Cellular Respiration Definition: Gradual release of energy by the break-down of food molecules in aerobic conditions (= O2 present)

Energy in Food Where does the energy in food come from? ________________________ Light provides the energy to make molecules from…

Water +

6CO2 +H2O  C6H12O6 +6O2 Occurs in grasses (and other plants) growing… Which are eaten by cattle

And end up as food on our Plates (Or vegetarians fill their plates with products made from green plants)

Question 1: Where does the energy in food come from? Originates in sunlight  During photosynthesis light energy is converted into chemical energy in food molecules

How does energy get released from food? In humans and many other vertebrates: Food particles get broken down in the digestive system. Chewing - teeth Acids - stomach Enzymes – small intestine

Role of the small intestine Tiny projections called villi line the small intestine (increases surface area), which absorb digested food into the capillaries (small blood vessels).*

Food, Energy and Blood Tiny food particles (glucose) is carried in the blood to each cell in the body. Glucose enters each cell by the process of _______________________ Facilitated diffusion

Which organelle releases the energy from glucose?

What happens next? 6O2 + C6H12O6  6H2O + 6CO2 __________ The chemical reaction for cellular respiration: 6O2 + C6H12O6  6H2O + 6CO2 __________ High energy bonds low energy bonds What is missing from the equation? + ENERGY

Cellular respiration Occurs in THREE STAGES This allows the energy found in glucose to be released slowly rather than all at once. The energy in glucose is found in chemical bonds. When the bonds are broken, the energy is released and stored in molecules of ATP.

What is missing from the equation? Stage 1 - Glycolysis What happens? 1 molecule of glucose is broken into 2 molecules of pyruvic acid. Bonds are broken and energy is released  C6H12O6  2 C3H4O3 + 4H+ _____________ (glucose) (pyruvic acid) What is missing from the equation? + ENERGY

Glycolysis (Cont) Glycolysis releases energy. The energy is stored in the chemical bonds of two molecules. ADP (low energy) is converted to ATP (high energy) and NAD+ (nicotinamide adenine dinucleotide) is converted into NADH (holds high energy electrons)  

Glycolysis (cont) The amount of energy produced from glycolysis is small but the process occurs quickly. Glycolysis nets 2 ATP molecules

Stage 2 – Krebs Cycle or Citric Acid Cycle Hans Krebs (1900–1980) Discovered the citric acid cycle, (aka) Krebs Cycle, in 1937. Awarded the Nobel Prize for his discovery in 1953.

Krebs Cycle Under aerobic conditions (O2 present), pyruvic acid, passes to the second stage of cellular respiration What happens? Pyruvic acid is broken down into CO2 (this is the CO2 we breathe out). A small amount of energy is stored in ATP

Krebs Cycle (cont) Occurs in the mitochondrion of Eukaryotes Occurs in the cytoplasm of Prokaryotes

Stage 3 – Electron Transport Chain Electron transport chain – series of reactions What happens? High energy NADH converts low energy ADP into ATP. About 34 ATP molecules are formed from the Krebs cycle and electron transport chain combined. Occurs in the mitochondrion of Eukaryotes Occurs in the cytoplasm of Prokaryotes

Question! Why are mitochondria called the POWERHOUSE OF THE CELL?

Cell Respiration Together ____________, the _______________and the _________________________________________ make up cell respiration. Glycolysis Krebs Cycle Electron Transport Chain In most cells, 1 molecule of glucose produces 36 molecules of ATP. This amounts to 38% of the total energy stored in glucose. The rest of the energy is released as body heat. Complete worksheet on Cell Respiration!

Aerobic vs. Anaerobic Aerobic = O2 present Anaerobic = No O2 present Can organisms break down glucose and release its energy in anaerobic conditions?

YES! Fermentation – an anaerobic cellular process by which glucose is broken down. Fermentation - used by organisms that need small quantities of energy: unicellular organisms or simple multicellular organisms AND Fermentation – used when energy is needed very quickly by muscle cells in animals.

Fermentation Two types of fermentation a) lactic acid fermentation b) alcohol fermentation.

Lactic Acid Fermentation Stage 1 - Glycolysis occurs. Glucose  ____________________    Stage 2 – Lactic acid fermentation Pyruvic acid broken down into lactic acid + NAD+ Lact = milk! pyruvic acid

Lactic Acid Fermentation The NAD+ restarts the glycolysis reaction which produces 2ATP molecules from 2ADP molecules. Used by bacteria for the breakdown of glucose. Used to produce yogurt and cheeses. Used by muscles when energy is needed quickly (a sprint), and O2 is in short supply. Lactic acid build up causes a burning sensation resulting in “sore muscles”.  

Alcoholic Fermentation Stage 1 - Glycolysis occurs. Glucose  pyruvic acid Stage 2 – Alcoholic fermentation - In yeast occurs. Pyruvic acid broken into CO2 + ethanol alcohol. When yeast is added to bread dough, the CO2 that’s produced is released and trapped in the dough—causes bread to rise.* The alcohol produced in the reaction evaporates when the bread is baked!  

Breaking down Glucose Cellular Respiration Fermentation Aerobic 3 Stages Glycolysis Krebs Cycle Electron Transport Chain Nets 36 ATP molecules Anaerobic Glycolysis followed by Lactic Acid Fermentation OR Alcoholic Fermentation Nets 2 ATP molecules