CELLULAR RESPIRATION CH 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 hill.com/sites/ /student_view0/ch apter25/animation__how_the_krebs_cycle_w orks__quiz_1_.html

4. Electron Transport Chain

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