Lecture 7

Question 1

What is ATP

Answer 1

Can be considered our energy currency.
The hydrolysis/Breaking of the phosphate bond in ATP (to convert into ADP) is what releases energy

Question 2

Difference between ATP, ADP, and AMP

Answer 2

Number of phosphates
ADP = two phosphates
AMP = one phosphate

Question 3

What is the ATP cycle

Answer 3

Describes the transfer of energy between complex and simple molecules in the body, with ATP as the mediator

We consume glucose but it can be stored as glycogen via anabolic reactions

Question 4

Describe a catabolic reaction

Answer 4

Catabolic reactions transfer energy from complex molecules - glycogen, proteins, and triglycerides - to ATP and form simple molecules - glucose, amino acids, glycerol, and fatty acids. Heat is released

Question 5

Describe an anabolic reaction

Answer 5

Anabolic reactions transfer energy from ATP to form complex molecules - glycogen, proteins, and triglycerides - from simple molecules - glucose, amino acids, glycerol, and fatty acids. Heat is released

Question 6

What are the main categories of fuel

Answer 6

Carbohydrates - broken down to simple sugars (glucose)
Proteins - broken down to amino acids
Fats - broken down to simple fats

The course only focused on cellular respiration and glucose

Question 7

What are the main categories of fuel

Answer 7

Carbohydrates - broken down to simple sugars (glucose)
Proteins - broken down to amino acids
Fats - broken down to simple fats

The course only focused on cellular respiration and glucos

Question 8

How does glucose enter cells

Answer 8

We eat food (some energy is lost for this and in faeces), and glucose enters our blood. Then it enters cells, which is facilitated by insulin - which is released by pancreas’s beta cells in the islet of langerhaans.

Once in cells, it can be used immediately for cellular respiration for cellular work, or it can be stored for harder times (stored as glycogen in liver and skeletal muscle), as having high amounts of glucose within blood is not good (homeostasis). If this happens, when energy is needed, glucagon will be released by alpha cells in pancreas’s islets to turn it back into glucose in the blood stream

Question 9

What is glycogen

Answer 9

It is formed via an anabolic reaction (heat release in this process) in liver and skeletal muscle, and can be broken down again to produce glucose (again, release of heat) when needed in bloodstream

ATP is used when transferring from glucose to glycogen and formed when glycogen goes back to glucose

Question 10

Overall chemical reaction of aerobic respiration

Answer 10

C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy (as ATP)

Carbon is oxidised and oxygen is reduced

Question 11

What are the steps of Cellular respiration

Answer 11

Glycolysis
Pyruvate oxidation
Citric acid/Krebs/TCA cycle
Electron transport chain (ETC)

Question 12

What are the parts of the Mitochondrion?

Answer 12

Outer membrane
Inter membrane space
Inner membrane
Cristae
Matrix

Question 13

Describe Glycolysis

Answer 13

Location: Occurs in the cytosol

Reactants (per glucose):
Glucose
2 ADP
2 NAD+ electron acceptor
(i.e. NOT OXYGEN)

Products:
2 Pyruvate acid molecules per glucose
4 ATP produced (2 ATP per pyruvate molecule)
2 NADH
2 H20

Net change:
- 2 pyruvate acid molecules, 2 ATP, 2 NADH, 2 H20
- 2 NAD+, and 1 glucose molecule lost.

Process:
Two ATP is invested in the glucose molecule, then the molecule splits in half, and NAD+ electron acceptors take electrons and hydrogen atoms from each of the two haves. Finally, 2 ATP is produced from each half, and 2 pyruvate acid molecules (3 carbon chains) are left

NAD+ - electron acceptor, NADH - electron donor

Question 14

Elaborate on the third step of glycolysis

Answer 14

The third step of glycolysis include phosphofructokinase

Phosphofructokinase is an enzyme that can be rate limiting for glycolysis. It operates under a negative feedback kind of loop; it is inhibited by citrate and ATP, so when high levels of citrate and ATP subsequently less ATP and citrate produced

On the other hand, it can be stimulated by AMP (which accumulates when ATP is being used rapidly)

Allows for homeostasis (is a homeostatic mechanism - the maintenance of relatively constant conditions within physiologically tolerable limits)

Question 15

Describe Pyruvate oxidation

Answer 15

Location: Matrix of mitochondria

Reactants: (per glucose)
2 Pyruvate acid molecules
2 O2 (OXYGEN)
2 NAD+
Coenzyme A

Products: (per glucose)
2 Acetyl CoA
2 CO2
2 NADH
(i.e. NO ATP)

Process:
In the presence of oxygen, the 2 molecules of pyruvate enter mitochondria, and each loses a carbon by reacting with O2 to produce CO2.
Then an electron is removed from each acid molecule to form an NADH. Then, a Coenzyme A attaches to each of the pyruvate acid molecules to produce Acetyl CoA.

Question 16

Extra things to note about pyruvate acid cycle

Answer 16

The two NADH produced via glycolysis can enter the matrix via two different electron shuttles. Depending on the protein it goes through, you end up with 2 NADH or 2 FADH, which can lead to a small difference in the amount of ATP produced in the end

Question 17

Describe the Citric acid cycle/Krebs cycle/TCA cycle

Answer 17

Location: Matrix

Reactants: (per glucose molecule)
2 Acetyl CoA
(2x) 4 chain carbon
6 NAD+
2 FAD
4 O2

Products:
2 ATP
6 NADH
2 FADH2
4 CO2
(2x) 4 chain carbons left over and recycled

Process:
The co-enzyme is removed from each Acetyl CoA and each two carbon chain is added to a four carbon chain to produce a six carbon chain. This is then partially broken down to produce 2 carbon dioxide per molecule (4 per glucose), and several electrons are captured by electron acceptors. Finally, an ATP is produced by each of the chains.

The citric acid cycle is a series of reactions: the product of one reaction is the substrate for the next (there are many intermediates).

It is when we have finished receiving the energy from the six carbons - but not done producing ATP
Important to recognise that there are intermediates within the citric acid cycle that feed into other pathways

Question 18

Describe the Electron transport chain

Answer 18

Location: Across inner membrane of mitochondria

Reactants:
NADH
FADH2
O2

Products:
26-28 ATP

Process:
Electron carriers (NADH and FADH2) are oxidised to deliver electrons to proton pumps
Electrons are transferred from one electron carrier to the next in a series of redox reactions and as they move along each step they give up energy - used to cause H+ ions to cross from matrix to intercellular space.
Importantly, Oxygen (associated with complex 4) in the matrix will pull electrons from the final proton pump to be reduced into water - oxygen is required for this reason to keep the passage of electrons going.
When this occurs, the H+ ions concentration of the IMS will be high, and as a results the H+ ions will naturally and without energy travel back down the concentration gradient (chemiosmosis). The H+ will travel through a protein called ATP synthase, and will cause it to drive the bottom part of the protein to spin. This spinning will cause ADP and free phosphates in the matric to be used to produce ATP.

Remember that there are four protein complexes and some other facilitative ones (protein Q and Cyt c). Protein complexes 1, 3, and 4 are called protein pumps - transmembrane proteins that are able to transfer hydrogen ions from the matrix up into the inter membrane space. Complex 2 is a peripheral protein

FADH2 starts at complex 2 but ultimately passes down the same pathway.

ATP synthase protein is also on inner membrane

Question 19

Where are the proteins involved in the electron transport chain

Answer 19

The proteins involved in the Electron transport chain are sitting on the inner membrane and are called complex 1, 2, 3, and 4. Complex 1, 3, and 4 are integral proteins, while Complex 2 protein is more of a peripheral protein.

Question 20

What can impact the ETC

Answer 20

Cyanide can act on protein 4 to block passage of electrons to oxygen in the end, and if the reduction of oxygen is blocked the whole chain won’t work

Will cause mitochondria and like cell to die

Question 21

In which process is most ATP produced from food

Answer 21

In the ETC

Question 22

Describe substrate phosphorylation

Answer 22

ATP generated by direct transfer (from a substrate) of a phosphate group to ADP (using an enzyme). Glycolysis and citric acid cycle make ATP via substrate phosphorylation. Not very efficient

Question 23

Describe oxidative phosphorylation

Answer 23

ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons (doesn’t need substrate, deals with free phosphates)

Question 24

How much ATP is produced in total from cellular respiration

Answer 24

30-32 ATP

Question 25

How can you derive energy

Answer 25

We can derive energy from more than just glucose - fats, proteins, and more complex carbohydrates generate ATP as well. They (their monomers) enter the same cellular respiration pathway (glycolysis and citric acid cycle), but enter at different points

Question 26

What is the normal blood glucose level

Answer 26

Should stay within ~70-110 mg/dL or 4-6 mmol/L (fasting)

Question 27

Define homeostasis

Answer 27

the maintenance of relatively constant conditions within physiologically tolerable limits

Question 28

What happens when there is too much glucose within the blood - hyperglycaemic

Answer 28

The beta cells in pancreas islets secrete insulin, which will act on all body cells to allow for increased glucose intake to cells (decrease blood glucose) and therefore increase rate of ATP generation. If not immediately required, glucose can be stored as glycogen - so this will caused increased conversion of glucose to glycogen

Question 29

What happens when there is too little glucose within the blood - hypoglycaemic

Answer 29

Need more glucose (hypoglycaemic), alpha cells in the pancreatic islets will secrete glucagon which will act on the liver, skeletal muscle and adipose cells/fat to increase breakdown of the glycogen to glucose to therefore increase blood glucose level.

Question 30

What is the hormone released by alpha cell

Answer 30

Glucagon - as it acts ON glycogen

Question 31

Describe diabetes mellitus

Answer 31

Loss of function of insulin receptors or not enough insulin - end up with elevated levels of blood glucose (equal to or above 7 mmol/L fasting). This means no glucose in cells, no ATP from glucose, no glycogen stored for harder times

Question 32

Describe Type 1/insulin-dependent diabetes

Answer 32

Body does not produce any or sufficient insulin, as beta cells of pancreas are destroyed - often this is autoimmune, or genetic or through environmental factors.
Causes hyperglycaemia
Affects 5 – 10 % of diabetics, and onset usually occurs in children or adolescents.
Requires insulin replacement

Question 33

Describe Type 2/non-insulin-dependent diabetes

Answer 33

Body produces insulin, but receptors are non functional (insulin resistance).
Causes hyperglycaemia
Most (>90%) diabetics are Type II, usually adults over the age of 40
Can be linked to other pathologies and obesity
Insulin not always required but sometime helps

Question 34

Describe the contradictory symptoms of Diabetes

Answer 34

Two of the symptoms of this disease are: Significantly increased hunger (because no energy)
but experience
Significant weight loss (as energy stores used up)

Question 35

What are the main categories of fuel

Answer 35

Carbohydrates - broken down to simple sugars (glucose)
Proteins - broken down to amino acids
Fats - broken down to simple fats