CELL RESPIRATION dinucleotide) and FAD (flavin adenine
dinucleotide).
Bioenergetics
• Reactions involving electron transfers are
- The study of the concept of energy flow known as oxidation-reduction
within living organisms. reactions (or redox reactions).
Cell Respiration • When NAD and FAD pick up electrons, they
also gain one or more hydrogen atoms,
• process by which the chemical energy from
switching to a slightly different form:
nutrients is released and partially captured
in the form of ATP • And when they drop electrons off, they go
neatly back to their original form:
• The reactions in which NADand FAD gain or
lose electrons are examples of a class of
reactions called redox reactions.
• Cellular respiration involves many reactions
in which electrons are passed from one
molecule to another. Reactions involving
electron transfers are known as oxidation-
reduction reactions (or redox reactions).
• You may have learned in chemistry that a
redox reaction is when one molecule loses
electrons and is oxidized, while another
molecule gains electrons (the ones lost by
the first molecule) and is reduced. Handy
mnemonic: “LEO goes
GER”: Lose Electrons, Oxidized; Gain Electro
ns, Reduced.
GLYCOLYSIS
- is a series of reactions that extract energy
Adenosine Triphosphate (ATP) from glucose by splitting it into two three-
carbon molecules called pyruvates.
- Primary carrier of energy in cells. - breakdown of glucose takes place in the
- In a cell, this overall reaction is broken cytoplasm with or without oxygen
down into many smaller steps. Energy The end products are:
contained in the bonds of glucose is 2 Pyruvate molecules - going to
released in small bursts, and some of it is mitochondrion matrix
captured in the form of adenosine 2 net ATP
triphosphate (ATP), a small molecule that 2 NADH – moves to ETC
powers reactions in the cell. Much of the
energy from glucose is dissipated as heat, KREBS CYCLE / TCA (TRICARBOXYLIC ACID CYCLE)
but enough is captured to keep the OR CITRIC ACID CYCLE
metabolism of the cell running. • Each pyruvic acid / pyruvate is converted
into acetyl CoA releasing carbon dioxide &
NADH .
• Takes place in the matrix of the
mitochondria
• Requires oxygen
• PRODUCTS: 2 ATP; 8 NADH; 2 FADH2; 6CO2
ELECTRON CARRIERS OXIDATIVE PHOSPHORYLATION/ELECTRON
TRANSPORT CHAIN
• Also called electron shuttles
• 10 NADH (2 from G; 8 from KC) and 2
• There are two types of electron carriers that FADH2 (from KC) uses high energy electrons
are particularly important in cellular from G and KC to convert ADP to ATP
respiration: NAD+ (nicotinamide adenine
• takes place in the cristae (folds in the • NADH yields 3 ATP which would result to 38
intermembrane of mitochondrion) ATP if malate shuttle is used. FADH 2 yields 2
ATP resulting to 36 ATP if the phosphero-
• requires oxygen
glycerol shuttle is used.
• PRODUCTS: 32/34 ATP; H2O
• The NADH and FADH2 made in other steps
ANAEROBIC RESPIRATION
deposit their electrons in the electron
transport chain, turning back into their
"empty" forms (NAD+ and FAD). As
electrons move down the chain, energy is
released and used to pump protons out of
the matrix, forming a gradient. Protons flow
back into the matrix through an enzyme
called ATP synthase, making ATP. At the end
of the electron transport chain, oxygen
accepts electrons and takes up protons to
Anaerobic cellular respiration is similar to aerobic
form water.
cellular respiration in that electrons extracted from
a fuel molecule are passed through an electron
transport chain, driving ATP synthesis.
What kinds of organisms use anaerobic cellular
respiration? Some prokaryotes—bacteria and
archaea—that live in low-oxygen environments rely
on anaerobic respiration to break down fuels.
o Ever wonder how yeast ferment barley malt
into beer? Or how your muscles keep working
when you're exercising so hard that they're
very low on oxygen?
o Both of these processes can happen thanks to
Where does the figure of 30-32 ATP come from? alternative glucose breakdown pathways that
Two net ATP are made in glycolysis, and another occur when normal, oxygen-using (aerobic)
two ATP are made in the citric acid cycle. Beyond cellular respiration is not possible
those four, the remaining ATP all come from o Fermentation is another anaerobic (non-
oxidative phosphorylation. oxygen-requiring) pathway for breaking down
glucose, one that's performed by many types
of organisms and cells. In fermentation, the
WHY 36 OR 38? only energy extraction pathway is glycolysis,
• Depends on which shuttle that is used to with one or two extra reactions tacked on at
transport the electrons from glycolysis into the end.
the mitochondria. o lactic acid fermentation, NADHNADHstart text,
N, A, D, H, end text transfers its electrons
• If malate-aspartate shuttle is used then 38 directly to pyruvate, generating lactate as a
ATP will be produced (trades cytoplasmic byproduct.
NADH for mitochondrial NADH)
• If the phosphero-glycerol shuttle was used
you get 36 ATP (trades cytoplasmic NADH
for mitochondrial FADH2).
