Chapter 5 Bio: Energy flows from the sun and through all life on earth

3 Organ/System Level Processes Related to Cellular Respiration

• Digestive system

  • We have to break it down so we can get access to molecules like glucose

• Cardiovascular system

  • Transporting oxygen and carbon dioxide

• Respiratory system

  • We're always breathing because we need to bring in oxygen and get rid of carbon dioxide

kinetic energy

• energy in motion

• ex.~ arms pushing water, birds flapping wings, etc.

potential energy

• stored energy

• ex.~ water trapped behind a dam, or a skier poised at the top of a hill

cellular respiration

• energy is released from the chemical bonds of food molecules and stored in the bonds of ATP molecules (useable form of energy for cells)

  • high energy

• All organisms perform this

• breaks down sugars back into CO2, H2O; ATP produced

• O2 plays crucial role

• some energy is lost as heat

• Energy is captured within ATP molecules, however, most of the energy from glucose is lost as heat (66%)

  • remember glucose is a monosaccharide (simple carbohydrate)

• occurs in mitochondria

Photosynthesis

• converts solar energy CO2 and H2O into chemical energy of sugars; O2 also produced

4 main structural features of mitochondria

• Outer membrane

• Inner membrane

• Cristae (folds of the inner membrane –lots of surface area!)

• Matrix (gel like substance)

• Cells differ in the number of mitochondria they have, usually correlating to the energy demands of the cell type (~1000-2500)

Nucleic Acid ATP

• important for cellular energy

• (adenosine triphosphate), the energy molecule used by cells, is another crucial nucleic acid

• Mitochondria (powerhouse of the cell!) are the major producers of ATP

glycolysis

• 1st step of cellular respiration

• splitting glucose into smaller molecules of pyruvate; 2 ATP created

  • (glyco = sugar, lysis = to break)

• Occurs in the cytosol (outside mitochondria)

• Preparatory phase: 2 ATP are invested to initiate glycolysis

• Payoff phase:

  • 4 ATP are made (net of:__2 ATP___)

  • Electrons are transferred from glucose to NAD+ to yield 2 NADH

• 6-carbon glucose is broken and modified into two 3-carbon pyruvates (10 enzymes involved)

  • Two pyruvates continue to next phase

citric acid cycle

• 2nd step of cellular respiration

• Generates electron carriers that take electrons to the electron transport chain; 2 ATP created

  • Loading energy carries with electrons in first steps

• the main goal of the citric acid cycle is to load more electron carriers (NADH and FADH2) with electrons taken from pyruvate

• Occurs in mitochondrial matrix

• Creating ATP and high energy electron carriers

• Carbon dioxide is a by-product

Pyruvate Modification and Citric Acid Cycle

• CO2 released

• NADH loaded with electrons

• Acetyl-CoA created

• enters the Citric Acid Cycle

  • Citrate is formed and converted to oxaloacetate which refuels citric acid cycle

  • 2 ATP produced

  • NADH and FADH2 loaded with electrons

  • CO2 released

electron transport chain

• 3rd step of cellular respiration

• uses repeated electron/energy transfers to create a gradient of H+ ions used to drive ATP production (~32 ATP created!)

• The electron transport chains are set up in the inner membrane

• Electron carriers “cashed in” to make A

• uses energy from electron-carrying molecules to pump H+ across inner mitochondrial membrane

• Oxygen accepts electrons at the end, producing water

• When the H+ ions rush down the concentration gradient, ATP synthase makes ATP (like a turbine)

• a collection of proteins in the inner mitochondrial membrane that pass electrons to each other

• The final electron acceptor is oxygen which combines with 2 H+ to become water

• release enough energy to carry H+ ions into the intermembrane space

• The result is a high concentration of H+ in the intermembrane space compared to the matrix

• The energy of electrons is used to build a concentration gradient of H+ across the inner membrane (potential energy)

ATP Synthase Function

• H+ diffuses through the enzyme this

• The flow of H+ causes rotation – kinetic energy

• Turning of the rotor adds a phosphate group to ADP to make ATP

• ~32 ATP created!

products of cellular respiration

• ATP is generated at each major step

• However, vastly more ATP is produced by the Electron Transport Chain and ATP synthase

• Glycolysis and the citric acid cycle also generate electron carrier molecules (NADH and FADH2) that carry electrons to be used in the electron transport chain

aerobic respiration

• Oxygen is present

• Produces a lot of ATP

anaerobic respiration

• oxygen not present

• produces less ATP

• If oxygen is not present, all ATP is generated using glycolysis

• Compared to aerobic respiration using the electron transport chain, generating ATP with anaerobic respiration is very inefficient!

• 2 types of fermentation

fermentation

• the breaking down of glucose without oxygen

lactic acid

• one thing fermentation produces

• animal muscle cells and some bacteria

ethanol

• one thing fermentation produces

• other bacteria and yeasts – results in alcoholic beverages

Energy can be harvested from a variety of food sources

• These molecules can be modified to enter glycolysis or the citric acid cycle

• Those things get sent into cellular respiration too

• Our diet is not only glucose