Biology - Cellular Respiration And Fermentation

Front 1

What are Photoautotrophs and

Chemoheterotrophs ?

Back 1

Photoautotrophs: use sunlight to reduce CO2

(trees/plants) into sugars

Chemoheterotrophs: oxidize sugars to make ATP

(animals) to run other reactions

Front 2

What is cellular respiration ?

Back 2

Cellular respiration produces ATP frommolecules with high

potential energy.

The energy released from sugar processing isused to transfer

a phosphate onto ADP to make ATP.

Front 3

What is the potential energy and chemical

energy?

Back 3

Potential energy is stored energy.

Potential energy is stored energy or energy atrest (ie. spring loaded mouse trap).

Chemical energy is storedin the position of

electrons.

Front 4

Recall: Carbohydrates and Energy Storage

Back 4

* Carbohydrates store and provide chemical energyin cells in the

form of C–H bonds.

* Carbohydrates - more free energy thanCO2; their electrons in

C–H bonds andC–C bonds are shared more equally and held

less tightly than the electrons in C–O bonds

* Fatty acids: have even more C–H bonds = more free energy

Front 5

Recall: Exchange of potential & kinetic energy

Back 5

Energy is constantly being exchanged between these twoforms.

Kinetic energy is energy of motion or energy inuse

(rolling car, bowling ball, heat, light)

Potential energy is stored energy.

i.e. when a rock tumbles down a waterfall, its potential energy

is converted intokinetic energy.

Front 6

Law of conservation of energy

Back 6

The law of conservation of energy says that

energy cannot be created or destroyed, but canchange from one form to another,i.e. a water molecule is sitting at the top of

a waterfall has a defined amount of potential energy. As it falls

some of this stored energy is converted to kinetic energy (energy

of motion).

Front 7

The 2nd Law of energy

Back 7

1. energy cannot be changed fromone form to another

without a loss of usable energy (most of the energy lost is heat).

2. Another way to state the second energy law is that every

energy transformation leads to more disorder or randomness

(the degree of disorder or disorganization is called "entropy").

Front 8

What Makes a Chemical Reaction

Spontaneous?

Back 8

* Chemical reactions are spontaneous, if they proceed ontheir own,

without any continuous external influence

* spontaneity of a reaction is determined by two factors:

1. The amount of potential energy: the products of the spontaneous

reaction have less potential energy than the reactants

2. The degree of order: The products are less ordered than the

reactants

Front 9

Exergonic and endergonic reactions

Back 9

Exergonic reaction:energy released (ex=out)

Endergonic reaction:energy required (endo=in)

Front 10

The second law of thermodynamics

Back 10

The second law of thermodynamics states that entropy (the

amount of disorder in a group ofmolecules) always increases.

In other words, chemical reactions result in products with

less ordered (usable)energy.

In general:

Physical + chemical processes result in

lower energy + more disorder

Front 11

What is "Gibbs Free-Energy Change" ?

Back 11

(ΔG) determines whether areaction is spontaneous or requires energy

– represented by the letter "G"

- defined as the energy of a system that is free to dowork

- ΔG < 0 is an exergonic spontaneous reaction

- ΔG > 0 is an endergonic reaction that requires energyinput

- ΔG = 0 is a reaction that is at equilibrium

Front 12

What are exergonic and endergonic

reactions in metabolism?

Back 12

EXERGONIC reaction (downhill) results in

* net release of free energy

* is spontaneous

* ΔG is negative

ENDERGONIC reaction (uphill)

* absorbs energy from its surroundings

* non-spontaneous

* ΔG is positive: energy is required to drive the reaction

Front 13

What is ATP ?

Back 13

* ATP (adenosine triphosphate) is the cellular currency for energy

- it provides the fuel for most cellular activities.

* ATP has high potential energy and allows cells to do work.

* ATP works by phosphorylating (transferring a phosphate group) target

molecules.

* Carbohydrates and fats are high energy storage moleculesthat,

when "burned", are used to generate ATP

Front 14

2 Forms of cellular metabolism?

Back 14

Catabolism = breaking down

Anabolism= building up

Anabolic reactions need ATP

Front 15

How does ATP power cellular work?

Back 15

* ATP couples exergonic and endergonic reactions

cells manage energy resources by "Energy coupling" =

* use of an exergonic process to power an endergonic one

* cells need energy for:

Transport: pump substance across membrane against a gradient

Chemical: pushing of endergonic reactions that require energy

Mechanical: muscle contraction/ beating of cilia,etc.

Front 16

Structure and Function of ATP

Back 16

* ATP: 3 phosphate groups, ribose

and adenine

* high potential energy because

thefour - charges in its 3

phosphate groups (O-) repel each

other (negative charges repel)

Front 17

Energy Stored in Glucose Is Transferred

to ATP

Back 17

cell needs energy > carbohydrates participate in exergonic

reaction that produces ATP:

CH2O + O2 + ADP + Pi → CO2 + H2O + ATP

The free energy in ATP is used to drive endergonic reactions

and perform cell work.

Front 18

Why does ATP hydrolysis release energy?

Back 18

When ATP is hydrolyzed to ADP and inorganicphosphate, there is

a large change in free energy

Hydrolysis of ATP = Exergonic = energy released

ATP → ADP + Pi + Energy

Higher ΔG (free energy) → Lower ΔG

(higher free energy) (lower energy=more stable)

Front 19

Exergonic vs. endergonic: differences

Back 19

Exergonic: Products have less energy

Energy released

Spontaneous

Entrophy (=disorder) increases

Endergonic: products have more energy than reactants

Energy required

Not spontaneous

Entrophy (=disorder) decreases

Front 20

What are coupled reactions?

Back 20

Coupled reactions occur in the

same place at the sametime.

One reaction provides the energy for a secondreaction that requires energy.

Front 21

ATP Coupling Helps many Cellular Processes

Back 21

chemical work: reactants + ATP

→ product formed+ ADP + P

Transport work: Transport protein

+ATP → solute tranported +ADP + P

Mechanical work: motor protein

+ATP → protein filament moved

+ ADP + P

Front 22

What Is a Redox Reaction?

Back 22

* Reduction–oxidation reactions (redox reactions) arechemical

reactions that involve electron transfer.

* When an atom or molecule gains an electron, it is reduced.

* When an atom or molecule loses an electron, it is oxidized

* Oxidation and reduction events are always coupled — if oneatom

loses an electron, another has to gain it.– Electron donors are

always paired with electron acceptors.

Front 23

Oxidation is the loss of electrons

Reduction is the gain of electrons

Back 23

atom is oxidized = has given up some of those negativelycharged

electrons = will increaseits overall charge

electrons are negatively charged, so an increase inelectrons =

a decrease in overall charge (thecompound becomes more negatively charged) = Hence,reduced.

Front 24

Photosynthesis

Back 24

* Co2 becomes reduced (gain of electrons) to sugar

water molecules are oxidized (loss of electrons) to O2

Thus, C atoms are reduced + O atoms are oxidized.

* This changes chemical energy.

* Electrons in the productsare held less tightly. Lessstable,

so more potentialenergy. Lower entropy[more order=usable]

* Photosynthesis is endergonic: light energy is captured, converted into chemical energy, then the energy is stored in chemical bonds of sugar

Front 25

What Happens When Glucose Is Oxidized?

Back 25

Glucose oxygen→ CO2 + water

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

+ energy

Much of the change in free energy

is used to synthesize ATP

from ADP and Pi.

Front 26

Electrons Are Usually Accompanied

by Protons

Back 26

Oxidized molecules have lower potential energy

They often lose a proton (H+) along with an electron and have

many or more C-O bonds,which are stronger & harder to break apart.

Follow the hydrogen atoms in redox reactions

Front 27

Nicotinamide adenine dinucleotide (NAD)

as an electron carrier

Back 27

When NADH is reduced, it readily donates electrons to other

molecules and is thus called an electroncarrier and

has “reducing power.”

Front 28

Breathing vs. Cellular Respiration

Back 28

Breathing supplies oxygen to our cells and removes Co2

Cellular respiration is a series of chemical reactions that oxidize

glucose into Co2 and H2O, generating ATP

Front 29

Cellular Respiration: Why do it ?

Back 29

It’s like harvesting glucose into smallerenergy packets (like ATP)

C6H12O6

one glucose molecule → several ATPs

$100 bill → several loonies ($1), plus change to buy gum!

Front 30

Overview of Cellular Respiration

Back 30

* All organisms use glucose to build fats, carbohydrates, and

other compounds;

* cells recover glucose by breaking downthese molecules.

* Glucose is used to make ATP through either cellular respiration

(produces ATP from a molecule withhigh potential energy,

usually glucose), or fermentation.

Front 31

The 4 Steps of Cellular Respiration

Back 31

1. Glycolysis – glucose is broken down to pyruvate.

2. Pyruvate processing – pyruvate is oxidized to form acetylCoA.

3. Citric acid cycle – acetyl CoA is oxidized to CO2.

4. Electron transport and chemiosmosis – compounds thatwere

reduced in steps 1–3 are oxidized in reactions leading to

ATP production

Front 32

The Steps of Cellular Respiration

Back 32

Note Three Things About Equation:

1. Bonds in Glucose (glc) Being Broken/Rearranged

2. Glucose is being COMPLETELY oxidized → CO2

3. Oxygen is being reduced → H2O

Front 33

1. Glycolysis: Processing Glucose to Pyruvate

(occurs in the cytoplasm)

Back 33

Glycolysis ("sugar splitting"), a series of 10 chemical reactions,

is the first stepin glucose oxidation.

glycolysis= glucose → two 3-carbonmolecules of pyruvate →

potential energy released → used to phosphorylate ADP to form ATP

Front 34

2. Pyruvate Processing

Back 34

Pyruvate processing is the second step in glucose oxidation.

Itis catalyzed by an enzyme.

In the presence of O2, pyruvate undergoes a series of reactions

that results in the product acetylCoA.

Front 35

3. the citric acid cycle = Krebs cycle

(takes place in Mitochondrial Matrix)

Back 35

During the third step of glucose oxidation, the acetyl CoAproduced by pyruvate processing enters the citric acidcycle,

Each acetyl CoA is oxidized to two molecules of CO2

Some of the potential energy released is used to

1. Reduce NAD+ to NADH.

2. Reduce (FAD) to FADH2(another electron carrier).

3. Phosphorylate GDP to form GTP (later converted toATP)

Front 36

Summary of the products of the

citric acid cycle

Back 36

from1 acetyl-CoA molecule the citric acid cycle generates:

•The acetyl-CoA has been oxidized to 2 molecules of Co2.

•3 molecules of NAD were reduced to NADH.

•1 molecule of FAD was reduced to FADH2.

•1 molecule of GTP (the equivalent of ATP) was produced

Front 37

Summary of glucose oxidization

Back 37

For each glucose molecule that is oxidized to 6 CO2,

the cell reduces 10 molecules of NAD+ to NADH

and 2 molecules of FAD to FADH2,

and produces 4molecules of ATP

by substrate-levelphosphorylation.

Front 38

what is Feedback

Inhibition ?

Back 38

Feedback inhibition: when an enzyme in a pathway is

inhibited by the product of that pathway

Feedback Inhibition Regulates Glycolysis:

During glycolysis, high levels of ATP inhibit an enzyme which

catalyzes one of the earlyreactions (glycolysis step 3).

Cells that are able to stop glycolytic reactions when ATP is abundant can conserve their stores of glucose for times when ATP is scarce.

Front 39

The Citric Acid Cycle Regulation and Summary

Back 39

* The citric acid cycle can be turned off at multiple points,

via several different mechanisms of feedback inhibition.

* To summarize, the citric acid cycle starts with acetyl CoA and

ends with CO2.

* The potential energy that is released is used to produce

NADH, FADH2, and ATP.

* When energy supplies are high, the cycle slows down.

Front 40

Free Energy Changes, NADH, and FADH2

Back 40

* For each glucose molecule that is oxidized to 6 CO2, the cell

reduces 10 molecules of NAD+ to NADH and 2 molecules of

FAD to FADH2, and produces 4 molecules of ATP by

substrate-level phosphorylation.

* The ATP can be used directly for cellular work.

* However, most of glucose's original energy is contained in the

electrons transferred to NADH and FADH2, which then carry them to

oxygen, the final electron acceptor.

Front 41

After glycolysis and the citric acid cycle are complete, where is most of the energy that was once contained in the bonds of glucose?

a. converted by the cell into ATP via substrate-level phosphorylation

b. in NADH and FADH2 that are carrying energy-rich electrons

c. in the CO2 that has been released

d. converted by the cell into ATP via oxidative phosphorylation

Back 41

b. in NADH and FADH2 that are carrying

energy-rich electrons

Front 42

The Electron Transport Chain

Back 42

* During the fourth step in cellular respiration, the high potential

energy of the electrons carried by NADH and FADH2 is gradually

decreased as they move through a series of redox reactions.

* The proteins involved in these reactions make up what is called

an electron transport chain (ETC).

* O2 is the final electron acceptor. The transfer of electrons along

with protons to oxygen forms water.

Front 43

What is Oxidative phosphorylation ?

Back 43

Oxidative phosphorylation is the process in which ATP is formed

as a result of the transfer of electrons from NADH or FADH2

to O2 by a series of electron carriers. This process, which takes

place in mitochondria, is the major source of ATP in aerobic organisms.