Lecture 17: Cellular Respiration and Earth's Climate

Cellular Respiration

releases the energy from glucose molecules broken down to the individual carbon dioxide molecules

photosynthesis in reverse

Aerobic Respiration: The opposite of photosynthesis

Aerobic Respiration occurs in which two parts of the cell?

Cytoplasm: This is where the first stage, Glycolysis, takes place.

Mitochondria: This is the site for the remaining stages of respiration

What are the electronic carriers and their function?

NADH and FADH2, they transport electrons for use in chemical reactions

Overview of Cellular Respiration

1. Glycolysis

2. Citric Acid Cycle

3. Electron Transport System

Step One: Glycolysis (Happens in Cytoplasm)

splits the glucose into 2 pyruvate molecules, gains a small amount of ATP, the electrons are transferred from NAD+ , forming NADH

Mitochondria

Is the site of cellular respiration reactions, similar to the structure of chloroplasts (inner folded membrane), contains proteins and enzymes

Function: Converts the pyruvate into ATP

2. Citric Acid (Krebs) Cycle

• Breaking pyruvate down, stripping it of electrons and protons (H+), and releasing carbon dioxide (CO2)

Net gain of 2 ATP (not a lot)

Citric Acid (Krebs) Cycle

In: 2 Pyruvate, 2 ADP, 6 NAD+, 6FAD

Out: 2 ATP, 6 NADH, 6 FADH2, CO2

3. Electron Transport System

• Establishes a proton (H+) gradient that is used to

produce ATP using ATP Synthase

In Electron Transport System

It happens in mitochondria.

Which step in cellular respiration harnesses the most ATP from glucose?

Electron Transport System Step gains a net of 38 ATP (lots)

Oxygen is the final electron acceptor

• Oxygen ”pulls” electrons through the Electron Transport System

• Without oxygen present, the electron transport system stops

functioning -> no proton gradient -> no more big ATP payoff!!!

Fermentation

Occurs when oxygen isn’t available in cells (anaerobic respiration)

Alcohol fermentation

Happens in yeast (Ethanol), this is plants, fungi, bacteria

Lactic acid fermentation

Occurs in humans (lactate) Animals, Bacteria

Greenhouse gases

are atmospheric gases that absorb in infrared radiation

this is water vapor, CO2, ozone, methane, nitrous oxide

Greenhouse effect

Long-wave infrared energy (heat) is re-radiated back to the Earth’s surface by the atmosphere, warming it up earth avg temp is 59 farenheit

When and why did CO2 levels start to spike?

Happened in 1880, caused by human activites of burning fossil fuels

When did temperatures start rising?

1900

Balanced budger of CO2

Natural fluxes of CO2 are mostly balanced,

Anthropogenic fluxes leave behind a net accumulation

Solutions to greenhouse gases

1. Increase photosynthesis

2. Decrease rate of deforestation

3. Increase rate of biomass accumulation

Why the fuss about CO2 emissions?

• CO2 is much more abundant in the atmosphere

Which greenhouse gas has the most heat-trapping ability (relative to CO2)?

Methane