AP Biology

AP Biology

Energy and Cell Respiration

Intro

• All org need energy to survive. Without E, death.

• Energy: capacity to do work. 2 forms: Kinetic E: energy of motion and Potential E: energy of location.

• Thermodynamics: study of energy. 2 Laws

First Law of Thermodynamics

• Energy can be changed from one form into

another, but cannot be created nor destroyed.

• We can store energy in chemical bonds. E is used to form bonds and when the bonds are broken E is released.

• Bonds contain potential E. When bonds are

broken some E is lost a heat..why?

2 ^nd Law of Thermodynamics

• In all of energy conversions, if no energy

enters or leaves, the potential E of the final

state is always less than the pot E of the initial state.

• Some E is lost as heat (EXERGONIC Rxn)

– A B + Heat

– ENDERGONIC add energy: Energy + A  B

Entropy

• Entropy also affects potential E.

• The final state has more Entropy than the initial state.

• Entropy: disorder of a system. Systems always move towards disorder or stability.

• Stability is disorder.

• Highly ordered systems need energy to be

maintained. Disorder doesn’t need to be maintained and is more stable.

• Examples: House, room, you….

Stable/Unstable

• Public Domain, Wikimedia Commons

• Corey coyle, 9/27/16, Wikimedia Commpons

Free Energy

• Highly ordered systems move to stability via

spontaneous rxns. You need to add E to combat against spontaneous rxns.

• Free energy is the amt of E needed to fight stability (entropy). Free energy is represented by G (Gibbs free energy).

• G is made up of three components:

– T (temperature in

K)

– H (enthalpy) the ability to produce energy

– S (entropy) movement towards stability

Gibbs Free Energy Equation

• The equation: ΔG = ΔH-TΔS

• Think of ΔG as the ability to combat stability.

The more ΔG, the more successful you are at fighting stability. The less ΔG, the less

successful you are at fighting stability.

• OLD AGE

• We use exergonic rxns to do endergonic rxns.

ATP

• We will remove a P from ATP to release energy (exergonic) we will use that E for rxns

(endergonic).

• The molecule used for E is ATP…this is our

energy currency. All of our cell’s usable E is

stored in this molecule.

What about ATP?

• Adenosine Triphosphate:

Public Domain, Wikimedia Commons

• P are neg charged. They repel each other, but are

bonded to each other by covalent bonds. When

the terminal P is removed, 7 Kcal of energy is

released…just the right amount of energy.

More about ATP

• Enzymes: Kinases will move the Phosphates from one mol to another. If another mol gets a phoshpate, it gets energized.

Public Domain, Wikimedia Commons

Redox Rxns

• Oxidation: lose e-

• Reduction: gain e-

• e- Carriers: undergo redox rxns. NAD+

(nicotinamide adenine dinucleotide) in

respiration and NADP+ (photosyn). These will accept and give up 2 e- and 1 H+.

• Enzymes that move the e- and H+:

Dehydrogenases.

Aerobic Respiration

• Steps: Glycolysis, Oxidative Decarboxylation, Kreb’s cycle, Electron Transport Chain,

Oxidative Phosphorylation.

Gycolysis

• In cytoplasm. Take Glucose  Pyruvate + 2ATP + 2 NADH

• 1) Glucose enters the cell via facilitated diffusion.

• 2) Glucose + ATP  Glucose-6-P + ADP enz:

hexokinase

• 3) Gluc-6-P  Fructose-6-P enz:

phosphoglucoisomerase

Glycolysis, 2

• 4) Fruc-6-P + ATP  Fruc 1,6 di P + ADP enz:

Phosphfructokinase. Rxn Coupling.

– Fruc-6-P is unstable…add E from P to keep rxn moving in one direction.

• 5) Fruc 1,6 diP  2 Glyceraldehyde-3-P enz:

aldolase

• 6) 2 3-Glyceraldehyde-3P + NAD+ +Pi

2Diphosphoglycerate (DPG)1,3P + NADH enz:

triosephosphate dehydrogenase

Glycolysis, 3

• 7) 2 DPG + ADP  2Phosphoglycerate-3-P (3 PG) + 2ATP enz: Phosphoglycerokinase

• 8) 2 3PG  2 2PG enz: phosphoglyceromutase.

• 9) 2 2PG  2 Phosphoenolpyruvate (PEP) + H2O enz:

enolase

• 10) 2 PEP + 2ADP  2 pyruvate + 2 ATP enz: pyruvate kinase.

• Net gain of 2 ATP in prokaryotes, the rxn almost stops here. Need to recycle NADH to NAD+ without NAD+

rxn stops.

Overall Rxn

• Lkate2014, 11/24/14, Wikimedia Commons

Anaerobic resp.

• Without O ₂ , you will only produce 2 ATP.

• Pyruvate can go in one of two ways.

1) 2 Pyruvate  2 acetaldehyde + 2 CO ₂ enz:

pyruvate decarboxylase

2) 2 acetaldehyde + NADH  2 ethanol enz:

alcohol dehydrogenase

• Arobsonl, 4/21/17, Wikimedia Commons

Anaerobic,2

• 2 pyruvate + 2 NADH  2 lactic acid enz:

pyruvate dehydrogenase

• We don’t produce ethanol. We produce lactic

acid when we do anaerobic resp.

• Sjantoni, 9/11, Wikimedia Commons

Mitochondrion

• Organelle, 2 membranes: picture: outer membrane, inner membrane (80%

proteins..proteins of ETC), cristae, matrix, nucleoid, ribosome (prok), intermembrane space.

• Draw picture on the next slide

Mitochondrion Picture

Kelvinsong, 12/6/12, Wikimedia Commons

Oxidative Decarboxylation

• Pyruvate enters the matrix via facilitated diffusion.

• 2 pyruvate + 2NAD+ + 2coenzyme A  2 acetyl CoA + 2NADH + 2CO

.

• Enz: pyruvate dehydrogenase.

• 2 aceytl CoA will enter the Krebs cycle. Discovered by Hans Krebs in 1930.

• Totally destroys the acetyl CoA. Happens in the matrix.

Krebs Cycle, TCA cycle, Citric Acid Cycle

• 2 acetyl CoA + 2 Oxaloacetate  2 citrate enz:

citrate synthase.

• 2 Citrate 2 Isocitrate enz: aconitase

• 2 Isocitrate + 2NAD+  2 αKetoglutarate + 2NADH 2CO ₂ enz: isocitrate dehydrogenase

• 2 αKetogultarate + 2 NAD+ +2 CoA 2 Succinyl CoA + 2NADH + 2CO ₂ enz:

αketoglutarate dehydrogenase

Krebs, 2

• 2 Succinyl CoA + 2GDP  2 Succinate + 2GTP + 2CoA. Enz: Succinate Thiokinase 2GTP 

2ADP  2ATP

• 2 Succinate + 2FAD  2Fumarate + 2FADH2 enz: succinate dehydrogenase

• 2 Fumarate + 2H ₂ O  Malate enz: Fumarase

• 2 Malate + 2NAD+  2 Oxaloacetate + 2

NADH enz: Malate dehydrogenase.

Diagram, pay attention to the steps

• YassinMrabet, 8/18/07, Wikimedia Commons

What do we have

• A giant mess.

• Totally destroyed Glucose. Only thing left: e- carried by e- carriers.

• Glycolysis: 2 ATP and 2NADH

• Ox. Decarbox.: 2 NADH + 2 CO ₂

• Krebs: 2 ATP + 6 NADH + 2 FADH2 + 4 CO ₂

• ATP used as E. CO ₂ into atmosphere…

photosyn and e- go to the ETC

ETC

• Inner membrane: protein chains.

• NADH FMN (flavin mononucleotide) FMN  Iron-Sulfur protein (Fe-S)  Ubiquinone (Q) takes 2e- and 2H

(into intermembrane space) QH

 Cyt b  Cyt C

(moves H+ into intermembrane space) Cyt C  Cyt a Cyt a

(moves H

into intermembrane space) O

 H

O (can form free radicals here…) Cyanide blocks this step.

• FADH

passes e- to Q

• Purpose: to increase H

into the intermembrane space.

Why?

ETC Diagram

• Public Domain, Wikimedia Commons

How’s this diagram?

Public Domain, Wikimedia Commons

How about this one?

• OpenStax College, 6/19/13, Wikimedia Commons

Oxidative Phosphorylation

• H+ move through ATP synthase back into the matrix. This will produce ATP (like photosyn).

• For each NADH produce 3 ATP

• For each FADH

produce 2 ATP

• 34 ATPs produced here. 38 total ATPs produced in the process. Each ATP is 7.3 Kcal.

• Glucose 686 Kcal of energy.

• 38 ATP X 7.3 = 277.4 Kcal of energy

• 277.4 Kcal of E/686 Kcal of E = 40% efficeint

• Other pot E…lost as heat

Catabolic Pathways

• CHO: monosacc enters glycolysis

• Fats: Split into glycerol and FA

• Glycerol: enters glycolysis as

Glyceraldehyde3P. Fatty Acids: cut into 2C

compounds… Enters Krebs as acetyl CoA. A lot of C.

• Proteins: cut into dipeptides and enters krebs.

Exercise

• Heavy exercise:

– Increase the lung volume – Heart gets stronger

– Increase blood vessel growth to muscles – Redistribute fat and glycogen molecules

• Anaerobic resp. produce lactic acid. Add O ₂ to lactic acid to produce pyruvate.

• Lactic acid to liver to produce glucose.

Wall

• No more CHO

• No more Fat

• Breaks down protein…bad!