Cellular Respiration

Cellular Respiration Conversion of glucose to ATP

Outline of what you will be learning… • 1. Overview • 2. Purpose: To Get ATP! • 3. Electron Carrier Molecules • 4. Mitochondria • 5. The Basics of Cell Respiration • 6. Glycolysis • 7.Pyruvate chemical “grooming” • 8. Kreb’s Cycle • 9. Electron Transport Chain (Oxidative Phosphorylation) • 10. Cell Respiration Summary • 11. Fermentation- Anaerobic Respiration

1. Overview • Who does it? • All living things: both autotrophs and heterotrophs • What is it? • Carbohydrates and O2 are used to make ATP (energy). CO2 and H20 are waste products. • Involves three steps: glycolysis, kreb’s cycle, and electron transport chain. • The opposite of photosynthesis. • Where does it occur? • The cytoplasm and the mitochondria of the cell

1. Overview • Cellular respiration releases energy by breaking down glucose and other food molecules in the presence of oxygen. • Equation: • C6H12O6 + 6O2 6CO2 + 6H20 + ATP • Glucose+ oxygen carbon dioxide + water + energy

2. Purpose: To Get ATP! • ATP: A modified nucleotide molecule that powers all cellular work directly.

2. Purpose: To Get ATP! • Phosphorylation • When ATP releases a phosphate + energy it produces ADP (adenosine diphosphate) • ADP can turn back to ATP by taking in a phosphate and energy by phosphorylation • Similar to recharging a battery

2. Purpose: To Get ATP!

3. Electron Carrier Molecules • There are two different molecules that are used to carry electrons and hydrogen ions to the last step cellular respiration. • NADH- NAD+ • FADH2- FAD

4. Mitochondria

5. The Basics of Cell Respiration • Cellular respiration takes place in small steps to minimize the loss of energy in the form of heat or light. • Processes that require oxygen to take place are called aerobic. • Processes that do not require oxygen to take place are anaerobic.

5. The Basics of Cell Respiration • Aerobic Cellular respiration consists of three major steps (when oxygen is present): • Glycolysis – occurs in the cytoplasm • The Krebs cycle – occurs in the matrix of mitochondrion • Electron transport chain – occurs along the innermembrane in the cristae of mitochondrion

5. The Basics of Cell Respiration

6. Glycolysis • Means “splitting sugar” • Occurs in the cytoplasm • Is anaerobic (doesn’t require oxygen) • Glucose (6-C) is split to two molecules of another organic compound, called pyruvate (3-C). • Makes 4 ATP, but uses 2 ATP, for a net gain of 2 ATP • ATP can be used by cell immediately • A net gain of 2 NADH molecules • NADH must pass down the ETC in mitochondria • Water is released as waste product

6. Glycolysis

7. Pyruvate chemical “grooming” • As pyruvate forms at the end of glycolysis, it is transported from the cytoplasm into the mitochondria • Pyruvate does not enter the Kreb’s Cycle as itself. • It undergoes major chemical “grooming”

7.Pyruvate chemical “grooming” • A carbon atom is removed from pyruvate (3-C) forming acetyl coA (2-C) • NADH molecules are made (per pyruvate-3C) • CO2 is released as a waste product (per pyruvate-3C)

7. Pyruvate chemical “grooming”

8. Kreb’s Cycle • Occurs in the matrix of the mitochondria • Compared with glycolysis, Kreb’s Cycle pays big energy dividends to the cell • This makes 1 ATP, 3 NADH and 1 FADH2, per acetyl coA (2-C) (double that for each glucose molecule) • Releases CO2 as waste • is aerobic (requires oxygen)

8. Kreb’s Cycle

9. Electron Transport Chain • Occurs along the inner membrane of the cristae of the mitochondria • NADH and FADH2 from glycolysis and Kreb’s Cycle give up their H+ and electrons to make ATP • 3 ATP for each NADH and 2 ATP for each FADH2 • O2 is the final electron acceptor and becomes water which is a waste product • Is aerobic and makes most of the energy in cell respiration.

9. Electron Transport Chain

10. Cell Respiration Summary • TOTAL= 38 ATP (theoretical) • Glycolysis • Occurs in cytoplasm • 2 ATP • 2 NADH • 2 H20 get released • 2 pyruvate • Kreb’s Cycle (including pyruvate grooming) • 2 ATP • 8 NADH • 2 FADH2 • 6 CO2 get released • Electron Transport Chain • H20 gets released • 10 NADH get converted to 3ATP= 30 ATP • 2 FADH2 get converted to 2 ATP= 4 ATP

11. Fermentation- Anaerobic Respiration • Glycolysis is the metabolic pathway that generates ATP during fermentation. • No O2 is required; it generates a net gain of 2 ATP and 2 NADH • Significantly less ATP is generated, but it is enough to keep your muscles contracting for a short while when the need for ATP outpaces the delivery of O2 via the blood stream • Many microorganisms supply all their energy needs with the 2 ATP yield of glycolysis.

11. Fermentation- Anaerobic Respiration • Fermentation provides an anaerobic step that recycles NADH back to NAD+; essential to harvest food energy by glycolysis. • Two types of fermentation: • Lactic acid • Alcohol

11. Fermentation- Anaerobic Respiration • Lactic acid fermentation • 1. Glycolysis occurs • 2. NADH is recycled to NAD+ as pyruvate becomes to lactic acid. • Lactate builds up in muscle cells during strenuous exercise is carried in the blood to the liver, where it is converted back to pyruvate • Dairy industry use this to with bacteria to make cheese and yogurt

11. Fermentation- Anaerobic Respiration • Alcohol fermentation • 1. Glycolysis occurs • 2. NADH is recycled to NAD+ while pyruvate (3-C) releases a CO2 and becomes ethanol (2-C) (ethyl alcohol). • Used by yeasts and bacteria • Used in brewing, winemaking, and baking • CO2 provides bubbles in beer and champagne, and bread dough to rise • Ethanol is toxic to organisms that produce it; must release it to their surroundings

Cellular Respiration