CP BIO

Chapter 9Cellular Respiration

How Cells Harvest

Chemical Energy

All life activities need energy

a. Maintain homeostasis; do life functions

breathe, circulate blood

active transport, synthesize

molecules

regulate temperature, etc.

b. Physical and mental activity

c. Cells use energy in ATP molecules

CP BIO: Ch. 9 Cell Respiration

Food energy is measured in calories

calorie = energy needed to raise the temperature of one mL water 1 degree Celsius

Food labels: Calorie (Kcal) = 1000 calories

Basics of Cellular Respiration

• Breaks down glucose in many small steps• a biochemical pathway

• Energy released is stored in molecules of ATP– Each ATP has enough energy for one cell task

• One glucose molecule yields 36 ATP

Cells use ATP for energyATP - adenosine triphosphate

High-energy bond between phosphate groups

- breaks easily, bond energy is released

Energy is used by cell to do work

7

Phosphorylate - add a phosphate group to a molecule - transfers energy to new molecule

When cell needs energy for work, 3rd phosphate

comes off ATP and attaches to molecule doing work

8

ATP – ADP Cycle• ATP breakdown products (ADP + P) stay in cell

• used again to make more ATP when needed

ATP made in cell respiration

ATP used for cellular work

Very fast!! 10 million ATP/second in a cell

All organisms do respiration

• Need oxygen - aerobic

• No oxygen - anaerobic

Energy flow is one-way

- sun plants ATP

Chemicals recycle

Oxygen and EnergyAerobic respiration harvests the most ATP from glucose

Aerobic AnaerobicBreaks down glucose completely Glucose partly broken down

Yields max amount of ATP Yields only 2 ATP/glucose

Most organisms Only a few microorganisms

Products: CO2 , H2O Products: depends

3 stages of breakdown 2 stages of breakdown Glycolysis Glycolysis Kreb’s cycle Fermentation Electron Transport Chain

Mitochondria – “power house”Compartments

- for different stages• Matrix

– Space enclosed by inner membrane

• Inner membrane– Deeply folded, more surface – Many reactions at the same time

• Cristae - folds in membrane

• Intermembrane space– Between inner and outer

membrane

Gas exchange is by diffusionIn the lungs:

Oxygen from air- diffuses into blood- carried to body cells

Carbon dioxide from blood- diffuses into air sacs- removed from body

Cells need oxygen for respiration

In cells: - oxygen diffuses IN - CO2 goes OUT

Electron Acceptors

• Help in reaction pathway, re-used

• 2 in respiration: NAD and FAD

• Accept hydrogen ions and electrons

from glucose as it breaks down

• Transfer them to another molecule

later in pathway

–makes ATP

Stages of Cell Respiration

1. Glycolysis• In cytoplasm• Splits glucose in half

2. Kreb’s Cycle• In mitochondria• Finishes glucose

breakdown3. Electron Transport Chain

• In mitochondria• Generates the most ATP

Glycolysis 1st stage in cell respiration

Glycolysis = “sugar splits”

Glucose two smaller molecules

small amount of energy released

Need 2 ATP to start

a. Two ATP attach to glucose

b. glucose splits in two

c. 3-carbon PGAL forms

d. PGAL goes through several more reactions

e. PGAL becomes pyruvic acid

Glycolysis breakdown 1) Each PGAL loses hydrogen to NAD+

a) makes NADH

b) PGAL changes to pyruvic acid

2) 4 ATP are produced, but net yield is 2

Products of glycolysis:

1) 2 ATP

2) 2 NADH

3) 2 pyruvic acid

All organisms do glycolysis• Need no oxygen or special organelles

• Probably evolved very early in history of life

• Can meet energy needs of some simple organisms

Sir Hans Krebs 1900-1981

• German chemist, 1930s• Described the cycle of reactions that

make energy in cells

• Received Nobel in 1953

• “Krebs Cycle” or “Citric Acid Cycle”

Pyruvic Acid BreakdownPREPARES pyruvic acid for Kreb’s cycle

NOT a separate stage

1) Hydrogen removed NADH2) Carbon removed CO2

3) Acetyl-CoA forms4) Ready for Kreb’s cycle

Kreb’s Citric Acid Cycle Stage 2 in aerobic respiration

In MATRIX

Completes breakdown of glucose to carbon

dioxide

Makes many molecules of NADH

and FADH2

(make energy later)

Products of Kreb’s Cycle

1. 2 ATP/glucose molecule (one each “turn”)

2. Several molecules of NADH and FADH2

– These will yield energy in stage 3

3. Last carbons in glucose form CO2 and

diffuse out of cell

Electron Transport ChainStage 3 in aerobic respiration

• SAME AS ETC IN PHOTOSYNTHESIS

• Chain of proteins in inner membrane

• Take electrons from NADH, FADH

• Electron energy makes ATP

MOST ATP made in this stage

ETC in Respiration

Only happens if oxygen is available to take electrons at end of

chain and form WATER

O + 2 H+ + 2 e- H2O

Chemiosmosis and ATP

• ATP Synthase – enzymes in cristae

• Electron energy creates H+ concentration

• H+ ions diffuse through ATP synthase

• activate synthase enzyme

• make (synthesize) ATP

ADP + P ATP

1)Starting molecules NADH, FADH2 release H+ and

electrons

2)Electron energy pumps H+ across

membrane- Forms H+ gradient

3) H+ ions diffuse through ATP

synthase(chemiosmosis)

4) ADP + P ATP

5) Final electron acceptor is oxygen

O + H+ + e- H2O

Electrons power ATP synthaseenzyme makes ATP

Total ATP yield per glucose:

Glycolysis – 2 ATP

Krebs – 2 ATP

ETC - 32 ATP

Total = 36 ATP

Summary of Aerobic RespirationPathway Reactants Products # ATP Location

Glycolysis Glucose + Pyruvic Acid NADH

2 cytoplasm

Krebs Cycle

Acetyl CoA CO2 NADHFADH2

2 Mitochondrial matrix

Electron Transport

Chain

NADH,FADH2

O2

 H2O 32 Mitochondrial cristae

Total ATP 36-38

Anaerobic Respiration

FERMENTATION follows glycolysis

– Needs no oxygen

– Makes no additional ATP after glycolysis

– NAD+ is reused

– Pyruvic acid is changed into a final product

Fermentation: two kinds

Alcohol lactic acid

Alcohol Fermentation

Some yeasts

• pyruvic acid ethyl alcohol + CO2

•Baking, brewing beer and wine

• CO2 gas makes bread dough rise, bubbles in beer and champagne

No more ATP made

Lactic Acid Fermentation• Pyruvic acid lactic acid

• Anaerobic bacteria -make lactic (and other) acids

• Commercial uses: cheese, yogurt, soy products, sauerkraut, vinegars

• Muscle cells – can do fermentation only temporarily

• lactic acids builds up “oxygen debt”

• Muscles fatigue, cramp

• With fresh oxygen: Lactic acid blood liver, changed back to pyruvic acid Kreb’s cycle

Other foods in respiration

Carbs are #1 choice for cell energy: 4 cal/g

Fats: twice the calorie store: 9cal/g

Proteins: LAST choice: – needed for many important roles 4 cal/g

-Fats and proteins are also broken down in many small steps-Amount of ATP depends on molecule

Photosynthesis – makes food

Light energy chemical energy

6 H2O + 6 CO2 C6 H12 O6 + 6 O2

Respiration – breaks down food for cell energy

C6 H12 O6 + 6 O2 6 H2O + 6 CO2

Energy in food energy in ATP

Photosynthesis and Respiration

Breathing supplies oxygen to cells1) Breathing brings oxygen into the body

2) Oxygen in lungs diffuses into blood

3) Blood delivers oxygen to all

body cells4) Oxygen is used in

cell respiration.

5) CO2 diffuses out of cells into blood

6) Blood carries CO2 back to lungs - exhaled

2) starting molecule – acetyl CoA

3) 4-C compound in matrix

4. Carbon “fixed” 6 C citric acid

5) two carbons CO2

6) one ATP forms

8) 4-C compound recycled

7) hydrogens removed - NAD, FADH reduced

1) Pyruvic acid is broken down to CO2

and acetyl (2-C) -- joins to coenzyme A