Cellular Respiration

Energy and Life 8-1 Page 201

The sun is the original source of energy for all living things. To live and perform life functions all organisms need… Autotrophs Able to make their own food using the sun’s energy. Heterotrophs Get their energy from feeding on autotrophs or other heterotrophs.

The food eaten must be turned into a chemical form to be used for life processes. Adenosine Triphosphate (ATP) the main chemical compound that cells use to store and release energy

Energy from ATP powers: - active transport across cell membranes - synthesis of proteins & nucleic acids - responses to chemicals at the cell surface - can even be used to produce light

ATP is made up 3 parts: –adenine –5-carbon sugar called ribose –three phosphate groups adenineribosephosphate groups

Phosphate groups are the key to ATPs ability to store and release energy. Energy is stored in the bond between the 2nd and 3rd phosphate. adenine ribose phosphate groups

When the 3 rd phosphate breaks off it is called ADP (adenosine diphosphate) adenine ribose phosphate groups

Breaking the chemical bond between the 2nd & 3rd phosphate RELEASES energy. adenine ribose phosphate groups ATPATPADPADP

Adding the chemical bond between the 2nd and 3rd phosphate STORES energy. Breaking the chemical bond between the 2nd & 3rd phosphate RELEASES energy. adenine ribose phosphate groups ADPADPATPATP

ADPATP Energy Adenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP) Partially charged battery Fully charged battery Most cells have only a small amount of ATP, enough to last them for a few seconds of activity. ATP’s ability to “recharge” is very important to its usefulness.

ATP is great for transferring energy, not good for long term energy storage. –A single molecule of glucose stores 90 times the chemical energy of one molecule of ATP. Cells regenerate ATP from ADP as needed.

Figure 9–2 Cellular Respiration: An Overview Electrons carried in NADH Glucose Cytoplasm Glycolysis Pyruvic acid Krebs Cycle Mitochondrion Electrons carried in NADH and FADH 2 Electron Transport Chain Mitochondrion Cellular Respiration Net gain of 2 ATP Net gain of 34 ATP Total ATP molecules formed during cellular respiration = 36 ATP

CELLULAR RESPIRATION 6O 2 + C 6 H 12 O 6  6CO 2 + 6H 2 O + Energy Oxygen + Glucose  Carbon + Water + Energy (ATP) Dioxide

Where did that glucose come from? ?

CELLULAR RESPIRATION After glycolosis, there are two possible pathways depending on the presence or absence of O 2

Chemical Pathways of Cellular Respiration Glucose Glycolysis Krebs cycle Electron transport Fermentation (without oxygen) Alcohol or lactic acid

CELLULAR RESPIRATION If oxygen is present aerobic respiration will begin If oxygen is not present anaerobic respiration will occur

After Glycolysis cont. If oxygen is not present one of two types of anaerobic respiration or Fermentation takes place; Alcoholic Fermentation Lactic Acid Fermentation Requires NADH to convert pyruvic acid into lactic acid

The Krebs Cycle If oxygen is present aerobic respiration begins The Krebs Cycle begins when the two molecules of pyruvic acid produced in glycolysis enter the Mitochondria and with the help of enzymes form Citric Acid. As a result the Krebs cycle is also referred to as the Citric Acid

The Krebs Cycle cont. Energy Extraction; The citric acid is broken down into carbon compounds and the following are released; 2 ATP 6 molecules of CO 2 Electron carriers (NADH and FADH 2 )

The Krebs Cycle cont. Citric Acid Production Mitochondrion

Electron Transport Chain The electron transport chain uses the high- energy electrons (donated electron carriers NADH and FADH2) from the Krebs cycle to convert ADP into ATP. High-energy electrons from NADH and FADH 2 are passed along the electron transport chain (carrier proteins). An enzyme at the end of the electron transport chain combines electrons with hydrogen ions and oxygen to form water. Oxygen is the final electron acceptor. Releases 6H 2 O and 32 molecules of ATP

Cellular Respiration Total ATP produced= 36