Cellular Respiration Vocabulary Glycolysis Krebs Cycle Pyruvic acid

Cellular Respiration Vocabulary: -Glycolysis -Kreb’s Cycle -Pyruvic acid -Fermentation -Aerobic Reaction -Anaerobic Reaction

Review • What is photosynthesis? • Where does this occur? • What is the difference between ATP and ADP? • What is the difference between NADPH and NADP+? • Light vs. Dark reactions

• After glucose is made in photosynthesis, how is the energy in the sugar molecules released so it can be used by the organism? – cellular respiration! • Cellular Respiration occurs in both plant & animal cells – WHERE? ? – CYTOPLASM & MITOCHONDRIA!!! The Power House of the Cell!!

Cellular Respiration… A Controlled Process • Food (glucose), like fuel, is "burned" by our cells for energy – if it's burned all at once, too much energy is released • therefore, the reaction is broken down into many small steps controlled by ENZYMES – Cells gradually release the energy from glucose and other compounds

• the energy is transferred to the bonds of ATP which stores and releases the energy in usable amounts to be used by the cell • energy is stored in bonds between phosphate groups AMP ADP P P ATP

Cellular Respiration • Process that releases ENERGY by breaking down food molecules in the presence of oxygen • Occurs in both plants and animals

Cell respiration occurs in 3 stages: • • • Glycolysis Citric (Krebs) cycle Electron transport chain

Glycolysis (glyco= sugar, lysis = breaks down) • Process occurs in the cytoplasm • Breaks glucose down from 6 -carbon compound into two 3 -carbon compounds (called pyruvate) Equation: enzymes in C 6 H 12 O 6 2 pyruvates + 2 ATP cytoplasm

• Glycolysis can occur if oxygen is present (aerobic) or absent (anaerobic) – Glycolysis is ALWAYS the first step in breaking down glucose • If oxygen IS present, then cells proceed with Respiration/Krebs • If oxygen is NOT present, then cells ferment

Cellular Respiration can be broken down into 2 processes: 1) Glycolysis: breaking down glucose 2) Respiration (Krebs Cycle & Electron Transport Chain): uses oxygen to finish breaking down products from Glycolysis & release energy

GLUCOSE CO 2 H 2 O & heat energy O 2 Glucose + Oxygen Carbon Dioxide + Water C 6 H 12 O 6 6 CO 2 + 6 O 2 Look familiar? ? ? + 6 H 2 O

Respiration/Krebs • Occurs in the Mitochondria of cell • Only if oxygen is PRESENT (aerobic) • Uses the pyruvic acid from glycolysis to produce carbon dioxide, water, and ATP • Products: – – – 34 ATP per molecule of glucose carbon dioxide water

So how does this happen? • The Citric (Krebs) cycle and the electron transport chain turn the pyruvate into CO 2, H 2 O, and ATP • To do this, pyurvate loses a carbon atom to make Acetyl Co. A

• Acetyl Co. A enters the Krebs Cycle to produce CO 2, NADH, and FADH 2 • The NADH and FADH 2 carry energy to the electron transport chain to make more ATP (this requires oxygen) C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + 36 ATP

Summary of Cellular Respiration GLYCOLYSIS “break sweetness” Location in the cell: It starts with: It ends with: Is Oxygen required? # of ATP’s Produced: RESPIRATION/ Kreb’s Cycle Cytoplasm Mitochondria C 6 H 12 O 6 (glucose) 2 (C 3 H 6 O 3) pyruvic acid NO 2 pyruvic acid 2 (tiny) H 2 O, CO 2, ATP YES! AEROBIC 34 (lots!)

GRAND TOTAL= 36 ATP!! • 2 are produced in Glycolysis and 34 in Respiration/ Kreb’s Cycle – 18 times more ATP are produced in the presence of Oxygen!!

How efficient is this? ? • The 36 ATP molecules the cell makes per 1 glucose represents about 38% of the total energy in glucose • Even though it doesn’t seem like much, this is more efficient than your car’s gas burning engine • What happens to the remaining 62%? ? ? – It is released as heat.

What happens if your cells aren’t getting enough oxygen? • Respiration/Kreb’s CANNOT proceed • Fermentation occurs – Pyruvic Acid builds up in animal muscle cells as LACTIC ACID… feel the burn! – In other organisms, the pyruvic acid builds up, ferments, and becomes alcohol

• Fermentation: release of energy from food molecules in absence of oxygen (anaerobic) • Enables cells to carry out energy production in the absence of Oxygen • result of glycolysis + fermentation yields 2 ATP molecules per 1 molecule of glucose (not nearly as much energy!!!!)

2 Fermentation Pathways: 1. Lactic Acid Fermentation: • pyruvic acid from glycolysis is converted to lactic acid • lactic acid is produced in muscles during rapid exercise (body can't supply enough O 2 to the tissues) • the build-up of lactic acid causes a burning, painful sensation in your muscles

Energy & Exercise: Quick Energy • Muscle cells only contain enough ATP for a few seconds of “burst” energy – emergency, starting gun of race • When this is gone, cells resort to lactic acid fermentation which can provide enough ATP for about 90 seconds

Long Term Energy • If a race or energy need is longer, your body must go through cellular respiration to get enough ATP to continue – Even well-conditioned athletes have to pace themselves – Your body stores energy in muscle • glycogen – these stores are enough to last for 15 -20 minutes of activity when broken down through cellular respiration – After this, your body begins to break down fats and other stored molecules

2. Alcoholic Fermentation: • Occurs in yeast cells & some other microorganisms • Pyruvic acid is broken down into a 2 -Carbon alcohol plus carbon dioxide

Alcoholic Fermentation • Important to brewers & bakers! – When yeast in dough runs out of oxygen it ferments, giving off bubbles of carbon dioxide gas—which forms air space in bread – Alcohol produced in the dough evaporates when bread is baked *(when the level of alcohol reaches 12%, yeast cells die)