Powers Unit 4 Cell Respiration

Cellular Respiration Notes

Unit 4: Cellular Energy

What is cellular

respiration? What is

required? What is made?
Where does this occur?

2

Cellular Respiration Overview

●Cellular Respiration - the process of breaking down food in the
presence of oxygen

●The goal of cellular respiration is to convert the chemical energy in
food to chemical energy stored in adenosine triphosphate (ATP).

●ATP can then release the energy for cellular metabolic processes
such as active transport across cell membranes, protein synthesis,
and muscle contraction.
○Any food (organic) molecule such as carbohydrates, lipids, and
proteins can be broken down into smaller molecules and then
used as a source of energy to produce ATP molecules

●Carbohydrates are our main source of energy

● To transfer the energy stored in glucose to the ATP

molecule, a cell must break down glucose slowly in a
series of steps and capture the energy in stages

● There a 3 stages in cellular respiration

○ The first is an anaerobic process which means no

oxygen is required

○ The second and third are aerobic processes

meaning oxygen is required

Cellular Respiration Overview

● A glucose molecule is broken in half into 2 pyruvic

acidmolecules with a net gain of2 ATP molecules

● Some electron(e-) carrying molecules are also

produced… 2 NADH

● Glycolysis is a series of reactions using enzymes

that takes place in the cytoplasm and does not
need oxygen
○ Glucose → 2 pyruvates + (2) ATP

Glycolysis

Glycolysis Review:

● Where does Glycolysis takes place?

○ cytoplasm

● What is the reactant of glycolysis?

○ glucose

● What are the products of glycolysis?

○ 2 ATP, 2 pyruvates, and 2 NADH

● Does this process require oxygen? What is this called?

○ No, it is called anaerobic

▪ If oxygen is available, then the 2-stage process of

aerobic respiration occurs in the mitochondria of
the cell.

▪ 2 Possible Pathways

● 1-Aerobic conditions glycolysis is followed by

cellular respiration in the mitochondria

● 2- Anaerobicconditions glycolysis is followed

by fermentation in the cytoplasm

After Glycolysis:

● Occurs in the mitochondrial matrix
● The pyruvic acid produced in glycolysis travels to the

mitochondriawhere it’s broken down in a series of
chemical reactions

● Carbon dioxide and energy (ATP) are released

○ Pyruvic acid → carbon dioxide + (2) ATP

● High energy carrying molecules are also produced here

(NADH and FADH2) that carry electrons (lots of
energy) to the final stage of cellular respiration

Krebs Cycle

Each Pyruvate Makes:

● 4 NADH
● 1 FADH2
● 1 ATP
● 3 CO2 (which is released to the atmosphere as

waste)

There are 2 pyruvate molecules, so there are
double of this made total.

Electron Transport Chain

● Occurs in the inner mitochondrial membrane

(cristae)

● The ETC is another series of chemical reactions

in which energy is transferred to form a large
number of ATP molecules (~32 ATP)

● At the end of ETC oxygen enters the process

and is combined with hydrogento form water

▪ High-energy electrons from NADH and FADH2 are

passed along the electron transport chain from
one carrier protein to the next.

▪ At the end of the chain, an enzyme combines

these electrons with hydrogen ions and oxygen to
form water

▪As the final electron acceptor of the electron
transport chain, oxygen gets rid of the low-energy
electrons and hydrogen ions.

▪ When 2 high-energy electrons move down the

electron transport chain, their energy is used to
move hydrogen ions (H+) across the membrane.

▪ During electron transport, H+ ions build up in the

intermembrane space, so it is positively charged.

▪The other side of the membrane, from which those
H+ ions are taken, is now negatively charged.

▪As it rotates, the enzyme grabs a low-energy ADP,
attaching a phosphate, forming high-energy ATP. Also
known as Chemiosmosis.

ADP

ATP
synthas
e

Channel

ETC Products:

●

The chemical equation for cellular respiration is:
C6H12O6 + 6O2→ 6CO2 + 6H2O + energy (~36 ATP)

●

Most of the energy released by cellular respiration that is not
used to make ATP is released in the form of heat

●

On average, each pair of high-energy electrons that moves
down the electron transport chain provides enough energy to
produce three molecules of ATP from ADP.

●

The products of the ETC are H2O and 32-34 molecules of ATP.

Total ATP from Cellular Respiration

Glycolysis, the Krebs cycle, and the electron transport chain release
about 36 molecules of ATP per molecule of glucose.

2

2

32

CO2

Total ATP?

30 to 42

Total Products:

● Glycolysis produces just 2 ATPmolecules

per molecule of glucose.

● The complete breakdown of glucose

through cellular respiration, including
glycolysis, results in the production of 36
moleculesof ATP.