Ch. 9 Cellular Respiration

Harvesting chemical energy

Living is lots of work Polymerization, Growth, highly organized,

and movement all require energy Energy enters Earth’s ecosystems as sunlight Harvesting of energy requires a series of

metabolic steps AEROBIC CELLULAR RESPIRATION

Glycolysis Kreb’s cycle Electron transport chain

Organic compounds

Energy stored in chemical bonds (position) Enzymes help regulate this metabolism Organic macromolecules are rich in potential

energy and are broken down to simpler compounds with less energy.

Breaking of bonds allows work to be done.

Organic + oxygen carbon + water + energy compounds dioxide

Exergonic reaction

Organic + oxygen carbon + water + energy compounds dioxide

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

(ATP + heat)

G = - 686 kcal

Possible pathways

Complete, aerobic cellular respiration Complete oxidation of carbohydrates using

Glycolysis Kreb’s cycle and Electron transport chain REQUIRES OXYGEN

Incomplete/ partial oxidation Gylcolysis only Glycolysis + Lactic acid fermentation Glycolysis + Alcoholic fermentation

Redox reactions

Movement of e- is what is used to store and release energy in bonds of organic cpds.

Redox reactions – “oxidation-reduction reactions” transfer an e- from one reactant to another

Reduction Addition/receipt of e-, more negative

Oxidation Loss of e- (often to O), more positive

Falling electrons

The step wise fall of electrons from organic compounds rich in bonds, to simpler compounds increases the entropy of the system.

Electrons are shuttled through a series of carriers (membrane proteins) that allows for release of energy to be in small (usable) increments.

Electron transport chains

Aerobic cellular respiration

Requires oxygen ( for e- acceptor at end of ETC) 3 parts

Glycolysis ( splitting of sugar molecules ) Some substrate level phosphorylation of ATP

Kreb’s cycle ( transfer of e- to NADH, FADH) Some substrate level phosphorylation of ATP

ETC ( generates ATP using ETC) Much oxidative phosphorylation of ATP

Occurs in eukaryotic cells – need mitochondrion (for Krebs and ETC) and oxygen supply for (ETC)

Glycolysis

Glyco = sugar, glucose Lysis = to split or break “sugar splitting” Cytoplasm ALL CELLS ! Doesn’t require mitochondrion or O2

1 glucose = 2 ATP and 2 NADH 2 ATP are net ( 4 generated – 2 invested ) Know steps on pgs. 168-169….green boxes Note color coding used in chapter – green =

glycolysis, salmon = Kreb’s and purple = ETC

Summary of Steps

1. Spend 1 ATP

Add P to glucose

2. Glucose converted to isomer (fructose) by an enzyme

3. Spend 2nd ATP

add 2nd P to fructose

now in debt ( 2ATP)

Molecule very unstable (primed)

Summary of Steps

4. 6 C sugar “cleaved” into 2 – 3C sugars

They are isomers

5. An enzyme called ‘isomerase’ converts both isomers into glyceraldehyde (PGAL)

From now on all steps are X2

PGAL

Summary of Steps

6. Enzyme adds an inorganic phosphate, sugar give e- and H+ to NAD making NADH…remember x2

7. MAKE ATP (X2) now out of debt, organic acid

8. Relocate P ( on both molecules)

Summary of Steps9. Generates water and creates double bond…. P bond now unstable10. P leaves – adds to ADP generates more ATP (2more) now have 2 net ATP. Glucose is now split into 2 – 3 C molecules PYRUVATE2 NADH can go to ETC and make ATP using oxidative phosphorylation

Krebs Cycle – aka Tricarboxylic Acid Cycle (TCA) and Citric Acid Cycle Sir Hans Krebs: 1900-1981, 1953 Nobel Prize, 1958 knighted 3 C pyruvate at end of glycolysis Not soluble in mitochondrial membrane Loses C (CO2) becomes acetyl Creates a NADH ( stores some energy ) Bonds to coenzyme for transport – now Acetyl CoA Crosses mitochondrial membrane Bonds to 4C oxaloacetate to make 6C citrate or citric acid Series of steps to lose C ( makes CO2 ) and Store energy as NADH and FADH and ATP Regenerates the oxaloacetic acid…. “cycle”

Electron Transport Chain

Collection of molecules embedded in the inner mitochondrial membrane

Folding increases surface area ( # of reactions) Most compounds are proteins (some pigments) cytochrome c

used to trace DNA lineage Function as enzymes directing the flow of reactions that move

e- (alternate between oxidized and reduced state) NADH and FADH2 are from Krebs and glycolysis NADH and FADH2 release H to these reactions H is split into H+ and e- The e- move through the carriers to the biggest e- acceptor

(moving down hill – releasing potential energy and increasing entropy)

The H+ accumulate in space btwn membranes

ETC continued

As the e- get to the last acceptor they have released all the energy they were carrying from C-C bonds in glycolysis and Krebs

The H+ can not accumulate indefinitely btwn membranes (high acidity)

H+ flows through protein pump called ATP synthase toward e- and their acceptor (OXYGEN)

This creates water and also Is used to generated energy to add P to ADP ATP is generated using oxidative phosphorylation