CP BIO Chapter 9 Cellular Respiration

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CP BIOChapter 9Cellular Respiration

• How Cells Harvest Chemical Energy

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All life activities need energy
CP BIO Ch. 9 Cell Respiration
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
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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
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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

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Cells use ATP for energy
ATP - adenosine triphosphate
High-energy bond between phosphate groups -
breaks easily, bond energy is released Energy is
used by cell to do work
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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
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• ATP ADP Cycle
• ATP breakdown products (ADP P) stay in cell
• used again to make more ATP when needed

ATP used for cellular work
ATP made in cell respiration
Very fast!! 10 million ATP/second in a cell
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All organisms do respiration

• Need oxygen - aerobic
• No oxygen - anaerobic
• Energy flow is one-way
• - sun? plants ? ATP
• Chemicals recycle

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Oxygen and Energy
Aerobic respiration harvests the most ATP from
glucose
Aerobic Anaerobic Breaks 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 Krebs
cycle Fermentation Electron
Transport Chain
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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

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Gas exchange is by diffusion
In the lungs Oxygen from air - diffuses into
blood - carried to body cells Carbon dioxide
from blood - diffuses into air sacs - removed
from body
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Cells need oxygen for respiration
In cells - oxygen diffuses IN - CO2 goes OUT
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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

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Stages of Cell Respiration

• Glycolysis
• In cytoplasm
• Splits glucose in half
• Krebs Cycle
• In mitochondria
• Finishes glucose breakdown
• 3. Electron Transport Chain
• In mitochondria
• Generates the most ATP

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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

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Glycolysis breakdown

• 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

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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

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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

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Pyruvic Acid Breakdown
PREPARES pyruvic acid for Krebs cycle NOT a
separate stage

1. Hydrogen removed ? NADH
2. Carbon removed ? CO2

1. Acetyl-CoA forms
2. Ready for Krebs cycle

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Krebs 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)
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Products of Krebs Cycle

• 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

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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

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ETC in Respiration
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Only happens if oxygen is available to take
electrons at end of chain and form WATER O 2
H 2 e- ? H2O
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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
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2)Electron energy pumps H across membrane -
Forms H gradient
3) H ions diffuse through ATP synthase (chemiosmo
sis)
1)Starting molecules NADH, FADH2 release H
and electrons
5) Final electron acceptor is oxygen O H
e- ? H2O
4) ADP P ? ATP
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Electrons power ATP synthaseenzyme makes ATP
Total ATP yield per glucose Glycolysis 2
ATP Krebs 2 ATP ETC - 32
ATP Total 36 ATP
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Summary of Aerobic Respiration
Pathway Reactants Products ATP Location
Glycolysis Glucose Pyruvic Acid NADH 2 cytoplasm
Krebs Cycle Acetyl CoA CO2 NADH FADH2 2 Mitochondrial matrix
Electron Transport Chain NADH, FADH2 O2  H2O 32 Mitochondrial cristae
Total ATP 36-38
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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

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• Fermentation two kinds

Alcohol lactic acid
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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
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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 ? Krebs cycle

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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

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Photosynthesis and Respiration

• 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

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Breathing supplies oxygen to cells

• 1) Breathing brings oxygen into the body

2) Oxygen in lungs diffuses into blood
6) Blood carries CO2 back to lungs - exhaled
5) CO2 diffuses out of cells into blood
3) Blood delivers oxygen to all body cells
4) Oxygen is used in cell respiration.
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2) starting molecule acetyl CoA

• Pyruvic acid is broken down to CO2 and acetyl
  (2-C)
• -- joins to coenzyme A

4. Carbon fixed ? 6 C citric acid
3) 4-C compound in matrix
8) 4-C compound recycled
5) two carbons ? CO2
7) hydrogens removed - NAD, FADH reduced
6) one ATP forms