How Cells Release Stored Energy

Chapter 7

“Killer” Bees- Aggressive descendents of African honeybees that were imported to Brazil in the 1950s

– Africanized bee’s muscle cells have

enlarged __________________

•Photosynthesizers get energy from the ___•Animals get energy second- or third-hand

from ____ or other ____________•Regardless, the energy is converted to the

chemical bond energy of ____

ATP Is ____________ Energy Source

Making ATP• All organisms- breakdown of

carbohydrates, fats, and protein

– Plants only - during photosynthesis

O2 required?

Process

Location

____________________________

_____________________,__________

Aerobic Anaerobic

___ ___

Two pathways

Aerobic Respiration

C6H1206 + 6O2 6CO2 + 6H20 ________ ______ ______

______

________Glucose (C6H12O6)

a simple sugar

2 Pyruvate (three carbons)

6CO2

Glucose 2 Pyruvate 6 CO2

2 ADP 2 ____ 2 ADP 2 _____

8 NADH2 NAD+ 2 ______ 8 NAD+

2 FAD+ 2 FADH2

_______6 ADP 28 ADP _______

1. ________ 2. _______

3. _______ ________

Add up total ATP generated : 2+2+6+28=____

Aerobic Respiration

Overview of Aerobic RespirationCYTOPLASM

MITOCHONDRION

GLYCOLYSIS

ELECTRON TRANSPORT

PHOSPHORYLATION

KREBS CYCLE ATP

ATP

energy input to start reactions

2 CO2

4 CO2

2

32

water

2 NADH

8 NADH

2 FADH2

2 NADH 2 pyruvate

e- + H+

e- + oxygen

(2 ATP net)

glucose

TYPICAL ENERGY YIELD: 36 ATP

e-

e- + H+

e- + H+

ATP

H+

e- + H+

1. ________(In cytoplasm)

2. ____________(in mitochondrial matrix)

3. ______________ (In inner

mitochondrial membrane)

End result: ATP is generated

_________

___________

Each of _____ steps in glycolysis is catalyzed by a specific _______.

Divided into two phases: 1. an _____________

phase• 2 ATP used

2. an _____________ phase.• 4 ATP + 2 NADH

produced

Net yield in glycolysis= __ATP + __NADH

1. Glycolysis

The Role of Coenzymes

• ____ and ______ accept electrons and hydrogen …then deliver them to the ______

_________ system

Glucose 2 Pyruvate 6 CO2

2 ADP 2 ATP 2 ADP 2 ATP

8 NADH2 NAD+ 2 NADH 8 NAD+

2 FAD+ 2 FADH2

2. Krebs cycle

______________

• If __________ is present, pyruvate enters the _____________ where enzymes of the Krebs cycle complete the _________ of the organic fuel to carbon dioxide.

Glucose 2 Pyruvate 6 CO2

2 ADP 2 ATP 2 ADP 2 ATP

These are generated by ____________________________

Enzyme•An ______ transfers a phosphate group from an organic molecule (the substrate) to ____, forming ____-.

What is substrate level phosphorylation?

• The Krebs cycle consists of ____ steps.

Fig. 9.11

• Each cycle produces

• one ATP by ________________ ______________• three _________• and one _______

Named after Hans Kreb – 1930s

2. Krebs cycle

• The conversion of pyruvate and the Krebs cycle produces large quantities of _____________.

Fig. 9.12

2 carbon atoms enter

2 carbon atoms released as CO2

Note the Krebs cycle is never depleted of ______: 2 in, 2 out

8 NADH2 NAD+ ___________ 8 NAD+

2 FAD+ 2 FADH2

__________6 ADP 28 ADP __________

___________ ____________

Electron transport

Add up total ATP generated : 2+2+6+28=_____

3. Electron transport

Coenzymes deliver electrons to electron transport systems

in-text, p. 116

ELECTRON TRANSPORT PHOSPHORYLATION

glucose

pyruvate

KREBS CYCLE

GLYCOLYSIS

Electron transport

Mitochondria

• Coenzymes deliver _________ to ET chain• H+ ions are delivered to ______ compartment• H+ _________ is created• ___ is final _____________

NADH

OUTER COMPARTMENT

Inner compartment

O2H20

ET chain

4 important facts:

Making ATP: __________________ Model

ATP

ADP+Pi

INNER COMPARTMENT

• H+ ions going back to _______ compartment generates _______

Fig. 7.5b, p. 114

Krebs Cycle

NADH

NADH

NADH

ATP ATP

ATP

ATP

ADP + Pi

INNER COMPARTMENT

OUTER COMPARTMENT

acetyl-CoA

free oxygen

6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation.

1 Pyruvate from cytoplasm enters inner mitochondrial compartment.

3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems.

2 Krebs cycle and preparatory steps: NAD+ and FADH2

accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms.

5 Oxygen accepts electrons, joins with H+ to form water.

4 As electrons move through the transport system, H+ is pumped to outer compartment.

Overview of respiration

• How efficient is respiration in generating ATP?– Complete oxidation of glucose = ____

kcal/mole.– Formation of each ATP requires = _____

kcal/mole.– Efficiency of respiration is

– __ kcal/mole x -_ ATP/glucose = __%. 686 kcal/mole glucose

• The other approximately 60% is lost as ______.

• Cellular respiration is remarkably ________ in energy conversion.

• Glycolysis generates ______ whether oxygen is present (aerobic) or not (anaerobic).

____________ enables some cells to produce ATP without the use of _________

Fig. 9.17a

Problem- Fermentation (anaerobic catabolism) still requires NAD+ to accept electrons.

Solution-In __________________, NAD+ comes from the conversion of pyruvate to ______________

Ethanol

• A second solution to the NAD+ problem: – ___________________________

• ( pyruvate is reduced directly by NADH to form ___________)

– Muscle cells switch from ______ respiration to lactic acid f____________ to generate ATP when -____ is scarce.• The waste product,

lactate causes muscle fatigue but ultimately it is converted back to pyruvate in the liver.

Lactate

A third solution to the NAD+ problem

• Certain anaerobic bacteria solve NAD+ problem by using compounds from environment (such as nitrate), NOT oxygen

• ATP yield is low

Compare respiration and fermentation

Respiration Fermentation

•Both use glycolysis to generate __________•Both use NAD+ as an _________________.

Similarities

Aerobic AnaerobicType

NAD+ regeneration

Organic molecules___

Energy yield

___ ATP___ATP

• At a cellular level, human ______ cells can behave as facultative anaerobes, but __________ cells cannot.

Fig. 9.18

•For facultative ________________, pyruvate is a fork in the metabolic road that leads to two alternative routes. Ethanol or

lactate

7. How do other ________________ fit into glycolysis and the Kreb cycle??

Answer- _________,______________________________ can all enter the pathway.

•_____ are degraded to amino acids, then deaminated (nitrogen secreted as urea, ammonia)

•______ must be digested to glycerol and fatty acids.

•________ are broken down to glucose.

• Glucose absorbed by blood

• Pancreas releases insulin

• Insulin stimulates glucose uptake by cells

• Cells convert glucose to __________________

• This traps glucose in cytoplasm where it can be used for glycolysis

• If ATP _____, glucose stored as _________ in muscle and liver

If glucose is the key to ATP production, then how do we store glucose??

Answer- ___________ (in animals)_______ and _______ (in plants)

Animals

Using Glycogen• When blood glucose low, pancreas

releases _____________

• Glucagon stimulates liver cells to convert

glycogen back to glucose and to release it

to the blood

• (Muscle cells do not _____________ their

stored glycogen)

Energy Reserves• Glycogen- ___%

• Proteins- ___ %

• Fat – ____%

in-text, p. 122

sunlight energy

water+

carbondioxide

PHOTOSYNTHESIS

AEROBICRESPIRATION

sugarmolecules

oxygen

Linking photosynthesis and respiration