Cellular Metabolism...Aerobic Cellular respiration In aerobic cellular respiration cells take in sugar (glucose) and breaks it down to into carbon dioxide and water, this requires

Cellular Metabolism

Biol 105

Lecture 6

Read Chapter 3 (pages 63 – 69)

Copyright © 2009 Pearson Education, Inc.

Metabolism

Consists of all of the chemical reactions

that take place in a cell


Metabolism

Animation—Breaking Down Glucose For Energy

http://wps.aw.com/bc_goodenough_boh_4/177/45509/11650544.cw/index.html


Cellular Metabolism

Aerobic cellular respiration – requires

oxygen, produces carbon dioxide

Anaerobic Fermentation – does not require

oxygen


Summary of Cellular Respiration

Figure 3.27

Blood

vessel

Carrier

protein

Glucose

Oxygen

Extracellular fluid

Plasma

membrane

Glycolysis

glucose pyruvate

Mitochondrion

Citric

Acid

Cycle

Electron

Transport

Chain

Transition

Reaction

Electrons

transferred

by NADHCytoplasm

Electrons

transferred

by NADH

and FADH2

Electrons

transferred

by NADH

+32 ATP 36 ATP+2 ATP +2 ATP


Aerobic Cellular respiration

In aerobic cellular respiration cells take in

sugar (glucose) and breaks it down to into

carbon dioxide and water, this requires

oxygen.

This process produces energy in the form

of ATP

C6H12O6 + 6O2 → 6CO2 +6H2O + Energy


Aerobic Cellular respiration

There are four steps of aerobic cellular

respiration:

1. Glycolysis

2. Transition Reaction

3. Citric Acid Cycle (Krebs Cycle)

4. Electron Transport Chain


NADH and FADH2 are important carriers of electrons


Cellular Respiration - Glycolysis

Phase 1: Glycolysis

Occurs in the cytoplasm

Splits one glucose into two pyruvate molecules

Generates a net gain of 2 ATP and 2 NADH

molecules

Does not require oxygen


Cellular Respiration - Glycolysis

Starts with glucose

Ends with 2 ATP, 2 NADH, 2 pyruvate


Glycolysis

Figure 3.23

Cytoplasm

2 ADP

Glucose

Energy-

investment

phase

Glycolysis (in cytoplasm)

2 NADH

2 NAD+

4 ATP

4 ADP

Energy-

yielding

phase

2 ATP

The two molecules of

pyruvate then diffuse

from the cytoplasm into

the inner compartment

of the mitochondrion,

where they pass through

a few preparatory steps

(the transition reaction)

before entering the citric

acid cycle.

During the remaining

steps, four molecules

of ATP are produced.

During the first steps,

two molecules of ATP are

consumed in preparing

glucose for splitting.

2 Pyruvate

Two molecules of nicotine

adenine dinucleotide

(NADH), a carrier of

high-energy electrons,

also are produced.

In Cytosol


Cellular Respiration – Transition Reaction

Phase 2: Transition reaction

Occurs within the mitochondria

Coenzyme A combines with pyruvate and

CO2 is removed from each pyruvate

Forms 2 acetyl CoA molecules

Produces 2 NADH


Transition Reaction

Start with:

2 pyruvate (3 carbon molecules)

2 Coenzyme A

End with:

2 CO2

2 NADH

2 Acetyl CoA (2 carbon molecule)


Transition Reaction

Figure 3.24

NADH

(electron passes

to electron

transport chain)

NAD+

Pyruvate (from glycolysis)

Acetyl CoA

CoA

Coenzyme A

CO2

Transition Reaction (in mitochondrion)

Citric Acid Cycle

A molecule of NADH is

formed when NAD+

gains two electrons

and one proton.

One carbon (in the form

of CO2) is removed

from pyruvate.

The two-carbon

molecule, called

an acetyl group,

binds to

coenzyme A

(CoA), forming

acetyl CoA,

which enters the

citric acid cycle.


Cellular Respiration – Citric acid cycle

Phase 3: Citric acid cycle

Occurs in the mitochondria

Acetyl CoA enters the citric acid cycle

Releases 2 ATP, 2 FADH2 and 6 NADH, 4

CO2 molecules

Requires oxygen


Citric Acid Cycle

Also called the Krebs Cycle

Start with 2 Acetyl CoA

End with:

4 CO2

2 ATP

6 NADH and 2 FADH2


Citric Acid Cycle

Figure 3.25

Acetyl CoA

CoA

Citrate

CO2leaves

cycle

NAD+

NADH

-Ketoglutarate

CO2 leaves cycle

NADH

FAD

Succinate

FADH2

Malate

NAD+

ATP ADP

Citric Acid Cycle

NADH

Oxaloacetate

NAD+

Pi+

Acetyl CoA, the

two-carbon compound

formed during the

transition reaction,

enters the citric acid

cycle.The citric acid cycle also

yields several molecules of

FADH2 and NADH, carriers of

high-energy electrons that

enter the electron transport

chain.

The citric acid cycle yields

One ATP from each acetyl

CoA that enters the cycle,

for a net gain of two ATP.

Citric Acid Cycle (in mitochondrion)

CoA


Cellular Respiration

Phase 4: Electron transport chain

Electrons of FADH2 and NADH are

transferred from one protein to another, until

they reach oxygen

Releases energy that results in 32 ATP

Requires oxygen


The Big Pay Off – Electron Transport Chain

NADH and FADH2 are important carriers of

electrons

They donate electrons to the electron transport

chain

At the end of the chain oxygen accepts the

electrons.


The Big Pay Off – Electron Transport Chain

Electron Transport Chain produces ATP using the

ATP synthase protein molecule

The Electron Transport Chain produces 32 ATP


Electron Transport Chain

Figure 3.26

The molecules of NADH andFADH2 produced by earlier phasesof cellular respiration pass their electrons to a series of protein molecules embedded in the inner membrane of the mitochondrion.

As the electrons are transferred from one protein to the next, energy is released and used to make ATP.2e

–

2e–

2e–

2e–

2e–

NAD+

High

Low

Membrane

proteins

H2O

2 H+ + O2Energy released is used

for synthesis of ATP

FADH2

NADH

Electron Transport Chain (inner membrane of mitochondrion)

FAD

12

Po

ten

tial en

erg

y

Eventually, the electrons are passed to oxygen, which combines with two hydrogens to form water.


How is ATP made using the ETC

1. In the mitochondria, the NADH and FADH donate electrons to the electron transport chain (ETC)

2. Oxygen is the final electron acceptor from the ETC

3. The ETC uses the energy from the electrons to transport H+ against the concentration gradient, transporting them from the lumen of the mitochondria to the intermembrane space.


How is ATP made using the ETC

4. The ATPsynthase transports the H+ back to the lumen of the mitochondria.

5. The H+ falling through the ATPsynthase provides the energy for the ATPsynthase to catalyze the reaction of ADP + P →ATP



Table 3.5



One molecule of glucose is broken down

and 36 ATP are generated.

Oxygen is used by the electron transport

chain – it accepts electrons from the ETC

Carbon dioxide is produced by the

Transition Reaction and the Citric acid

cycle


Glycolysis: Starts the process by taking in

glucose. Produces 2 ATP

The Transition Reaction produces CO2 and

NADH

The Citric acid cycle: Produces 2 ATP but

also produces lots of NADH and FADH2.

Produces CO2.



Electron transport chain

Takes electrons from NADH and FADH2and uses them to produce ATP using the

ATP synthase molecule.

Requires oxygen. Oxygen is the final

electron acceptor on the electron

transport chain

One glucose can produce a total of 36 ATP



Complex Carbohydrates

must first be broken

down into glucose before

entering glycolysis

Fats and proteins enter

the process at different

steps


Oxygen

Cellular respiration requires oxygen – this is

aerobic cellular respiration

Sometimes organisms, including humans,

need to produce energy without using oxygen

When you need energy quick, or if there is

not enough O2 then the cell will use only

glycolysis


Anaerobic Fermentation

Breakdown of glucose without oxygen

Takes place entirely in the cytoplasm

It is very inefficient - results in only two ATP


Anaerobic Fermentation

Anaerobic Fermentation: Anaerobic pathway

to produce ATP from glycolysis without the

Krebs and ETC


Fermentation in Animals

When cells need energy quick they will use this

pathway for a short time

2 pyruvic acid + 2 NADH → 2 lactate and 2

NAD+

End result = lactate and 2 ATP produced (from

glycolysis) and NAD+ is regenerated


What is the starting molecule of glycolysis?

1. Acetyl CoA

2. Protein

3. Glucose

4. Pyruvate (pyruvic

acid)


Which stage produces CO2

1. Glycolysis

2. Electron

Transport Chain

3. Transition

4. Citric acid Cycle

5. Both 3 and 4


Which stage uses O2

1. Glycolysis

2. Krebs Cycle

3. Electron

Transport Chain


Which stage produces the most NADHs

1. Glycolysis

2. Krebs Cycle

3. Electron

Transport Chain


Which stage produces the most ATP

1. Glycolysis

2. Krebs Cycle

3. Electron

Transport Chain


Important Concepts

Read Ch 4

What is Cellular respiration and Anaerobic

Fermentation and what are the differences

between them.

What are the four steps of aerobic cellular

respiration, what happens in each step, what

are the starting molecules, what comes out of

each step, where in the cell does each step

occur, how many ATP and NADH/FADH2 are

produced in each step.


Important Concepts

Describe in detail how is ATP made using the electron transport chain

What is the role of ATPsynthase, H+, O2, NADH and FADH2 and the electron transport chain in ATP production?

Know the overall picture of cellular respiration (summary slides)


Important Concepts

What is the role of oxygen in cellular respiration, what steps produce carbon dioxide

What is anaerobic fermentation, what steps are involved in fermentation, what end products are produced in humans, is oxygen required? when is it used.


Definitions

Aerobic cellular respiration, anaerobic

fermentation , ATP synthase, metabolism

Documents

Cellular Metabolism...Aerobic Cellular respiration In aerobic cellular respiration cells take in sugar (glucose) and breaks it down to into carbon dioxide and water, this requires