Energy in Living Organisms: Cellular Respiration

Review: Autotrophs Autotrophs get their energy from the sun. Convert light energy into stored chemical energy (glucose) via photosynthesis.

Review: Heterotrophs Heterotrophs get their energy from the autotrophs. Convert stored chemical energy (glucose) into usable chemical energy (ATP). This process is called cellular respiration.

Cellular Respiration (aerobic) Process by which glucose (C6H12O6) is broken down to release energy for making ATP, another form of chemical energy.

What is ATP? Energy used by all cells! Adenosine Triphosphate Organic molecule containing high-energy Phosphate bonds

How does ATP supply us with energy? By breaking the high- energy bonds between the last two phosphates in ATP! Think of a piggy bank...

How? Hydrolysis! (adding H2O)

Aerobic Respiration – Equation C6H12O6 + 6 O2 6 H2O + 6 CO2 + 36 ATP food (glucose, a carbohydrate) oxygen water carbon dioxide

A Huge Theme in Biology… Interdependence! Photosynthesis: 6 H2O + 6 CO2 + energy (sun) → C6H12O6 + 6 O2 Aerobic Cellular Respiration: C6H12O6 + 6 O2 → 6 H2O + 6 CO2 + energy (ATP) Any Observations?

Why ATP? An analogy to money… Glucose in our food is a great source of energy! ($100 bill) However, individual cell processes may only require a small amount of energy ($1 bill) Analogy: most vending machines do not accept $100 bills! We need a smaller form of “currency” for these processes. ATP (adenosine triphosphate) is this important cellular “currency” for life. ATP releases more appropriate amounts of energy for the individual cellular processes that require energy.

Do only animals respire? Or do plants respire too? The BIG Question is… Do only animals respire? Or do plants respire too? Only plants perform photosynthesis Plants AND animals perform cellular respiration! (Can you explain why??)

Steps of Cell Respiration Stage Occurs in the… Glycolysis Cytoplasm Krebs Cycle Matrix of mitochondria Electron Transport Chain Mitochondrial membrane

Glycolysis BIG IDEA: Splits glucose into 2 three-carbon molecules called pyruvate! Anaerobic – doesn’t require oxygen! Releases CO2 Net production of 2 ATP Takes 2 ATP to get started, produces 4 ATP  overall gain of 2 ATP!

Summary: Produces 2 ATP, NADH & FADH2, CO2 Krebs Cycle Aerobic – requires oxygen! Produces 2 ATP Summary: Produces 2 ATP, NADH & FADH2, CO2

The Electron Transport Chain 32-34 ATP are produced! Aerobic – requires oxygen H2O is also produced

Significant ATP Production Aerobic cellular respiration releases energy SLOWLY, using oxygen to convert ONE molecule of glucose to 36 ATP! It’s a good thing too! Each cell uses 1-2 BILLION ATP per minute!

But… What happens when cells don’t have enough oxygen? Some organisms live in an oxygen-free environment. How do they get their energy?

Cellular Respiration (anaerobic) Anaerobic respiration is also called fermentation  the process by which energy is released from glucose when oxygen is NOT available. Allows organisms to continue to produce energy until oxygen is available. However, this process only releases 2 ATP per molecule of glucose.

Fermentation Anaerobic way of converting energy for yeast and other microorganisms Glucose broken down to produce alcohol, CO2 and energy (ATP) C6H12O6  ethanol + CO2 + 2 ATP EX: baking bread with yeast

Fermentation - Bread Source of sugar? DOUGH! (sugar and/or flour) Yeast use up the O2 and ferment sugar Produce CO2, which is trapped within tiny bubbles & results in the dough rising Produce ethanol, which evaporates in the baking process

Lactic Acid Fermentation Anaerobic way of converting energy in animal cells and some microorganisms Glucose broken down to produce lactic acid, CO2 and energy (ATP) C6H12O6  lactic acid + CO2 + 2 ATP EX: muscle cells during strenuous exercise (causes the “burn”) fermenting cheese, yogurt, sour cream

Comparing ATP Production First, your body breaks down glucose through aerobic respiration to produce 36 ATP per glucose molecule; however, this is a slow process. When muscle cells cannot get enough O2 they break down glucose through lactic acid fermentation to produce 2 ATP per glucose… Therefore, AEROBIC RESPIRATION is much more efficient in terms of ATP production – 36 ATP compared to 2 ATP!

Aerobic Training Ex: long runs, biking, swimming Can increase the size and number of mitochondria in muscle cells Can increase the delivery of O2 to muscles by improving the heart and lungs

Anaerobic Training Ex: sprints, strides, quick bursts of energy Increase the glycogen levels in the muscles Increase body’s tolerance to lactic acid