Chapter 9: Cellular Respiration and Fermentation

Chapter 9: Cellular

Respiration and Fermentation

Essential Knowledge

2.a.1 – All living systems require constant input of free energy (9.1-9.5).

2.a.2 – Organisms capture and store free energy for use in biological processes (9.1-9.5).

Cellular Respiration - Preview

Def - The process of releasing energy/ATP from food

Food - Stored energy in chemical bonds (provides fuel)

ATP - Useable energy for cellular processes

Wastes – CO2 and H2O Mitochondrion store most of

equipment needed for rxn

Respiration (Rs) - Equation

C6H12O6 + 6 O2 6 CO2 + 6 H2O +

energy (ATP or heat) Rxn is spontaneous (-∆G) The energy is released (exergonic) from

the bonds in the org moleculesRemember: Org molecules store energy in

their arrangement of atomsOrg molecules can be carbs, proteins or

fats/lipids

Focus of Chapter

Cellular Rs1. Purpose - what is the reaction suppose

to do for the cell?2. Location - where does it occur?3. Requirements - what is needed to

make it run?4. Products - what does it produce?

Other Fermentation, Redox

Fuel? What is used?

Organic molecules with a large amt of hydrogen make great fuel! Why?H becomes oxidized (only has one e-)

very easily and energy is releasedRemember: Carbs, fats, proteins are

storage bins for e- associated with hydrogen

Oxidation - definitions Loss of electrons Loss of energy Loss of hydrogens from

carbons Ex: Na+ (of NaCl)

Food and Oxidation

Food (organic molecules) contain a lot of H atomsThese serve as great long-term

fuelsWhy?○ Because H becomes easily oxidized

(releases energy frequently)

Reduction - definitions Gain of electrons (REDUCING +

charge) Gain of energy Gain of hydrogens to carbons Ex: O is often reduced!

Why? Because electrons are pulled closer

to O

Redox reactions

Equation for Rs

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy (ATP/heat)

General Redox Equation: Xe- + Y X + Ye-

Reduced

Oxidized

Redox reactions Involves transfer of e- and energy

releaseSometimes doesn’t involve complete

transfer Red and Oxd reactions are usually

paired or linked together. Why?Because e- transfer requires donor

and acceptor Many of the reactions will be done

by phosphorylation Redox video

Phosphorylation

Adding a phosphate group to a moleculeEx: ATP cycle (add P to ADP = ATP)

Two types: Oxidative AND substrate-level

The phosphate group adds “energy” to the molecule for chemical reactions (think ATP cycle)Endergonic rxn

Phosphorylation

Cell Respiration – 3 parts1. Glycolysis2. Krebs Cycle3. Electron Transport Chain

**Use page 167 as a starting point: Cellular Respiration - A Preview

Glycolysis

Glyco- glucose -lysis: to split Formula for glucose: C6H12O6

Universal step in all Rs types. Likely the earliest type of cell energy

processes Overview:

Glucose splits into 2 3-C sugars (then oxidizes to form pyruvate)

STEP 1

Glycolysis Function - To split glucose and

produce NADH and ATPATP made by substrate-level

phosphorylation○ Enzyme transfers phosphate group

from substrate/reactant to ADP to make ATP

Location – Cytoplasm of the cell

Electron Carrier Compounds

Molecules that transport or shuttle electrons within the cell

Exist in two forms: Oxidized (ox)Reduced (red)

Ex: NAD and FAD

NAD

Nicotinamide Adenine Dinucleotide NAD+ + 2 e- NADH NAD+ = oxidized form NADH = reduced form*

*Reduced by e- from food oxidation

Glycolysis Requirements

Glucose 2 ATP 4 ADP 2 NAD+

Can occur with or without O2

Glycolysis - Products 2 Pyruvic Acids (a 3-Carbon acid) 2 ADP, 4 ATP, 2 NADH NET RESULT:

2 ATP per glucose2 NADH2 pyruvateH2O

Notice:No CO2 made during

this step!

Glycolysis Intro

Krebs Cycle

Oxidizes fuel from pyruvate molecules Remember? Pyruvate formed during

glycolysis Also called:

Citric Acid CycleTricarboxylic Acid Cycle

STEP 2

Krebs Cycle Function: Oxidize pyruvic acid (to

make CO2 ) Produces: NADH and FADH2

Location: Mitochondria matrix Before Krebs: Acetyl CoA must be

formedAcetyl CoA is needed to actually start

Krebs

Pyruvate moved into mito?

Why? How?Pyruvate is moved into mitochondria

(from cytoplasm) Why? This is where the 2nd step

occurs (specific enzymes are in mito)Serves as a checkpointUses active transport and transport

proteins. ○Why? Pyruvate is a charged molecule!

Formation of Acetyl CoA

Krebs Cycle Requirements

Pyruvic acid (3C acid) Acetyl coenzyme A 4 NAD+

1 ADP 1 FAD Double this list for each glucose

Krebs Cycle Products 3 CO2

Acetyl CoA 4 NADH 1 FADH2

1 ATP

Double this list for each glucose

Made from pyruvate

LOADS of energy stored in these molecules

Krebs Cycle Intro

Krebs Cycle notes Notice:

Only 1 ATP made per cycleProduces most of the cell's energy in

the form of NADH and FADH2

Does NOT require O2

Comment about ATP The ATPs produced directly in Krebs

Cycle and Glycolysis are by:Substrate-level phosphorylation

The P group is transferred from a substrate to ADPMaking ATP

At this point…

After the Krebs and glycolysis cycles, the cell has made a total of 4 ATP. Remember: some ATP had to be used to

power the cycles. Most energy (at this point) comes from

NADH and FADH2

Electron Transport System

ETC/S or Electron Transport Chain This is a collection of proteins that are

structurally linked Located in inner membrane of mito

Folding of mito (cristae) allows for lots of places (large surface area!) for ETC to occur

STEP 3

ETC/S Uses sets of Cytochromes

Fe (Iron)-containing proteins to pass electrons The Cytochromes alternate between Red

and Ox forms and pass electrons down to O2

Remember: LEO, GER; LEO the lion goes GERLosing Electrons is Oxidation; Gaining

Electrons is Reduction

As e- moves

down the ETC, free energy

decreases

ETC/S

Function: Convert NADH and FADH2 into ATP

Location: Mitochondria cristae/folds

ETC Requirements NADH or FADH2

ADP O2

We finally see the need/requirement of Oxygen

ETC Products NAD+ and FAD ATP (LOTS!!!) H2O

Remember: Water was also produced during glycolysis

ETC explanation

ETC - ATP Yields

Each NADH 3 ATP Each FADH2 2 ATP

TOTAL: 34 ATP

Chemiosmotic Hypothesis ETC energy is used to move H+

(protons) across the mito/cristae membrane

ATP is generated as the H+ diffuse back into the matrix

ATP Synthase Enzyme An enzyme that uses the flow of H+ to

make ATP Works like an ion pump in reverse, or like

a waterwheel under the flow of H+ “water”

Power source: H+ concentration difference on opposite sides

of mitochondrial membrane

Oxidative Phosphorylation

ATP synthase uses oxidative phosphorylation to make ATP during ETC

Uses H ions to make ATP and water (using Oxygen)

ATP Synthase

Alcoholic Fermentation

Done by yeast A kind of fungus

Used in brewing beer, winemaking, and bakingCO2 bubbles generated give:○ Bread a rising effect○ Wine/Beer the carbonated effect

Alcoholic Fermentation Uses only Glycolysis An incomplete oxidation - energy

is still left in the products (alcohol) Does NOT require O2

Produces ATP (when O2 is not available)

Alcohol

Lactic Acid Fermentation Uses only Glycolysis An incomplete oxidation - energy is

still left in the products (lactic acid) Does NOT require O2

Produces ATP (when O2 is not available)

Lactic acid

Lactic Acid Fermentation

Done by human muscle cells under oxygen debtLactic Acid is a toxin and can cause

soreness and stiffness in musclesOxygen intake can’t keep up with sugar

breakdown Used in dairy industry (yogurt/cheese) Also used to produce methanol and

acetone

Fermentation - Summary Way of using up NADH so

Glycolysis can still run Provides ATP to a cell even when O2

is absent

Fermentation

*Alcoholic OR*Lactic acid

Aerobic vs Anaerobic

Aerobic - Rs with O2

Anaerobic - Rs without O2

Aerobic - All three Rs steps Anaerobic - Glycolysis only

Strict vs. Facultative

Strict - can only do Rs this one way Either aerobic OR anaerobic-NOT both!

Facultative - can switch types depending on O2 availabilityEx - yeast

Question??

Since yeast can do both aerobic and anaerobic Rs, which is the better process if given a choice?Hint: Check the ATP yields from both

processes.

ATP yields by Rs type

Anaerobic - Glycolysis only gets 2 ATPs per glucose

Aerobic - Glycolysis, Krebs, and ETC. Generates many more ATPs per

glucose.

Aerobic ATP yield

Glycolysis - 2 ATPS, 2 NADHs Krebs - 2 ATPS, 8 NADHs, 2 FADH2

Each NADH = 3 ATP Each FADH2 = 2 ATP

Aerobic ATP Sum

10 NADH x 3 = 30 ATPs 2 FADH2 x 2 = 4 ATPs 2 ATPs (Gly) = 2 ATPs 2 ATPs (Krebs) = 2 ATPs

Max = 38 ATPs per glucose

However...

Some energy (2 ATP) is used in shuttling the NADH and pyruvate from Glycolysis into the mitochondria

Actual ATP yield ~ 36/glucose

Yeast Would rather do aerobic Rs;

This has 18x more energy per glucose than anaerobic

But, anaerobic will keep you alive if oxygen is not present.

Importance of Rs

Convert food to ATPLiving orgs use ATP to fuel body

processesEx: reproduction, cell division

Provides materials for use in other cellular pathways

Other Respiration Items of Importance

Alcohol Industry - almost every society has a fermented beverage

Baking Industry - many breads use yeast to provide bubbles to raise the dough

Alcohol Matching Game!

Sugar Cane GinBarley RumGrapes

WineJuniper Cones

VodkaAgave Leaves

BeerRice TequilaPotatoes Saki

Summary

Identify the basic chemical equation for cellular respiration.

Identify the main reaction sequences of cellular respiration.

Recognize the location, function, requirements, and products, for each cellular respiration reaction.

Recognize and be able to discuss the chemiosmotic model for ATP generation.

Recognize the reactions and importance of fermentation. Contrast and compare aerobic and anaerobic respiration. Identify the biological and commercial importances of

respiration.

Exclusion Statements

You do NOT need to memorize the steps in glycolysis and the Krebs cycle, the structures of the molecules, or the names of the enzymes that are involved.

You do NOT need to memorize the names of the specific electron carriers in the electron transport chain (ETC).