CELLULAR RESPIRATIONCH 9

• All cells require energy from an outside source

• Some organisms obtain energy by producing it (photoautotrophs and chemoautotrophs)

• Some organisms obtain energy by consuming other organisms (heterotrophs)

What does this diagram tell?

• energy enters ecosystem as sun and leaves as heat

• photosynthesis uses sunlight to make glucose which is used in cell respiration

• cell respiration makes ATP which is used for work

I. Catabolism of glucose • Cellular respiration = catabolism of glucose to

produce ATP • Is a series of redox reactions

• 3 types of cellular respiration: • Aerobic respiration (nearly all organisms) • Anaerobic respiration (only a few types of

bacteria) • Fermentation (when aerobic can’t work)

II. Aerobic Respiration • A. Overview

• Requires O2 • Occurs in most organisms • In eukaryotes, most of it occurs in the

mitochondria • Produces 36 ATP • Occurs in 4 stages: – Glycolysis – Oxidation of pyruvate – Kreb’s citric acid cycle – Electron transport chain and oxidative

phosphorylation

B. Redox and Cell Respiration

• Glucose gives up electrons to NAD+ and FAD+– Glucose is oxidized and NAD+ and FAD+ get

reduced• NADH and FADH2 donate electrons to ETC

and then to O2– NADH and FADH2 become oxidixed and O2

becomes reduced

C. Stages of Aerobic Respiration

• 1. Glycolysis: oxidizes glucose to pyruvate

• Occurs in ALL cells • Is anaerobic• Occurs in the cytoplasm • Breaks down glucose to 2 3-carbon molecules

called pyruvate • Electrons from glucose are donated to NAD+

making NADH

2. Oxidation of Pyruvate

• Converts pyruvate to acetyl CoA linking glycolysis to citric acid cycle

• Electrons from pyruvate are donated to NAD+ making NADH

• Occurs in the mitochondria

3. Kreb’s citric acid cycle cycle

• Occurs in the mitochondrial matrix

• Electrons from molecules in citric acid cycle are used to reduce NAD+ and FAD+ to NADH and FADH2

http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

4. Electron Transport Chain

http://www.science.smith.edu/departments/Biology/Bio231/etc.html http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter9/

• Occurs on inner membrane of mitochondria• At this point, majority of energy from food is in NADH

and FADH2• NADH and FADH2 donate e- to ETC which moves thru a

series of proteins by redox• NRG in e- is used to actively pump protons across the

inner membrane • As the protons diffuse down their concentration

gradient, ATP synthase uses the energy in the gradient to make 32ATP by chemiosmotic phosphorylation

• O2 is final acceptor of e- . It becomes reduced to water

D. Compare Chemiosmosis in photosynthesis and respiration

In both, electrons are shuttled thru ETC and protons are pumped up their gradient. As the protons diffuse thru ATP synthase ATP Iis made

Aerobic respiration: the big picture

III. Regulation of Aerobic Respiration By feedback regulation

• High ATP means cell has enuf ATP and ATP acts like allosteric inhibitor to turn off 2nd enzyme in glycolysis (phosphofructokinase)

• • High NADH means not enuf O2 and ETC is shutting.

NADH acts as allosteric inhibitor to the oxidation of pyruvate

• • High ADP means cell needs more ATP and ADP acts as

allosteric activator to activate phosphofructokinase

Aerobic respiration in prokaryotes

• Same 4 parts but ETC occurs on cell membrane and everything else in cytoplasm

IV. Anaerobic respiration

• Occurs in certain bacteria (abligate anaerobes)

• Has the same stages as aerobic respiration• However, O2 is NOT the final e- acceptor.

V. Fermentation

• Without O2 ETC shuts• Pyruvates from glycolysis enter into

fermentation• Produces limited ATP (only 2) when compared to

aerobic respiration • NADH produced in glycolysis is converted back

to NAD to keep glycolysis running • 2 types: lactic acid fermentation and alcoholic

fermentation

1. Lactic acid fermentation Occurs in muscle cells Produces lactic acid 2. Alcoholic fermentation Occurs in yeast cells Produces alcohol and CO2

VI. RELATIONSHIP BETWEEN PHOTOSYNTHESIS AND RESPIRATION