Cellular Respiration

CR is the process by which cells convert the energy in food, in the form of glucose, into usable energy (ATP)

Terms to know Oxidation=the loss of electrons,

compound becomes more positive Reduction=the gain of electrons,

compound becomes more negative Electrons and protons (H+) travel

TOGETHER, 2 electrons for every 1 H+(Proton)

Two types of cellular respiration include aerobic (with O2) and anaerobic (without O2)

“glucose-breaking Glycolysis is the first step in both forms

of CR, thus it does not need oxygen

Glycolysis

Big Picture Glucose, C6H12O6 (a 6 carbon molecule)

is broken down into 2 molecules of (a 3 carbon molecule) pyruvate

Occurs in the cytosol Releases about 2% of the energy in

glucose

Input 2 ATP, ”charged batteries” to use 2 NAD Glucose, energy storage molecule from

food, C6H12O6

Output: 4 ATP (2 net ATP) 2 NADH from NAD+ 2 pyruvates – also known as pyruvic acid

Glucose breaks in half forming 2, 3 carbons chains

If oxygen is absent, anaerobic respiration occurs Fermentation

If plants, bacteria, or yeast is alcoholic fermentation

If animals is lactic acid fermentation If oxygen is present, aerobic respiration

occurs

Anaerobic Respiration: Fermentation 2 major types: alcoholic and lactic acid Fermentation is used as a way to

dispose of H+ produced during glycolysis If the supply of NAD+ runs out, then

glycolysis would stop Thus the purpose of fermentation is to

recycle NAD

Anaerobic Respiration: Fermentation Alcoholic Fermentation

Occurs in plans, bacteria, and yeast-Normal process-Carbon dioxide is released from

pyruvate (3C) forming acetaldehyde (2C)-Acetaldehyde is reduced by NADH

(gains an electron) forming ethyl alcohol (ethanol)

-NAD+ is regenerate allowing glycolysis to continue

-Used to produce beer and wine

Anaerobic Respiration: Fermentation Lactic Acid Fermentation

Occurs in animal cells Normal process Pyruvate is reduced by NADH (gains an

electron), forming lactic acid NAD+ is regenerated allowing glycolysis to

continue Occurs in muscle cells, causing muscle pain

and fatigue during rapid exercise when the body cannot supply enough oxygen to tissues

Aerobic Respiration After glycolysis, most of the energy

from glucose remains “locked” in 2 molecules of pyruvate

If oxygen is present, pyruvate enters the mitochondrial matrix to complete the Kreb’s Cycle/The Citric Acid cycle (TCA)

First pryuvate gets “groomed” in the mitochondria by removing 1 C (CO2) and adding Coenzyme A

Aerobic Respiration

Aerobic Respiration Kreb’s Cycle

The next step in aerobic respiration occurring in the matrix of the mitochondria

It’s a series of redox reactions starting with Acetyl CoA

Acetyl CoA (2C) binds with oxaloacetate (4C) forming a 6C compound.

Eventually the carbons from acetyl CoA get released as CO2, allowing oxaloacetate to go through the cycle again

Aerobic Respiration Kreb’s Cycle

Named after Hans Krebs, Nobel prize winner 1953 for discovering the cycle

Also called the citric acid cycle Yields per pyruvate molecule:

4 NADH, 1 FADH2, 1 ATP Yields per glucose:

8 NADH, 2 FADH2, 2 ATP

Aerobic Respiration

Aerobic Respiration Electron Transport Chain and

Chemiosmosis The ETC is the last step in aerobic

respiration It receives all the electron carriers (NADH,

FADH2) from glycolysis and Kreb’s cycle It then converts NADH and FADH2 into

NAD+ and FAD+ Occurs in the inner membrane of the

mitochondria

Aerobic Respiration Electron Transport Chain and

Chemiosmosis 1 NADH -> 3 ATP 1 FADH2 -> 2 ATP The electrons from NADH and FADH2 are

passed from one electron acceptor protein to another

Oxygen is the final electron acceptor and makes water when it combines with hydrogens

Aerobic Respiration Chemiosmosis

The energy the electrons lose along the way moves H+ (off of NADH and FADH2) out of the matrix and into the intermembrane space of the mitochondria

As H+ ions diffuse through the membrane, the enzyme ATP synthase uses the energy to join ADP and a phosphate group -> ATP

Aerobic Respiration Electron Transport Chain

38% efficient (some energy lost as heat) 62% is released as heat (why you feel warmer

after exercise) 1 glucose yields 34-38 ATP ATP made from glucose provides energy to sleep,

exercise, eat, and study – allows cells to function Glycolysis: 2 ATP, 2 NADH -> 6 ATP in ETC Kreb’s: 2 ATP, 8 NADH-> 24 ATP in ETC, 2 FADH2 -> 4 ATP in ETC