAD or NADP accepts H’s and are reduced into NADH or
NADPH.
OXIDATION AND REDUCTION REACTIONS OCCUR
TOGETHER. WHEN ONE MOLECULE IS OXIDIZED,
ANOTHER IS REDUCED.
Cellular Respiration
A.
Overview – page 222
 Know major parts and where they occur (3)
 Glycolysis – occurs in the cytoplasm
1.
is part of both anaerobic and aerobic respiration
 Krebs Cycle - occurs in the mitochondria

B.
1.
is part of aerobic/ cellular respiration only
Electron Transport Chain – occurs in the mitochondria
1.
is part of aerobic/ cellular respiration only
Steps:
1.
Glycolysis – page 223
a.
Pathway:
 Glucose is split into 2 molecules of pyruvic acid
 2 ATP’s are put in
 2 H’s are removed and are given to 2NAD, forming
2NADH
 4 ATP’s are formed
 Net gain in ATP = 2
b.
Reactants
 Glucose
 2 ATP’s
 2 NAD’s
c.
Products
 4 ATP’s
 4 NADH’s
 2 pyruvic acids
d.
Fate of Pyruvic Acid
 Cellular respiration
 Alcoholic Fermentation – page 224
 Types of organisms – yeast, which is either
aerobic or anaerobic, therefore this process
must occur in sealed containers
 Products
 Alcohol
 Carbon dioxide
 NAD
 Total amount of ATP produced – 2 ATP’s
 Lactic Acid Fermentation
 Types of organisms – small microorganisms
Large organisms during
times of strenuous exercise
 Products
 Lactic acid
 NAD
 Total amount of ATP produced – 2 ATP’s
 Oxygen debt
 Cellular respiration begins with intermediate step
2.
Intermediate Step – page 227
 Where - mitochondria
a.
Pathway (everything is counted twice – why)
3.
 Pyruvic acid is oxidized by NAD
 NAD accepts H’s to form NADH
 Pyruvic acid is decarbozylated
 Fragments combines with CO A
 Acetyl-CO A forms
b.
Reactants
 Pyruvic acid - 2
 NAD - 2
 CO A - 2
c.
Products
 2 Carbon dioxide
 2 NADH
 2 acetyl- CO A
Citric Acid/Kreb’s Cycle – why it is called a cycle
 Where - mitochondria
a. Pathway
 Acetyl-CO A joins with a 4 c compound
 CO A drops off and goes back into intermediate step
 Citric acid is formed
 Citric acid is decarboxylated and oxidized
 Carbon dioxide and NADH are formed
 A 5 c compound is formed




b.
c.
The 5 c compound is decarboxylated
The 5 c compound is oxidized and NADH is formed
ATP is formed
A 4 c compound is fromed
 The 4 c compound is oxidized by FAD to form
FADH2
 The 4 c compound is oxidized and NADH is formed
 If more acetyl CO A enters, citric acid is formed
Reactants
 Acetyl CO A
 ADP
 NAD
 FAD
Products – why is everything counted twice
 2 ATP’s
 2 FADH2
 6 NADH’s
 4 carbon dioxides
d.
4.
Summary - at the end of the Krebs cycle, glucose has
been completely oxidized
 All the H’s have been removed from glucose
Electron Transport
a.
Reason – even though glucose has been oxidized very
little energy has been released. It is all tied up in
NADH.
 Energy must be released by passing the electrons to
lower energy levels. This is done by electron
transport.
b.
Components – see p. 228
 Electron Transport chain – consists of special electron
carriers that transfer electrons over a series of
carrier proteins.
 These electron carriers are located in the protein
portion of the mitochondrial membrane.
 Hydrogen Pump – located on membrane proteins.
 The pumps send H protons to one side of the
membrane.
 The energy to operate the H pumps comes from
passing electron over the electron transport
system.
c.
Events:
 All hydrogens from NADH and FADH2 are ionized.
 The electrons pass over the electron transport chain.
 There are 10 NADH’s and 2 FADH2.



d.
The energy creates a hydrogen pump which sends
all the H’s to the opposite side of the membrane.
When the H’s travel down the pump (to a lower
concentration) enough energy is available to form
ATP
The hydrogen protons and electrons join with each
other to form H’s.
 There are 24 hydrogens which join with 12 oxygens
to form 12 water molecules.
Reactants
 10 NADH’s (2-glycolysis; 2 – intermediate step; 6 –
Krebs cycle.)
 2 FADH2
 electron carriers
 6 O2
e.
C.
Products
 4 ATP’s from 2 FADH2
 30 ATP’s from oxidation of NADH
 12 waters (12H2 + 602) = 24 H and 12 O
Balance Sheet with Equation:
 C6H12O6 + 6O2 ->
(1)
(2)
1.
2.
3.
4.
5.
H2O
(4)
+ 38 ATP
(5)
Glucose is split in glycolysis
Oxygens are the final H acceptors at the end of electron
transport.
Carbon dioxide is released during the Kreb’s cycle
Water is produced during the electron transport chain.
It is a total of 12 water’s but 6 were put in during the
Kreb’s cycle.
34 ATP’s as a result of electron transport:
 3 for every NADH2 (30)
 2 for every FADH2 (4)
 4 from glycolysis
 2 from Kreb’s cycle

III.
6CO2 +
(3)
Less 2 put in during glycolysis
Other Organic Molecules Supply Energy
 How other nutrients can be used for energy – other molecules can
release energy, fats & proteins.
 They must be converted into some molecule that can enter
respiration, such as acetyl-CO A