Cellular RespirationDefinition:

Gradual release of

energy by the break-down of food molecules

in aerobic conditions

(= O2 present)

Energy in Food

________________________

Light provides the energy to make molecules from…

Where does the energy in food come 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?

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.

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

ChainElectron 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.

GlycolysisElectron Transport Chain

Krebs Cycle

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 ____________________ pyruvic

acid 

Stage 2 – Lactic acid fermentation Pyruvic acid broken down into lactic acid + NAD+

Lact = milk!

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 GlucoseCellular Respiration

Aerobic

3 StagesGlycolysis

Krebs Cycle

Electron Transport Chain

Nets 36 ATP molecules

Fermentation

Anaerobic

Glycolysis followed by

Lactic Acid Fermentation OR

Alcoholic Fermentation

Nets 2 ATP molecules