1. Maintaining Blood Glucose
The Role of Glucose

2. What is glucose Glucose is the ultimate biofuel.
Glucose is a simple sugar (monosacharide), a building block of complex carbohydrates and a common source of energy for all living things.

3. What is glucose
In nature, glucose exists in the D-glucose form. D-glucose can exist in a straight chain, however most D-glucose is in the six-member ring form.

4. Importance of glucose
Glucose is oxidized in the process cellular respiration to provide the energy for metabolism (all chemical reactions within cells).
Without glucose, the human body would shut down, deprived of the fuel it needs to power its most basic functions.

5. Importance of glucose
Glucose (from carbs) provide the energy (ATP) for metabolism (chem reactions in cells)

6. Glucose source So, glucose is important... Where do we get it???
Humans get their glucose from the food they eat.
The primary source of glucose is carbohydrates,
which may consist of chains of glucose molecules,
or they may also include other sugars like fructose
and sucrose.
The digestive system breaks these carbohydrates down and releases glucose into the blood, where it can fuel the body.
Faced with a lack of carbohydrates, the body can convert fats and proteins into glucose for fuel as well.

7. Utilization So...we get it from food...what do we do with it now?
The body will do one of two things with the glucose:
Cellular respiration:
When glucose enters the bloodstream, some of it flows directly to the brain and other organs where it serves as fuel for respiration.
Glucose oxidation by respiration provides the energy that organisms need to survive
Storage of extra glucose:
Excess glucose in the bloodstream triggers the insulin response, which stores the glucose in fat, muscles and the liver.
The body can use this stored glucose during periods of low blood glucose to provide a consistent fuel source.

8. Cellular Respiration
So... One of the things we do with glucose is use it in cellular respiration... What's that?
In our tissues nutrients such as glucose can be broken down to release energy.
The energy is used to make a substance called ATP (Adenosine Tri-Phosphate).
ATP can provide energy for other
processes such as muscle contractions.
So cellular respiration is: The process of converting biochemical energy from nutrients into ATP

9. Aerobic vs Anaerobic respiration
There are two kinds of cellular respiration:
1. Aerobic respiration is the release of
energy from glucose or another organic
substrate in the presence of Oxygen.
Strictly speaking aerobic means in air, but it is the Oxygen in the air which is necessary for aerobic respiration.
2. Anaerobic respiration is the release of energy from glucose or another organic substrate in the absence of air.

10. Aerobic vs Anaerobic respiration
Aerobic respiration takes place in almost all living things.
Anaerobic respiration is used by some organisms.
Anaerobic respiration does not release as much energy and it produces more toxic waste products.
However, if Oxygen is not available, anaerobic respiration is better than nothing.
Example: During strenuous exercise our muscles don't receive oxygen quick enough for the required muscle contractions. We switch to anaerobic respiration and lactic acid builds up in our muscles.

11. Aerobic vs Anaerobic respiration
In the cytosol (liquid part of cell), glucose is converted to 2 pyruvate molecules in a process called glycolysis which produces 2 ATP
Anaerobic: In absence of oxygen this pyruvate is converted to lactic acid by fermentation as a waste product and releasing no extra ATP
Aerobic respiration: In presence of oxygen this pyruvate enters the mitochondria where it undergoes further reactions in the Krebs cyle involving oxygen at the final step, releasing 34 extra ATP and producing CO2 and water as waste products (also 2 extra ATP from conversion of NADH molecule)

12. Aerobic vs Anaerobic respiration

13. Aerobic vs Anaerobic respiration
The overall equations (glucose):
Below is the word equation and the balanced chemical equation for the process of aerobic respiration of glucose.
Glucose + Oxygen => Carbon Dioxide + Water + Energy (ATP)
C6H12O6 + 6O2 => 6CO2 + 6H2O + Energy (ATP)
Below is the word equation and the balanced chemical equation for the process of anaerobic respiration.
Glucose => Lactic acid + Energy (ATP)
C6H12O6 => 2C3H6O3 + Energy (ATP)

14. Aerobic vs Anaerobic respiration
Does it use glucose as a possible fuel source
Yes
Where it occurs
Step 1 cytosol
Step 2 mitochondria
cytosol
Oxygen required? No
How much ATP 2
= 38
Waste products produced
CO2 and H2O
Lactic acid (animal)
Alcohol (yeast)
Word equation
Glucose + Oxygen => Carbon Dioxide + Water + Energy (ATP)
Glucose => Lactic acid (or alcohol) + Energy (ATP)

15. Storage of extra glucose
So... we've got enough glucose for respiration... What do we do with the rest?
We store excess glucose
in the liver and muscle
cells as Glycogen, a
polymer or glucose.
Glycogen is synthesized depending on the demand for glucose and ATP.
If both are present in relatively high amounts, then insulin promotes the conversion of glucose into glycogen for storage in liver and muscle cells.

16. Glucose ---> Glycogen
So... we store extra glucose as glycogen...how do we make glycogen?
Glycogen consists of long, branched, polymer chains of glucose units.
Glycogen is formed from glucose by the process Glycogenesis.
Glycogenesis involves glucose
molecules being joined together
by dehydration synthesis where H2O
is lost to form the link between
2 glucose molecules, adding on
to the glycogen chain.
The glycogen can be converted back to glucose when it is needed!