General Biology I - Cellular Respiration & Fermentation

All living cells require energy from

outside sources to do work

Animals can obtain energy by

feeding on other animals or organisms

Energy will enter ecosystem

as light energy

Photosynthesis uses

light energy to generate organic molecules and O2

By-product is heat of photosynthesis

Energy will enter and exit as heat

Cellular Respiration

generates CO2 and water

Cellular Respiration is a

catabolic pathway

Catabolic pathways break down

larger molecules

Electrons play a major role in the

catabolic pathways and are central to cellular respiration

Redox Reactions are

transfer of electrons between reactants

Oxidation is a

loss of electrons

Reduction is a gain

of electrons

An example redox reaction

Xe- + Y → X + Ye-

The electron donor or reducing agent

reduces Y

Aerobic

Uses O2

Anaerobic

Does not use O2

Equation of Cellular Respiration

Glucose + Oxygen → Water + CO2 + ATP + Heat

There is high energy

in the Products

The reaction of cellular respiration

Is an exergonic reaction and spontaneous

3 Stages of Cellular Respiration

1. Glycolysis

2. Oxidation of Pyruvate & Citric Acid Cycle

3. Oxidative Phosphorylation

Glycolysis occurs in Eukaryotes

Cytosol

Glycolysis occurs in prokaryotes

in the cytosol

Glycolysis does not

require O2

In glycolysis,

there is an investment and payoff phase

Energy Investment Phase

Glucose will be split into 2, 3 Carbon molecules and use 2 ATP

Energy Payoff Phase

2, 3-Carbon molecules are oxidized and atoms will be rearranged into pyruvate

ATP is formed in

the Energy Payoff Phase of Glycolysis

Per glucose molecule in Glycolysis

2 pyruvate, 2 NADH, 2 ATP (net) will be formed

In substrate-level phosphorylation

the ADP & Pi get transferred to ATP

ATP gets generated in

Glycolysis

Electron carriers were moelcules that can

accept food bring it to ATP

NAD+ and FAD

form that accepts electron through food

NAD+ picks up two electrons from substrates by

dehydrogenase, 2 electrons and 1 proton will be delivered by the enzyme on NADH

The other proton goes into the

surrounding cell

Oxidation of Pyruvate

2nd Step of Cellular Respiration

Oxidation of Pyruvate occurs in Eukaryotes

occurs in mitochondrial matrix

Oxidation of Pyruvate of prokaryotes occurs in

the cytosol

Steps of Oxidation of Pyruvate

1. Pyruvate will enter the matrix of the mitochondria through active transport

2. Once entered, it will check for the carboxyl group given off as CO2

3. 2 Carbon Molecule will be oxidized and acetate is formed and the electron and proton are accepted by NAD+ and NADH

4. Coenzyme 3 is added to Acetyl CoA

Per glucose molecule in Oxidation of Pyruvate

2 Acetyl CoA, 2 NADH, 2 CO2

The Citric Acid Cycle in Eukaryotes

Matrix of the mitochondria

The Citric Acid Cycle in prokaryotes

Cytosol of prokaryotes

There is a presence of O2 in the

Citric Acid Cycle

Steps of the Citric Acid Cycle

1. Acetyl CoA - coenzyme A will be removed from Acetate and add oxaloacetate is added to 2-Carbon molecule to form citrate

2. (2-4) Citrate will decompose into a 4-Carbon molecule and each carbon is lost as CO2

   1. Intermediates are oxidized and NAD + picks up electrons and protons and forms NADH

5. ATP is made by substrate-level phosphorylation

6. Intermediate is oxidized as a FAD picks up electrons and protons to form FADH2

7-8. Oxidation of Intermediate forming NADH and forming oxaloacetate

Per glucose molecule of the Citric Acid Cycle

2 ATP, 6 NADH, 2 FADH2, 6 CO2

Oxidative Phosphorylation in Eukarya

Inner membrane of the mitochondria

Oxidative Phosphorylation in prokarya

Plasma Membrane

Oxidative Phosphorylation occurs in

the presence of oxygen

Oxidative phosphorylation

powers about 90% of ATP synthesis

Electron Transport Chain

Collection of proteins that are inner membrane of mitochondria or Plasma membrane of prokaryotes

Chemiosmosis

Use of ATP synthase to make ATP

Electron Transport Chain

passed through carrier molecules that will alternate between reduced and oxidized states

Electrons in the ETC

drop in free energy as they are passed down the chain from H20 to 02

In the ETC,

there are 4 protein complexes and each complex will be more electronegative than the one before it

I - Least electronegative

II

III

IV - Most electronegative

Electrons from NADH

are transfered and start at I

Electrons from FADH2 are transfered

to II

H20 is formed when O2 picks up protons from

the aqueous solution

Chemiosmosis

Energy that is lost in the electron transport chain is used to pump protons from matrix to IM space

Protons will move across the membrane through

ATP synthase

Protons from FADH2 and NADH

get pumped from matrix to intermembrane space creating a high concentration of protons in that space

Protons will move through ATP synthase to make ATP by ADP+Pi

to make ATP

ATP production

ration of each electron carrier to ATP made is not a whole number

1 NADH = 2.5 ATP

1 FADH2 = 1.5 ATP

ATP yield will vary

depending on whether electrons are passed to NAD+ and FAD from the cytosol or the mitochondria

You have _ ATP from

2 ATP from Glycolysis

2 ATP from Citric Acid Cycle

10 NADH x 3 = 30

2 FADH x 2 = 4

around ~ 38 total ATP made

in cellular respiration

There are two less ATP made in prokarya

due to transport of glucose into matrix

Versatility of Catabolism

Proteins into amino acid, most will be used to make new proteins

Excess amino acids will

enter as intermediates in glycolysis and CAC

Fats will get broken down in glycerol

Glycerol - Glycolysis, FA - Acetyl CoA

Without O2,

glycolysis + anaerobic respiration or fermentation to produce ATP

Anaerobic respiration

Prokaryotes, consumes O2 and yields ATP but uses the ETC with a final electron acceptor such as sulfate

Fermentation

Extension of glycolysis by substrate level phosphorylation

The two types of fermenation are

Lactic Acid and Alcohol

Alcohol Fermenting

Occurs in bacteria and yeast where glycolysis occurs

Pyruvates will lose -COO-

as CO2 and acetaldyhyde

Regenerate ATP

where it can lose electrons and protons and gives a proton to form ethanol

Lactic Acid Fermentation occurs in

Muscle cells and fungi and bacteria

Lactic Acid Fermentation

1. Glycolysis

2. NADH loses e-/H+ and gives it to pyruvate to make lactate

Feedback inhibition

more ATP - CR drops

less ATP - CR increases