Cellular Respiration

Harvesting Chemical Energy So we see how energy enters food chains (via

autotrophs) we can look at how organisms use that energy to fuel their bodies.

Plants and animals both use products of photosynthesis (glucose) for metabolic fuel

Heterotrophs: must take in energy from outside sources, cannot make their own e.g. animals

When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them

When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use themAnimals use cellular respiration to transform

chemical energy in food into chemical energy cells can use: ATP

These reactions proceed the same way in plants and animals.

Overall Reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O

How much energy is actually present in food? 1 g of sugar glucose (C6H12O6) when burned in

the presence of O2 releases 3811 calories of heat energy

How many calories do you burn a day?

How many calories do you burn a day? Male 150 lb 5’9” Somewhat active Burns 3023 kcal a day or 3023 Calories or

3,023,000 calories

1 g of glucose produces 3811 calories

Calorie calorie: The amount of energy needed to raise the

temperature of 1 gram of water 1 degree Celsius

Calorie: food labels 1000 calories Cells don’t burn glucose – cells gradually release

energy from glucose and other food compounds Cells release energy from glucose by performing

cellular respiration

Cellular Respiration Overview Breakdown of glucose begins in the cytoplasm:

the liquid matrix inside the cell At this point life diverges into two forms and two

pathways Anaerobic cellular respiration (aka fermentation) Aerobic cellular respiration

Cellular Respiration Cellular respiration is the process that releases

energy by breaking down glucose and other food molecules in the presence of oxygen

C6H12O6 + 6O2 → 6CO2 + 6H2O

Cellular Respiration Glycolysis The Krebs Cycle Electron Transport

Glycolysis The process in which one molecule of glucose is

broken in half, producing two molecules of pyruvic acid

http://upload.wikimedia.org/wikipedia/commons/1/17/Glycolysis2.svg

Glycolysis – ATP Production 2 ATP used 4 ATP produced

Net gain of 2 ATP

Glycolysis – NADH Production NAD+ accepts a pair of high-energy electrons

until they are transferred to other molecules

Anaerobic Respiration When oxygen is not present, glycolysis is followed

by a different pathway – FERMENTATION

Alcoholic fermentation (yeast) Pyruvic acid + NADH alcohol + CO2 + NAD+ Causes bread to rise – CO2 forms the air spaces that

you see in bread Lactic acid fermentation (muscles)

Pyruvic acid + NADH lactic acid + NAD+

Substrate Level Phosphorylation

Glycolysis

Krebs Cycle

Citric Acid Production Pyruvic acid enters the mitochondrion A carbon is removed, forming CO2 Electrons are removed: NAD+ NADH Coenzyme A joins the 2-carbon molecule, forming

Acetyl-Co-A Acetyl-Co-A then adds the 2-carbon acetyl group

to a 4-carbon compound (oxaloacetate), forming Citric Acid

Krebs Cycle

Cytoplasm

Inner Mitochondrial Space

Acetyl Co A Citric Acid

Energy Extraction Citric acid is broken down into a 5-carbon

compound, then into a 4 carbon compound Produces

2 more molecules of CO2 NAD+ NADH FAD+ FADH2 1 ATP

Electron Transport Electrons from NADH and FADH2 are used in the

electron transport chain to convert ADP to ATP

Electron Transport Chain Composed of carrier proteins located in the inner membrane of

the mitochondrion High-energy electrons are passed from one carrier protein to the

next An enzyme combines these electrons with hydrogen ions and

oxygen H2O Oxygen is the final electron acceptor of the electron transport chain Oxygen is essential for getting rid of low-energy electrons and

hydrogen ions Low-energy electron and hydrogen ions are waste products of cellular

respiration

Hydrogen Ion Movement Every time 2 high-energy electrons transport down

the electron transport chain, their energy is used to transport hydrogen ions (H+) across the membrane

H+ build up in the intermembrane space, making it positively charged

The other side of the membrane is negatively charge

ATP Production The cell uses the build up of charge differences As H+ escape through the ion channels, the ATP

synthase (a protein enzyme) spins Each time the ATP synthase spins, the enzyme

grabs an ADP and attaches a phosphate, forming ATP

Each pair of high-energy electrons that moves down the electron transport chain provides enough energy to produce three molecules of ATP